JP4610404B2 - Diesel engine control device - Google Patents

Description

  The present invention relates to a control device for a diesel engine that temporarily controls an air-fuel ratio of an air-fuel mixture to a richer side than a stoichiometric air-fuel ratio and performs the enrichment control according to a misfire state.

  Conventionally, as a control device for controlling the amount of EGR gas in accordance with the misfire state of the engine, for example, one disclosed in Patent Document 1 is known. This control device detects the number of misfires that occur per predetermined number of ignitions of the engine, and reduces the amount of EGR gas as the number of misfires detected increases, thereby reducing the frequency of misfires. I have to.

  However, when such control is performed during the enrichment control of the diesel engine, there are the following problems. That is, the exhaust pipe of the diesel engine is provided with a NOx trapping material, and in order to reduce NOx trapped by the NOx trapping material, the air-fuel ratio of the air-fuel mixture is temporarily set to a richer side than the theoretical air-fuel ratio. The enrichment control to be controlled is performed. This enrichment control is performed by reducing the amount of fresh air supplied to the combustion chamber by increasing the amount of EGR gas in addition to increasing the amount of fuel. For this reason, during the enrichment control, the combustion state becomes unstable and misfire tends to occur. On the other hand, as described above, the conventional control device merely reduces the amount of EGR gas every time a misfire occurs, and such control is repeatedly performed. For this reason, every time enrichment control is performed, it is inevitable that misfires occur repeatedly, and drivability deteriorates.

  The present invention has been made to solve the above-described problems, and provides a diesel engine control device that can appropriately avoid the occurrence of misfire during enrichment control and improve drivability. The purpose is to do.

JP-A-8-28365

  In order to achieve the above object, the diesel engine control device 1 according to claim 1 is a misfire determination means for determining whether or not the diesel engine 3 is misfired (in the embodiment (hereinafter, the same applies in this section)). Angle sensor 30, ECU2, steps 21 to 23) and air-fuel ratio enrichment means (injector 6, temporarily controlling the air-fuel ratio of the air-fuel mixture combusted in combustion chamber 3c to a richer side than the stoichiometric air-fuel ratio. ECU 2, step 3), load detection means (crank angle sensor 30, accelerator opening sensor 34, ECU 2, step 11) for detecting the load of the diesel engine (engine speed NE, required torque PMCMD), and detected diesel The amount of EGR gas that recirculates from the exhaust system (exhaust pipe 5) to the intake system (intake pipe 4) according to the engine load (target EG Determination means (ECU2) for determining at least one control parameter among the gas amount EGRCMD), the injection pressure of fuel injected into the combustion chamber 3c (target injection pressure PRAILCMD), and the fuel injection timing (target injection timing ΦINJCMD) , Steps 32, 45, 46, 60, 62, 72, 85, 86, 100, 102, 112, 125, 126, 140, 142), and misfire determination during air-fuel ratio enrichment control by the air-fuel ratio enrichment means When the means determines that the diesel engine 3 has misfired, the correction means (ECU2, steps 49, 89, 129) corrects at least one control parameter determined by the determination means in a direction to cancel the misfire condition. ) And at least one corrected control obtained when it is determined that the misfire condition has been resolved. Learning means (ECU2, steps 52, 92, 132) for calculating learning values EGRG, PRAILG, and ΦINJG based on the parameters, and the determining means determines at least one control parameter as the learning value during the enrichment control. It is determined based on EGRG, PRAILG, and ΦINJG (steps 58, 67, 98, 107, 138, and 147).

  According to the control device for this diesel engine (hereinafter simply referred to as “engine”), misfire of the engine is determined by misfire determination means, and the air-fuel ratio of the mixture is made richer than the stoichiometric air-fuel ratio by the air-fuel ratio enrichment means. The enrichment control is controlled to be performed. Further, according to the detected engine load, at least one control parameter among the amount of EGR gas, the injection pressure, and the injection timing is determined by the determining means, and the engine is misfired during the enrichment control. When the determination is made, the correction means corrects the determined at least one control parameter in a direction to eliminate the misfire state. Further, when it is determined that the misfire state has been resolved, a learning value is calculated by the learning means based on the corrected at least one control parameter obtained at that time. Further, when the learning value is calculated, at least one control parameter is determined based on the calculated learning value during the enrichment control.

  In general, the greater the amount of EGR gas, the smaller the injection pressure, the later the injection timing, and the later the timing at which the injected fuel ignites, the engine combustion state during the enrichment control becomes unstable. . Therefore, if the amount of EGR gas is reduced, the injection pressure is increased, the injection timing is advanced, etc., the fuel ignition timing is advanced and the combustion state is stabilized. Therefore, as described above, during the enrichment control, when it is determined that the engine has misfired, the combustion state is stabilized by correcting these at least one control parameter in a direction to eliminate the misfire state. So that the misfire condition can be resolved. Further, as described above, the learning value is calculated based on at least one control parameter when the misfire is actually eliminated, and at least one control parameter is calculated based on the learning value during the enrichment control. Since it is determined, a stable combustion state can be secured and the occurrence of misfire can be avoided. Therefore, the occurrence of misfire during the enrichment control can be appropriately avoided, and drivability can be improved.

  According to a second aspect of the present invention, in the control apparatus 1 for a diesel engine according to the first aspect, during the enrichment control, a determination means (ECU2, Steps 57, 97, and 137) are further provided, and the determining means determines that the state in which the diesel engine 3 has not misfired continues in a state in which at least one control parameter is determined to be the learned values EGRG, PRAILG, and ΦINJG. When this is done, at least one control parameter is determined according to the load of the diesel engine (steps 60, 63, 100, 103, 140, 143).

  According to this configuration, when it is determined that the state in which the engine has not misfired continues in the state in which the at least one control parameter is determined as the learning value, the at least one control parameter is set as the engine load. Decide accordingly. When the learning value obtained as described above is used as the control parameter during the enrichment control, misfire can be avoided, but the fuel consumption and exhaust gas characteristics may be deteriorated. According to the present invention, when the state of no misfire continues during the enrichment control, at least one control parameter is determined to a value corresponding to the engine load. Therefore, the fuel consumption and exhaust gas characteristics can be maintained in a good state while appropriately avoiding misfire.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a diesel engine (hereinafter referred to as “engine”) 3 to which the present invention is applied. The engine 3 is a 4-cylinder type mounted on a vehicle (not shown).

  A combustion chamber 3c is formed between the piston 3a of the engine 3 and the cylinder head 3b. An intake pipe 4 (intake system) and an exhaust pipe 5 (exhaust system) are connected to the cylinder head 3b, and a fuel injection valve (hereinafter referred to as “injector”) 6 (air-fuel ratio enrichment means) is connected to the combustion chamber. It is attached to face 3c.

  The injector 6 is disposed at the central portion of the top wall of the combustion chamber 3c, and is sequentially connected to a high-pressure pump 6a and a fuel tank (not shown) via a common rail (not shown). The high-pressure pump 6a boosts the fuel in the fuel tank to a high pressure and then sends it to the injector 6 through the common rail. The injector 6 injects this fuel into the combustion chamber 3c. The fuel injection pressure PRAIL is controlled by controlling the high pressure pump 6a with the ECU 2 described later (see FIG. 2), and is detected by the fuel pressure sensor 35 provided on the common rail, and the detection signal is output to the ECU 2. The In addition, the valve opening time and the on-off valve timing of the injector 6 are controlled by a drive signal from the ECU 2, thereby controlling the fuel injection amount and the injection timing, respectively.

  A magnet rotor 30a is attached to the crankshaft 3d of the engine 3. A crank angle sensor 30 (misfire determination means, load detection means) is constituted by the magnet rotor 30a and the MRE pickup 30b. The crank angle sensor 30 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft 3d rotates.

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

  The intake pipe 4 is provided with a supercharging device 7. The supercharging device 7 includes a supercharger 8 constituted by a turbocharger, an actuator 9 connected thereto, and a vane opening control valve 10. I have.

  The supercharger 8 includes a rotatable compressor blade 8a provided in the intake pipe 4, a rotatable turbine blade 8b provided in the exhaust pipe 5, and a plurality of rotatable variable vanes 8c (only two are shown). And a shaft 8d for integrally connecting these blades 8a and 8b. The turbocharger 8 pressurizes the intake air in the intake pipe 4 by rotationally driving the compressor blade 8a integrated therewith as the turbine blade 8b is rotationally driven by the exhaust gas in the exhaust pipe 5. Perform supercharging operation.

  The actuator 9 is of a diaphragm type that is operated by negative pressure, and is mechanically connected to each variable vane 8c. A negative pressure is supplied to the actuator 9 from a negative pressure pump through a negative pressure supply passage (both not shown), and a vane opening degree control valve 10 is provided in the middle of the negative pressure supply passage. The vane opening control valve 10 is composed of an electromagnetic valve, and the negative pressure supplied to the actuator 9 changes when the opening is controlled by a drive signal from the ECU 2, and accordingly, the variable vane 8c The supercharging pressure is controlled by changing the opening degree.

  A water-cooled intercooler 11 and a throttle valve 12 are provided downstream from the supercharger 8 of the intake pipe 4 in order from the upstream side. The intercooler 11 cools the intake air when the temperature of the intake air rises due to the supercharging operation of the supercharging device 7 or the like. The throttle valve 12 is connected to an actuator 12a made of, for example, a DC motor. The opening degree of the throttle valve 12 (hereinafter referred to as “throttle valve opening degree”) is controlled by controlling the duty ratio of the current supplied to the actuator 12 a by the ECU 2.

  The intake pipe 4 is provided with an air flow sensor 31 upstream of the supercharger 8 and a supercharging pressure sensor 32 between the intercooler 11 and the throttle valve 12. The air flow sensor 31 detects the intake air amount QA, the supercharging pressure sensor 32 detects the supercharging pressure PACT in the intake pipe 4, and these detection signals are output to the ECU 2.

  Further, the intake manifold 4a of the intake pipe 4 is partitioned into a swirl passage 4b and a bypass passage 4c from the collecting portion to the branch portion, and each of the passages 4b and 4c is connected to each combustion chamber 3c via an intake port. Communicating with A swirl device 13 is provided in the bypass passage 4c. The swirl device 13 includes a swirl valve 13a, an actuator 13b for opening and closing the swirl valve 13a, and a swirl control valve 13c. By controlling the opening degree of the swirl control valve 13c by the ECU 2, the strength of the swirl generated in the combustion chamber 3c is controlled by changing the opening degree of the swirl valve 13a.

  The engine 3 is provided with an EGR device 14 having an EGR pipe 14a and an EGR control valve 14b. The EGR pipe 14 a is connected between the intake pipe 4 and the exhaust pipe 5, specifically, so as to connect the swirl passage 4 b of the collecting portion of the intake manifold 4 a and the upstream side of the supercharger 8 of the exhaust pipe 5. Has been. Through this EGR pipe 14a, a part of the exhaust gas of the engine 3 is recirculated to the intake pipe 4 as EGR gas, thereby reducing the combustion temperature in the combustion chamber 3c, thereby reducing NOx in the exhaust gas. .

  The EGR control valve 14b is configured by a linear electromagnetic valve attached to the EGR pipe 14a, and the EGR gas amount is controlled by controlling the valve lift amount linearly by a drive signal from the ECU 2.

  The EGR device 14 is provided with an EGR cooling device 15 for cooling the EGR gas. The EGR cooling device 15 includes a bypass passage 15a, an EGR passage switching valve 15b, and an EGR control valve 14b of the EGR pipe 14a. It has EGR cooler 15c provided in the lower stream side. The bypass passage 15a is provided downstream of the EGR control valve 14b of the EGR pipe 14a so as to bypass the EGR cooler 15c, and the EGR passage switching valve 15b is attached to a branch portion of the bypass passage 15a. The EGR passage switching valve 15b selectively switches a portion of the EGR pipe 14a on the downstream side of the EGR passage switching valve 15b between the EGR pipe 14a side and the bypass passage 15a side under the control of the ECU 2.

  As described above, when the EGR passage switching valve 15b is switched to the bypass passage 15a side, the EGR gas passes through the bypass passage 15a and returns to the intake pipe 4. On the other hand, when switched to the reverse side, the EGR gas is cooled by the EGR cooler 15c and then returned to the intake pipe 4.

  Further, a three-way catalyst 16 and a NOx catalyst 17 are provided on the exhaust pipe 5 downstream of the supercharger 8 in order from the upstream side. The three-way catalyst 16 purifies the exhaust gas by oxidizing HC and CO in the exhaust gas and reducing NOx under a stoichiometric atmosphere. When the oxygen concentration in the exhaust gas is high (oxidizing atmosphere), the NOx catalyst 17 purifies the exhaust gas by capturing NOx in the exhaust gas and reducing the captured NOx with a reducing agent in the exhaust gas.

  Further, a LAF sensor 33 is provided immediately upstream of the three-way catalyst 16 in the exhaust pipe 5. The LAF sensor 33 linearly detects the oxygen concentration VLAF in the exhaust gas in a wide air-fuel ratio region from the rich region to the lean region. Based on the oxygen concentration VLAF detected by the LAF sensor 33, the ECU 2 calculates an actual air-fuel ratio A / FACT that represents the air-fuel ratio of the actual air-fuel mixture burned in the combustion chamber 3c. Further, a detection signal representing an operation amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown) is output from the accelerator opening sensor 34 (load detection means) to the ECU 2.

  The ECU 2 is composed of a microcomputer including an I / O interface, CPU, RAM, ROM, and the like. The detection signals from the various sensors 30 to 35 described above are each input to the CPU after A / D conversion and shaping by the I / O interface.

  In accordance with these input signals, the CPU discriminates the operating state of the engine 3 according to a control program stored in the ROM, etc., and controls the fuel injection amount, the injection timing, and the EGR gas amount according to the discriminated operating state. The control of the engine 3 including is executed. Further, it is determined whether or not the engine 3 has misfired, and enrichment as a reduction operation of NOx trapped by the NOx catalyst 17 is executed. In the present embodiment, the ECU 2 constitutes misfire determination means, air-fuel ratio enrichment means, load detection means, determination means, correction means, learning means, and determination means.

  Next, the fuel injection amount control process will be described with reference to FIG. This process and the process to be described later are executed in synchronization with the input of the TDC signal. First, in step 1 (illustrated as “S1”, the same applies hereinafter), it is determined whether or not the enrichment flag F_RICH is “1”.

  The enrichment flag F_RICH is set to “1”, assuming that the enrichment execution condition is satisfied when the estimated capture amount of NOx captured by the NOx catalyst 17 is larger than a predetermined amount. When the time elapses, it is reset to “0” because NOx is sufficiently reduced. Thereby, enrichment is performed over this predetermined time. The amount of NOx trapped by the NOx catalyst 17 is estimated according to the operating state and operating time of the engine 3.

  If the answer to step 1 is NO and the enrichment execution condition is not satisfied, a target for normal operation is searched by searching a map (not shown) according to the engine speed NE and the accelerator pedal opening AP. The fuel injection amount TOUT is calculated (step 2), and this process is terminated. In this map, the target fuel injection amount TOUT is set so that the actual air-fuel ratio A / FACT is leaner than the stoichiometric air-fuel ratio (hereinafter referred to as “stoichiometric”). Further, a drive signal based on the calculated target fuel injection amount TOUT is output to the injector 6 to control the fuel injection amount.

  On the other hand, if the answer to step 1 is YES and the enrichment execution condition is satisfied, the target fuel injection amount TOUT for enrichment is calculated (step 3), and this process ends.

  The target fuel injection amount TOUT for enrichment is calculated as follows. That is, first, the basic fuel injection amount is obtained by searching a map (not shown) according to the engine speed NE and the accelerator pedal opening AP. Next, an F / B correction term is calculated by a predetermined feedback (hereinafter referred to as “F / B”) control algorithm according to the target air-fuel ratio and the actual air-fuel ratio A / FACT. This target air-fuel ratio is calculated by searching a map (not shown) according to the engine speed NE and the required torque PMCMD (the load of the diesel engine). Is set to the value of Further, the required torque PMCMD is calculated by searching a map (not shown) in step 11 of FIG. 4 according to the engine speed NE and the accelerator pedal opening AP. Then, the target fuel injection amount TOUT is calculated by adding the F / B correction term to the basic fuel injection amount. Thereby, the F / B control is performed so that the actual air-fuel ratio A / FACT becomes the target air-fuel ratio.

  By controlling the fuel injection amount as described above, combustion is performed at an air-fuel ratio that is leaner than stoichiometric during normal operation in which enrichment is not performed. On the other hand, at the time of enrichment, the fuel injection amount is controlled to a larger value than during normal operation, and combustion is performed at an air-fuel ratio richer than stoichiometric. As a result, the exhaust gas is controlled to a reduced state, and NOx trapped by the NOx trapping material 17 during normal operation is reduced.

  Next, a process for determining misfire of the engine 3 will be described with reference to FIG. First, in step 21, it is determined whether or not the elapsed time TCRK between pulses is greater than a predetermined determination value TCREF. This inter-pulse elapsed time TCRK is the time required from the output of the previous CRK signal to the output of the current CRK signal, and is calculated by the ECU 2. Further, the determination value TCREF is obtained by searching a map (not shown) according to the engine speed NE and the accelerator pedal opening AP.

  If the answer to step 21 is YES and TCRK> TCREF, it is determined that the rotation of the engine 3 has greatly fluctuated and the engine 3 has misfired, and the misfire flag F_MF is set to “1” (step 22). Then, this process is terminated. On the other hand, if the answer to step 21 is NO, it is determined that the engine 3 has not misfired, the misfire flag F_MF is set to “0” (step 23), and then the present process is terminated.

  Next, an EGR control process for controlling the amount of EGR gas will be described with reference to FIG. First, in step 31, it is determined whether or not the enrichment flag F_RICH is “1”. If the answer is NO and the enrichment execution condition is not satisfied, the target EGR gas amount EGRCMD (EGR gas amount) for normal operation is calculated (step 32), and this process is terminated.

  The target EGR gas amount EGRCMD for normal operation is calculated as follows. That is, first, a default value for normal operation is calculated by searching a map (not shown) according to the engine speed NE and the required torque PMCMD. Next, an F / B correction term is calculated by a predetermined F / B control algorithm so that the actual intake air amount QA becomes the target intake air amount. This target intake air amount is calculated by searching a map (not shown) according to the engine speed NE and the required torque PMCMD.

  Next, the target EGR gas amount EGRCMD is calculated by adding the F / B correction term to the default value. A drive signal based on the target EGR gas amount EGRCMD calculated as described above is output to the EGR control valve 14b, so that the intake air amount QA becomes the target intake air amount by controlling the EGR gas amount. F / B control is performed.

  On the other hand, if the answer to step 31 is YES and the enrichment execution condition is satisfied, the target EGR gas amount EGRCMD for enrichment is calculated (step 33), and this process is terminated.

  7 and 8 show processing for calculating the target EGR gas amount EGRCMD for enrichment. First, in step 41 of FIG. 7, it is determined whether or not the learning status LESTSE corresponding to the engine speed NE and the required torque PMCMD at that time is “1”. This learning status LESTSE is set for each combination of the engine speed NE and the required torque PMCMD, and is set to “1” when the learning value EGRG of the target EGR gas amount EGRCMD is calculated.

  When the answer to step 41 is NO and the learning value EGRG is not calculated, the counter value CCR of the release counter is set to a predetermined value CREF (step 42), and whether or not the correction flag F_COE is “1”. Is discriminated (step 43). As will be described later, the in-correction flag F_COE is set to “1” when the target EGR gas amount EGRCMD is corrected to decrease. When the answer is NO, it is determined whether or not the misfire flag F_MF is “1” (step 44).

  If the answer is NO and the engine 3 has not misfired, a default value EGRDF for enrichment is calculated by searching a map (not shown) according to the engine speed NE and the required torque PMCMD (step) 45). Next, the target EGR gas amount EGRCMD is calculated by adding the F / B correction term to the calculated default value EGRDF (step 46), and this process is terminated. This F / B correction term is calculated by a predetermined F / B control algorithm so that the actual intake air amount QA becomes the target intake air amount for enrichment. This target intake air amount is calculated by searching a map (not shown) in accordance with the engine speed NE and the required torque PMCMD. In the map, the normal intake air amount is normal in all regions of the engine speed NE and the required torque PMCMD. It is set to a value smaller than the target intake air amount for operation. Further, the target EGR gas amount EGRCMD for enrichment is calculated to be larger than the target EGR gas amount EGRCMD for normal operation. As described above, the target EGR gas amount EGRCMD is calculated so that the intake air amount QA becomes the target intake air amount for enrichment.

  On the other hand, if the answer to step 44 is YES and a misfire of the engine 3 has occurred, the correction of the target EGR gas amount EGRCMD is started to eliminate this misfire state, and the in-correction flag F_COE is set to “1”. (Step 48). The correcting flag F_COE is reset to “0” during normal operation other than enrichment.

  Next, a value obtained by subtracting a predetermined correction value CEGR from the target EGR gas amount EGRCMD obtained so far is set as the target EGR gas amount EGRCMD (step 49), and the target EGR gas amount EGRCMD is corrected to decrease. Next, a limit process is performed on the corrected target EGR gas amount EGRCMD (step 50), and this process ends. In this limit processing, the target EGR gas amount EGRCMD is compared with a predetermined lower limit value. When EGRCMD <lower limit value, the target EGR gas amount EGRCMD is set to the lower limit value, and when EGRCMD ≧ lower limit value, it is obtained in step 49 above. The target EGR gas amount EGRCMD is used as it is.

  By executing step 48, the answer to step 43 becomes YES. In this case, it is determined whether or not a misfire flag F_MF is “1” (step 51). When the answer is YES, that is, when the misfire state has not been resolved, step 49 and the subsequent steps are executed to further reduce and correct the target EGR gas amount EGRCMD. On the other hand, if the answer to step 51 is NO and the misfire state is resolved, the target EGR gas amount EGRCMD at that time is set as a learning value EGRG (step 52). This learning value EGRG is stored in association with the engine speed NE and the required torque PMCMD at that time.

  Next, in order to indicate that the learning value EGRG has already been calculated, the learning status LESTSE is set to “1” (step 53). This learning status LESTSE is also stored in association with the engine speed NE and the required torque PMCMD at that time. Next, the correcting flag F_COE is reset to “0” (step 54), and this process is terminated.

  As described above, when the learning value EGRG corresponding to the engine speed NE and the required torque PMCMD has not been calculated (step 41: NO) and the engine 3 has not misfired (step 44: NO), the target EGR gas The amount EGRCMD is calculated based on the default value EGRDF corresponding to the engine speed NE and the required torque PMCMD (steps 45 and 46).

  When it is determined that the engine 3 has misfired (step 44: YES), the target EGR gas amount EGRCMD is corrected to decrease in order to eliminate this misfire state. This correction is repeated until the misfire state is resolved by subtracting the correction value CEGR from the target EGR gas amount EGRCMD (step 49). By this correction, the ignition delay is shortened by reducing the amount of EGR gas, and the misfire state can be eliminated by advancing the ignition timing. When the misfire state is resolved (step 51: NO), the target EGR gas amount EGRCMD at that time is set as a learned value EGRG (step 52) and stored in correspondence with the engine speed NE and the required torque PMCMD. .

  On the other hand, when the answer to step 41 is YES and LESTSE = 1, that is, when the learning value EGRG has already been calculated, it is determined in step 55 in FIG. 8 whether the misfire flag F_MF is “1”. Determine. If the answer is NO and the engine 3 has not misfired, the counter value CCR of the release counter set in step 42 is decremented (step 56).

  Next, it is determined whether or not the counter value CCR is 0 (step 57). When this answer is NO, the target EGR gas amount EGRCMD is set to the learning value EGRG (step 58), and this process is terminated.

  On the other hand, when the answer to step 57 is YES, that is, when the target EGR gas amount EGRCMD is set to the learning value EGRG and the state in which no misfire has occurred for a time corresponding to the predetermined value CREF, learning is performed. The learning value EGRG is updated by adding a predetermined return correction value CCREGR to the value EGRG (step 59).

  Next, the default value EGRDF is calculated in the same manner as in step 45 (step 60), and it is determined whether or not the learning value EGRRG updated in step 59 is equal to or greater than the calculated default value EGRDF (step 61). When the answer is NO, the step 58 is executed. When the answer is YES, the target EGR gas amount EGRCMD is set to the default value EGRDF (step 62), and the learning value EGRRG is set to the default value EGRDF (step 63). ). Next, the learning status LESTSE is reset to “0” (step 64), and this process is terminated.

  On the other hand, when the answer to step 55 is YES, that is, when the engine 3 misfires with the target EGR gas amount EGRCMD set to the learned value EGRG, the counter value CCR of the release counter is set to a predetermined value CREF ( Step 65) After the learning value EGRG is updated by subtracting the correction value CEGR from the learning value EGRG (step 66), the updated learning value EGRG is set as the target EGR gas amount EGRCMD (step 67). Next, limit processing similar to that in step 50 is performed on the target EGR gas amount EGRCMD (step 68), and this processing is terminated.

  As described above, when the learning value EGRG is calculated (step 41: YES), the target EGR gas amount EGRCMD is then set to the learning value EGRG (step 58). When the state where the misfire has not occurred for a time corresponding to the predetermined value CREF in the state where the learning value EGRG is set as described above, the learning value EGRG is gradually increased and corrected (step 59). Used as the target EGR gas amount EGRCMD. Then, when EGRG ≧ EGRDF is established (step 61: YES), the target EGR gas amount EGRCMD and the learning value EGRG are finally set to the default value EGRDF (steps 62 and 63). Further, after the learning status LESTSE is reset to “0” (step 64), the original EGR gas amount control based on the default value EGRDF is performed.

  Further, as described above, when a misfire occurs in the engine 3 with the target EGR gas amount EGRCMD set to the learning value EGRG (step 55: YES), the correction value CEGR is subtracted from the learning value EGRG, The learning value EGRG is updated and corrected so that the misfire state is eliminated (step 66) and used as the target EGR gas amount EGRCMD (step 67).

  Next, a fuel injection pressure control process for controlling the injection pressure PRAIL will be described with reference to FIG. First, in step 71, it is determined whether or not the enrichment flag F_RICH is “1”. If the answer is NO and the enrichment execution condition is not satisfied, a map (not shown) is searched according to the engine speed NE and the required torque PMCMD to obtain the target injection pressure PRAICMD ( Fuel injection pressure) is calculated (step 72), and the process is terminated. In addition, a drive signal based on the calculated target injection pressure PRAILCMD is output to the high-pressure pump 6a, whereby the injection pressure PRAIL is controlled to become the target injection pressure PRAILCMD.

  On the other hand, if the answer to step 71 is YES and the enrichment execution condition is satisfied, the enrichment target injection pressure PRAILCMD is calculated (step 73), and the process ends.

  FIG. 10 and FIG. 11 show the processing for calculating the enrichment target injection pressure PRAILCMD. In this process, the target injection pressure PRAILCMD is calculated according to the misfire of the engine 3 as in the rich EGRCMD calculation process of FIG. 7 and FIG. 8 described above. First, steps 81 to 94 in FIG. 10 are executed in the same manner as steps 41 to 54 in FIG. That is, when the learning value PRAILG corresponding to the engine speed NE and the required torque PMCMD at that time is not calculated (step 81: NO), the counter value CCRP of the release counter is set to the predetermined value CREF (step 82).

  When the target injection pressure PRAILCMD for canceling the misfire state is not being corrected (step 83: NO) and the engine 3 is not misfired (step 84: NO), the default value PRAILDF is set to the engine speed NE and Calculation is performed by searching a map (not shown) according to the required torque PMCMD (step 85). Next, the target injection pressure PRAILCMD is set to the calculated default value PRAILDF (step 86), and this process ends. As a result, the target injection pressure PRAILCMD is set to a larger value than during normal operation.

  When the misfire of the engine 3 occurs (step 84: YES), the correction of the target injection pressure PRAILCMD for eliminating this misfire state is started, and the correcting flag F_COP is set to “1” (step 88). . This correction is performed as follows. That is, a value obtained by adding a predetermined correction value CPRAIL to the target injection pressure PRAILCMD at that time is set as the target injection pressure PRAILCMD (step 89), and the target injection pressure PRAILCMD is increased and corrected. This correction is repeated after the start (step 83: YES) until the misfire condition is resolved (step 91 is NO). Thereby, the injection pressure PRAIL is increased, the degree of fuel atomization is increased, and the ignition timing is advanced, whereby the combustion state can be stabilized and the misfire state can be eliminated.

  Further, a limit process is performed on the corrected target injection pressure PRAILCMD (step 90), and this process ends. In this limit processing, when the target injection pressure PRAILCMD> the upper limit value, the target injection pressure PRAILCMD is set to the upper limit value, and when PRAILCMD ≦ the upper limit value, the corrected target injection pressure PRAILCMD is used as it is.

  Then, when the misfire state is resolved (step 91: NO), the target injection pressure PRAILCMD at that time is set as a learning value PRAILG (step 92). Next, in order to indicate that the learning value PRAILG has been calculated, the learning status LESTSP is set to “1” (step 93), and this learning status LESTSP is stored in association with the engine speed NE and the required torque PMCMD. . Next, the in-correction flag F_COP is reset to “0” (step 94), and this process ends.

  When the learning value PRAILG is calculated as described above (step 81: YES), steps 95 to 108 in FIG. 11 are executed in the same manner as steps 55 to 68 in FIG. That is, when the engine 3 has not misfired (step 95: NO), the counter value CCRP of the release counter set in step 82 is decremented (step 96), and the target injection pressure PRAILCMD is set to the learning value PRAILG (step 96). 98) At the same time, this process is terminated.

  When the target injection pressure PRAILCMD is set to the learning value PRAILG and the state in which the engine 3 has not misfired continues for a time corresponding to the predetermined value CREF (step 97: YES), a predetermined return from the learning value PRAILG is performed. By subtracting the correction value CCRPRAIL, the learning value PRAILG is updated (step 99) and gradually decreased.

  Next, the default value PRAILDF is calculated in the same manner as in step 85 (step 100). When PRAILG> PRAILDF (step 101: NO), step 98 is executed, while when PRAILG ≦ PRAILDF (step 101: YES), the target injection pressure PRAILCMD is set to the default value PRAILDF calculated in step 100 above. (Step 102). Next, the learning value PRALG is set to the default value PRAILDF (step 103), the learning status LESTSP is reset to “0” (step 104), and this processing is terminated.

  On the other hand, when a misfire occurs in the state where the target injection pressure PRAILCMD is set to the learning value PRAILG as described above (step 95: YES), the counter value CCRP of the release counter is set to a predetermined value CREF (step 105). Next, the learning value PRALG is updated by adding the correction value CPRAIL to the learning value PRAILG (step 106), and is corrected so as to eliminate the misfire state, and the updated learning value PRAILG is set as the target injection pressure PRAICMD. (Step 107). Next, in the same manner as in Step 90, a limit process is performed on the target injection pressure PRAILCMD (Step 108), and this process is terminated.

  Next, a fuel injection timing control process for controlling the injection timing will be described with reference to FIG. First, in step 111, it is determined whether or not the enrichment flag F_RICH is “1”. If the answer is NO and the enrichment execution condition is not satisfied, a map (not shown) is searched according to the engine speed NE and the required torque PMCMD, so that the target injection timing ΦINJCMD for normal operation ( Fuel injection timing) is calculated (step 112), and this process ends. A drive signal based on the calculated target injection timing ΦINJCMD is output to the high-pressure pump 6a, whereby the injection timing is controlled to the target injection timing ΦINJCMD.

  On the other hand, if the answer to step 111 is YES and the enrichment execution condition is satisfied, the enrichment target injection timing ΦINJCMD is calculated (step 113), and the process ends.

  FIG. 13 and FIG. 14 show processing for calculating the enrichment target injection timing ΦINJCMD. In this process, the target injection timing ΦINJCMD is calculated according to the misfire of the engine 3 as in the rich EGRCMD calculation process of FIG. 7 and FIG. 8 described above. First, similarly to steps 41 to 54 in FIG. 7, steps 121 to 134 in FIG. 13 are executed. That is, when the learned value ΦINJG corresponding to the engine speed NE and the required torque PMCMD at that time is not calculated (step 121: NO), the counter value CCRΦ of the release counter is set to a predetermined value CREF (step 122).

  When the target injection timing ΦINJCMD for eliminating the misfire state is not being corrected (step 123: NO) and the engine 3 is not misfiring (step 124: NO), the default value ΦINJDF of the target injection timing is set to the engine. Calculation is performed by searching a map (not shown) according to the rotational speed NE and the required torque PMCMD (step 125), the target injection timing ΦINJCMD is set to the calculated default value ΦINJDF (step 126), and this process is terminated. To do. As a result, the target injection timing ΦINJCMD is set to a value on the advance side than during normal operation.

  When the misfire of the engine 3 occurs (step 124: YES), the correction of the target injection timing ΦINJCMD for canceling the misfire state is started, and the correcting flag F_COΦ is set to “1” (step 128). . Further, this correction is performed as follows. That is, a value obtained by adding a predetermined correction value CΦINJ to the target injection timing ΦINJCMD at that time is set as the target injection timing ΦINJCMD (step 129), and the target injection timing ΦINJCMD is corrected to the advance side. This correction is repeated after the start (step 123: YES) until the misfire condition is resolved (step 131 is NO). Thereby, by accelerating the injection timing, it is possible to stabilize the combustion state by reliably igniting the air-fuel mixture, and to eliminate the misfire state.

  Further, limit processing is performed on the corrected target injection timing ΦINJCMD (step 130), and this processing is terminated. In this limit processing, when the target injection timing ΦINJCMD> the upper limit value, the target injection timing ΦINJCMD is set to the upper limit value, and when ΦINJCMD ≦ the upper limit value, the corrected target injection timing ΦINJCMD is used as it is.

  When the misfire state is resolved (step 131: NO), the target injection timing ΦINJCMD at that time is set as a learning value ΦINJG (step 132). Next, in order to indicate that the learning value ΦINJG has been calculated, the learning status LESTSΦ is set to “1” (step 133), and stored in correspondence with the engine speed NE and the required torque PMCMD. Next, the in-correction flag F_COΦ is reset to “0” (step 134), and this process ends.

  When the learning value ΦINJG is calculated as described above (step 121: YES), steps 135 to 148 in FIG. 14 are executed in the same manner as steps 55 to 68 in FIG. That is, when the engine 3 has not misfired (step 135: NO), the counter value CCRΦ of the release counter set in step 122 is decremented (step 136), and the target injection timing ΦINJCMD is set to the learned value ΦINJG (step). 138), the process is terminated.

  When the target injection timing ΦINJCMD is set to the learning value ΦINJG and the state in which the engine 3 has not misfired continues for a time corresponding to the predetermined value CREF (step 137: YES), the correction value is returned from the learning value ΦINJG. The learning value ΦINJG is updated by subtracting CCRΦINJ (step 139), and gradually corrected to the retard side.

  Next, the default value ΦINJDF is calculated in the same manner as in step 125 (step 140). When ΦINJG> ΦINJDF (step 141: NO), step 138 is executed. When ΦINJG ≦ ΦINJDF (step 141: YES), the target injection timing ΦINJCMD is set to the default value ΦINJDF calculated in step 140 above. (Step 142). Next, the learning value ΦINJG is set to the default value ΦINJDF (step 143), the learning status LESTSΦ is reset to “0” (step 144), and this processing is terminated.

  On the other hand, when a misfire has occurred with the target injection timing ΦINJCMD set to the learned value ΦINJG as described above (step 135: YES), the counter value CCRΦ of the release counter is set to a predetermined value CREF (step 145). Next, by adding the correction value CΦINJ to the learning value ΦINJG, the learning value ΦINJG is updated (step 146), corrected in a direction to eliminate the misfire state, and the updated learning value ΦINJG is set as the target injection timing ΦINJCMD. (Step 147). Next, in the same manner as in step 130, a limit process is performed on the target injection timing ΦINJCMD (step 148), and this process ends.

  15 and 16 show an operation example of the control device 1. As shown in FIG. 15, when the enrichment is started (time point t1), the target EGR gas amount EGRCMD, the target injection pressure PRAILCMD, and the target injection timing ΦINJCMD are the default values EGRDF corresponding to the engine speed NE and the required torque PMCMD. , PRAILDF and ΦINJDF, respectively. Further, if the engine 3 misfires during the enrichment (time t1a), it is determined that the engine 3 is misfiring due to the accompanying fluctuation in the engine speed NE, and the target EGR gas amount EGRCMD decreases accordingly. Furthermore, the target injection pressure PRAILCMD is corrected to the increase side, the target injection timing ΦINJCMD is corrected to the advance side, and both are corrected in a direction to eliminate misfire.

  This correction stabilizes the combustion state, thereby eliminating the misfire state and stabilizing the rotation of the engine 3 (time point t1b). If it is determined that the misfire state has been resolved, the correction is completed, and the target EGR gas amount EGRCMD, the target injection pressure PRAILCMD, and the target injection timing ΦINJCMD are held at the previous values (time points t1b to t2). , Learning values EGRG, PRAILG, and ΦINJG. During the next enrichment (time points t3 to t4), the target EGR gas amount EGRCMD, the target injection pressure PRAILCMD, and the target injection timing ΦINJCMD are set to the learned values EGRG, PRAILG, and ΦINJG, respectively.

  As described above, according to the present embodiment, when the engine 3 is misfiring during enrichment, the target EGR gas amount EGRCMD, the target injection pressure PRAICMD, and the target injection timing ΦINJCMD are set in a direction to eliminate the misfire state. By correcting, the combustion state can be stabilized, thereby eliminating the misfire state. Further, since the learned values EGRG, PRAILG, and ΦINJG obtained as described above when the misfire state is resolved are used as the target EGR gas amount EGRCMD, the target injection pressure PRAICMD, and the target injection timing ΦINJCMD, respectively, a stable combustion state is used. Can be ensured, and misfires can be avoided. Therefore, the occurrence of misfire during enrichment can be appropriately avoided, and drivability can be improved.

  Further, during the enrichment, the EGR gas amount, the injection pressure PRAIL, and the injection timing are only changed in order to eliminate the misfire state. The actual air-fuel ratio A / FACT is determined by controlling the fuel injection amount. By the B control, the target air-fuel ratio suitable for enrichment is maintained. Therefore, NOx trapped by the NOx trapping material 17 can be sufficiently reduced.

  Further, the learning values EGRG, PRAILG, and ΦINJG are stored in correspondence with loads represented by the engine speed NE and the required torque PMCMD, and the learning values EGRG, PRAILG, and ΦINJG are used corresponding to the loads at that time. The occurrence of misfire can be appropriately avoided according to the load.

  As shown in FIG. 16, when the target EGR gas amount EGRCMD is set to the learning value EGRG and the state in which no misfire has continued for a time corresponding to the predetermined value CREF (time point t5), the target EGR gas amount EGRCMD is set. The learning value EGRG is corrected to increase (time points t5 to t6, t7 to t8). Then, the target EGR gas amount EGRCMD and the learning value EGRG are finally set to the default value EGRDF (time point t8).

  As described above, when the engine 3 is misfiring during the enrichment, in order to solve this, the target EGR gas amount EGRCMD is decreased, the target injection pressure PRAICMD is increased, and the target injection timing ΦINJCMD is advanced. Correct each corner. If such control is performed when the engine 3 has not misfired, the combustion speed becomes too high due to the decrease in the amount of EGR gas or the increase in the injection pressure PRAIL, and as a result, the combustion pressure becomes high. May grow. In addition, the combustion temperature becomes too high due to the decrease in the amount of EGR gas, the amount of NOx generated by combustion increases, and the injection timing, that is, the ignition timing is advanced, so that a sufficient output cannot be obtained, There is a risk that fuel economy will deteriorate.

  On the other hand, according to the present embodiment, when the state of no misfire continues as described above, the target EGR gas amount EGRCMD, the target injection pressure PRAILCMD, and the target injection timing ΦINJCMD are set to the learning values EGRG, PRALG, and ΦINJG. To the original default values EGRDF, PRAILDF and ΦINJDF according to the load. Therefore, while appropriately avoiding misfire, noise can be suppressed and fuel consumption and exhaust gas characteristics can be maintained in a good state. In addition, since these return operations are gradually performed, the EGR gas amount, the injection pressure PRAIL, and the injection timing can be gradually changed. Therefore, it is possible to smoothly shift to the original control while maintaining a stable combustion state. it can.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the present embodiment, the air-fuel ratio enrichment means is intended to reduce NOx trapped by the NOx trapping material 17, but is not limited to this, and the air-fuel ratio is richer than the stoichiometric air-fuel ratio. Any object other than the above may be achieved as long as it is temporarily controlled to the side. In the embodiment, the target EGR gas amount EGRCMD, the target injection pressure PRAILCMD, and the target injection timing ΦINJCMD are all corrected as control parameters for eliminating the misfire state, but any one or two of these are corrected. Of course, you may do.

  Further, in the embodiment, the target EGR gas amount EGRCMD, the target injection pressure PRAILCMD, and the target injection timing ΦINJCMD are gradually returned to the default values EGRDF, PRAILDF, and ΦINJDF, respectively, but these may be temporarily returned. In the embodiment, the misfire of the engine 3 is determined based on the elapsed time TCRK between pulses, but may be determined based on another appropriate parameter, for example, the detected pressure in the cylinder. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

It is a figure which shows roughly the control apparatus by this invention with the engine to which this is applied. It is a figure which shows the control apparatus by this invention. It is a flowchart which shows a fuel injection amount control process. It is a flowchart which shows a request torque calculation process. It is a flowchart which shows a misfire determination process. It is a flowchart which shows an EGR control process. It is a flowchart which shows the subroutine of the EGRCMD calculation process for enrichment in FIG. It is a flowchart which shows the continuation of the process of FIG. It is a flowchart which shows a fuel injection pressure control process. 10 is a flowchart showing a subroutine of enrichment PRAILCMD calculation processing in FIG. 9. 11 is a flowchart showing a continuation of the process of FIG. It is a flowchart which shows a fuel injection timing control process. 13 is a flowchart illustrating a subroutine of ΦINJCMD calculation processing for enrichment in FIG. 12. It is a flowchart which shows the continuation of the process of FIG. It is a figure which shows the operation example of a control apparatus until this misfire state is eliminated from the state where the engine misfires. It is a figure which shows the operation example of a control apparatus after a misfire state is eliminated.

Explanation of symbols

1 control device 2 ECU (misfire determination means, air-fuel ratio enrichment means, load detection means, determination means,
Correction means, learning means, discrimination means)
3 Engine 3c Combustion chamber 4 Intake pipe (intake system)
5 Exhaust pipe (exhaust system)
6 Injector (means to enrich air / fuel ratio)
30 Crank angle sensor (misfire determination means, load detection means)
34 Accelerator opening sensor (load detection means)
NE engine speed (diesel engine load)
PMCMD required torque (load of diesel engine)
EGRCMD Target EGR gas amount (EGR gas amount)
PRAILCMD target injection pressure (fuel injection pressure)
ΦINJCMD target injection timing (fuel injection timing)
EGRG Learning value PRAILG Learning value ΦINJG Learning value

Claims (2)

Misfire determination means for determining whether the diesel engine has misfired, and
Air-fuel ratio enrichment means for temporarily controlling the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber to be richer than the theoretical air-fuel ratio;
Load detecting means for detecting the load of the diesel engine;
At least one control parameter among the amount of EGR gas recirculated from the exhaust system to the intake system, the injection pressure of the fuel injected into the combustion chamber, and the fuel injection timing according to the detected diesel engine load A determination means for determining
During the air-fuel ratio enrichment control by the air-fuel ratio enrichment means, the at least one control parameter determined by the determination means when the misfire determination means determines that the diesel engine is misfiring, Correction means for correcting in a direction to eliminate the misfire state;
Learning means for calculating a learning value based on the corrected at least one control parameter obtained when it is determined that the misfire state has been resolved,
The said determination means determines the said at least 1 control parameter based on the said learning value during the said enrichment control, The control apparatus of the diesel engine characterized by the above-mentioned. The enrichment control further includes a determination unit that determines whether or not the diesel engine has not misfired.
The determining means determines the at least one control parameter when it is determined that the diesel engine has not misfired while the at least one control parameter is determined as the learning value. The control device for a diesel engine according to claim 1, wherein the control device is determined according to a load of the diesel engine.

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