JP2010121516A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for an internal combustion engine, performing proper pilot fuel injection in idling of the internal combustion engine. <P>SOLUTION: The fuel injection control device (100) for an internal combustion engine (10) has a fuel injection means performing at least main fuel injection injecting fuel into a combustion chamber of the internal combustion engine, and the pilot fuel injection before the main fuel injection. The fuel injection control device (100) includes: a detection means (21) disposed in an intake pipe (11) and detecting a temperature of sucked outside air; and a determination means (101) determining an idle state of the internal combustion engine. When the idle state of the internal combustion engine is determined, the fuel injection control device corrects (102) the detected outside air temperature and controls (103, 104) the pilot fuel injection according to the corrected outside air temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control apparatus for an internal combustion engine comprising fuel injection means for performing at least main fuel injection for injecting fuel into a combustion chamber of an internal combustion engine mounted on a vehicle and pilot fuel injection prior to the main fuel injection. More particularly, the present invention relates to a control device for pilot fuel injection during idling.

  Diesel engines aim to reduce noise, vibration, and exhaust gas by performing multiple fuel injections in a single combustion stroke. The pilot fuel injection is a fuel injection that is performed prior to the main fuel injection included in the multiple fuel injections, and a very small amount of fuel is injected and burned to increase the gas temperature in the cylinder. Since the ignition delay time at the time of injection can be shortened, a rapid pressure increase in the cylinder is suppressed. As a result, combustion noise is also suppressed. Thus, the combustion noise is improved in the diesel engine by performing the pilot fuel injection.

  In the combustion of an internal combustion engine, it is necessary to manage an appropriate mixing ratio between the intake air amount and the fuel, that is, a so-called air-fuel ratio. The specific gravity of air changes with temperature. Therefore, in order to know an accurate intake air amount, the temperature of the intake air is important.

For example, when the atmospheric temperature is low, the amount of fuel increases and white smoke is generated. If the fuel injection timing is advanced in order to improve such a situation, noise will increase. Therefore, a technique for correcting pilot fuel injection based on atmospheric temperature has been developed (see, for example, Patent Document 1).
Japanese Patent No. 3721873

  In the above-described known technique (Patent Document 1), the atmospheric temperature used for correcting the pilot fuel injection is usually detected by an atmospheric temperature sensor provided in the intake pipe of the internal combustion engine. The atmospheric temperature sensor (intake air temperature sensor) is installed near the air flow meter or installed near the intake manifold depending on the vehicle type. The indication value of the atmospheric temperature sensor may be affected by the heat generated in the engine body in any case.

  In the normal operating state of the internal combustion engine, the amount of air to be sucked is large and the time during which the fluid stays in the intake pipe is small, so that it is not easily affected by a heat source such as a combustion chamber. However, when the internal combustion engine is in an idle state, in particular, a so-called long idle state for a long period of time, the amount of air sucked is smaller than in a normal operation state. The amount of air is small, so the heat capacity of the gas is small, and the flow rate is small, so the residence time of the air in the intake pipe is long.Therefore, due to the effect of convection due to heat conduction from the heat source and temperature rise in the gas, The temperature of the air in the vicinity of the sensor is higher than the actual atmospheric temperature, and the temperature indicated by the atmospheric temperature sensor is similarly higher than the actual atmospheric temperature.

  In such a situation, the fuel amount for pilot fuel injection is calculated according to a temperature higher than the actual atmospheric temperature. The calculated amount of fuel for pilot fuel injection is smaller than the actual intake air amount at a low temperature, and an appropriate combustion state is not obtained, so there is a possibility that a sufficient combustion noise reduction effect cannot be obtained.

  An object of the present invention is to provide a fuel injection control device for an internal combustion engine that performs pilot fuel injection with an appropriate amount of fuel even when the internal combustion engine is idle.

  In order to solve the above-described problems, a fuel injection control device according to the present invention includes fuel injection means for performing at least main fuel injection for injecting fuel into a combustion chamber of an internal combustion engine and pilot fuel injection prior to the main fuel injection. Controls fuel injection of the internal combustion engine. This device is provided in the intake pipe, and includes detection means for detecting the temperature of the outside air to be sucked, and determination means for determining an idle state of the internal combustion engine. This apparatus is configured to correct the detected outside air temperature when it is determined that the internal combustion engine is in an idle state, and to control the pilot fuel injection according to the corrected outside air temperature.

  According to the above configuration, the detected outside air temperature is corrected to be close to the actual outside air temperature in an idle state in which the value detected by the sensor that measures the outside air temperature may not correctly indicate the atmospheric temperature (outside air temperature). By doing so, an appropriate control amount of pilot fuel injection can be calculated. By performing pilot fuel injection with the control amount, it contributes to the reduction of combustion noise.

  In the above configuration, the pilot fuel injection may be configured to control both or one of the fuel injection amount and the fuel injection timing based on the corrected outside air temperature.

  In the above configuration, the outside air temperature can be corrected by maintaining the outside air temperature at the temperature detected immediately before the idling state in response to the internal combustion engine entering the idling state.

  In the above-described configuration, the correction of the outside air temperature may be configured such that the current value detected by the detection means is compared with the previous value, and the lower temperature is set as the corrected outside air temperature.

  The present invention can provide a fuel injection control device that calculates an appropriate control amount for pilot fuel injection even when the internal combustion engine is idle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of an engine system including a fuel injection control device for an internal combustion engine according to the present embodiment.

  FIG. 1 illustrates one cylinder 10 of a multi-cylinder diesel engine that can include the fuel injection control device according to the present embodiment. The mechanical configuration itself of this diesel engine is the same as a well-known one and includes a turbocharger 20.

  The air taken in from the outside passes through the intake pipe 11 from the direction of the white arrow A and is compressed by the compressor of the turbocharger 20. In the intake pipe 11, an outside air temperature sensor 21 that measures the temperature TE of the outside air flowing into the combustion chamber 12 is provided upstream of the turbocharger 20. The position of the outside air temperature sensor 21 is an example, and is not limited to this position.

  The intake air compressed by the compressor of the turbocharger 20 flows into the combustion chamber 12 when the intake valve 16 is opened. The intake valve 16 is closed, the piston 14 is raised, and the air in the combustion chamber 12 is compressed, so that the combustion chamber 12 is in a high pressure state. When an appropriate pressure is reached, an amount of fuel with an appropriate mixing ratio is injected from the injector 17 and then spontaneous ignition occurs. The piston 14 is urged by pressure to push down the connecting rod 18, which causes the crankshaft 19 to rotate. Thereafter, the exhaust valve 15 is opened, and the exhaust passes through the turbine of the turbocharger 20 and is exhausted from the exhaust pipe 13 in the direction of the hatching arrow E while rotating the turbine.

  Fuel is supplied to the injector 17 from the direction of the black arrow F. Fuel is supplied at a high pressure from a fuel tank (not shown) via a filter, a high-pressure supply pump, a common rail, and the like. The injector 17 is controlled for fuel injection amount, fuel injection timing, timing, etc. by a solenoid or a piezo element. The fuel pressure is extremely high (for example, 2000 atmospheres), and the solenoid and the piezo element have excellent responsiveness and can realize an extremely short injection interval. Therefore, the injector 17 can inject an optimal amount of fuel at an optimal timing. it can. Note that an intermediate cooler (not shown) or the like may be provided in the intake passage to the intake pipe 11.

  The fuel injection is performed a plurality of times in one combustion stroke by the injector 17. This multiple times means, for example, pilot fuel injection, pre-fuel injection, after-fuel injection, post-fuel injection, etc. after main fuel injection, and reduction of exhaust gas generated at each stage. Noise and vibration are reduced.

  In the pilot fuel injection, since a very small amount of fuel is injected and burned to increase the gas temperature in the cylinder, the ignition delay time during the main fuel injection can be shortened. By performing the pilot fuel injection, the combustion noise is greatly improved.

  Next, the function of the fuel injection control device will be described with reference to the drawings. FIG. 2 is a functional block diagram of the fuel injection control device in the present embodiment.

  The fuel injection control device of this embodiment can be realized by an ECU (electronic control unit) 100. The ECU 100 is a kind of computer, a processor (CPU) that executes calculations, a storage area that temporarily stores various data, a random access memory (RAM) that provides a work area for calculations performed by the processor, and a program executed by the processor And a read-only memory (ROM) in which various data used for the operation are stored in advance, and a rewritable storage for storing the result of the operation by the processor and the data obtained from each part of the engine system A non-volatile memory is provided. The nonvolatile memory can be realized by a RAM with a backup function that is always supplied with a voltage even after the system is stopped.

  The fuel injection control function of the ECU 100 mainly includes an input interface 120 that receives signals output from a plurality of sensors 110, 111, 112, 113, 115 and the like that measure the engine speed NE, an idle determination unit 101, and the like. The outside air temperature correction unit 102, the pilot fuel injection control amount calculation unit 103, the injector control unit 104, the fuel injection amount calculation unit 105, and an output interface 121 that outputs a control signal and the like to the injector 17. . ECU 100 is programmed to realize the functions of idle determination unit 101 and outside air temperature correction unit 102. The ECU 100 may be dedicated to the fuel injection control device, but each function may be incorporated in the ECU 100 that controls the internal combustion engine system.

  The input interface 120 is an interface unit between the ECU 100 and each part of the engine system, receives information indicating the driving state of the vehicle sent from various parts of the engine system, performs signal processing, and analog information is converted into a digital signal. These are converted and transferred to the ECU 100 including the idle determination unit 101, the outside air temperature correction unit 102, and the control device for the internal combustion engine system. Although FIG. 2 shows the engine speed NE, the vehicle speed, the engine temperature, the accelerator opening, and the outside air temperature TE, the present invention is not limited to this, and various other information is input. For example, the temperature of a DPF (diesel particulate filter: not shown) provided in the exhaust pipe 13 of FIG. 1 can be detected and used as an idle determination parameter described later.

  Here, the engine speed NE is detected based on a signal from the engine speed sensor 110 that detects the rotation of the crankshaft 19. The vehicle speed is detected based on a signal output at every predetermined rotation of the drive shaft by a vehicle speed sensor 111 provided in the vicinity of the drive shaft that drives the wheels of the vehicle. The engine temperature is detected based on a signal from an engine temperature sensor 112 that detects the water temperature of the engine cooling water. The accelerator opening is detected based on a signal from an accelerator opening sensor 113 provided on an accelerator pedal operated by a driver. The outside air temperature TE is detected based on a signal output from the outside air temperature sensor 21 provided in the intake pipe 11 as described above (see FIG. 1).

  The idle determination unit 101 acquires the engine speed NE detected by the engine speed sensor 110, the vehicle speed detected by the vehicle speed sensor 111, the engine temperature detected by the engine temperature sensor 112, and the like via the input interface 120. . These detected values are signal-processed and used as parameters for idle determination. The idle determination unit 101 compares whether each parameter is within a predetermined range with a threshold value. If each parameter is within a predetermined range, it is determined that the engine is in an idle state. When it is determined that the engine is in an idle state, the idle determination unit 101 sends a signal to the outside air temperature correction unit 102.

  In this embodiment, in order to avoid the case where each parameter satisfies the condition for idle determination for a moment, the idle determination unit 101 performs delay time T as shown in FIG. Is added. The engine is determined to be in the idle state when the idle determination condition is satisfied even after the delay time T has elapsed.

  The outside air temperature correction unit 102 receives a signal indicating that the engine is in an idle state from the idle determination unit 101, and performs determination and correction as to whether or not the outside temperature sensor 21 correctly indicates the outside air temperature based on a process described later. .

  When the correction is executed, the pilot fuel injection control amount calculation unit 103 calculates a pilot fuel injection amount and a fuel injection timing with reference to a preset map or the like based on the corrected outside air temperature. A method for calculating these control amounts will be described later.

  The output interface 121 has a function of outputting a pilot fuel injection control amount calculated by the ECU 100 to the injector 17. However, the present invention is not limited to this, and another controller or the like can be connected to the output interface 121.

  Next, calculation of the control amount of pilot fuel injection will be described with reference to FIGS. 3 and 4. The control amount of pilot fuel injection includes a pilot fuel injection amount and a pilot fuel injection timing. FIG. 3 is a block diagram relating to the correction of the pilot fuel injection amount, and FIG. 4 is a block diagram relating to the correction of the pilot fuel injection timing. 3 and 4 explain details of the fuel injection amount calculation unit 105 and the pilot fuel injection control amount calculation unit 103 of the ECU 100 in FIG.

  Referring to FIG. 3, the fuel injection amount calculation unit 105 inputs the detection value of the engine speed NE and the detection value of the accelerator opening, and calculates the total fuel injection amount TOUT. The signal of the calculated total fuel injection amount TOUT is input to the basic pilot fuel injection amount calculation unit provided in the pilot fuel injection control amount calculation unit 103. The basic pilot fuel injection amount calculation unit further inputs a signal of the engine speed NE, refers to a map stored in the memory of the ECU 100, calculates a basic pilot fuel injection amount POUT signal, and outputs it.

  Further, the signal of the calculated total fuel injection amount TOUT is input to the correction pilot fuel injection amount calculation unit provided in the pilot fuel injection control amount calculation unit 103. The correction pilot fuel injection amount calculation unit further inputs the signal of the engine speed NE, refers to the map stored in the memory of the ECU 100, calculates the signal of the correction pilot fuel injection amount POUT2, and outputs it.

  The pilot fuel injection control amount calculation unit 103 further includes a correction coefficient k1 calculation unit. The correction coefficient k1 calculation unit calculates a correction coefficient k1 for calculating a correction amount of the pilot fuel injection amount based on a signal of the corrected outside air temperature TEE calculated by a process described later. As shown in the correction coefficient map of FIG. 3, the correction coefficient k1 is large when the outside air temperature TEE is low and small when the outside air temperature TEE is high. This is because if the outside air temperature TEE is low, the intake air density is high and the amount of intake air increases, making it difficult to ignite the pilot fuel. Accordingly, a large amount of pilot fuel injection is required. On the other hand, if the outside air temperature TEE is high, the density of the intake air is low, so the amount of intake air is reduced and the pilot fuel is easily ignited. This is because the pilot fuel injection amount must be reduced accordingly.

  The calculated correction coefficient k1 is multiplied by the signal of the correction pilot fuel injection amount POUT2, and the signal of the pilot fuel injection amount outside air temperature correction amount CPOUT is calculated. The pilot fuel injection amount outside air temperature correction amount CPOUT signal is added to the basic pilot fuel injection amount POUT signal, and the corrected pilot fuel injection amount FPOUT signal is calculated and output to the injector control unit 104.

  Next, referring to FIG. 4, the fuel injection amount calculation unit 105 inputs the detection value of the engine speed NE and the detection value of the accelerator opening, and calculates a signal of the total fuel injection amount TOUT. The signal of the calculated total fuel injection amount TOUT is input to the basic pilot fuel injection timing calculation unit provided in the pilot fuel injection control amount calculation unit 103. The basic pilot fuel injection timing calculation unit further inputs a signal of engine speed NE, refers to a map stored in the memory of ECU 100, calculates a signal of basic pilot fuel injection timing PINT, and outputs it. In this map, the relationship between the crank angle and the injection timing is also stored as information, and an appropriate injection timing is calculated according to the crank angle.

  Further, the signal of the calculated total fuel injection amount TOUT is input to a correction pilot fuel injection timing calculation unit provided in the pilot fuel injection control amount calculation unit 103. The correction pilot fuel injection timing calculation unit further inputs the signal of the engine speed NE, refers to the map stored in the memory of the ECU 100, calculates the signal of the correction pilot fuel injection timing PINT2, and outputs it.

  The pilot fuel injection control amount calculation unit 103 further includes a correction coefficient k2 calculation unit. The correction coefficient k2 calculation unit calculates a correction coefficient k2 for calculating the correction amount of the pilot fuel injection control amount based on the corrected outside air temperature TEE calculated by the process described later. As shown in the correction coefficient map of FIG. 4, the correction coefficient k2 is large when the outside air temperature TEE is low and small when the outside air temperature TEE is high. This means that if the outside air temperature TEE is low, the intake air density is high and the pilot fuel injection timing is adjusted accordingly. On the other hand, if the outside air temperature TEE is high, the intake air density is low and the pilot fuel injection timing is adjusted accordingly. Because it is necessary to do. Here, the lower the outside air temperature TEE, the more difficult the pilot fuel is ignited, and the correction amount increases. Therefore, it is preferable to control the injection timing so as to be retarded in the direction of compression top dead center.

  The calculated correction coefficient k2 is multiplied by the signal of the correction pilot fuel injection timing PINT2, and the signal of the pilot fuel injection timing outside temperature correction amount CPINT is calculated. The signal of the pilot fuel injection timing outside temperature correction amount CPINT is added to the signal of the basic pilot fuel injection timing PINT, and the corrected pilot fuel injection timing FPINT signal is calculated and output to the injector control unit 104.

  Such a configuration first detects an idle state, in particular, a so-called long idle state over a long period of time, in which the amount of air sucked is smaller than in a normal operating state. In this idle state, since the amount of air is small, the heat capacity of the gas is reduced, and since the flow rate is small, the residence time of the air in the intake pipe is increased. Due to the influence, the air temperature in the vicinity of the outside air temperature sensor 21 becomes higher than the actual atmospheric temperature. There is a possibility that the value detected by the so-called sensor does not correctly indicate the outside air temperature. In such an environment, in order to avoid such a situation of the sensor, an appropriate control of the pilot fuel injection is realized by correcting the outside air temperature detected from the outside air temperature sensor 21 according to a process described later. I am letting.

  FIG. 5 is a flowchart of the outside air temperature determination and correction process according to the present embodiment. FIG. 6 is a flowchart of an outside temperature determination and correction process according to a modification of the present embodiment. FIG. 7 is an explanatory diagram showing the corrected outside air temperature state. FIG. 8 is an explanatory diagram showing one correction method. In the following description, FIGS.

  The outside temperature determination and correction process shown in FIG. 5 is executed by the CPU of the ECU 100, and more specifically, is mainly executed by the idle determination unit 101 and the outside temperature correction unit 102 shown in FIG. This process can be performed at predetermined time intervals.

  In step S201, the idle determination unit 101 determines whether or not the idling operation is performed. The idle determination unit 101 first compares each detected engine speed NE, vehicle speed, and engine temperature with a predetermined value. When the engine speed NE and the vehicle speed are less than or equal to the predetermined value and the engine temperature is within the predetermined value range (step S201: Yes), it is determined that the engine is idling, and the process proceeds to step S202.

  On the other hand, in step S201, if the engine speed NE is equal to or higher than the predetermined value, the vehicle speed is equal to or higher than the predetermined value, and the engine temperature falls outside the predetermined value range (step S201: No), the normal operation state is assumed. judge. The pilot fuel injection control amount calculation unit 103 refers to a map or the like that is preset and stored in the memory of the ECU 100 based on the outside air temperature TE detected by the temperature sensor 21, the engine speed NE, and the required torque. Then, a control amount of pilot fuel injection is calculated (step S208). The control amount of the pilot fuel injection includes a fuel injection amount and a fuel injection amount timing. As described above with reference to FIGS. 3 and 4, the pilot fuel injection control amount calculation unit 103 provided in the ECU 100 calculates the injector fuel injection amount. Command the control amount.

  As described with reference to FIG. 2, the idle determination unit 101 may add a delay time T in order to avoid erroneous determination of idle determination. Further, a temperature of a DPF (diesel particulate filter: not shown) provided in the exhaust pipe 13 may be added as an idle determination parameter to determine whether the temperature is within a predetermined range.

  Next, in step S202, the result that the idle determination unit 101 determines to be in the idle state is sent to the outside temperature correction unit 102 as an idle signal. The outside air temperature correction unit 102 acquires a sample value TE1 of the outside air temperature detected at the idle determination time. Next, the outside air temperature correction unit 102 determines whether the idle state is newly started or continued. This determination can be made by setting a flag or setting a timer or the like when it is first determined to be in an idle state, and a known technique can be applied.

When the idle state is newly started (step S202: No), the outside air temperature correction unit 102 refers to the sample value TE0 of the outside air temperature before the outside air temperature TE1 from the memory of the ECU 100, and formula (1) Thus, this TE0 is set as the outside air temperature TEP (step S0204).
TEP = TE0 (1)

  Here, TE1 is a so-called current value, and TEP is a so-called previous value, which is used in subsequent determinations. As the sample value, it is preferable to use a moving average or a smoothed value of instantaneous values of the sensor output.

When the idling state is continued (step S201: Yes), the outside air temperature correction unit 102 is the previous determination result stored in the memory of the ECU 100, and is finally set to the outside air temperature. With reference to the result TEE, as shown in the equation (2), the determination result TEE is set as the previous value TEP (step S203). This determination result TEE is the result of the previous determination, and is the outside air temperature sent to step S208 and used to calculate the control amount of pilot fuel injection.
TEP = TEE (2)

  Next, the outside air temperature correction unit 102 acquires the outside air temperature detected by the outside air temperature sensor 21, and executes a process for determining and correcting whether or not the detected outside air temperature has greatly increased (step S205). .

In step S205, the current value TE1 is compared with the previous value TEP calculated from the equation (1) or (2) as in the equation (3).
TE1> TEP (3)

Here, if the current value TE1 is lower than or equal to the previous value TEP, it is determined that there is no temperature increase due to the idle state, and the outside air temperature sensor 21 correctly indicates the outside air temperature (Step S205: No). ). At this time, the outside air temperature correction unit 102 sets the current value TE1 as the determination result TEE according to the determination result as shown in Equation (4) (step 206).
TEE = TE1 (4)

  The pilot fuel injection control amount calculation unit 103 calculates a pilot fuel injection control amount based on the determination result TEE (step S208). The calculated pilot fuel injection control amount is sent to the injector control unit 104, and the injector control unit 104 sends the control amount of pilot fuel injection to the injector 17 as a signal via the output interface 121. Here, the determination result TEE is stored in the memory of the ECU 100.

On the other hand, in the equation (3), if the current value TE1 is higher than the previous value TEP, it is determined that the outside air temperature sensor 21 does not correctly indicate the outside air temperature due to the temperature rise caused by the idle state (step S205: Yes). As shown in the equation (5), correction is performed using the previous value TEP as a new corrected outside air temperature correction value TEC. Subsequently, as shown in the equation (6), the outside air temperature correction unit 102 sets the correction value TEC as the determination result TEE (step S207).
TEC = TEP (5)
TEE = TEC (6)

  The ECU 100 calculates a control amount for pilot fuel injection based on the determination result TEE. The description of step S208 is as described above.

  The necessity for such determination and correction will be described with reference to FIG.

  Since the outside air temperature before entering the idling operation is large, the heat influence from a heat source such as a combustor is relatively small. Therefore, the difference between the detected outside air temperature and the atmospheric temperature is small, and a temperature state with little fluctuation is maintained.

  When shifting to idle operation, the detected outside air temperature may increase rapidly as indicated by the broken line in region C of FIG. The engine speed is low during idling, and the amount of air for combustion is much smaller than during normal driving. Therefore, the weight of the air present in the intake pipe is small and the heat capacity is small, so that the temperature is likely to rise due to heat transfer from the external heat source. Further, the air staying in the intake pipe is raised to the entire temperature in the intake pipe by convection caused by the temperature rise. As a result, the detected value of the outside air temperature detected by the outside air temperature sensor 21 provided in the intake pipe also increases. That is, the value detected by the outside air temperature sensor 21 may not indicate the outside air temperature.

  Thereafter, when shifting from the idle operation to the normal running state, a large amount of air is inhaled, the heat capacity becomes large, and it becomes difficult to be influenced by the surrounding heat sources. In addition, since the flow rate increases and the air stays in the intake pipe, the temperature rise due to natural convection is mitigated, while the temperature drops due to forced convection heat transfer due to the incoming outside air. Thereafter, the outside air temperature detection value also indicates the outside air temperature as shown by overlapping the solid line and the broken line in the region M in FIG. 7 representing the normal operating state.

  However, since there is an influence of the temperature state of the outside air temperature sensor 21 itself, the temperature of the structure around the outside air temperature sensor 21, the amount of stored heat, and the like, the transition from the region C to the region M in FIG. This is represented by a thermal inertia temperature change delay (represented by region L). Such a situation may also be a situation where the outside air temperature detection value does not indicate the temperature of the outside air together with the region C.

  Air passes through devices such as a filter from the periphery of the vehicle and is sucked into the internal combustion engine, but the temperature of the sucked outside air is not significantly different from the atmospheric temperature. Furthermore, it is extremely rare that the atmospheric temperature will cause a large temperature fluctuation in a short time such as the detected outside air temperature shown in FIG.

  As described above, for region C in FIG. 7, it is possible to calculate an appropriate control amount for pilot fuel injection by correcting the outside air temperature. Furthermore, for the region L, it is possible to calculate an appropriate control amount for pilot fuel injection by using the outside air temperature corrected in the region C until the outside air temperature sensor 21 returns to the state indicating the outside temperature correctly. Become.

  The correction process described above is performed as shown in FIG. In other words, the current value TE1 and the previous value TEP are compared at every minute time Δt after shifting to the region C where the idling operation is determined, and the determination result TEE is the lower one. When the idle operation is determined, it is determined whether or not the outside air temperature correctly indicates the outside air temperature, and if not, it is corrected (correction region C). This determination and correction are continued until the idle operation is completed.

As shown in FIG. 7, normally, when entering the idle state, the temperature detected by the outside air temperature sensor 21 is often higher than the temperature immediately before the idle state. When the temperature detected by the outside air temperature sensor 21 is always high due to the installation of the sensor or the like, the outside air temperature is corrected according to the expressions (7) and (8) according to the internal combustion engine entering the idle state. As described above, during the idle period, the outside air temperature can be held at the sample value TE0 of the outside air temperature detected immediately before the idle state.
TEC = TE0 (7)
TEE = TEC (Hold during idle period) (8)

Further, when the idle operation is finished and the intake air amount increases, the outside air temperature detection value decreases. However, as described above, it is assumed that the actual outside air temperature is not observed until the outside air temperature detection value decreases and stabilizes. Therefore, as shown in FIG. 7, a ramp region L may be provided to provide a descending gradient so that the outside air temperature detection value is slowly lowered. Even during this time, the temperature used for the control of the pilot fuel injection becomes the corrected outside air temperature which is shifted by the solid line in FIG.

For example, a predetermined time after the end of the idling operation is set in advance as the ramp region L, and the outside air temperature detection value TEend at the end of the idling operation is used and the determination result TEE at that time is used as shown in equation (9). An annealing calculation can be performed.
TEE (smoothing calculation) = kc x TEE + (1-kc) x TEend (9)

  Here, kc is an annealing coefficient.

  During this time, the determination result TEE in the correction region C may also be given an ascending slope, and when the ramp region L ends, the current value TE1 and the determination result TEE may coincide. The period of the lamp region L is preferably set in consideration of the time during which the detected outside air temperature is stable. After the lamp region L, in the normal operation region M, the outside air temperature detection value can be set to the outside air temperature.

In the above-described embodiment, the previous value of the outside air temperature is simply the sample value TE0 of the outside air temperature before the current value TE1, but when the load on the internal combustion engine decreases before reaching the idle state, it is determined that the engine is in the idle state. In addition, there is a possibility that the detected outside air temperature value is not correctly indicating the outside air temperature. In order to avoid such a situation, after the idle determination in step S201, the first previous value TEP is changed to the sample values TE0, TE of the outdoor temperature detected a plurality of times before the current value TE1, as shown in equation (10). It may be an average value of -1, TE-2, ..., TE-n. Here, 0, -1, -2, and -n represent the previous sample values, and n represents the number of samples.
TEP (first previous value) = (TE0 + TE-1 + TE-2 + .. + TE-n) / (n + 1) (10)

  In determining and correcting whether or not the sensor correctly indicates the outside air temperature in the present embodiment, it is also important to more accurately grasp the previous value of the outside air temperature when the idle state is started. The correction described above can improve the accuracy of determination and correction.

[Modification]
Next, a modification will be described with reference to FIG. Even in the idling state, the internal combustion engine is operated, so that air is sucked from the intake pipe. Therefore, depending on the position where the outside air temperature sensor 21 is disposed, the influence of forced convection heat transfer from the intake air may not be negligible. In order to consider the thermal effect of the intake air, the following determination and correction can be performed. Steps S201, S202, S203, S204, and S208 are the same as those shown in FIG.

If it is determined in step S305 that the previous value TEP and the current value TE1 are as shown in the equation (11) and the increment of the current value TE1 exceeds a predetermined threshold th (step S305: Yes), the outside air The temperature sensor 21 does not correctly indicate the outside air temperature. Therefore, as shown in equation (12), in step 306, the previous value TEP having a low temperature is set as the correction value TEC.
(TE1 (current value) −TEP (previous value))> th (threshold value) (11)
TEC (correction value) = TEP (previous value) (12)

However, even if the current value is higher than the previous value, if the difference between the current value and the previous value does not exceed a predetermined threshold value, the state in which the outside air temperature sensor 21 does not correctly indicate the outside air temperature is slight, and inhalation It may also be affected by heat from the air. Therefore, when the difference between the current value and the previous value is equal to or less than the threshold value th (step S307: No), the current value TE1 and the previous value TEP are compared as in equation (13) (step S307).
TE1 (current value)> TEP (previous value) (13)

  If the current value TE1 is lower than or equal to the previous value TEP (step S308: No), it is determined that the outside air temperature sensor 21 correctly indicates the outside air temperature, and the current value TE1 is set as the determination result TEE (step S308). .

  If the current value TE1 is higher than the previous value TEP (step S307: Yes), the outside air temperature sensor 21 does not correctly indicate the outside air temperature, but it is determined that the heat influence from the intake air cannot be ignored. In step S309, for example, As in the equation (14), a weighted average of the previous value and the current value is taken, and this can be used as the corrected outside air temperature.

TEC (correction value) = (a × TEP (previous value) + b × TE1 (current value)) / (a + b) (14)
a and b are weighting factors.

  In the measurement of the temperature in the tube through which the gas having a low flow rate flows, there may be a difference in the response and the indicated value depending on the size, position and characteristics of the sensor. The weighting factors a and b can be determined by reflecting the behavior of the outside air temperature TE at the place where the outside air temperature sensor 21 is provided during the idling operation, which is obtained by experiment or analysis.

  As described above, the correction method can be appropriately selected according to the situation in which the sensor is placed, as described in one embodiment or modification.

Further, the temperature increase ΔT per unit time of the outside air temperature sensor 21 caused by the heat effect from the heat source such as the internal combustion engine in the idle period C is acquired in advance by experiment and analysis. The difference between the temperature rise ΔT at this time may be a correction value TEC as shown in equation (15).
TEC = TE1−ΔT (15)

  According to the configuration of the present embodiment, the control amount of pilot fuel injection can be calculated according to the corrected outside air temperature that has been corrected to be close to the actual outside air temperature. Then, the ECU 100 appropriately controls the fuel injection amount, fuel injection timing, etc. of the pilot fuel injection based on this control amount, and can effectively reduce the combustion noise.

  Further, such a configuration sets the outside air temperature after determining whether or not the temperature sensor correctly indicates the outside air temperature by comparing the detected outside air temperature with the previous value of the corrected outside air temperature. In setting, as described above, the method of selecting the outside temperature which is lower of the previous value and the current value, the method of holding the outside temperature at the temperature detected immediately before the idling state, or the difference between the previous value and the current value. A method of performing correction according to the above, a method of taking a weighted average, and the like can be appropriately selected according to the arrangement state of the sensor and the like.

  By applying the determination method and the correction method as in the present embodiment, it is also possible to dispose an outside air temperature sensor at a location that is affected by heat from the combustion chamber as a heat source. In this way, the degree of freedom of the arrangement position of the temperature sensor is expanded, and a compact outfitting design is possible.

  The preferred embodiments of the present invention have been described above. The present invention is not limited to the one described in the drawings, and design changes can be made without departing from the spirit of the present invention.

1 is a schematic diagram of an engine system including a fuel injection control device for an internal combustion engine according to an embodiment of the present invention. It is a functional block diagram of the fuel-injection control apparatus in one Embodiment. It is a functional block diagram concerning pilot fuel injection amount calculation of the fuel injection control device in one embodiment. It is a functional block diagram concerning pilot fuel injection timing calculation of the fuel injection control device in one embodiment. It is a flowchart of the determination and correction | amendment process of the external temperature in one Embodiment. It is a detailed flowchart of the determination and correction | amendment process of the outside temperature concerning the modification of one Embodiment. It is explanatory drawing showing the state of the corrected outside temperature. It is explanatory drawing showing the one correction method concerning an Example.

Explanation of symbols

10 cylinder 11 intake pipe 12 combustion chamber 13 exhaust pipe 14 piston 15 exhaust valve 16 intake valve 17 injector 18 connecting rod 19 crankshaft 20 turbocharger 21 outside air temperature sensor 100 ECU
DESCRIPTION OF SYMBOLS 101 Idle determination part 102 Outside temperature correction part 103 Pilot fuel injection control amount calculation part 104 Injector control part 120 Input interface 121 Output interface

Claims (4)

A fuel injection control device for an internal combustion engine comprising fuel injection means for performing at least main fuel injection for injecting fuel into a combustion chamber of the internal combustion engine and pilot fuel injection prior to the main fuel injection,
A detecting means provided in the intake pipe for detecting the temperature of outside air to be sucked;
Determination means for determining an idle state of the internal combustion engine,
A fuel injection of the internal combustion engine configured to correct the detected outside air temperature when the internal combustion engine is determined to be in an idle state and to control the pilot fuel injection according to the corrected outside air temperature Control device.   2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the pilot fuel injection is configured to control a fuel injection amount and / or a fuel injection timing based on the corrected outside air temperature.   The fuel injection of the internal combustion engine according to claim 1 or 2, wherein the correction of the outside air temperature maintains the outside air temperature at a temperature detected immediately before the idling state in response to the internal combustion engine entering an idling state. Control device.   The fuel for an internal combustion engine according to claim 1 or 2, wherein the correction of the outside air temperature is performed by comparing a current value detected by the detecting means with a previous value, and setting a lower temperature as a corrected outside air temperature. Injection control device.

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