JP2008286070A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve learning accuracy by removing influence of temperature change in learning individual difference or the like of oxygen concentration detection means in an internal combustion engine. <P>SOLUTION: ECU 52 executes atmosphere learning for correcting individual difference or the like of the oxygen concentration sensors 46 during executing fuel cut operation. In this case, when the operation condition of the internal combustion engine 10 is changed over or right after start of electricity supply to a heater 46c of the oxygen concentration sensor 46, it is determined that the temperature condition of the oxygen concentration sensor 46 has not been stabilized and atmosphere learning is prohibited until a predetermined stand-by time passes. It is avoided that atmosphere learning is provided using low accuracy detection signal outputted form the oxygen concentration sensor 46 when the temperature condition of the oxygen concentration sensor 46 is not stabilized. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for controlling the operating state of an internal combustion engine, and more particularly to a control device for an internal combustion engine configured to control an air-fuel ratio in accordance with an oxygen concentration in exhaust gas.

  Conventionally, as disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-3903), a control device that performs air-fuel ratio control using an oxygen concentration sensor provided in an exhaust passage is known. In this case, the oxygen concentration sensor has a unique error for each sensor including manufacturing variations (individual differences), deterioration with time, and the like. Therefore, in a conventional control device, learning control called atmospheric learning is performed in order to correct a sensor-specific error.

  In this air learning, first, when a predetermined delay time has elapsed since the start of engine fuel cut control, it is determined that the exhaust passage has become an air atmosphere, and air learning is started. Here, the delay time is a time required from the start of fuel cut until the inside of the exhaust passage becomes an atmospheric atmosphere. For this reason, after the delay time has elapsed, a detection signal corresponding to the oxygen concentration in the atmosphere is output from the oxygen concentration sensor.

  In the air learning, the detection signal value during the fuel cut is compared with the final reference output value stored in the control device. Here, the final reference output value is a signal value obtained by detecting the oxygen concentration in the atmosphere with an oxygen concentration sensor serving as a standard device that eliminates an error inherent to the sensor, and appropriately correcting the detected value. As a result, the amount of deviation between the detection signal value during the fuel cut and the final reference output value becomes a value corresponding to an error specific to the oxygen concentration sensor. This deviation amount is stored in the control device as a learning value for correcting an error inherent to the sensor, and is used for subsequent air-fuel ratio control.

JP 2003-3903 A

  In the prior art, by providing a delay time after the start of fuel cut, air learning is not started when the atmosphere in the exhaust passage is unstable. However, immediately after the start of the fuel cut, not only the atmosphere in the exhaust passage becomes unstable, but also the temperature of the oxygen concentration sensor tends to fluctuate according to the temperature of the exhaust gas and the like. Such a temperature change of the sensor may affect the output characteristics of the sensor, and may reduce the learning accuracy of atmospheric learning.

  For this reason, in the prior art, even if the air learning is started after the delay time has elapsed, the oxygen concentration sensor may still be at a low temperature or the sensor temperature may not be stable. That is, there is a problem that it is difficult to perform atmospheric learning with high accuracy only by setting a delay time in consideration of the atmosphere in the exhaust passage.

  The present invention has been made to solve the above-described problems, and can prevent the learning value from being influenced by a temperature change when learning an error or the like of the oxygen concentration detecting means. An object of the present invention is to provide a control device for an internal combustion engine capable of improving accuracy.

1st invention detects the oxygen concentration in the exhaust gas discharged | emitted from an internal combustion engine, The oxygen concentration detection means which outputs a detection signal,
Temperature state determination means for determining whether or not the temperature of the oxygen concentration detection means is in a stable state when a fuel cut operation of the internal combustion engine is being performed;
Learning means for performing learning using a detection signal output from the oxygen concentration detection means when the temperature state determination means determines that the temperature of the oxygen concentration detection means is in a stable state;
Learning prohibiting means for prohibiting the operation of the learning means when the temperature state determining means determines that the temperature of the oxygen concentration detecting means is in an unstable state;
It is characterized by providing.

  According to a second aspect of the present invention, the temperature state determination means is such that the temperature of the oxygen concentration detection means is in an unstable state until a standby time elapses from the time when the operating state of the internal combustion engine shifts from high output operation to normal operation. It is determined that the temperature of the oxygen concentration detection unit has shifted to a stable state when the standby time has elapsed from the time when the operating state has shifted.

  According to a third aspect of the present invention, the temperature state determination means is such that the temperature of the oxygen concentration detection means is in an unstable state until a standby time elapses from the time when the operation state of the internal combustion engine has shifted from the fuel cut operation to the idle operation. It is determined that the temperature of the oxygen concentration detection unit has shifted to a stable state when the standby time has elapsed from the time when the operating state has shifted.

  According to a fourth aspect of the present invention, the oxygen concentration detection unit includes an element unit capable of detecting the oxygen concentration in a heated state, and a heater that heats the element unit when energized, and the temperature state determination unit includes: The temperature of the oxygen concentration detection means is determined to be in an unstable state until the standby time elapses from the time when energization of the heater is started, and when the standby time elapses from the time of the energization start, It is configured to determine that the temperature of the oxygen concentration detection means has shifted to a stable state.

  According to a fifth aspect of the present invention, there is provided an exhaust temperature detecting means for detecting the temperature of the exhaust gas, and the temperature state determining means is configured such that the temperature of the oxygen concentration detecting means is in accordance with the exhaust gas temperature detected by the exhaust temperature detecting means. It is configured to determine whether or not it is in a stable state.

6th invention detects the oxygen concentration in the exhaust gas discharged | emitted from an internal combustion engine by an element part, and the oxygen concentration detection means which derives | leads-out the detection signal output from the said element part by a lead part,
Exhaust temperature detecting means for detecting the temperature of the exhaust gas;
Temperature correction means for correcting the detection signal of the oxygen concentration detection means using the temperature of the exhaust gas detected by the exhaust temperature detection means when the fuel cut operation of the internal combustion engine is being performed;
Learning means for performing learning using the detection signal corrected by the temperature correction means;
It is characterized by providing.

  In the seventh invention, the temperature correction means estimates the temperature of the lead portion of the oxygen concentration detection means according to the temperature of the exhaust gas, and corrects the detection signal of the oxygen concentration detection means using the estimated temperature. It is configured.

  In an eighth aspect of the invention, the oxygen concentration detection means includes a heater that heats the element portion when energized, and the temperature correction means includes the time elapsed since the energization of the heater was started and the exhaust gas. The temperature of the lead portion of the oxygen concentration detecting means is estimated according to the temperature of the oxygen concentration, and the detection signal of the oxygen concentration detecting means is corrected using this estimated temperature.

  According to the first invention, the temperature state determining means can determine whether or not the temperature of the oxygen concentration detecting means is in a stable temperature equilibrium state when the fuel cut operation of the internal combustion engine is being performed. it can. Thereby, when the temperature of the oxygen concentration detection means is not stable, the learning means can be prohibited until the temperature is stabilized, and the learning means can be implemented after the temperature is stabilized.

  For this reason, the oxygen concentration detection means can output an accurate detection signal in a stable temperature state when the learning means is implemented. The learning means can learn the error of the oxygen concentration detection means with high accuracy using this accurate detection signal. Therefore, it is possible to prevent the learning value from being influenced by the temperature change of the oxygen concentration detection means, and the learning accuracy can be improved.

  According to the second aspect of the invention, when the internal combustion engine shifts from the high output operation (high load or high rotation) to the normal operation, the temperature of the exhaust gas decreases, so the temperature of the oxygen concentration detection means is transiently unstable. It is easy to be in a state. In this state, even if the fuel cut operation is started before a sufficient standby time has elapsed, the temperature state determination unit can determine that the temperature of the oxygen concentration detection unit is in an unstable state. When the standby time has elapsed, it can be determined that the temperature of the oxygen concentration detection means has stabilized. Therefore, it is possible to prevent the learning accuracy from being lowered when returning from the high output operation.

  According to the third invention, when the internal combustion engine shifts from the fuel cut operation to the idle operation, the temperature of the exhaust gas rises, so that the temperature of the oxygen concentration detection means tends to become transiently unstable. In this state, the temperature state determination unit can easily determine the temperature state of the oxygen concentration detection unit depending on whether or not a sufficient standby time has elapsed from the time when the operation has shifted. Therefore, it is possible to prevent the learning accuracy from being lowered due to the shift to the idle operation.

  According to the fourth aspect of the present invention, the temperature tends to become transiently unstable from the start of energization to the heater of the oxygen concentration detection means until the whole is warmed. In this state, the temperature state determination means can easily determine the temperature state of the oxygen concentration detection means depending on whether or not a sufficient standby time has elapsed since the start of energization. Therefore, it is possible to prevent the learning accuracy from being reduced immediately after the oxygen concentration detecting means is started.

  According to the fifth aspect, when the temperature of the exhaust gas changes, the temperature of the oxygen concentration detecting means exposed to the flow tends to become transiently unstable. In this case, the temperature state determination means can easily determine the temperature state of the oxygen concentration detection means according to the temperature of the exhaust gas detected by the exhaust temperature detection means. That is, the execution and prohibition of the learning means can be switched according to simple determination conditions that encompass changes in the driving state and the like, and the determination process can be simplified.

  According to the sixth aspect of the invention, the temperature of the oxygen concentration detecting means tends to be unstable due to temperature variation between the element portion and the lead portion when the temperature of the exhaust gas changes. On the other hand, the temperature correction means can appropriately correct the detection signal of the oxygen concentration detection means including the temperature variation according to the temperature of the exhaust gas. For this reason, the learning means can perform highly accurate learning using the corrected detection signal even when the temperature of the oxygen concentration detection means is unstable. In addition, the learning operation can be performed at a high frequency regardless of the temperature state of the oxygen concentration detection means, so that the learning efficiency can be improved.

  According to the seventh aspect, the temperature correction means can estimate the temperature of the lead portion of the oxygen concentration detection means using the temperature of the exhaust gas. The detection signal of the oxygen concentration detection means can be corrected with high accuracy according to the estimated temperature.

  According to the eighth invention, the temperature correction means can estimate the temperature of the lead portion more accurately according to the temperature of the exhaust gas and the energization time (temperature) of the heater. As a result, for example, the temperature of the lead portion can be accurately grasped including immediately after the start of the oxygen concentration detecting means. And the temperature correction means can perform highly accurate correction according to this exact temperature. Therefore, learning opportunities can be increased including immediately after the start of the internal combustion engine, and the learning efficiency can be increased.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. An internal combustion engine 10 shown in FIG. 1 is configured by, for example, a four-cylinder diesel engine.

  An intake passage 12 for sucking air (intake air) is provided in each cylinder on the intake side of the internal combustion engine 10. The intake passage 12 is connected to an intake port of each cylinder via an intake manifold 14. The intake passage 12 is provided with a throttle valve 16 for adjusting the intake air amount of the internal combustion engine 10.

  On the other hand, on the exhaust side of the internal combustion engine 10, an exhaust passage 18 for exhausting exhaust gas generated in each cylinder to the outside is provided. The exhaust passage 18 is connected to an exhaust port of each cylinder via an exhaust manifold 20. Further, an exhaust purification catalyst 22 is provided in the exhaust passage 18. The exhaust purification catalyst 22 purifies components such as NOx contained in the exhaust gas and collects particulates (PM) in the exhaust gas.

  Each cylinder of the internal combustion engine 10 is provided with a fuel injection valve 24 that directly injects fuel into the cylinder. A fuel pump 28 is connected to these fuel injection valves 24 via a common rail 26. A fuel addition valve 32 is connected to the fuel pump 28 via a fuel passage 30. The fuel addition valve 32 is for adding fuel to the exhaust gas flowing in the exhaust passage 18 (exhaust manifold 20). The fuel passage 30 is provided with a shut-off valve 34 that opens and closes the fuel passage 30.

  Further, an EGR passage 36 for performing EGR (Exhaust Gas Recirculation) control is provided between the intake passage 12 and the exhaust passage 18 (exhaust manifold 20). The EGR passage 36 is provided with an EGR valve 38 that adjusts the flow rate of exhaust gas flowing through the EGR passage 36. A turbocharger 40 is provided between the intake passage 12 and the exhaust passage 18 to supercharge intake air using the pressure of the exhaust gas.

  Next, a sensor system of the internal combustion engine 10 will be described. The intake passage 12 is provided with an air flow meter 42 for detecting the intake air amount of the internal combustion engine 10. In the exhaust passage 18, an exhaust temperature sensor 44 serving as an exhaust temperature detecting means for detecting the temperature of the exhaust gas upstream of the exhaust purification catalyst 22, and an oxygen concentration serving as an oxygen concentration detecting means for detecting the oxygen concentration in the exhaust gas. A sensor 46 is provided. Further, the internal combustion engine 10 includes a rotation sensor 48 that outputs a signal corresponding to its operating rotational speed (engine rotational speed), and an accelerator opening sensor 50 that detects an operation amount (accelerator opening) of an accelerator pedal (not shown). Is provided.

  Further, the system configuration of the present embodiment includes an ECU (Electronic Control Unit) 52 that controls the operating state of the internal combustion engine 10. A sensor system including the air flow meter 42 and the above-described sensors 44, 46, 48 and 50 is connected to the input side of the ECU 52. Various actuators including a fuel injection valve 24, a fuel pump 28, a fuel addition valve 32, a shutoff valve 34, an EGR valve 38, and the like of each cylinder are connected to the output side of the ECU 52. Then, the ECU 52 controls these actuators while detecting the operating state of the internal combustion engine 10 using the sensor system described above.

  Further, the ECU 52 includes a storage circuit 52a composed of a ROM, a RAM, and the like. Here, the RAM also includes a non-volatile updatable storage element, and a learning value that is updated by atmospheric learning or the like described later is stored in the storage element. The ROM stores programs for executing various controls, constants, and the like in advance.

  Next, various controls (operations) executed by the ECU 52 will be described. First, the ECU 52 detects the intake air amount by the air flow meter 42 and controls the fuel injection amount of the fuel injection valve 24 according to the intake air amount and the like. This fuel injection control is performed so that the air-fuel ratio of the air-fuel mixture becomes the target air-fuel ratio.

  Further, the ECU 52 detects this state by detection signals from the rotation sensor 48, the accelerator opening sensor 50, etc., for example, when deceleration from a high rotation operation is performed, and temporarily stops fuel injection. Perform fuel cut control. Further, when the operator does not perform the accelerator operation, the ECU 52 detects this state by a detection signal from the accelerator opening sensor 50 or the like, and keeps the rotational speed of the internal combustion engine 10 at a predetermined low idle rotational speed. Take control.

  On the other hand, the ECU 52 detects the oxygen concentration in the exhaust gas by the oxygen concentration sensor 46 during the fuel injection control. Then, the fuel injection amount is feedback-controlled so that the actual air-fuel ratio obtained according to the detection result of the oxygen concentration becomes the target air-fuel ratio, thereby performing the air-fuel ratio control.

  In this case, the oxygen concentration sensor 46 has a unique error for each sensor including manufacturing variations (individual differences), deterioration with time, and the like. Therefore, the ECU 52 performs atmospheric learning for learning a sensor-specific error based on the known atmospheric oxygen concentration.

  This air learning is performed by storing, for example, a detection signal output from the oxygen concentration sensor 46 as a learning value when the inside of the exhaust passage 18 becomes an air atmosphere by the fuel cut operation. The learning value at this time includes a numerical component corresponding to the actual oxygen concentration in the atmosphere and a numerical component corresponding to the sensor-specific error. On the other hand, the standard signal value of the sensor signal is stored in advance in the storage circuit 52a of the ECU 52. This standard signal value is a detection signal value obtained by detecting the oxygen concentration in the atmosphere using, for example, an oxygen concentration sensor that is a standard device that eliminates errors inherent in the sensor.

  When performing air-fuel ratio control, first, the reference signal value is calculated by correcting the standard signal value according to the current operating environment (for example, the pressure loss of the exhaust system, the magnitude of atmospheric pressure, etc.). To do. Next, the difference between the reference signal value and the learned value read from the storage circuit 52a is obtained as a sensor-specific error, and the actual detection signal of the oxygen concentration sensor 46 is corrected according to this error.

  Next, the structure of the oxygen concentration sensor 46 will be described with reference to FIG. The oxygen concentration sensor 46 includes an element portion 46 a exposed to the exhaust gas flowing in the exhaust passage 18, a lead portion 46 b connected to the element portion 46 a, and a heater 46 c disposed in the vicinity of the element portion 46. ing.

  The heater 46c is connected to the output side of the ECU 52, and generates heat when energized from the ECU 52. The element portion 46a is activated by being heated by the heater 46c, and in this state, the oxygen concentration in the exhaust gas is detected. The lead part 46b is connected to the input side of the ECU 52 via a connector, wiring, or the like, and is configured to derive a detection signal output from the element part 46a toward the ECU 52.

[Features of Embodiment 1]
As described above, the ECU 52 performs air learning using the detection signal of the sensor in the air atmosphere in order to correct the individual difference of the oxygen concentration sensor 46. In this case, the accuracy of the detection signal is easily affected by the temperature state of the sensor. Therefore, the ECU 52 controls the energization state of the heater 46c so that the AC resistance (impedance) of the sensor becomes constant, for example. For this reason, if the temperature state of the oxygen concentration sensor 46 is stable, the temperature of the element portion 46a should be maintained at a substantially constant temperature corresponding to the impedance of the entire sensor.

  However, when the temperature of the exhaust gas changes around the oxygen concentration sensor 46, the effect of this temperature change is different in each part of the sensor, so that a transient temperature difference occurs between the element part 46a and the lead part 46b, for example. There is a case. In this case, even when the impedance of the entire sensor is controlled to be substantially constant, the impedance of the element portion 46a changes so as to compensate for the temperature change (change in resistance value) of the lead portion 46b included therein. . Therefore, in such a transition period of temperature change, the temperature of the element unit 46a deviates from the target value, and an error occurs in the detection signal of the sensor, so that the accuracy of air learning is likely to be lowered.

  For this reason, in the present embodiment, the temperature state of the oxygen concentration sensor 46 is determined based on a predetermined determination condition, and atmospheric learning is prohibited according to the determination result. Hereinafter, this determination condition will be described with three specific examples.

(First judgment condition)
First, the ECU 52 performs a predetermined time when the operation state of the internal combustion engine 10 shifts from a high output operation (hereinafter, a combination of a high rotation operation and a high load operation to a high output operation) to a normal operation. Atmospheric learning is prohibited until the time has passed. That is, when the internal combustion engine 10 shifts from the high output operation to the normal operation, the temperature of the exhaust gas flowing around the oxygen concentration sensor 46 decreases from the high temperature to the temperature during the normal operation.

  At this time, the ECU 52 determines that the temperature of the oxygen concentration sensor 46 is in a transient non-stable state (that is, a state in which temperature variation occurs between the element portion 46a and the lead portion 46b), and performs predetermined standby. Air learning is prohibited until time t1 has elapsed. Then, atmospheric learning is performed after the waiting time t1 has elapsed. This standby time t1 is defined as the time required for the temperature of the oxygen concentration sensor 46 (or the exhaust gas around the sensor) to stabilize after the operating state shifts, and is stored in advance in the storage circuit 52a. Is.

  Here, the determination process of the high output operation and the normal operation will be described. The ECU 52 performs a high rotation when the operating rotational speed (engine rotational speed) of the internal combustion engine 10 detected by the rotation sensor 48 is larger than a predetermined determination value. Judge as driving. Further, the ECU 52 uses a number of appropriate parameters including the engine speed, the intake air amount detected by the air flow meter 42, and the accelerator opening detected by the accelerator opening sensor 50 to load the internal combustion engine 10. The state is calculated as a numerical value. When the load state value is larger than a predetermined determination value, it is determined that the operation is a high load operation. Furthermore, when it is determined that neither high-speed operation nor high-load operation is performed, it is determined that the operation is normal.

(Second determination condition)
Further, when the operation state of the internal combustion engine 10 shifts from the fuel cut operation to the idle operation, the temperature of the exhaust gas flowing around the sensor rises from the low temperature in the unburned state to the temperature during normal operation. Also in this case, the ECU 52 determines that the temperature of the sensor is in an unstable state, and prohibits atmospheric learning until a predetermined standby time t2 has elapsed. The standby time t2 is also defined in the same manner as the standby time t1, and is stored in advance in the storage circuit 52a.

(Third determination condition)
On the other hand, the ECU 52 measures the time that has elapsed since the energization of the heater 46c of the oxygen concentration sensor 46 was started. Then, it is determined that each part of the sensor has not reached a stable temperature equilibrium state after the energization of the heater 46c is started and until a predetermined waiting time t3 elapses. Also in this case, atmospheric learning is prohibited until a predetermined waiting time t3 has elapsed. This standby time t3 is defined as the time required from the start of energization to the heater 46c until the sensor element portion 46a and the lead portion 46b reach a stable temperature state, and is stored in advance in the storage circuit 52a. ing.

[Specific Processing for Realizing Embodiment 1]
FIG. 3 is a flowchart of a routine executed by the ECU 52 in order to realize the system operation of the present embodiment. Note that this routine is started immediately after the internal combustion engine 10 is started, and the processing of steps 100 to 118 is repeated until the internal combustion engine 10 is stopped.

  First, in step 100, the ECU 52 performs normal fuel injection control. When the operator performs a deceleration operation or the like, fuel cut control is performed as necessary. In step 102, it is determined whether or not the fuel cut operation is started. If it is started, it is determined in step 104 whether or not the inside of the exhaust passage 18 is an atmospheric atmosphere.

  Specific examples of the determination conditions in step 104 include (1) whether or not the engine is decelerating from an operating state where the engine speed is equal to or greater than a predetermined value, and (2) a predetermined value from the start of deceleration (or the end of accelerator operation) Whether or not time has passed, (3) whether or not a certain time has passed since fuel addition control, and the like. The fuel addition control is a process for reducing the exhaust purification catalyst 22 by adding fuel from the fuel addition valve 32 to the exhaust passage 18.

  If these conditions (1) to (3) are satisfied, it is determined that the exhaust passage 18 is in the atmosphere, and in step 106, the operation state of the internal combustion engine 10 is high output operation (ie, high load or It is determined whether or not the normal operation is shifted from the high rotation state. In this case, the load state of the internal combustion engine 10 can be detected according to the intake air amount, the engine speed, the accelerator opening, and the like.

  When it is determined in step 106 that there has been a transition from high output operation to normal operation, in step 108, the timer counter that has started the timing operation from this transition time is read out, so that a predetermined standby is performed after the operation state has shifted. It is determined whether time t1 has elapsed. Further, when it is determined in step 106 that there is no shift in operation, the process proceeds to the next determination process in step 110.

  If the standby time t1 has already elapsed at the time of processing in step 108, the temperature change of the exhaust gas that occurs during the transition from the high output operation to the normal operation reaches an equilibrium state, and the element of the oxygen concentration sensor 46 It is determined that the temperature of the portion 46a and the lead portion 46b is stabilized. Therefore, in this case, the process proceeds to the next determination process in step 110.

  When the standby time t1 has not elapsed in step 108, it is determined that the temperature change of the exhaust gas is still transient and the temperature of the oxygen concentration sensor 46 is also in an unstable state. In this case, therefore, the routine proceeds to step 118 where atmospheric learning is prohibited and the current routine is terminated.

  Next, in step 110, it is determined whether or not the operating state of the internal combustion engine 10 has shifted from the fuel cut operation to the idle operation. If it is determined in step 110 that there has been a shift in operation, it is determined in step 112 whether or not a predetermined waiting time t2 has elapsed since the shift point. Further, when it is determined in step 110 that there is no shift in operation, the process proceeds to the next determination process in step 114.

  When the standby time t2 has already elapsed at the time of processing in step 112, it is determined that the temperature of the oxygen concentration sensor 46 has stabilized, as in step 108. Therefore, in this case, the process proceeds to the next determination process in step 114. If the standby time t2 has not elapsed in step 112, it is determined that the temperature of the oxygen concentration sensor 46 is in an unstable state, and atmospheric learning is prohibited in step 118.

  Next, in step 114, it is determined whether or not a predetermined waiting time t3 has elapsed since the energization of the heater 46c of the oxygen concentration sensor 46 was started. Then, when the standby time t3 has already elapsed at the time of processing in step 114, it is determined that the temperature of the oxygen concentration sensor 46 is stabilized in substantially the same manner as in step 108. Therefore, in this case, atmospheric learning is performed in step 116.

  Further, when the standby time t3 has not elapsed in step 114, it is determined that the heating of the element portion 46a and the lead portion 46b by the heater 46c has not been completed. That is, in this case, since the temperature of the oxygen concentration sensor 46 is in an unstable state, air learning is prohibited in step 118.

  Thus, in the system according to the present embodiment, it is possible to determine whether or not the temperature of the oxygen concentration sensor 46 is in a stable temperature equilibrium state when performing atmospheric learning. Thereby, when the temperature of the sensor 46 is not stable, atmospheric learning can be prohibited until the temperature is stabilized, and atmospheric learning can be performed at an appropriate timing when the temperature is stable. For this reason, at the time of atmospheric learning, an accurate detection signal output from the oxygen concentration sensor 46 can be used, and its error and the like can be learned with high accuracy. Therefore, the learning value can be prevented from being affected by the temperature change of the sensor 46, and the learning accuracy can be improved.

  In this case, as a first determination condition, the ECU 52 determines that the sensor 46 is in an unstable state from when the internal combustion engine 10 shifts from the high output operation to the normal operation until a predetermined waiting time t1 elapses. ing. Further, as a second determination condition, it is determined that the sensor 46 is in an unstable state until a predetermined standby time t2 elapses after the internal combustion engine 10 shifts from the fuel cut operation to the idle operation. Further, as a third determination condition, it is determined that the sensor 46 is in an unstable state from when the energization of the sensor heater 46c is started until the standby time t3 elapses.

  For this reason, when the temperature of the exhaust gas changes due to switching of the operation state or the like, the temperature state of the oxygen concentration sensor 46 can be appropriately determined based on the first and second determination conditions. In addition, the temperature state of the sensor 46 can be appropriately determined based on the third determination condition from when the heating of the sensor 46 is started until the entire sensor is warmed. Therefore, by combining these conditions, it is possible to appropriately set the execution timing of the atmospheric learning for various operating states of the internal combustion engine 10. Then, it is possible to prevent the learning accuracy from being lowered by performing atmospheric learning under inappropriate conditions.

  In the first embodiment described above, steps 106 to 114 in FIG. 3 show specific examples of the temperature state determination means in the first to fourth inventions. Step 116 shows a specific example of learning means, and step 118 shows a specific example of learning prohibiting means.

  In the first embodiment, the atmosphere learning execution timing is set by combining the first to third determination conditions. However, the present invention is not limited to this, and any one or two of the first to third determination conditions may be used.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. The system of the present embodiment uses the system configuration shown in FIGS. 1 and 2 as in the first embodiment. However, the present embodiment is different from the first embodiment in that it is realized by using the routine shown in FIG. 4 instead of the routine shown in FIG.

[Features of Embodiment 2]
In the system of the present embodiment, the exhaust gas temperature sensor 44 first detects the exhaust gas temperature Tg. For example, when the change amount ΔT per time of the temperature Tg is larger than a predetermined determination value T0, the standby time t4 is calculated according to the magnitude of the change amount ΔT, and atmospheric learning is performed until the standby time t4 elapses. The configuration is prohibited.

  In this case, the determination value T0 is defined as a large change amount of the exhaust gas temperature that causes a temperature variation in each part of the oxygen concentration sensor 46. The determination value T0 is stored in advance in the storage circuit 52a of the ECU 52. The waiting time t4 is configured as map data whose value changes according to the magnitude of the change amount ΔT, for example, and is stored in advance in the storage circuit 52a.

[Specific Processing for Realizing Embodiment 2]
FIG. 4 is a flowchart of a routine executed by the ECU 52 in order to realize the system operation of the present embodiment. In the description of this routine, the same steps as those in the first embodiment (FIG. 3) are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, first, similarly to the first embodiment, the processing of steps 100 to 104 is performed. Next, at step 200, the exhaust gas temperature sensor 44 detects the exhaust gas temperature Tg. In step 202, it is determined whether or not the change amount ΔT per unit time of the temperature Tg is larger than the determination value T0. When the change amount ΔT of the exhaust gas temperature is larger than the determination value T 0, it is determined that the oxygen concentration sensor 46 is affected by the temperature, and the waiting time t 4 is calculated in step 204.

  In this step 204, first, the waiting time t4 having a time length corresponding to the magnitude of the change amount ΔT is calculated by referring to the map data in the storage circuit 52a using the change amount ΔT. In step 206, it is determined whether or not the standby time t4 has elapsed since the change in the exhaust gas temperature was detected.

  Here, when the standby time t4 has elapsed, it is determined that sufficient time has passed for the temperature of the oxygen concentration sensor 46 to return to a stable state even after the exhaust gas temperature Tg has changed significantly. That is, in this case, if attention is paid only to the temperature change of the exhaust gas, it is in a state where the air learning may be executed, so the process proceeds to step 114 and the same processing as in the first embodiment is performed.

  Further, when the waiting time t4 has not elapsed in step 206, there is a possibility that the influence of the temperature change of the exhaust gas still remains in the oxygen concentration sensor 46. Therefore, in this case, atmospheric learning is prohibited in step 118.

  On the other hand, when it is determined in step 202 that the exhaust gas temperature change amount ΔT is equal to or less than the determination value T 0, it is determined that the temperature of the oxygen concentration sensor 46 is in a stable state, and the routine proceeds to step 114 and the first embodiment. The same process is continued.

  As described above, in the system according to the present embodiment, when the change amount ΔT of the exhaust gas temperature Tg is larger than the determination value T0, the air learning is prohibited until the standby time t4 elapses. Thereby, the ECU 52 can easily determine the temperature state of the oxygen concentration sensor 46 according to the temperature Tg of the exhaust gas. That is, the execution and prohibition of atmospheric learning can be switched according to simple determination conditions that include changes in operating conditions, etc., and the determination process can be simplified.

  Moreover, the standby time t4 is set to a time length corresponding to the temperature change amount ΔT. For this reason, for example, when the change amount ΔT is large, a long time until the influence of the temperature change is eliminated can be set as the standby time t4. When the temperature change amount ΔT is small, the standby time t4 can also be set to a small value, and the standby time t4 can be minimized to increase the learning opportunities.

  In the second embodiment described above, steps 200 to 206 in FIG. 4 show specific examples of the temperature state determination means in the first and fifth inventions. Step 116 shows a specific example of learning means, and step 118 shows a specific example of learning prohibiting means.

  In the second embodiment, the exhaust temperature sensor 44 is used as the exhaust temperature detecting means. However, the present invention is not limited to this, and the exhaust gas temperature may be estimated by software or the like without using the exhaust temperature sensor 44, for example.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG. The system of the present embodiment uses the system configuration shown in FIGS. 1 and 2 as in the first embodiment. However, the present embodiment is different from the first embodiment in that it is realized by using the routine shown in FIG. 5 instead of the routine shown in FIG.

[Features of Embodiment 3]
The system of the present embodiment executes atmospheric learning while correcting the learning value according to the state even when the temperature of the oxygen concentration sensor 46 is unstable. In the learning value correction process, the temperature of the lead portion 46b of the oxygen concentration sensor 46 is estimated and the estimated temperature Te is obtained. In this case, the estimated temperature Te of the lead part 46b is calculated as a temperature reflecting the heating time of the sensor by the heater 46c and the history of the exhaust gas temperature. In air learning, a temperature correction coefficient K including the estimated temperature Te is calculated, and the learning value L is corrected using the temperature correction coefficient K.

[Specific Processing for Realizing Embodiment 3]
FIG. 5 is a flowchart of a routine executed by the ECU 52 in order to realize the system operation of the present embodiment. In the description of this routine, the same steps as those in the first embodiment (FIG. 3) are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, first, similarly to the first embodiment, the processing of steps 100 to 104 is performed. Next, in step 300, the fuel cut operation is started, and the detection signal Va of the oxygen concentration sensor 46 is read in a state where the precondition for performing the air learning is satisfied.

  Next, in step 302, a temperature correction coefficient K for correcting a learning value obtained by atmospheric learning is calculated. The temperature correction coefficient K calculation process will be specifically described below. First, the ECU 52 measures the energization time ts that has elapsed since the energization of the heater 46c of the oxygen concentration sensor 46 was started.

  Then, the temperature Ts of the oxygen concentration sensor 46 is estimated by referring to predetermined map data using the energization time ts. This map data is data representing the relationship between the energization time ts and the temperature Ts, and is stored in advance in the storage circuit 52a of the ECU 52 together with other map data and constants described later.

  Further, the ECU 52 refers to predetermined map data using the temperature Ts and the energization time ts, and thereby calculates the energization correction coefficient α (Ts, ts). Here, the energization correction coefficient α (Ts, ts) is obtained by converting the thermal influence on the lead portion 46b according to the sensor temperature Ts and the heating time of the heater 46c (energization time ts) into a correction coefficient. .

  On the other hand, the ECU 52 refers to predetermined map data using the temperature Tg of the exhaust gas detected by the exhaust temperature sensor 44 before the start of the fuel cut and the duration tg that the temperature Tg has continued until the start of the fuel cut. Thus, the exhaust temperature correction coefficient β (Tg, tg) is calculated. Here, the exhaust temperature correction coefficient β (Tg, tg) is obtained by converting the thermal influence on the lead portion 46b according to the history of the exhaust gas temperature into a correction coefficient.

  Then, the ECU 52 estimates the lead portion 46b of the oxygen concentration sensor 46 using the energization correction coefficient α (Ts, ts) and the exhaust temperature correction coefficient β (Tg, tg) as shown in the following equation (1). The temperature Te is estimated and calculated. Further, as shown in the following equation 2, a temperature correction coefficient K is calculated using the estimated temperature Te and the constants A and B stored in advance.

(Equation 1)
Te = α (Ts, ts) + β (Tg, tg)

(Equation 2)
K = A x Te + B

  As described above, the temperature correction coefficient K is a correction coefficient that reflects the temperature of the lead portion 46b that changes according to the heating time of the heater 46c and the temperature history of the exhaust gas. Since the temperature correction coefficient K has been calculated as described above, in step 304, the detection signal Va of the oxygen concentration sensor 46 is corrected using the temperature correction coefficient K as shown in the following equation (3).

(Equation 3)
L = Va × K

  That is, in step 304, the product of the detection signal Va and the temperature correction coefficient K is calculated as the learning value L. In step 306, the learning value L is stored in the storage circuit 52a of the ECU 52, thereby performing atmospheric learning.

  Thus, in the system according to the present embodiment, the temperature Te of the lead portion 46b can be estimated using the energization time ts of the heater 46c of the oxygen concentration sensor 46, the exhaust gas temperature Tg, and the like. The ECU 52 can correct the detection signal Va in accordance with the estimated temperature Te, and can store the corrected learning value L.

  For this reason, in the present embodiment, highly accurate learning can be performed even when the temperature of the oxygen concentration sensor 46 is in an unstable state. Further, since the learning operation can be performed at a high frequency regardless of the temperature state of the sensor 46, the learning efficiency can be improved. Moreover, since the energization time ts of the heater 46c is also used for calculating the estimated temperature Te, for example, even when the sensor 46 is started, the temperature Te of the lead portion 46b can be accurately grasped. Increase learning opportunities.

  In the third embodiment described above, steps 302 and 304 (formulas of the equations 1, 2 and 3) in FIG. 5 show specific examples of the temperature correction means in the sixth invention. Step 306 shows a specific example of learning means.

  In the first to third embodiments, the diesel engine is described as an example of the internal combustion engine 10. However, the present invention is not limited to this, and can also be applied to a gasoline engine or an internal combustion engine using other fuel.

  Further, in the first to third embodiments, the detection signal of the oxygen concentration sensor 46 is stored as a learning value for atmospheric learning. However, the present invention is not limited to this. For example, the difference or ratio between the detection signal value of the sensor and the reference signal value may be stored as a learning value.

It is a figure for demonstrating the system configuration | structure of the control apparatus of the internal combustion engine in Embodiment 1 of this invention. It is an enlarged view for demonstrating the structure of an oxygen concentration sensor. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

Explanation of symbols

10 Internal combustion engine 12 Intake passage 14 Intake manifold 16 Throttle valve 18 Exhaust passage 20 Exhaust manifold 22 Exhaust purification catalyst 24 Fuel injection valve 26 Common rail 28 Fuel pump 30 Fuel passage 32 Fuel addition valve 34 Shut-off valve 36 EGR passage 38 EGR valve 40 Turbocharger 42 Air flow meter 44 Exhaust temperature sensor (exhaust temperature detection means)
46 Oxygen concentration sensor (oxygen concentration detection means)
46a Element portion 46b Lead portion 46c Heater 48 Rotation sensor 50 Accelerator opening sensor 52 ECU
52a Memory circuit

Claims (8)

Oxygen concentration detection means for detecting the oxygen concentration in the exhaust gas discharged from the internal combustion engine and outputting a detection signal;
Temperature state determination means for determining whether or not the temperature of the oxygen concentration detection means is in a stable state when a fuel cut operation of the internal combustion engine is being performed;
Learning means for performing learning using a detection signal output from the oxygen concentration detection means when the temperature state determination means determines that the temperature of the oxygen concentration detection means is in a stable state;
Learning prohibiting means for prohibiting the operation of the learning means when the temperature state determining means determines that the temperature of the oxygen concentration detecting means is in an unstable state;
A control device for an internal combustion engine, comprising:   The temperature state determination means determines that the temperature of the oxygen concentration detection means is in an unstable state until a standby time elapses from the time when the operating state of the internal combustion engine shifts from high output operation to normal operation, 2. The control device for an internal combustion engine according to claim 1, wherein when the standby time has elapsed from the time when the operating state has shifted, it is determined that the temperature of the oxygen concentration detecting means has shifted to a stable state.   The temperature state determination means determines that the temperature of the oxygen concentration detection means is in an unstable state until the standby time elapses from the time when the operating state of the internal combustion engine shifts from the fuel cut operation to the idle operation. 2. The control device for an internal combustion engine according to claim 1, wherein when the standby time has elapsed from the time when the operating state has shifted, it is determined that the temperature of the oxygen concentration detecting means has shifted to a stable state.   The oxygen concentration detection unit includes an element unit capable of detecting an oxygen concentration in a heated state, and a heater that heats the element unit when energized, and the temperature state determination unit energizes the heater. It is determined that the temperature of the oxygen concentration detection means is in an unstable state until the standby time elapses from the start time, and when the standby time has elapsed from the start of energization, the oxygen concentration detection means The control device for an internal combustion engine according to claim 1, wherein the control device determines that the temperature has shifted to a stable state.   Exhaust temperature detection means for detecting the temperature of the exhaust gas is provided, and the temperature state determination means determines whether or not the temperature of the oxygen concentration detection means is stable according to the temperature of the exhaust gas detected by the exhaust temperature detection means. The control device for an internal combustion engine according to claim 1, wherein the control device is configured to determine whether or not. Oxygen concentration detection means for detecting the oxygen concentration in the exhaust gas discharged from the internal combustion engine by the element portion and deriving the detection signal output from the element portion to the outside by the lead portion;
Exhaust temperature detecting means for detecting the temperature of the exhaust gas;
Temperature correction means for correcting the detection signal of the oxygen concentration detection means using the temperature of the exhaust gas detected by the exhaust temperature detection means when the fuel cut operation of the internal combustion engine is being performed;
Learning means for performing learning using the detection signal corrected by the temperature correction means;
A control device for an internal combustion engine, comprising:   The temperature correction means is configured to estimate the temperature of the lead portion of the oxygen concentration detection means according to the temperature of the exhaust gas, and to correct the detection signal of the oxygen concentration detection means using the estimated temperature. The control apparatus of the internal combustion engine described in 1.   The oxygen concentration detection unit includes a heater that heats the element portion when energized, and the temperature correction unit is responsive to a time elapsed from the start of energization of the heater and a temperature of the exhaust gas. The control apparatus for an internal combustion engine according to claim 6, wherein the temperature of the lead portion of the oxygen concentration detection means is estimated, and the detection signal of the oxygen concentration detection means is corrected using the estimated temperature.

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