JP6173930B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device that includes an air-fuel ratio sensor disposed in an exhaust passage of an internal combustion engine and performs air-fuel ratio control according to the output of the air-fuel ratio sensor, and in particular, supplies blow-by gas generated in a crankcase to an intake system. The present invention relates to a control device for an internal combustion engine including a passage.

  Patent Document 1 discloses a control device that includes an air-fuel ratio sensor disposed in an exhaust passage of an internal combustion engine and performs air-fuel ratio control according to the output of the air-fuel ratio sensor. According to this apparatus, during the fuel cut operation in which the fuel supply to the engine is temporarily stopped, the scavenging promotion control for increasing the intake air flow rate of the engine is executed, and the detection characteristics of the air-fuel ratio sensor are executed after the scavenging promotion control is executed. Output value correction for correcting the deviation of the detected air-fuel ratio due to the variation is performed.

JP 2008-64007 A

  According to the above-described conventional device, in the scavenging promotion control, the intake air flow rate is increased, so that the pumping loss increases and the execution period of the fuel cut operation is shortened, and the unnecessary air increase increases the exhaust passage. Oxidation of the provided exhaust purification catalyst is promoted, and the amount of fuel supply increases due to the reduction of the exhaust purification catalyst at the end of the fuel cut operation (when the fuel supply is resumed). As a result, there is a problem that fuel consumption deteriorates.

  In addition, when the execution period of the scavenging acceleration control reaches a predetermined period, or when the oxygen concentration calculated from the output value of the air-fuel ratio sensor becomes equal to or higher than the predetermined value, the output value correction of the air-fuel ratio sensor is performed. There is a possibility that the output value correction is performed before the influence of blow-by gas is completely eliminated, and the correction is not properly performed. In this specification, “blow-by gas” refers to the gas itself (direct component) flowing into the crankcase from the combustion chamber and the inflowing gas (particularly fuel component) mixed into the lubricating oil, and the mixed gas is Including evaporated fuel and fuel adhering to the combustion chamber wall during cold operation of the engine flows into the crankcase as a liquid and enters the lubricating oil, and the mixed fuel evaporates (evaporated component) In particular, during fuel cut operation, the fuel mixed in the lubricating oil in a liquid state evaporates, so that there is a high possibility that proper correction will not be performed.

  The present invention has been made in consideration of the above-described points, and the correction of the detection characteristic of the air-fuel ratio sensor arranged in the exhaust passage of the internal combustion engine is more appropriately executed during the fuel cut operation, and the correction accuracy is improved. It is an object to provide a control device that can be enhanced.

In order to achieve the above object, an invention according to claim 1 is directed to an air-fuel ratio detection means (27) disposed in an exhaust passage (10) of an internal combustion engine (1), and a fuel supply means (27) for supplying fuel to the engine. 6) and a blow-by gas supply means (9) for supplying blow-by gas generated in the engine to an intake system (2) of the engine, wherein the engine is in a predetermined operating state. A fuel cut operation executing means for executing a fuel cut operation for temporarily stopping fuel supply to the fuel, and a correction for correcting the detection characteristics of the air-fuel ratio detection means during the fuel cut operation period during which the fuel cut operation is being executed It means and estimates the occurrence of the blow-by gas, according to the blow-by gas occurrence estimated, command means for commanding implementation or prohibition of correction by the correction means , And a temperature parameter detecting means (25) for detecting the engine temperature parameter (TW) indicative of the temperature of the engine, said command means, the air-fuel ratio detection in the predetermined first detection timing during the fuel cut operation period The first output value (VINI) of the means and the second output of the air-fuel ratio detection means at the second detection timing, which is the time when a predetermined re-detection condition is satisfied during the fuel cut operation period after the first detection timing. When the difference (DVLAF) from the value (VDET) is equal to or greater than the determination threshold value (DVTH), correction by the correction unit is prohibited, and the predetermined re-detection condition is that the engine temperature parameter ( state TW) is the predetermined temperature (tWTH) above is characterized that you satisfied by continuing predetermined time (TWAIT) above.

According to this configuration, the fuel cut operation is performed in a predetermined operation state of the engine, and the detection characteristic correction for correcting the detection characteristic of the air-fuel ratio detection means is performed in the fuel cut operation period in which the fuel cut operation is being performed. A first output value of the air-fuel ratio detection means at a predetermined first detection timing during the fuel cut operation period and a second detection when a predetermined redetection condition is satisfied during the fuel cut operation period after the first detection timing. Detection characteristic correction is prohibited when the difference from the second output value of the air-fuel ratio detection means at the timing is greater than or equal to the determination threshold. The predetermined re-detection condition is that the engine temperature parameter is greater than or equal to the predetermined temperature after the first detection timing. It is established by continuing for a predetermined time or more. If the state where the engine temperature parameter is equal to or higher than the predetermined temperature continues for a predetermined time or longer, the amount of blow-by gas generated is surely reduced. There is a high possibility that proper correction of characteristics cannot be performed. Therefore, by prohibiting detection characteristic correction in such a situation, erroneous correction can be surely prevented, and the correction accuracy can be improved. Further, since it is not necessary to increase the intake air flow rate as in the prior art described above, it is possible to prevent deterioration of fuel consumption.

According to a second aspect of the present invention, in the control apparatus for an internal combustion engine according to the first aspect, the command unit maintains a command for prohibiting correction by the correction unit until the engine stops. .

According to this configuration, the command for prohibiting the correction of the detection characteristic of the air-fuel ratio detection means is maintained until the engine stops.

  According to a third aspect of the present invention, in the control apparatus for an internal combustion engine according to the first or second aspect, the intake air flow rate correlation parameter detection for detecting an intake air flow rate correlation parameter (GAIR) correlated with the intake air flow rate of the engine. Means (21), wherein the command means determines that the intake air amount (SUMGA) of the engine is greater than or equal to a predetermined intake amount (SUMGATH) based on the intake air flow rate correlation parameter (GAIR) during the fuel cut operation period. When it is detected that the correction has occurred, the correction unit is instructed to perform correction regardless of the generation state of the blowby gas.

  According to this configuration, when it is detected that the intake air amount of the engine has become a predetermined amount or more during the fuel cut operation period, the detection characteristic correction is performed regardless of the generation state of blow-by gas. When it is detected that the intake air amount of the engine exceeds the predetermined intake amount, even if blow-by gas is generated, the degree of influence on the output value of the air-fuel ratio detection means is low. Therefore, by performing the detection characteristic correction regardless of the blowby gas generation state, it is possible to increase the frequency of the correction and improve the control accuracy of the air-fuel ratio feedback control based on the output value of the air-fuel ratio detection means.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a figure for demonstrating correction | amendment of the air fuel ratio detection characteristic of an air fuel ratio sensor. 6 is a time chart showing a transition of an air-fuel ratio sensor output (VLAF) when a fuel cut operation is started when a large amount of blow-by gas is generated. 7 is a time chart showing a transition between an output value (VLAFS) and an operation continuation time (TOP) when the air-fuel ratio sensor output is stabilized after the fuel cut operation is started when the amount of blow-by gas generated is large. It is a flowchart of the process which performs air fuel ratio detection characteristic correction | amendment. 5 is a flowchart of processing for determining a condition for prohibiting air-fuel ratio detection characteristic correction (first embodiment); 7 is a flowchart of processing for setting a redetection condition flag (FCOND) referred to in the processing of FIG. 6. 6 is a flowchart of a process for setting an intake air amount flag (FGAH) referred to in the process of FIG. 5. It is a time chart for demonstrating the estimation method (2nd Embodiment) of a blowby gas generation condition. It is a flowchart of the process which determines the conditions which prohibit air-fuel-ratio detection characteristic correction | amendment (2nd Embodiment).

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a diagram showing the configuration of an internal combustion engine (hereinafter referred to as “engine”) and its control device according to an embodiment of the present invention. For example, a throttle valve 3 is placed in the middle of an intake passage 2 of a four-cylinder engine 1. Is arranged. The throttle valve 3 is configured to be driven by an actuator 7, and the actuator 7 is connected to an electronic control unit (hereinafter referred to as “ECU”) 5. The ECU 5 controls the opening degree TH of the throttle valve 3 via the actuator 7.

  The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) in the intake passage 2, and each injection valve is connected to a fuel pump (not shown). At the same time, it is electrically connected to the ECU 5 and the valve opening time of the fuel injection valve 6 is controlled by a signal from the ECU 5.

  A blow-by gas passage 9 for supplying blow-by gas generated in the crankcase of the engine 1 to the intake passage 2 is provided. One end of the blow-by gas passage 9 is connected to the cylinder head of the engine 1, and a one-way valve 8 is provided at the connecting portion. The one-way valve 8 opens when the pressure in the crankcase is higher than the pressure on the intake passage side by a predetermined pressure or more. The blow-by gas includes the gas itself (direct component) flowing into the crankcase from the combustion chamber, the direct component (particularly the fuel component) mixed in the lubricating oil, and the mixed gas evaporated, and the cold operation of the engine 1 The fuel adhering to the wall surface of the combustion chamber flows into the crankcase as a liquid and enters the lubricating oil, and the mixed fuel evaporates when the engine temperature rises due to the operation of the engine 1 (evaporation component). And is supplied to the intake passage 2 through the blow-by gas passage 9.

  A catalyst 11 for exhaust purification is provided in the exhaust passage 10. The catalyst 11 has an oxygen storage capacity, the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is set to be leaner than the stoichiometric air-fuel ratio, and in the exhaust lean state where the oxygen concentration in the exhaust gas is relatively high, Oxygen is accumulated, and conversely, the air-fuel ratio of the air-fuel mixture supplied to the engine 1 is set to a richer side than the stoichiometric air-fuel ratio, accumulated in an exhaust rich state where the oxygen concentration in the exhaust gas is low and HC and CO components are large. It has the function of oxidizing HC and CO in the exhaust with oxygen.

  An intake air flow rate sensor 21 that detects an intake air flow rate GAIR is provided upstream of the throttle valve 3, and a throttle valve opening degree sensor 22 that detects a throttle valve opening TH is connected to the throttle valve 3. An intake pressure sensor 23 for detecting the intake pressure PBA and an intake air temperature sensor 24 for detecting the intake air temperature TA are provided on the downstream side of the throttle valve 3. A cooling water temperature sensor 25 for detecting the engine cooling water temperature TW is mounted on the main body of the engine 1, and detection signals from these sensors 21 to 25 are supplied to the ECU 5.

  The ECU 5 is connected to a crank angle position sensor 26 that detects a rotation angle of a crankshaft (not shown) of the engine 1, and a signal corresponding to the rotation angle of the crankshaft is supplied to the ECU 5. The crank angle position sensor 11 is a cylinder discrimination sensor that outputs a pulse (hereinafter referred to as “CYL pulse”) at a predetermined crank angle position of a specific cylinder of the engine 1, and relates to a top dead center (TDC) at the start of the intake stroke of each cylinder. A TDC sensor that outputs a TDC pulse at a crank angle position before a predetermined crank angle (every 180 degrees of crank angle in a four-cylinder engine) and one pulse (hereinafter referred to as “CRK”) with a constant crank angle cycle shorter than the TDC pulse (for example, a cycle of 6 °). The CYL pulse, the TDC pulse, and the CRK pulse are supplied to the ECU 5. These pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of the engine speed NE.

  A proportional oxygen concentration sensor 27 (hereinafter referred to as “LAF sensor 27”) is mounted on the upstream side of the catalyst 14 and on the downstream side of the collection portion of the exhaust manifold communicating with each cylinder. A detection signal substantially proportional to the oxygen concentration (air / fuel ratio) in the exhaust gas is output and supplied to the ECU 5.

  The ECU 5 includes an accelerator sensor 31 for detecting an accelerator pedal depression amount (hereinafter referred to as “accelerator pedal operation amount”) AP of a vehicle driven by the engine 1 and a vehicle speed sensor 32 for detecting a vehicle speed VP driven by the engine 1. Etc. are connected, and detection signals of these sensors are supplied to the ECU 5. The throttle valve opening TH is controlled by the ECU 5 in accordance with the accelerator pedal operation amount AP. That is, the target opening THCMD of the throttle valve 3 is calculated according to the accelerator pedal operation amount AP, and the actuator 7 is driven so that the detected throttle valve opening TH matches the target opening THCMD.

  The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, a central processing unit (CPU), It comprises a storage circuit for storing various calculation programs and calculation results executed by the CPU, an output circuit for supplying a drive signal to the fuel injection valve 6, and the like.

  The fuel injection amount by the fuel injection valve 6 is controlled by correcting the basic fuel amount calculated according to the intake air flow rate GAIR with the air-fuel ratio correction coefficient KAF corresponding to the air-fuel ratio AF detected by the LAF sensor 27. The The air-fuel ratio correction coefficient KAF is calculated so that the detected air-fuel ratio AF coincides with the target air-fuel ratio AFCMD.

  Since the relationship (detection characteristics) between the output voltage (hereinafter referred to as “sensor output”) VLAF and the air-fuel ratio AF of the LAF sensor 27 varies for a large number of sensors, the sensor output VLAF is used as the air-fuel ratio in this embodiment. Air-fuel ratio detection characteristic correction is performed to correct the detection characteristic applied when converting to AF during the fuel cut operation of the engine 1. The fuel cut operation is an operation that temporarily stops the fuel supply to the engine 1 and is executed when a predetermined fuel cut execution condition is satisfied during deceleration of the engine 1.

  FIG. 2 is a diagram for explaining the correction of the air-fuel ratio detection characteristic, and FIG. 2A shows the relationship (detection characteristic) between the sensor output VLAF and the air-fuel ratio AF. A solid line L1 indicates an average characteristic, a broken line L2 indicates an upper limit characteristic on the side where the inclination increases, and a broken line L3 indicates a lower limit characteristic on the side where the inclination decreases. In addition, AFST shown in the figure is a theoretical air-fuel ratio, and AFATM is an air-fuel ratio conversion value corresponding to the oxygen concentration in the atmosphere. Since the value (stoichiometric output) VST of the sensor output VLAF corresponding to the theoretical air-fuel ratio AFST hardly varies, the detection characteristic varies in the range of the broken lines L1 to L3 with the operating point PST corresponding to the theoretical air-fuel ratio AFST as the center. It is shown.

  FIG. 2B is a time chart showing the transition of the sensor output VLAF when the operation is shifted from the operation with the stoichiometric air-fuel ratio AFST to the target air-fuel ratio to the fuel cut operation at time tFC. As shown in FIGS. 2A and 2B, the sensor output VLAF at time tS takes an average value VLAFM, an upper limit value VLAFH, and a lower limit value VLAFL corresponding to variations in detection characteristics. The time tS is a time when the sensor output VLAF is substantially stabilized after the start of the fuel cut operation. The sensor output VLAF at the time tS, that is, the sensor output VLAF corresponding to the atmosphere is hereinafter referred to as “stabilized output VLAFS”.

  By acquiring the stabilized output VLAFS during execution of the fuel cut operation, the detection characteristic of the LAF sensor 27 in use can be specified, and the average detection characteristic (L1) that is initially set is specified. By correcting the characteristics, it is possible to calculate an accurate air-fuel ratio AF from the sensor output VLAF.

  However, if a large amount of blow-by gas is generated during the fuel cut operation and supplied through the blow-by gas passage 9, the stabilized output VLAFS deviates from the value corresponding to the atmosphere, so that the detection characteristics are corrected accurately. I can't.

  FIG. 3 is a time chart showing the transition of the sensor output VLAF when the amount of blow-by gas generated (supply amount) is an assumed maximum amount, and shows an example in which the fuel cut operation is started at time tFC. Yes. In this case, the stabilized output VLAFS becomes a bias voltage value VDEV, which is about 10% lower than the normal voltage value VRMM when no blowby gas is supplied. Therefore, if the air-fuel ratio detection characteristic correction is performed based on the bias voltage value VDEV, the accuracy of the correction is reduced, and the actual air-fuel ratio after the correction is deviated from the target air-fuel ratio (in the example of FIG. 3, the maximum is nearly 10%). Problem).

  Therefore, in the present embodiment, when the generation state of blow-by gas is estimated, and when it is estimated that the amount of blow-by gas generated is large, the correction of air-fuel ratio detection characteristics is prohibited to prevent a reduction in correction accuracy. Yes.

  FIG. 4 is a diagram showing the relationship between the stabilized output VLAFS and the operation duration time TOP in a state where the amount of blow-by gas generated is large, and the time t0 is the time when the warm-up is completed after the engine 1 is started ( For example, this corresponds to the time when the engine coolant temperature TW reaches 80 ° C.).

  At time t0, which is the time point when warm-up is completed, the stabilized output VLAFS takes a relatively small initial voltage value (value indicating a rich air-fuel ratio) VINI due to the influence of blow-by gas. As the operation continues thereafter, the fuel mixed in the lubricating oil evaporates, and the amount of blow-by gas supplied to the intake passage 2 decreases. Therefore, the stabilized output VLAFS gradually increases and the normal voltage value VRMM Approaching.

  Accordingly, when the difference DVLAF (= VDET−VINI) between the initial voltage value VINI and the determination voltage value VDET at the time tDET after the elapse of a predetermined standby time TWAIT (for example, 20 minutes) is equal to or greater than the determination threshold DVTH, the lubricating oil It can be estimated that the amount of fuel mixed in the fuel is large, that is, the amount of blow-by gas generated is large. In the present embodiment, the generation status of blow-by gas is estimated using this method.

FIG. 5 is a flowchart of processing for performing the above-described air-fuel ratio detection characteristic correction. This process is executed at predetermined time intervals in the ECU 5 (the processes in FIGS. 6 to 8 are the same).
In step S11, it is determined whether or not a fuel cut flag FFC is “1”. The fuel cut flag FFC is set to “1” when a predetermined fuel cut execution condition is satisfied during deceleration of the engine 1, and is set to “0” when the predetermined fuel cut execution condition is not satisfied. The predetermined fuel cut execution condition includes a condition that the warm-up of the engine 1 is completed.

  If the answer to step S11 is negative (NO), the process is immediately terminated. If the answer is affirmative (YES), it is determined whether or not an intake air amount flag FGAH is “1” (step S12). In the process of FIG. 8 described later, the intake air amount flag FGAH indicates that the state where the intake air flow rate GAIR is equal to or higher than a predetermined flow rate GATH (for example, 5 g / sec) continues for a predetermined time TGATH (for example, 5 seconds) after the start of the fuel cut operation. Set to “1”. When the intake air amount of the engine 1 is increased, the influence on the air-fuel ratio becomes negligible even if the amount of blow-by gas generated is large. Accordingly, when the intake air amount flag FGAH is “1”, the process immediately proceeds to step S15 to acquire the stabilized output VLAFS and perform air-fuel ratio detection characteristic correction. That is, the conversion coefficient for converting the sensor output VLAF of the LAF sensor 27 in use into the air-fuel ratio AF is updated using the stabilized output VLAFS and the atmospheric pressure corresponding value AFATM, the stoichiometric output VST and the theoretical air-fuel ratio AFST. To do.

  If the answer to step S12 is negative (NO), it is determined whether or not a situation estimation completion flag FDEND is “1” (step S13). The situation estimation completion flag FDEND is set to “1” when the estimation of the blowby gas generation situation is completed in step S30 of the process shown in FIG. Initially, this answer is negative (NO), and the processing is immediately terminated.

  When the situation estimation completion flag FDEND is set to “1”, it is determined whether or not the prohibition flag FINH is “1” (step S14). The prohibition flag FINH is set to “1” when it is determined that the amount of blow-by gas generated (supply amount) is large in the process of FIG. When the prohibition flag FINH is “0”, the process proceeds to step S15 to update the conversion coefficient, and when the prohibition flag FINH is “1”, the process is immediately terminated.

  When the situation estimation completion flag FDEND is set to “1”, it is maintained until the engine 1 stops. Therefore, if the intake air amount flag FGAH is not set to “1”, the engine 1 stops and starts next. The conversion coefficient is not updated until it is done.

FIG. 6 is a flowchart of a correction prohibition determination process for setting the prohibition flag FINH.
In step S21, it is determined whether or not the fuel cut flag FFC is “1”. If the answer to step S21 is negative (NO), the process is immediately terminated. When the fuel cut flag FFC is “1”, it is determined whether or not the current fuel cut operation is the first fuel cut operation after the engine 1 is started (step S22). If the answer is affirmative (YES), the sensor output value VLAFP at that time is stored as the initial voltage value VINI, and the initialization flag FINI is set to “1” (step S23).

  If the answer to step S22 is negative (NO), it is determined whether or not a re-detection condition flag FCOND is “1” (step S24). The redetection condition flag FCOND is set in the process of FIG. 7 described later, and is set to “1” when a predetermined redetection condition is satisfied. In the present embodiment, from the time when the initial voltage value VINI is acquired (first detection timing), when the operation of the engine 1 is continued (in a state where the engine cooling water temperature TW is equal to or higher than the predetermined temperature TWTH) and the standby time TWAIT has elapsed ( At the second detection timing), a predetermined re-detection condition is satisfied, and the re-detection condition flag FCOND is set to “1”.

  While the re-detection condition flag FCOND is “0” in step S24, the processing is immediately terminated. When the re-detection condition flag FCOND is set to “1”, the process proceeds to step S25, and the determination voltage VDET is set at that time (second detection timing). The sensor output value VLAFP is set, and then the difference DVLAF (= VDET−VINI) between the determination voltage value VDET and the initial voltage value VINI is calculated (step S26). In step S27, it is determined whether or not the difference DVLAF is greater than or equal to a determination threshold DVTH (for example, 0.3V). If the answer is negative (NO), the prohibition flag FINH is set to “0” (step S27). S29) On the other hand, if the determination is affirmative (YES), the prohibition flag FINH is set to “1” (step S28). Thereafter, the status estimation completion flag FDEND is set to “1”, the re-detection condition flag FCOND is returned to “0”, and the process is terminated (step S30).

FIG. 7 is a flowchart of processing for setting the re-detection condition flag FCOND.
In step S31, it is determined whether or not the initialization flag FINI (see FIG. 6, step S23) is “1”. If the answer is negative (NO), the value of the timer TCOND is set to “0”. (Step S33), the re-detection condition flag FCOND is set to “0” (step S36).

  When the initialization flag FINI is “1”, it is determined whether or not the engine coolant temperature TW is equal to or higher than a predetermined temperature TWTH (for example, 80 ° C.) (step S32). If the answer to step S33 is negative (NO), the process proceeds to step S33. If the engine coolant temperature TW is equal to or higher than the predetermined temperature TWTH, the timer TCOND is counted up (step S34), and the value of the timer TCOND is set to the standby time TWAIT. It is determined whether or not this is the case (step S35).

  If the answer to step S35 is negative (NO), the process proceeds to step S36. If the answer is affirmative (YES), the process proceeds to step S37, and the re-detection condition flag FCOND is set to “1”.

FIG. 8 is a flowchart of processing for setting the intake air amount flag FGAH.
In step S41, it is determined whether or not the fuel cut flag FFC is “1”. If the answer is negative (NO), the value of the timer TGA is set to “0” (step S43). The intake air amount flag FGAH is set to “0” (step S46).

  When the fuel cut flag FFC is “1”, it is determined whether or not the intake air flow rate GAIR is equal to or higher than a predetermined flow rate GATH (for example, 5 g / sec) (step S42). If the answer to step S43 is negative (NO), the process proceeds to step S43. If the intake air flow rate GAIR is equal to or greater than the predetermined flow rate GATH, the timer TGA is counted up (step S44), and the value of the timer TGA is set to the predetermined time TGATH. It is determined whether or not (for example, 5 sec) or more (step S45).

  If the answer to step S45 is negative (NO), the process proceeds to step S46. If the answer is affirmative (YES), the process proceeds to step S47, and the intake air amount flag FGAH is set to “1”. The state in which the answer to step S45 is affirmative (YES) corresponds to a state in which the intake air amount SUMGA as an integrated value of the intake air flow rate GAIR is equal to or greater than the predetermined intake air amount SUMGATH.

  As described above, in the present embodiment, the fuel cut operation is performed when the predetermined fuel cut execution condition is satisfied while the engine 1 is decelerating, and the detection characteristics of the LAF sensor 27 during the fuel cut operation period in which the fuel cut operation is being performed. The air-fuel ratio detection characteristic correction for correcting is performed. Then, the generation state of blow-by gas is estimated by the processing of FIG. 6, and the prohibition flag FINH is set according to the estimated generation state of blow-by gas, and execution or prohibition of air-fuel ratio detection characteristic correction is commanded. . Therefore, in a situation where the amount of blow-by gas generated is large, it is possible to surely prohibit air-fuel ratio detection characteristic correction, and the correction accuracy can be improved. Further, in the present embodiment, since it is not necessary to increase the intake air flow rate as in the above-described prior art, it is possible to prevent deterioration of fuel consumption.

  More specifically, an initial voltage value VINI that is a sensor output value at the time (first detection timing) when the first fuel cut operation is started after the engine 1 is started, and a fuel cut operation period after the first detection timing. The difference DVLAF from the determination voltage value VDET, which is the sensor output value at the time when the predetermined re-detection condition is satisfied, that is, the time when the re-detection condition flag FCOND becomes “1” (second detection timing) is greater than or equal to the determination threshold DVTH When it is, it is estimated that the amount of blow-by gas generated is large, and correction of air-fuel ratio detection characteristics is prohibited.

  Focusing on the fact that the difference DVLAF increases as shown in FIG. 4 when the amount of blow-by gas generated is large, the re-detection condition flag FCOND is in a predetermined standby state when the engine coolant temperature TW is equal to or higher than the predetermined temperature TWTH. Since it is set to “1” when the time TWAIT is continued, it is possible to accurately estimate a state where the amount of blow-by gas generated is large, and to reliably prevent erroneous correction.

  Further, when it is detected that the intake air amount SUMGA of the engine 1 is equal to or greater than the predetermined intake amount SUMGATH during the fuel cut operation period (FIG. 8, when the answer to step S45 is affirmative (YES)) Then, the intake air amount flag FGAH is set to “1” (step S47), and the process immediately proceeds to step S15 from step S12 in FIG. 5, and the detection characteristic correction is performed regardless of the blowby gas generation state. When it is detected that the intake air amount SUMGA is equal to or greater than the predetermined intake amount SUMGATH, the degree of influence on the sensor output VLAF is low even if blow-by gas is generated. Therefore, by performing the detection characteristic correction regardless of the blowby gas generation state, the correction execution frequency can be increased and the control accuracy of the air-fuel ratio feedback control based on the sensor output VLAF can be increased.

In the present embodiment, the LAF sensor 27 corresponds to air-fuel ratio detection means, the fuel injection valve 6, a fuel passage for supplying fuel to the fuel injection valve 6 and the like, and the ECU 5 constitutes fuel supply means, and the blow-by gas passage 9 is provided. It corresponds to the blow-by gas supply means, the ECU5 fuel cut operation execution means, correcting means, the 及 beauty command means. The intake air flow rate sensor 21 corresponds to intake air flow rate correlation parameter detection means, the cooling water temperature sensor 25 corresponds to temperature parameter detection means, and the throttle valve 3 and the actuator 7 correspond to intake air flow rate change means.

[Modification]
In the embodiment described above, the second detection timing (determination voltage value VDET acquisition) is the time point when the operation state in which the engine coolant temperature TW is equal to or higher than the predetermined temperature TWTH continues from the first detection timing (initial voltage value VINI acquisition time). However, from the first detection timing, the fuel injection amount integrated value SUMQI is calculated by integrating the fuel injection amount QINJ, and the time point when the fuel injection amount integrated value SUMQI reaches the predetermined fuel amount threshold value SUMQITH is determined as the second time point. It is good also as a detection timing. Further, the number of executions NFC of the fuel cut operation after the first detection timing may be counted, and the time when the fuel cut operation is executed when the execution number NFC reaches the predetermined number NFCTH may be set as the second detection timing. However, in this case, in order to secure a period during which the fuel mixed in the lubricating oil evaporates, it is necessary to set the predetermined number NFCTH slightly larger in consideration of the standby time TWAIT.

[Second Embodiment]
In the present embodiment, the generation status of blow-by gas is estimated more quickly than in the first embodiment. Except for the points described below, the second embodiment is the same as the first embodiment.

  FIG. 9 is a time chart for explaining the method for estimating the blow-by gas generation state in the present embodiment. The throttle valve opening TH is set to the first opening during the fuel cut operation with a large amount of blow-by gas generated. The transition of the sensor output VLAF when changing from TH1 (time t1) to the second opening TH2 (time t2) ((a) in the same figure) is shown ((b) in the same figure). As is apparent from this figure, when the amount of blow-by gas generated is large, the sensor output VLAF also increases from the initial voltage value VINI to the determination voltage value VDET corresponding to the increase in the throttle valve opening TH. On the other hand, when blowby gas is not supplied (or is low), the sensor output VLAF becomes a substantially constant value equal to or higher than the determination voltage value VDET in the period from time t1 to t2.

  Therefore, in the present embodiment, when the difference DVLAF (= VDET−VINI) between the initial voltage value VINI and the determination voltage value VDET shown in FIG. 9B is equal to or larger than the determination threshold value DVTHa (for example, 0.3 V), blow-by is performed. It is determined that the amount of gas generated is large, and the air-fuel ratio detection characteristic correction is prohibited.

  FIG. 10 is a flowchart of the correction prohibition determination process in the present embodiment. Note that the throttle valve opening TH is almost fully closed at the start of the fuel cut operation and is equal to the first opening TH1.

  In step S51, it is determined whether or not the fuel cut flag FFC is “1”. If the answer to step S51 is negative (NO), the processing is immediately terminated. When the fuel cut flag FFC is “1”, the initial voltage value VINI is set to the sensor output value VLAFP at that time (step S52), and the target opening THCMD of the throttle valve 3 is set to the second opening TH2. (Step S53). The drive control of the actuator 7 for opening the throttle valve 3 to the target opening THCMD is executed by a process (not shown), and the valve opening speed to the second opening TH2 is set to a predetermined speed (for example, 1 deg / sec). 3 valve opening drive is performed.

  In step S54, the process waits until the detected throttle valve opening TH reaches the second opening TH2, and when the throttle valve opening TH reaches the second opening TH2, the determination voltage value VDET is set to the sensor output value at that time. Set to VLAFP (step S55). In step S56, a difference DVLAF (= VDET−VINI) is calculated, and it is determined whether or not the calculated difference DVLAF is greater than or equal to a determination threshold value DVTHa (step S57). If this answer is negative (NO), the prohibition flag FINH is set to “0” (step S59), while if the difference DVLAF is greater than or equal to the determination threshold value DVTHa, the prohibition flag FINH is set to “1”. (Step S58). In step S60, the situation estimation completion flag FDEND is set to “1”, and the process ends.

In the present embodiment, at the first detection timing immediately after the start of the fuel cut operation, the initial voltage value VINI is acquired, and the throttle valve opening TH is increased by a predetermined angle value DTHD (for example, 5 deg) to the second opening TH2. When the determination voltage value VDET is acquired and the difference DVLAF between the initial voltage value VINI and the determination voltage value VDET is equal to or greater than the determination threshold value DVTHa, it is estimated that the amount of blow-by gas generated is large, and air-fuel ratio detection characteristic correction is prohibited. The By increasing the throttle valve opening TH and increasing the intake air flow rate, the determination voltage value VDET is acquired in a state in which the degree of influence is reliably reduced when the amount of blow-by gas generated is large. It is possible to accurately estimate the generation status of blow-by gas.
In the present embodiment, the process of FIG. 10 constitutes a directive means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the sensor output value VLAFP acquired as the initial voltage value VINI and the determination voltage value VDET is the current value of the sensor output VLAF. However, it is considered that the sensor output value VLAFP is affected by noise and pulsation. Then, an average value obtained by performing an averaging process for several seconds may be used.

  In the above-described embodiment, the intake air flow rate GAIR is used as the intake air flow rate correlation parameter, but the engine speed NE and the intake pressure PBA may be used. Further, although the engine coolant temperature TW is used as the engine temperature parameter, for example, a sensor that detects the temperature TOIL of the lubricating oil may be provided, and the oil temperature TOIL detected by the sensor may be used. In addition, although the throttle valve is used as the intake air flow rate changing means, a bypass passage that bypasses the throttle valve, an electromagnetic valve that can change the flow rate of air flowing through the bypass passage, or an intake valve that changes the valve opening period of the intake valve A variable operating characteristic mechanism can also be used.

  In the second embodiment described above, the throttle valve opening TH is increased by the predetermined angle value DTHD after the first detection timing, but the intake air flow rate GAIR is increased by the predetermined flow rate DGAIR. The throttle valve opening TH may be increased.

  Further, in the above-described embodiment, the engine control device including the fuel injection valve that injects the fuel into the intake passage is shown. However, the present invention relates to the engine control device including the fuel injection valve that directly injects the fuel into the combustion chamber. It is also applicable to. Furthermore, the present invention can also be applied to a control device such as a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

1 Internal combustion engine 2 Intake passage 3 Throttle valve (intake air flow rate changing means)
5 Electronic control unit (fuel supply means, the fuel cut operation execution means, correcting means, directive means)
6 Fuel injection valve (fuel supply means)
7 Actuator (intake air flow rate changing means)
9 Blow-by gas passage (Blow-by gas supply means)
10 Exhaust passage 21 Intake air flow rate sensor (intake air flow rate correlation parameter detection means)
22 Throttle valve opening sensor 25 Cooling water temperature sensor (temperature parameter detection means)
27 Proportional oxygen concentration sensor (air-fuel ratio detection means)
DVLAF difference DVTH determination threshold DTHD predetermined angle value (predetermined control amount)
GAIR intake air flow rate (intake air flow rate correlation parameter)
SUMGA Intake air amount SUGATH Predetermined intake amount TH Throttle valve opening TW Engine cooling water temperature (engine temperature parameter)
TWAIT waiting time (predetermined time)
TWTH Predetermined temperature VINI Initial voltage value (first output value)
VDET judgment voltage value (second output value)
VLAF LAF sensor output

Claims (3)

An air-fuel ratio detection unit disposed in an exhaust passage of the internal combustion engine; a fuel supply unit that supplies fuel to the engine; and a blow-by gas supply unit that supplies blow-by gas generated in the engine to an intake system of the engine. In a control device for an internal combustion engine,
Fuel cut operation execution means for executing a fuel cut operation for temporarily stopping fuel supply to the engine in a predetermined operation state of the engine;
Correction means for correcting the detection characteristics of the air-fuel ratio detection means in a fuel cut operation period in which the fuel cut operation is being performed;
Command means for estimating the generation status of the blow-by gas and commanding execution or prohibition of correction by the correction means according to the estimated blow-by gas generation status ;
Temperature parameter detection means for detecting an engine temperature parameter indicating the temperature of the engine ,
The command means includes a first output value of the air-fuel ratio detection means at a predetermined first detection timing during the fuel cut operation period, and a predetermined redetection condition during the fuel cut operation period after the first detection timing. When the difference from the second output value of the air-fuel ratio detection means at the second detection timing, which is the time when is established, is greater than or equal to a determination threshold, the correction by the correction means is prohibited,
Wherein the predetermined re-detection condition, the control device for an internal combustion engine states the engine temperature parameter in after the first detection timing is equal to or higher than a predetermined temperature, characterized that you satisfied by continuing more than a predetermined time. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the command means maintains a command for prohibiting correction by the correction means until the engine stops . An intake air flow rate correlation parameter detecting means for detecting an intake air flow rate correlation parameter correlated with the intake air flow rate of the engine;
When the command means detects that the intake air amount of the engine exceeds a predetermined amount based on the intake air flow rate correlation parameter during the fuel cut operation period, the command means relates to the blow-by gas generation state. 3. The control apparatus for an internal combustion engine according to claim 1 or 2, wherein an instruction to perform correction by the correction means is issued.

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