JP2011085020A - Atmosphere learning device for oxygen concentration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxygen concentration sensor improved in oxygen concentration detecting accuracy by properly executing atmosphere learning of the oxygen concentration sensor. <P>SOLUTION: An ECU 40 executes atmosphere learning of output values of an oxygen concentration sensor 32 based on the output values thereof when an exhaust passage is in the atmospheric state in an engine 10 including: opening/closing valves (an intake valve 21, an exhaust valve 22 and a throttle valve 14) for adjusting a state of gas to be sucked or exhausted into/from a combustion chamber 23 of the engine 10; and an oxygen concentration sensor 32 for detecting concentration of oxygen included in the exhaust in the exhaust passage of the engine 10. Especially, the ECU 40 determines that an operation stop request of the engine 10 has been made, and in the case wherein it is determined that the operation stop request have been made, controls the opening/closing valves to a predetermined valve opening state. After controlling the opening/closing valve into the predetermined opening state, the ECU 40 carries out the atmosphere learning. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an atmospheric learning device for an oxygen concentration sensor, and more particularly to an atmospheric learning device for performing atmospheric learning of an output value of an oxygen concentration sensor that detects an oxygen concentration in exhaust gas of an internal combustion engine.

  2. Description of the Related Art Conventionally, an oxygen concentration sensor (so-called A / F sensor) that detects an oxygen concentration (air-fuel ratio) in an exhaust gas discharged from an internal combustion engine is known. This oxygen concentration sensor is configured such that the element current flowing through the sensor element changes according to the oxygen concentration in the exhaust gas. In the internal combustion engine, air-fuel ratio control is performed based on the measurement result of the element current flowing through the sensor element.

  In the oxygen concentration sensor, an output error may occur due to manufacturing variation, secular change, and the like. Therefore, conventionally, during a fuel cut period such as when the vehicle is decelerated, the measurement value measured by the oxygen concentration sensor during the same period is regarded as a value corresponding to the oxygen concentration in the atmosphere, and the relationship between the output value of the oxygen concentration sensor and the oxygen concentration It has been proposed to perform atmospheric learning of a so-called oxygen concentration sensor that performs calibration (see, for example, Patent Document 1).

JP 2003-3903 A

  However, after the start of the fuel cut, a sufficient scavenging time is required for the exhaust passage to be in the atmospheric state. Therefore, the fuel cut period may end before the air learning is completed. It cannot be said that a sufficient time for suitably performing atmospheric learning during driving can be secured. On the other hand, if atmospheric learning is not performed, the relationship between the sensor output value and the oxygen concentration cannot be calibrated, and as a result, there is a concern that the detection accuracy of the oxygen concentration is lowered.

  The present invention has been made to solve the above-described problems, and can perform atmospheric learning of an oxygen concentration sensor appropriately, and consequently improve atmospheric oxygen concentration detection accuracy. The main purpose is to provide a device.

  The present invention employs the following means in order to solve the above problems.

  The present invention is applied to an internal combustion engine having an on-off valve that adjusts the state of intake or exhaust of gas into a combustion chamber of the internal combustion engine and an oxygen concentration sensor that detects an oxygen concentration in exhaust gas in an exhaust passage of the internal combustion engine. In addition, the present invention relates to an atmosphere learning device for an oxygen concentration sensor that performs atmosphere learning of the sensor output value based on an output value of the oxygen concentration sensor when the exhaust passage is in an atmospheric state. The invention according to claim 1 is the stop request determining means for determining that there has been a request for stopping the operation of the internal combustion engine, and the on-off valve when the stop request determining means determines that there is an operation stop request. Open / close valve control means for controlling the open / close valve to a predetermined open state, and learning execution means for executing the air learning after the open / close valve control means controls the open / close valve to the open state. And

  In general, the learning of the atmosphere of the oxygen concentration sensor is performed while the internal combustion engine is in operation until the operating state becomes a state (for example, fuel cut) in which an atmospheric state can be formed in the exhaust passage. Further, in order to bring the exhaust passage into an atmospheric state, the above operating state needs to be continued for a predetermined time. However, since the operating state of the internal combustion engine changes from time to time, it is considered that the above operating state is not continued for a sufficiently long time, and as a result, atmospheric learning cannot be performed.

  In view of that, in the present invention, when there is a request to stop the operation of the internal combustion engine, the amount of gas passing through the exhaust system of the internal combustion engine is increased by controlling the on-off valve to a predetermined valve open state, thereby After scavenging the exhaust passage, atmospheric learning is performed. After the operation of the internal combustion engine is stopped, it is not affected by changes in the engine operating state, so that sufficient time can be secured for scavenging the exhaust passage, and atmospheric learning is performed in a state where the oxygen concentration sensor is in the atmospheric state. Can be executed. Therefore, according to the present invention, it is possible to properly carry out air learning, and consequently improve the accuracy of oxygen concentration detection.

  Here, the control of the on-off valve after the request for stopping the operation of the internal combustion engine may be started before the stop of the rotation of the internal combustion engine, or after the stop of the rotation of the internal combustion engine as long as the request for stopping the operation is made. May be.

  Specifically, as in the invention according to claim 2, as the valve open state, the total valve opening amount in a state where the intake valve and the exhaust valve of the internal combustion engine are simultaneously opened after the internal combustion engine is stopped. It is preferable to control the opening mode of at least one of the intake valve and the exhaust valve so that a predetermined scavenging acceleration amount is obtained. The valve opening amount may be controlled, for example, by changing the rotational phase of the cam shaft relative to the engine output shaft (crankshaft) or by changing the valve lift amount. In addition, the intake valve and the exhaust valve may be opened and closed by an engine-driven mechanism that is driven by the rotational force of the internal combustion engine or by an electric mechanism.

  Specifically, with respect to the configuration for controlling the opening mode of the on-off valve based on the sum of the valve opening amounts of the intake valve and the exhaust valve (Claim 2), the valve opening state as in the invention of Claim 3 The total valve opening amount may be controlled to the scavenging acceleration amount by adjusting a valve overlap amount in which the intake valve opening period and the exhaust valve opening period overlap. By controlling the valve overlap amount, the total valve opening amount can be increased, and as a result, scavenging of the exhaust system can be performed efficiently.

  When the exhaust gas remaining in the exhaust passage and the fresh air are replaced (scavenging), the exhaust gas and the fresh air can be efficiently replaced. If the scavenging state is good, the exhaust can be performed in a relatively short time. The passage becomes atmospheric. On the other hand, if the efficiency at the time of replacement is low and the scavenging state is not so good, the time until the exhaust passage becomes an atmospheric state becomes long. Therefore, if the scavenging time is the same when scavenging can be performed efficiently and when it is not, scavenging cannot be performed efficiently, and air learning is performed even though the exhaust passage is not in an atmospheric state. It is thought that it is done.

  In view of this point, the invention according to claim 4 is based on the scavenging state detecting means for detecting the scavenging state of the exhaust passage after the rotation of the internal combustion engine is stopped, and the scavenging state detected by the scavenging state detecting means. And a time setting means for setting a required time from the predetermined timing after the operation stop request to the execution of the atmospheric learning. According to this configuration, by setting the time required for executing the air learning according to the degree of the scavenging promotion of the exhaust passage, even if the exhaust passage is not efficiently scavenged, the exhaust passage Atmospheric learning can be executed after waiting for certainty that the atmospheric condition is reached.

  Note that, with regard to “the required time from the predetermined timing after the operation stop request to the execution of the atmospheric learning”, the predetermined timing that is the starting point of the required time is after the operation stop request and the execution start timing of the atmospheric learning. If it is before, it will not specifically limit. For example, the predetermined timing may be a timing when the on-off valve is in a desired valve opening state, or may be a timing when a request for stopping the operation of the internal combustion engine is made. Or it is good also as the timing of the rotation stop of an internal combustion engine.

  In the configuration in which the required time is variably set according to the scavenging state (Claim 4), the valve timing of at least one of the intake valve and the exhaust valve of the internal combustion engine is variably controlled as in the invention according to Claim 5. The valve is applied to an internal combustion engine having an engine-driven variable valve mechanism, and the opening / closing valve control means has the valve opening period in which the valve opening period of the intake valve and the valve opening period of the exhaust valve overlap as the valve open state. The amount of overlap is adjusted by the variable valve mechanism, the scavenging state detection means detects the valve overlap amount after rotation of the internal combustion engine as the scavenging state, and the time setting means detects the scavenging state The required time may be set based on the valve overlap amount detected by the means.

  As the variable valve mechanism, an engine drive type is generally known in which the valve timing of the intake valve or the exhaust valve is variably controlled by controlling the hydraulic pressure or the like with a pump driven by the rotational force of the internal combustion engine. In such a system equipped with an engine-driven variable valve mechanism, the hydraulic pressure of the variable valve mechanism decreases as the engine rotational speed decreases after a request to stop the internal combustion engine, and before the valve timing reaches the target timing, It is conceivable that the timing advance angle change or delay angle change stops. Here, since the rate of decrease in engine speed after a request to stop the internal combustion engine can vary depending on various operating conditions, the amount of valve overlap after the rotation of the internal combustion engine stops varies. Further, when variation occurs in the valve overlap amount after the rotation is stopped, the degree of scavenging promotion in the exhaust passage varies depending on the valve overlap amount. In this regard, according to the above configuration, by setting the time required until the air learning is performed according to the valve overlap amount after the rotation stop, the exhaust passage is set regardless of the valve overlap amount after the rotation stop. Atmospheric learning can be executed after waiting for certainty that the atmospheric condition is reached.

  In each of the above configurations, when the on-off valve is a throttle valve that adjusts the cross-sectional area of the intake passage of the internal combustion engine, the on-off valve control means preferably has the on-off valve control means as in the invention according to claim 6. When it is determined by the stop request determination means that there is an operation stop request, the throttle valve is fully opened. By so doing, scavenging of the exhaust passage can be performed efficiently.

1 is an overall schematic configuration diagram of an engine control system. The flowchart which shows the process sequence of the air | atmosphere learning process in 1st Embodiment. The time chart which shows the specific aspect of 1st Embodiment. The figure which shows the relationship between valve overlap amount and the scavenging required time. The flowchart which shows the process sequence of the air | atmosphere learning process in 2nd Embodiment. The time chart which shows the specific aspect of 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. This embodiment is embodied in a control device of an engine control system applied to an on-vehicle multi-cylinder engine. In this control system, an electronic control unit (hereinafter referred to as ECU) is used as a center to control the fuel injection amount, control the ignition timing, and the like. FIG. 1 is a configuration diagram showing an overall outline of the engine control system.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11 (intake passage), and an air flow meter 13 for detecting the intake air amount is provided downstream of the air cleaner 12. . A throttle valve 14 whose opening degree is adjusted by a throttle actuator 15 such as a DC motor is provided on the downstream side of the air flow meter 13. The opening degree of the throttle valve 14 (throttle opening degree) is detected by a throttle opening degree sensor built in the throttle actuator 15. A surge tank 16 is provided on the downstream side of the throttle valve 14, and the surge tank 16 is provided with an intake pipe pressure sensor 17 for detecting the intake pipe pressure. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10. In the intake manifold 18, an electromagnetically driven fuel injection that injects fuel near the intake port of each cylinder. A valve 19 is attached.

  An intake valve 21 and an exhaust valve 22 are provided at an intake port and an exhaust port of the engine 10, respectively. The intake valve 21 and the exhaust valve 22 (intake / exhaust valves 21 and 22) are engine-driven types that open and close as the engine 10 rotates, and specifically, the cam shafts 27 and 28 rotate as the engine 10 rotates. As a result, the cams (not shown) attached to the cam shafts 27 and 28 rotate, and open and close by the rotation of the cams. Then, the air / fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust gas after combustion is discharged to the exhaust pipe 24 (exhaust passage) by the opening operation of the exhaust valve 22.

  The intake valve 21 and the exhaust valve 22 are respectively provided with variable valve mechanisms 25 and 26 that can change the opening / closing timing (valve timing) of the valves 21 and 22. In the variable valve mechanisms 25 and 26, the hydraulic oil pump (not shown) is driven by the rotational force of the engine 10, and the hydraulic pressure of the hydraulic circuit (not shown) is controlled accordingly, thereby adjusting the valve timing of the intake valve 21 and the exhaust valve 22. Is done. In the present embodiment, the valve timing of at least one of the intake valve 21 and the exhaust valve 22 is changed by changing the phase of the cam shafts 27 and 28 with respect to the engine output shaft (crankshaft). Moreover, the valve overlap amount by which the valve opening period of the intake valve 21 and the valve opening period of the exhaust valve 22 overlap is changed by changing the valve timing.

  A spark plug 29 is attached to the cylinder head of the engine 10 for each cylinder. A high voltage is applied to the spark plug 29 at a desired ignition timing through an ignition device (not shown) including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 29, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.

  The exhaust pipe 24 is provided with a catalyst 31 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas. Further, in the exhaust pipe 24, an oxygen concentration sensor 32 for detecting the air-fuel ratio (oxygen concentration) of the air-fuel mixture with exhaust gas as a detection target is provided upstream of the catalyst 31. Specifically, the oxygen concentration sensor 32 is a wide-area detection type A / F sensor that outputs a wide-range air-fuel ratio signal proportional to the oxygen concentration in the exhaust gas by applying a voltage to the sensor element.

  In addition, the present system includes a coolant temperature sensor 34 that detects the coolant temperature, a crank angle sensor 35 that outputs a rectangular crank angle signal for each predetermined crank angle of the engine (for example, at a cycle of 30 ° CA), a predetermined cam angle. A cam angle sensor 36 or the like for outputting a rectangular cam angle signal is attached every time. Further, an air conditioner, an alternator, and the like (not shown) are provided as engine auxiliary machines, and these auxiliary machines are driven by the rotational force of the engine 10.

  The ECU 40 is composed mainly of a microcomputer (hereinafter referred to as a microcomputer) 41 composed of a CPU, ROM, RAM, EEPROM, etc., as is well known, and executes various control programs stored in the ROM so that each engine operation can be performed. Various controls of the engine 10 are performed according to the state. That is, the microcomputer 41 of the ECU 40 receives signals from an ignition switch (IG switch) 51 and the like in addition to the various sensors described above, calculates a fuel injection amount and an ignition timing based on the various signals, and calculates a fuel injection valve. 19 and the drive of the ignition device are controlled, or the opening / closing timings of the intake and exhaust valves 21 and 22 are controlled.

  Specifically, the ECU 40 controls the target of the intake and exhaust valves 21 and 22 based on the outputs of various sensors that detect the engine operating state such as the intake pipe pressure sensor 17 and the cooling water temperature sensor 34. The valve timing is calculated, and the actual valve timings of the intake and exhaust valves 21 and 22 are calculated based on the outputs of the crank angle sensor 35 and the cam angle sensor 36. Then, the actual valve timing is made to coincide with the target valve timing by controlling the hydraulic pressure in the hydraulic circuit of the variable valve mechanisms 25 and 26 to change the camshaft phase of the intake and exhaust valves 21 and 22.

  A battery 54 is connected to the ECU 40 via a switch 53 of the main relay 52. When an on signal is input from the IG switch 51, the ECU 40 energizes the relay drive coil 55 of the main relay 52 to turn on the switch 53 of the main relay 52 and receives power supply from the battery 54. The electric power supplied from the battery 54 through the main relay 52 is supplied not only to the ECU 40 but also to an actuator such as the throttle valve 14. The main relay 52 is continuously kept on for a predetermined time after the IG switch 51 is turned off. In the period in which the main relay 52 is on, power supply from the battery 54 to the ECU 40 is continued even after the IG switch 51 is turned off.

In the present embodiment, the ECU 40 performs atmospheric learning as a process for calibrating the relationship between the sensor output value and the oxygen concentration for the oxygen concentration sensor 32. For details on atmospheric learning, in the period in which the fuel supply to the engine 10 is stopped while the vehicle is operating (for example, the fuel cut period during vehicle deceleration), the oxygen concentration sensor 32 has an oxygen concentration similar to that of the atmosphere. This is a process of determining and calibrating the relationship between the sensor output value and the oxygen concentration based on the output value of the oxygen concentration sensor 32 at that time. More specifically, as atmospheric learning, for example, the output value Vatm of the oxygen concentration sensor 32 is read when a fuel cut is being executed and a predetermined time has elapsed since the start of the fuel cut, and the read output value Vatm is read. Then, a learning value Flea (= Vstd / Vatm) is calculated from the ratio with the reference output value Vstd in the atmospheric condition stored in advance in the ROM, and this is stored in a backup memory such as an EEPROM or a backup RAM. Then, the actual output value Vaf of the oxygen concentration sensor 32 is set to a value Vlea that does not include an output error due to manufacturing variation, deterioration with time, or the like by the following equation (1), using the learning value Flae obtained by atmospheric learning.
Vlea = Vaf × Flea (1)

  However, during vehicle operation such as during the fuel cut period, the operating state of the engine 10 changes each time, so a sufficiently long fuel cut period cannot be secured, and the IG switch 51 is turned off after the IG switch 51 is turned on. It is conceivable that atmospheric learning cannot be carried out until it is done. Specifically, since exhaust gas remains in the exhaust pipe 24 immediately after the start of the fuel cut, a sufficient scavenging time is required to bring the exhaust pipe 24 into the atmospheric state after the start of the fuel cut. For this reason, even if the fuel cut is started, for example, by performing an accelerator operation or the like, it is conceivable that the fuel cut ends before the air learning is completed and the combustion control is resumed. In this case, the relationship between the sensor output value and the oxygen concentration cannot be calibrated. In addition, when the period during which the air learning is not performed is prolonged, there is a possibility that the accuracy of detecting the oxygen concentration by the oxygen concentration sensor 32 may decrease during that period.

  Therefore, in the present embodiment, atmospheric learning is performed when the engine 10 is stopped. Specifically, the intake / exhaust valve 21 as an on-off valve that adjusts the state of intake or exhaust of gas into the combustion chamber 23 of the engine 10 when an engine operation stop request such as an off operation of the IG switch 51 is made. 22 and the throttle valve 14 are controlled to a predetermined valve-opening state for promoting scavenging of the exhaust system, and thereafter air learning is performed. Thereby, after the scavenging promotion of the exhaust passage is performed in the operation stop state of the engine 10, the air learning is performed. At this time, as the valve opening control of the intake / exhaust valves 21, 22, specifically, the sum of the valve opening amounts when the intake valve 21 and the exhaust valve 22 are simultaneously opened after the rotation of the engine is stopped is a predetermined scavenging acceleration amount. To be. In particular, in the present embodiment, the valve overlap amount of the intake and exhaust valves 21 and 22 after the rotation of the engine 10 is maximized to make the sum of the valve opening amounts a predetermined scavenging acceleration amount, and further the throttle valve 14 is fully opened. By setting the state, the exhaust passage is scavenged as efficiently as possible after the rotation of the engine 10 is stopped.

  FIG. 2 is a flowchart showing the processing procedure of the atmospheric learning process. This process is executed by the ECU 40 at predetermined intervals. This process is executed by supplying power from the battery 54 to the ECU 40 as the main relay 52 is kept on for a predetermined time after the IG switch 51 is turned off.

  In FIG. 2, first, in step S101, it is determined whether or not a value 0 is set in the valve opening execution flag FVL. The valve opening execution flag FVL is a flag indicating that after the IG switch 51 is turned off, a command signal indicating that the intake and exhaust valves 21 and 22 and the throttle valve 14 are in a predetermined valve opening state for promoting scavenging is output. Yes, set to 1 when the command is output.

  If it is before the command to set the intake / exhaust valves 21 and 22 and the throttle valve 14 to the predetermined open state, an affirmative determination is made in step S101 and the process proceeds to step S102, and the IG switch 51 is switched from the on state to the off state. It is determined whether or not it is the timing. In the case of the switching timing of the IG switch 51 from on to off, the processes of steps S103 to S106 are executed.

That is, in step S103, the throttle valve 14 is controlled to a predetermined valve open state. At this time, in the present embodiment, the throttle valve 14 is fully opened. In step S104, the rotational phase of the camshafts 27 and 28 with respect to the crankshaft is changed by hydraulic control of the variable valve mechanisms 25 and 26, so that the valve between the intake valve 21 and the exhaust valve 22 after the engine 10 stops rotating. The valve timings of the intake and exhaust valves 21 and 22 are changed so that the overlap amount becomes a predetermined scavenging acceleration amount (in this embodiment, the maximum overlap amount) . For example, the valve timing of the intake valve 21 is changed to the advance side by the variable valve mechanism 25 on the intake side, and the valve timing of the exhaust valve 22 is changed to the retard side by the variable valve mechanism 26 on the exhaust side. Note that the valve overlap amount may be set to a predetermined scavenging acceleration amount by changing only the valve timing of the intake valve 21 to the advance side or changing only the valve timing of the exhaust valve 22 to the retard side.

  In step S105, the stop position of the piston when the rotation of the engine 10 is stopped is adjusted by engine stop position control such as alternator drive control so that the stop position of any piston is at or near the exhaust top dead center. . Thereafter, in step S106, a value 1 is set to the valve opening execution flag FVL.

  In subsequent step S107, for example, based on the output value of the crank angle sensor 35, it is determined whether or not the rotation of the engine 10 has stopped. If it is determined that the rotation of the engine 10 has stopped, a predetermined amount of time from the ignition off is determined. It is determined whether the scavenging time has elapsed. This time required for scavenging is set as a time sufficient to replace the exhaust gas in the exhaust passage with fresh air in a state where the valve overlap amount is maximum and the throttle is fully opened.

  If it is before the time required for scavenging has elapsed since the ignition was turned off, a negative determination is made in step S107, and this processing is temporarily terminated. On the other hand, if the required scavenging time has elapsed since the ignition was turned off, the process proceeds to step S108, and atmospheric learning is executed. Specifically, the output value of the oxygen concentration sensor 32 after the elapsed scavenging time from the ignition off is regarded as an output when the vicinity of the oxygen concentration sensor 32 is in the atmospheric state, and the output value Vatm and the reference output value Vstd are The learning value Flea is calculated from the ratio and stored in the backup memory. Then, the valve opening execution flag FVL is reset to 0, and this process is terminated.

  FIG. 3 is a time chart showing a specific mode of atmospheric learning of this system. In FIG. 3, (a) shows the transition of on / off of the IG switch 51, (b) shows the transition of the engine speed, and (c) shows the transition of the opening degree of the throttle valve (throttle opening degree). (D) shows the transition of the valve overlap amount of the intake / exhaust valves 21, 22, and (e) shows the transition of execution / stop of the atmospheric learning.

  In FIG. 3, when the IG switch 51 is turned off at timing t11, the throttle opening TH is changed to the fully open position, and the variable valve mechanisms 25, 26 are set so that the valve overlap amount OL becomes the maximum value Lmax. The hydraulic pressure is controlled. Further, the engine speed NE gradually decreases as the IG switch 51 is turned off, and the rotation of the engine 10 is stopped at the timing 12 after the valve overlap amount OL reaches the maximum value Lmax. Then, when the required scavenging time TA has elapsed from the off timing t11 of the IG switch 51, the execution of atmospheric learning is started at the timing t13. Note that, after the air learning is completed, the throttle opening TH is maintained at a predetermined intermediate opening Tlmp for securing an intake air amount for retreat travel (limp home).

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  When the IG switch 51 is turned off, the intake / exhaust valves 21 and 22 and the throttle valve 14 are controlled to be in a predetermined valve opening state for promoting scavenging of the exhaust system, and thereafter the air learning is performed. It is not affected by changes in engine operating conditions when performing atmospheric learning. As a result, a sufficient time required for scavenging the exhaust passage can be secured, and atmospheric learning can be performed in a situation where the vicinity of the oxygen concentration sensor is in an atmospheric state. Therefore, it is possible to appropriately perform air learning, and consequently improve the accuracy of detecting the oxygen concentration.

  The intake / exhaust valves 21 and 22 are opened so that the sum of the valve opening amounts when the intake valve 21 and the exhaust valve 22 are simultaneously opened after the rotation of the engine 10 is stopped becomes a predetermined scavenging acceleration amount. Since the valve opening mode of 21 and 22 is controlled, specifically, the valve overlap amount in which the valve opening period of the intake valve overlaps the valve opening period of the exhaust valve is set to a predetermined amount. The amount of fresh air introduced into the system can be increased, and consequently the scavenging of the exhaust system can be performed efficiently.

  Since the valve overlap amount of the intake and exhaust valves 21 and 22 is maximized and the throttle valve 14 is fully opened, scavenging of the exhaust passage can be performed efficiently.

  Since the throttle is opened (throttle fully opened) after the IG switch 51 is turned off, the pump loss during engine inertia rotation is reduced as compared with the case where the throttle is not opened, and the rate of decrease in the engine rotation speed after the IG is turned off is reduced. As a result, a time for increasing the valve overlap amount after the IG is turned off can be secured, and as a result, scavenging of the exhaust system can be performed efficiently.

(Second Embodiment)
Next, a second embodiment of the present invention will be described focusing on differences from the first embodiment. In the first embodiment, the case where the air learning is performed after the predetermined scavenging time has elapsed since the ignition is turned off has been described. The scavenging state at the time of switching to the gas is detected, and the required scavenging time is variably set based on the detected scavenging state. Then, air learning is performed after the required scavenging time has elapsed since the ignition was turned off. This is because, when the exhaust gas in the exhaust passage is replaced with fresh air, the time required for the exhaust passage to be in an atmospheric state is different when comparing the case where scavenging can be performed efficiently and the case where it is not.

  In particular, in the present embodiment, as the scavenging state, the valve overlap amount after the engine rotation is stopped is detected, and the required scavenging time is variably set based on the detected valve overlap amount.

  The reason is as follows. That is, after the IG switch 51 is turned off, the hydraulic pressures of the variable valve mechanisms 25 and 26 decrease as the rotational speed of the engine 10 decreases. If the engine speed decreases to a speed at which hydraulic oil cannot be pumped, the advance or change of valve timing stops at that point, and the valve timing cannot be changed to the target time. It is done. On the other hand, the decrease rate of the engine rotation speed after the IG is turned off varies depending on various operating conditions such as machine differences, rotation load of the engine output shaft (for example, driving state of the air conditioner, alternator, etc.), engine friction, pump loss, etc. For example, as the rotational load on the engine output shaft is larger, the engine rotational speed is significantly reduced after the IG switch 51 is turned off. Therefore, it can be said that the amount of valve overlap after the rotation of the engine 10 stops varies depending on the operation conditions. It is also conceivable that variation occurs in the scavenging state after the rotation of the engine 10 stops due to variations in the valve overlap amount. Therefore, in the present embodiment, the scavenging time is set according to the valve overlap amount after the rotation of the engine 10 is stopped.

  FIG. 4 shows an example of the relationship between the valve overlap amount after the engine stops and the required scavenging time. As illustrated in FIG. 4, the required scavenging time becomes longer as the valve overlap amount after the engine rotation stops is smaller.

  Note that the valve overlap amount after the engine is stopped is estimated based on, for example, the time required from the ignition-off timing to the engine rotation stop and the required stop time. At this time, the shorter the required stop time, the smaller the valve overlap amount after the engine stops. Further, the valve overlap amount after stopping the engine rotation is estimated based on a parameter related to engine friction (for example, engine water temperature) and a parameter related to the rotational load of the engine output shaft (for example, driving state of an air conditioner or an alternator). Specifically, in view of the fact that the larger the engine friction and the rotational load of the engine output shaft, the lower the engine speed after the ignition is turned off. The larger the engine friction or rotational load, the smaller the valve overlap amount after the engine stops. To do. Alternatively, it may be estimated based on the crank angle signal from the crank angle sensor 35 and the cam angle signal from the cam angle sensor 36. Further, intake valve timing and exhaust valve timing when IG is off may be taken into consideration.

  FIG. 5 is a flowchart showing the processing procedure of the atmospheric learning process. This process is executed by the ECU 40 at predetermined intervals. This process is executed by supplying power from the battery 54 to the ECU 40 as the main relay 52 is kept on for a predetermined time after the IG switch 51 is turned off. In the following description, the same processing as in FIG. 2 is given the same step number as in FIG.

  In FIG. 5, first, in step S201, it is determined whether or not the value 0 is set in the time setting flag FTM, and in step S202, it is determined whether or not the value 0 is set in the valve opening execution flag FVL. The time setting flag FTM is a flag indicating that the required scavenging time until the atmospheric learning is executed after the IG switch 51 is turned off, and is set to a value of 1 when the required scavenging time has been set. .

  If it is before the command to set the intake / exhaust valves 21 and 22 and the throttle valve 14 to the predetermined open state and the required scavenging time is not set, an affirmative determination is made in steps S201 and S202. Then, in steps S203 to 206, the same processing as in steps S102 to S104 and S106 in FIG.

  In the subsequent step S207, for example, it is determined whether or not the rotation of the engine 10 has stopped based on the output value of the crank angle sensor 35. If it is determined that the rotation of the engine 10 has stopped, in step S208, the valve overlap amount after the rotation of the engine 10 is detected as the scavenging state of the exhaust passage, and the detected valve overlap amount and FIG. Based on this map, the required time (scavenging required time) until the atmosphere learning is executed after the IG is turned off is set. Also, the value 1 is set in the time setting flag FTM.

  In step S209, it is determined whether or not the required scavenging time has elapsed since the IG was turned off. If the required scavenging time has not elapsed, the present process is terminated. On the other hand, when the required scavenging time has elapsed since the IG was turned off, the process proceeds to step S210, and atmospheric learning is executed. Then, after resetting the time setting flag FTM and the valve opening execution flag FVL to the value 0, the present process is terminated.

  FIG. 6 is a time chart showing a specific mode of atmospheric learning of the present system. 6A to 6E are the same as those in FIG. In FIG. 6, it is assumed that after the IG is turned off, the rotation of the engine 10 stops before the valve overlap amount reaches a predetermined scavenging acceleration amount (here, the maximum overlap amount).

  In FIG. 6, when the IG switch 51 is turned off at timing t21, the throttle opening TH is fully opened, and the valve overlap amount OL is controlled by hydraulic control of the variable valve mechanisms 25 and 26 so as to become the maximum value Lmax. The timing is changed to the advance side or the retard side. When the engine rotational speed NE gradually decreases as the IG switch 51 is turned off, and eventually decreases to a rotational speed at which the hydraulic oil cannot be pumped, the advance or retard change of the valve timing is stopped at the timing t22. The valve overlap amount OL is smaller than the maximum value Lmax. In this case, a longer time TB is set as the required scavenging time than when the valve overlap amount OL is set to the maximum value Lmax.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  Since the scavenging state of the exhaust passage after the rotation of the engine 10 is detected and the required scavenging time is variably set based on the detected scavenging state, the time required for executing the air learning is set as the scavenging time of the exhaust passage. It can be set according to the degree of promotion. Therefore, even in a situation where scavenging of the exhaust passage cannot be performed efficiently, it is possible to execute atmospheric learning after waiting for the exhaust passage to reliably enter the atmospheric state.

  In view of the fact that the rate of decrease in engine speed after a request to stop the engine 10 varies depending on various operating conditions, the amount of valve overlap after engine rotation stops varies. As described above, the valve overlap amount after stopping the rotation of the engine 10 is detected and the scavenging time is set based on the detected valve overlap amount. Therefore, regardless of the valve overlap amount after stopping the engine rotation, After learning that the exhaust passage is surely in the atmospheric state, the air learning can be executed.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In the embodiment described above, the valve overlap amount is controlled by the engine-driven variable valve mechanisms 25 and 26 when the IG switch 51 is turned off, and the throttle valve 14 is fully opened. After the IG switch 51 is turned off, the valve overlap amount may be controlled after the rotation of the engine 10 is stopped, and the throttle valve 14 may be fully opened. In this case, the variable valve mechanism 25 is electrically operated.

  -By controlling the valve overlap amount, the total valve opening amount in a state where the intake valve 21 and the exhaust valve 22 are simultaneously opened after the engine is stopped is set to a predetermined scavenging acceleration amount. The total opening amount of the valve may be controlled to be a predetermined scavenging acceleration amount.

  In the above embodiment, the valve overlap amount is changed by making the camshaft phase variable, but even if the valve overlap amount is changed by making the valve lift amounts of the intake and exhaust valves 21 and 22 variable. Good. Alternatively, the valve overlap amount may be changed depending on both the phase of the cam shaft and the valve lift amount.

  In the second embodiment, the valve overlap amount after the engine rotation is stopped is detected as the scavenging state of the exhaust passage, and the required scavenging time is variably set based on the detected valve overlap amount. Instead of or in addition to the valve overlap amount, it is also possible to detect the valve lift amount after stopping the engine rotation as the scavenging state of the exhaust passage and variably set the required scavenging time based on the detected valve lift amount. .

  In the second embodiment, the time until the atmospheric learning is performed after the IG switch 51 is turned off is set as the scavenging time, and the scavenging time is set according to the scavenging state of the exhaust passage. The required time may be a time from when at least one of the throttle valve 14 and the intake / exhaust valves 21 and 22 is in a predetermined open state until the air learning is executed. Or it is good also as time from the rotation stop of the engine 10 to performing atmospheric learning. In other words, the scavenging time is not limited as long as it indicates the time required for the exhaust passage to be in the atmospheric state before the atmospheric learning is performed, and any timing may be used as the starting point.

  When performing atmospheric learning, the atmospheric air learning may be performed by closing the throttle valve 14 from the fully open state (for example, the fully closed state or limp home opening). In this case, the exhaust flow velocity in the exhaust passage is smaller than that in the throttle fully opened state. Thereby, the gas atmosphere around the oxygen concentration sensor 32 can be stabilized, and the sensor output can be stabilized.

  In the above-described embodiment, the variable valve mechanisms 25 and 26 are engine driven types that variably control the valve timing by controlling the hydraulic pressure of the hydraulic circuit by the hydraulic oil pump driven by the rotational force of the engine 10, The configuration of the variable valve mechanisms 25 and 26 is not limited to this. For example, the hydraulic oil pump may be an electric type instead of an engine driving type driven by the rotational force of the engine. Further, instead of the configuration in which the valve timing is changed by controlling the hydraulic pressure of the hydraulic circuit by the hydraulic oil pump, for example, an electric variable valve that changes the valve timing by electrically rotating the cam shafts 27 and 28, for example. The mechanism may be applied to the present invention.

  In the above embodiment, after the IG switch 51 is turned off, the three open / close valves of the intake valve 21, the exhaust valve 22 and the throttle valve 14 are controlled to be in a predetermined open state. It is good also as a structure which controls an on-off valve to a predetermined valve opening state. In this case, a variable valve mechanism for a valve to be controlled in the valve opening mode may be mounted.

  In the above embodiment, a gasoline engine has been described. However, the engine 10 is not limited to a gasoline engine, and the present invention may be applied to a diesel engine.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 14 ... Throttle valve (open / close valve), 21 ... Intake valve (open / close valve), 22 ... Exhaust valve (open / close valve), 25, 26 ... Variable valve mechanism, 32 ... Oxygen concentration sensor, 40 ... ECU (stop) Request determination means, on-off valve control means, learning execution means, scavenging state detection means, time setting means).

Claims (6)

Applied to an internal combustion engine having an on-off valve that adjusts the state of intake or exhaust of gas into a combustion chamber of the internal combustion engine and an oxygen concentration sensor that detects an oxygen concentration in exhaust gas in an exhaust passage of the internal combustion engine, In the oxygen concentration sensor atmospheric learning device that performs atmospheric learning of the sensor output value based on the output value of the oxygen concentration sensor when the passage is in the atmospheric state,
Stop request determination means for determining that there has been a request to stop the internal combustion engine;
An open / close valve control means for controlling the open / close valve to a predetermined open state when it is determined by the stop request determination means that there is an operation stop request;
Learning control means for executing the atmospheric learning after controlling the open / close valve to the open state by the open / close valve control means;
An atmosphere learning device for an oxygen concentration sensor, comprising: The on-off valve is at least one of an intake valve and an exhaust valve of the internal combustion engine;
The on-off valve control means sets the intake air state so that a sum of valve opening amounts when the intake valve and the exhaust valve are simultaneously opened after the internal combustion engine is stopped becomes a predetermined scavenging acceleration amount as the valve opening state. The atmosphere learning device for an oxygen concentration sensor according to claim 1, wherein the valve opening mode of at least one of the valve and the exhaust valve is controlled.   The on-off valve control means adjusts a valve overlap amount in which the valve opening period of the intake valve and the valve opening period of the exhaust valve overlap as the valve open state, thereby calculating the sum of the valve opening amounts. The atmosphere learning device for an oxygen concentration sensor according to claim 2, which controls the scavenging acceleration amount. A scavenging state detecting means for detecting a scavenging state of the exhaust passage after rotation of the internal combustion engine is stopped;
Based on the scavenging state detected by the scavenging state detection means, a time setting means for setting a required time from the predetermined timing after the operation stop request to the execution of the atmospheric learning;
An atmosphere learning device for an oxygen concentration sensor according to claim 1 or 2. Applied to an internal combustion engine comprising an engine-driven variable valve mechanism that variably controls the valve timing of at least one of an intake valve and an exhaust valve of the internal combustion engine;
The on-off valve control means adjusts the valve overlap amount in which the valve opening period of the intake valve and the valve opening period of the exhaust valve overlap as the valve open state by the variable valve mechanism,
The scavenging state detection means detects the valve overlap amount when the rotation of the internal combustion engine is stopped as the scavenging state,
The oxygen concentration sensor atmosphere learning device according to claim 4, wherein the time setting means sets the required time based on a valve overlap amount detected by the scavenging state detection means. The on-off valve is a throttle valve that adjusts a cross-sectional area of an intake passage of the internal combustion engine;
The oxygen concentration sensor atmosphere learning according to any one of claims 1 to 5, wherein the on-off valve control unit opens the throttle valve when the stop request determination unit determines that there is an operation stop request. apparatus.

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