JP2010025085A - Control device for internal combustion engine - Google Patents

Abstract

A control apparatus applied to an internal combustion engine capable of using an alcohol-mixed fuel in which alcohol and gasoline are mixed, and capable of increasing learning opportunities while maintaining the accuracy of alcohol concentration learning. Providing the device.
An internal combustion engine can use a mixed fuel in which ethanol and gasoline are mixed. A PCV passage having a PCV valve is provided on the way from the crank chamber of the internal combustion engine to the intake passage. An air-fuel ratio sensor is provided in the exhaust passage of the internal combustion engine. The electronic control device performs air-fuel ratio feedback control and alcohol concentration learning control for learning the alcohol concentration of the fuel of the internal combustion engine. The electronic control unit calculates a contribution degree P that is a ratio of the amount of blow-by gas recirculated to the intake air amount sucked into the intake passage, and the alcohol concentration learning control is performed on the condition that the contribution degree P is equal to or less than the determination value TP. Execute.
[Selection] Figure 4

Description

  The present invention relates to a control device for an internal combustion engine that can use an alcohol-mixed fuel.

  There is known an internal combustion engine that can use an alcohol-mixed fuel in which alcohol and gasoline are mixed. In such an internal combustion engine, for example, an air-fuel ratio sensor is provided in the middle of the exhaust passage, and air-fuel ratio feedback control is performed based on the output value of the air-fuel ratio sensor. Then, alcohol concentration learning control for learning the alcohol concentration of the engine fuel is performed based on the air-fuel ratio feedback control, and various controls of the engine are performed based on the learned alcohol concentration.

On the other hand, as a device provided in an internal combustion engine, there is known a blow-by gas processing device that discharges unburned fuel and combustion gas (blow-by gas) leaking into a crankcase from a gap between a cylinder and a piston into an intake passage for processing. It has been. For example, in the blow-by gas processing apparatus described in Patent Document 1, the blow-by bus is refluxed through a reflux passage connected from the crankcase to the intake passage. Note that the amount of blow-by gas to be recirculated is adjusted by a PCV (Positive Crankcase Ventilation) valve provided in the middle of the recirculation passage. The PCV valve adjusts the flow rate of blow-by gas that is returned to the intake passage in accordance with the differential pressure between the crankcase and the intake passage.
JP 2004-239227 A

  By the way, in an internal combustion engine in which alcohol-mixed fuel can be used, for example, when the internal combustion engine is at a low temperature immediately after starting, fuel is not sufficiently vaporized, and unburned fuel is generated and engine oil is discharged by the unburned fuel. There is a risk of dilution. The unburned fuel that has flowed into the engine oil in this manner evaporates in the crankcase as the temperature of the internal combustion engine rises, and then returns to the intake passage together with the blowby gas by the blowby gas processing device described above. The recirculated unburned fuel forms an air-fuel mixture with the fuel supplied by injection and flows into the combustion chamber and then flows into the exhaust passage as exhaust.

  Here, since the output value of the air-fuel ratio sensor is affected by both the fuel supplied by injection and the unburned fuel, if the alcohol concentration learning as described above is performed, it deviates from the alcohol concentration of the original engine fuel. May be learned. On the other hand, when there is a possibility that unburned fuel evaporated in the crankcase may return to the intake passage by the blow-by gas processing device, it is possible to prohibit alcohol concentration learning. There is a problem that opportunities for learning decrease.

  The present invention has been made in view of the above circumstances, and an object of the present invention is a control device applied to an internal combustion engine that can use an alcohol-mixed fuel in which alcohol and gasoline are mixed. It is an object of the present invention to provide a control device capable of increasing learning opportunities while maintaining the above.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is capable of using an alcohol-mixed fuel obtained by mixing alcohol and gasoline, and a blow-by gas recirculation passage provided so that the blow-by gas recirculates from the crank chamber to the intake passage. A flow rate adjusting valve that is provided in the middle of the recirculation passage and adjusts the flow rate of blow-by gas to be recirculated according to the pressure difference between the intake passage and the crank chamber, and is provided in the exhaust passage and is emptied according to the exhaust component. An air-fuel ratio sensor that outputs a value corresponding to the fuel ratio, and an air-fuel ratio feedback control that is performed based on an output value of the air-fuel ratio sensor; and a fuel of the engine that is based on the air-fuel ratio feedback control A control device for performing alcohol concentration learning control for learning the alcohol concentration of the intake air, Calculating a contribution that is a ratio of the amount of the blow-by gas to be recirculated with respect to the amount of intake air sucked in, and executing the alcohol concentration learning control on condition that the contribution is equal to or less than a determination value The gist.

  According to the above configuration, the degree of contribution, which is the ratio of the amount of blow-by gas recirculated to the amount of intake air sucked into the intake passage, is calculated, and the alcohol concentration learning control is performed on condition that the contribution is equal to or less than a determination value. For example, when the contribution exceeds the determination value, it is determined that the influence of blow-by gas on the alcohol concentration learning is large, and the execution of the alcohol concentration learning control can be prohibited. On the other hand, for example, even if the amount of blow-by gas to be recirculated is large, if the intake amount is large and the contribution is equal to or less than the determination value, it is determined that the influence of the blow-by gas on the alcohol concentration learning is small, and the alcohol concentration Learning control can be executed. Accordingly, it is possible to increase learning opportunities while maintaining the accuracy of alcohol concentration learning.

  Specifically, according to claim 2, the engine further includes a throttle opening sensor that outputs an opening degree of a throttle valve provided in the intake passage, and the amount of the blow-by gas to be returned is the output of the throttle opening sensor. The engine is further provided with an engine rotation speed sensor that outputs the rotation speed of the output shaft of the engine, and the amount of blow-by gas to be returned is determined by the engine rotation. A configuration that is estimated based on the output value of the speed sensor can be employed.

  According to a fourth aspect of the present invention, in the control device for an internal combustion engine according to any one of the first to third aspects, the determination value is set according to a degree of dilution of the lubricating oil by the fuel in the engine. This is the gist.

  The amount of unburned fuel that evaporates from the lubricating oil increases and decreases according to the degree of dilution of the lubricating oil with unburned fuel, and further, the amount of unburned fuel contained in the blow-by gas that flows back into the intake passage also increases and decreases. .

  Therefore, according to the above configuration, the determination value is set according to the degree of dilution of the lubricating oil by the fuel in the engine. As a method for setting the determination value, for example, when the degree of dilution is large, it is estimated that the amount of fuel in the blow-by gas recirculated into the intake passage is large, so the determination value is set smaller. Maintain the accuracy of alcohol concentration learning. In addition, when the degree of dilution is small, it is estimated that the amount of fuel in the blow-by gas recirculated into the intake passage is small, so that the determination value is set larger to increase the chance of learning the alcohol concentration. To do. By setting the determination value as described above, it is possible to increase learning opportunities while appropriately maintaining the accuracy of alcohol concentration learning.

  A fifth aspect of the present invention is the control device for an internal combustion engine according to any one of the first to fourth aspects, wherein the determination value is set according to a temperature of lubricating oil in the engine. And

The amount of alcohol that evaporates increases or decreases depending on its temperature.
Therefore, according to the above configuration, the determination value is set according to the temperature of the lubricating oil in the engine. As a method for setting the determination value, for example, when the temperature of the lubricating oil is high, it is estimated that the amount of fuel in the blow-by gas recirculated into the intake passage is large, so the determination value is set smaller. To maintain the accuracy of alcohol concentration learning. Further, when the temperature of the lubricating oil is low, it is estimated that the amount of fuel in the blow-by gas recirculated into the intake passage is small, so the determination value is set larger to increase the chance of learning the alcohol concentration. Like that. As described above, by setting the determination value, it is possible to increase learning opportunities while appropriately maintaining the accuracy of alcohol concentration learning.

  Further, according to the configuration of the sixth aspect, the control device for the internal combustion engine according to any one of the first to fifth aspects is driven by the differential pressure between the intake passage and the crank chamber, and the engine operating state It can be embodied in a control device for an internal combustion engine that includes a mechanical PCV valve that recirculates an amount of blow-by gas according to the flow rate adjustment valve.

  According to such a configuration, even if the mechanical PCV valve is difficult to perform drive control suitable for alcohol concentration learning, such as reducing the flow rate of blow-by gas to be returned to the intake passage when performing alcohol concentration learning, the flow rate is lower than usual. It is possible to increase learning opportunities while maintaining the accuracy of alcohol concentration learning.

(First embodiment)
FIG. 1 to FIG. 6 show a first embodiment in which an internal combustion engine control device according to the present invention is embodied as an internal combustion engine electronic control device capable of using an alcohol-mixed fuel in which alcohol and gasoline are mixed. To explain.

FIG. 1 shows a schematic configuration of an internal combustion engine that can use an alcohol-mixed fuel (hereinafter simply referred to as an internal combustion engine).
As shown in FIG. 1, the internal combustion engine 10 ignites a fuel injection valve 14 that directly injects fuel into the combustion chamber 12 and a mixture of fuel and air injected by the fuel injection valve 14. A spark plug 16 is provided. A mixed fuel obtained by mixing ethanol and gasoline is supplied to the fuel injection valve 14 from a fuel tank (not shown).

  The exhaust passage 18 connected to the combustion chamber 12 is provided with a catalyst device 20 that purifies HC, CO, and NOx contained in the exhaust. On the other hand, the intake passage 22 connected to the combustion chamber 12 is provided with a throttle valve 26 that is opened and closed by a throttle motor 24. A surge tank 28 is provided in the intake passage 22 at the intake downstream side of the throttle valve 26. The amount of air supplied to the combustion chamber 12 through the intake passage 22 is adjusted by the opening degree of the throttle valve 26.

  Further, the internal combustion engine 10 is provided with a blow-by gas reduction device 30 for reducing the blow-by gas in the crank chamber 40 to the intake passage 22. The blow-by gas reduction device 30 includes an introduction passage 32 that introduces air into the crank chamber 40 from the intake upstream side of the throttle valve 26 in the intake passage 22, and an intake downstream side of the throttle valve 26 in the intake passage 22 from the crank chamber 40. A PCV passage 34 for refluxing the blowby gas and a PCV valve 36 that is provided in the middle of the PCV passage 34 and adjusts the flow rate of the blowby gas to be refluxed. The PCV passage 34 corresponds to a blow-by gas recirculation passage, and the PCV valve 36 corresponds to a flow rate adjustment valve. The PCV valve 36 is driven by the pressure difference between the intake passage 22 and the crank chamber 40 to operate the internal combustion engine 10. This is a mechanical PCV valve that recirculates an amount of blow-by gas according to the state.

  Furthermore, the internal combustion engine 10 is provided with various sensors for detecting the operating state. For example, an engine rotational speed sensor 51 that detects the rotational speed (hereinafter referred to as engine rotational speed NE) is provided in the vicinity of the crankshaft 42 corresponding to the output shaft of the internal combustion engine 10. Further, an accelerator sensor 52 that outputs an operation amount (hereinafter referred to as an accelerator operation amount ACCP) is provided in the vicinity of the accelerator pedal 44. In the vicinity of the throttle valve 26, there is provided a throttle opening sensor 53 for outputting the opening (hereinafter referred to as the throttle opening TA). An air flow meter 54 that outputs a flow rate of intake air sucked into the intake passage 22 (hereinafter referred to as an intake air amount GA) is provided on the intake upstream side of the throttle valve 26. A pressure sensor 55 that outputs a pressure in the intake passage 22 (hereinafter referred to as a pressure PM) is provided on the intake downstream side of the throttle valve 26. The cylinder block 11 is provided with a water temperature sensor 56 that outputs the temperature of engine cooling water (hereinafter referred to as engine cooling water temperature THW). Further, an air-fuel ratio sensor 57 that outputs a value corresponding to the air-fuel ratio of the exhaust gas from the oxygen concentration of the exhaust gas is provided on the exhaust gas upstream side of the catalyst device 20. Detection signals of these sensors 51 to 57 are input to an electronic control unit 60 that executes various controls of the internal combustion engine 10.

  The electronic control unit 60 includes a memory for storing a program for executing various controls, a calculation map, various data calculated when the control is executed, and the like. Then, for example, the following respective controls are executed based on the operating state of the internal combustion engine 10 that is grasped from the output values of various sensors including the sensors 51 to 57. That is, throttle control for adjusting the intake air amount according to the driver's request and fuel injection control for adjusting the fuel injection amount according to the intake air amount or the like are executed. Also, air-fuel ratio feedback control for maintaining the air-fuel ratio at the target air-fuel ratio based on the air-fuel ratio of the exhaust, and alcohol concentration learning control for learning the alcohol concentration of the fuel of the internal combustion engine 10 based on the air-fuel ratio feedback control are executed. .

  Here, in throttle control, the opening degree of the throttle valve 26 is controlled by operating the throttle motor 24 based on output values of various sensors including the accelerator operation amount ACCP.

In the fuel injection control, the valve opening period of the fuel injection valve 14 is controlled based on the output values of various sensors including the intake air amount GA.
Here, the air-fuel ratio feedback control among the above-described controls by the electronic control unit 60 will be described in detail with reference to the flowchart shown in FIG. FIG. 2 is a flowchart showing a processing procedure of air-fuel ratio feedback control, and a series of processing shown in this flowchart is repeatedly executed by the electronic control device 60 as interrupt processing for each predetermined crank angle.

  As shown in FIG. 2, in this series of processes, it is first determined whether or not the conditions for executing the air-fuel ratio feedback control are satisfied (step S110). The execution conditions of the air-fuel ratio feedback control include, for example, when the engine is not started, fuel cut is not performed, the engine cooling water temperature is equal to or higher than a predetermined temperature, or the air-fuel ratio sensor 57 is activated. Can do.

  When at least one of these conditions is not satisfied, it is determined that the execution condition of the air-fuel ratio feedback control is not satisfied (step S110: NO), and this series of processes is temporarily terminated. Here, the feedback correction value FAF is a correction value of the fuel injection amount calculated in the air-fuel ratio feedback control, and is set as a correction value for canceling the temporary divergence of the actual air-fuel ratio with respect to the target air-fuel ratio. Note that, in the internal combustion engine 10 in the present embodiment, a theoretical air-fuel ratio is basically set as the target air-fuel ratio. Further, depending on the engine operating state, an air-fuel ratio richer or leaner than the stoichiometric air-fuel ratio may be set as the target air-fuel ratio.

On the other hand, when all the above conditions are satisfied and execution of the air-fuel ratio feedback control is permitted (step S110: YES), the process proceeds to steps S120 to S140.
In these steps S120 to S140, the air-fuel ratio of the air-fuel mixture is fed back based on the voltage difference ΔV so as to reduce the difference between the output voltage VAF of the air-fuel ratio sensor 57 and the reference voltage VTRG (hereinafter referred to as voltage difference ΔV). A correction value for control is calculated as the previous feedback correction value FAF.

In calculating the feedback correction value FAF, first, the magnitude relationship between the output voltage VAF and the reference voltage VTRG is determined (step S120).
As shown in FIG. 3, the output voltage VAF of the air-fuel ratio sensor 57 increases as the oxygen concentration of the exhaust gas increases, that is, as the amount of deviation of the air-fuel ratio of the air-fuel mixture from the stoichiometric air-fuel ratio increases toward the lean side. It becomes larger and becomes smaller as the oxygen concentration in the exhaust gas becomes lower, that is, as the amount of deviation of the air-fuel ratio of the mixture to the rich side from the stoichiometric air-fuel ratio increases.

  When it is determined in step S120 of FIG. 2 that the output voltage VAF exceeds the reference voltage VTRG (step S120: YES), that is, the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio. If it is determined, a predetermined amount KUP is added stepwise to the feedback correction value FAF at that time. Then, the calculation result (FAF + KUP) is set as a new feedback correction value FAF (step S130).

  On the other hand, when it is determined that the output voltage VAF is equal to or lower than the reference voltage VTRG (step S120: NO), that is, when it is determined that the air-fuel ratio of the air-fuel mixture is richer than the stoichiometric air-fuel ratio, The predetermined amount KDWN is subtracted stepwise from the feedback correction value FAF at the time. Then, the calculation result (FAF-KDWN) is set as a new feedback correction value FAF (step S140). Through either step S130 or step S140, the process proceeds to step S150, which is the next step.

Subsequently, an average value FAFAVE of the feedback correction value FAF is calculated (step S150).
Here, when there is no tendency to steadily deviate between the air-fuel ratio of the air-fuel mixture and the target air-fuel ratio, the feedback correction value FAF varies around the reference value “1.0”. It becomes like this. Therefore, the average value FAFAVE of the feedback correction value FAF is substantially equal to “1.0”. On the other hand, when the air-fuel ratio of the air-fuel mixture tends to steadily deviate from the target air-fuel ratio to the rich side or the lean side due to individual differences of the fuel injection valves 14, for example, the feedback correction value FAF is a reference value. The value fluctuates around a value different from “1.0”. Therefore, the average value FAFAVE of the feedback correction value FAF converges to a value different from “1.0” according to the deviation tendency. For this reason, the deviation tendency between the air-fuel ratio of the air-fuel mixture and the target air-fuel ratio can be grasped based on the degree of deviation between the reference value “1.0” of the feedback correction value FAF and the average value FAFAVE.

  Therefore, in the subsequent steps S160 to S190, the air-fuel ratio learning value FG is updated based on a comparison between the average value FAFAVE of the feedback correction value FAF and the predetermined value a and the predetermined value b (a <1.0 <b). I do. This air-fuel ratio learning value FG is set as a correction value for canceling the steady divergence of the actual air-fuel ratio with respect to the target air-fuel ratio of the air-fuel mixture.

  If it is determined that the average value FAFAVE of the feedback correction value FAF is less than the predetermined value a (step S160: YES), it is determined that the air-fuel ratio of the air-fuel mixture tends to deviate to the rich side with respect to the target air-fuel ratio. Then, the air-fuel ratio learning value FG is updated to a smaller value to compensate for this divergence tendency (step S170). On the other hand, after it is determined that the average value FAFAVE of the feedback correction value FAF is greater than or equal to the predetermined value a (step S160: NO), when it is determined that the average value FAFAVE exceeds the predetermined value b (step S180: YES) ), It is determined that the air-fuel ratio of the air-fuel mixture tends to deviate toward the lean side with respect to the target air-fuel ratio, and the air-fuel ratio learning value FG is updated to a larger value to compensate for this deviation tendency (step S190).

  On the other hand, when the average value FAFAVE of the feedback correction value FAF is in a range between the predetermined value a and the predetermined value b (a ≦ FAFAVE ≦ b) (step S180: NO), the average value FAFAVE is It is determined that the air-fuel ratio of the air-fuel mixture does not tend to deviate from the target air-fuel ratio because it fluctuates in the vicinity of the reference value “1.0”. In this case, the value at that time is held without updating the air-fuel ratio learning value FG. After the air-fuel ratio learning value FG is set in this way, this series of processes is temporarily terminated.

  In the present embodiment, alcohol concentration learning control for learning the alcohol concentration of the fuel used in the internal combustion engine 10 based on the air-fuel ratio learning value FG calculated in the above-described air-fuel ratio feedback control is performed and learned. Various controls of the internal combustion engine 10 are performed based on the alcohol concentration.

  By the way, in an internal combustion engine that can use an alcohol-mixed fuel as in the present embodiment, for example, when the internal combustion engine is at a low temperature immediately after start-up, fuel vaporization is not sufficient, and unburned fuel is generated and the same. Engine oil may be diluted by unburned fuel. Thus, the unburned fuel that has flowed into the engine oil evaporates in the crankcase as the temperature of the internal combustion engine rises, and is then returned to the intake passage together with the blowby gas by the blowby gas processing device. The recirculated unburned fuel forms an air-fuel mixture with the fuel supplied by injection and flows into the combustion chamber and then flows into the exhaust passage as exhaust.

  Here, since the output value of the air-fuel ratio sensor is affected by both the fuel supplied by injection and the unburned fuel, if the alcohol concentration learning as described above is performed, it deviates from the alcohol concentration of the original engine fuel. May be learned. On the other hand, when there is a possibility that unburned fuel evaporated in the crankcase may return to the intake passage by the blow-by gas processing device, it is possible to prohibit alcohol concentration learning. There is a problem that opportunities for learning decrease.

  Therefore, in the present embodiment, a contribution that is a ratio of the amount of blow-by gas recirculated to the intake amount sucked into the intake passage is calculated, and if the contribution is equal to or less than a determination value, it affects alcohol learning. Alcohol concentration learning control is executed by determining that the influence of blow-by gas is small. Details will be described next.

  FIG. 4 is a flowchart showing a processing procedure of ethanol concentration learning control corresponding to the alcohol concentration learning control, and a series of processing shown in this flowchart is repeatedly executed by the electronic control device 60 with a predetermined cycle.

  As shown in FIG. 4, in this series of processes, first, it is determined whether or not the ethanol concentration learning execution condition is satisfied (step S210). Here, the execution condition includes a condition that the air-fuel ratio sensor 57 is activated, and that the value of the feedback correction value FAF calculated by the air-fuel ratio feedback control deviates from “1.0” by a predetermined amount or more. Can be mentioned. Here, if it is determined that the above-described ethanol concentration learning execution condition is not satisfied (step S210: NO), this series of processes is temporarily terminated.

On the other hand, if it is determined that the ethanol concentration learning execution condition is satisfied (step S210: YES), the contribution calculation process shown in FIG. 5 is executed (step S220).
As shown in FIG. 5, in the contribution calculation process, first, the intake air amount GA output from the air flow meter 54 and the pressure PM in the intake passage 22 output from the pressure sensor 55 are acquired (step S310). Then, the blow-by gas amount GB that is recirculated based on the pressure PM is estimated (step S320).

  Specifically, the amount of blow-by gas to be refluxed GB is estimated based on the graph shown in FIG. The relationship between the pressure PM and the reflux blow-by gas amount GB shown in FIG. 6 corresponds to the driving mode of the PCV valve 36. For example, when the pressure PM in the intake passage 22 is small, such as when the internal combustion engine 10 is in an idle operation state, the differential pressure between the intake passage 22 and the crank chamber 40 increases. Then, the valve opening degree of the PCV valve 36 driven by the differential pressure is reduced, and the blow-by gas amount GB recirculated into the intake passage 22 is also reduced as shown on the left side of the figure. Further, when the pressure PM in the intake passage 22 is large, for example, when the internal combustion engine 10 is in a high load operation state, the differential pressure between the intake passage 22 and the crank chamber 40 becomes small. Then, the valve opening degree of the PCV valve 36 driven by the differential pressure is reduced, and the blow-by gas amount GB recirculated into the intake passage 22 is also reduced as shown on the right side of FIG. That is, as an aspect of increase / decrease of the blow-by gas amount GB, after the opening degree of the PCV valve 36 is increased and the blow-by gas amount is increased as the pressure PM is increased from the idle operation state, the high-load operation state is changed. As the pressure PM increases, the opening of the PCV valve decreases and the blow-by gas amount GB decreases. The relationship between the differential pressure between the intake passage 22 and the crank chamber 40 and the opening degree of the mechanical PCV valve 36 is set so as to achieve the above characteristics.

  Using the blow-by gas amount GB estimated based on the pressure PM in the graph shown in FIG. 6, as shown in the previous FIG. 5, the intake air GA sucked into the intake passage 22 is recirculated. The ratio (GB / GA) of the blow-by gas amount GB is calculated, and the calculated value is input as the contribution degree P (step S330). Then, the process proceeds to step S230 of the process shown in FIG.

  Next, as shown in FIG. 4, it is determined whether or not the contribution P calculated as described above is equal to or less than a determination value TP (step S230). Here, the determination value TP is a value for which it is determined that the influence of blow-by gas on the alcohol concentration learning control is large when the contribution P exceeds the determination value TP. Specifically, for example, “0.1” is set as a value by which it can be determined whether or not the influence of the blow-by gas on the alcohol concentration learning control is large regardless of the ratio of the fuel vapor in the blow-by gas. If it is determined that the contribution degree P exceeds the determination value TP (step S230: NO), this series of processes is temporarily ended.

  On the other hand, when it is determined that the contribution P is equal to or less than the determination value TP (step S230: YES), the air-fuel ratio learning value FG calculated from the feedback correction value FAF in the air-fuel ratio feedback control shown in FIG. Based on the above, the ethanol concentration ALC of the mixed fuel of the internal combustion engine 10 is learned (step S240).

  Specifically, as the ethanol concentration of the mixed fuel increases, the air-fuel ratio of the air-fuel mixture tends to steadily deviate toward the lean side with respect to the target air-fuel ratio. The air-fuel ratio learning value FG is updated to a larger value. Therefore, when the air-fuel ratio learned value FG updated immediately before deviates to the larger side with respect to the average value of the air-fuel ratio learned value FG in a predetermined period, the ethanol of the mixed fuel becomes larger as the degree of deviation is larger. Learn the concentration greatly. On the other hand, when the air-fuel ratio learned value FG updated immediately before deviates to the smaller side with respect to the average value of the air-fuel ratio learned value FG in the predetermined period, the larger the degree of deviation is, the more the mixed fuel becomes. Learn less ethanol concentration.

Thus, when the ethanol concentration ALC of the mixed fuel of the internal combustion engine 10 is learned, a series of processing is completed.
According to the embodiment described above, the following effects can be obtained.

  (1) The contribution P, which is the ratio of the recirculated blow-by gas amount GB to the intake air amount GA sucked into the intake passage 22, is calculated, and the ethanol concentration on the condition that the contribution P is equal to or less than the determination value TP In order to execute the learning control, for example, when the contribution P exceeds the determination value TP, it is determined that the influence of blow-by gas on the ethanol concentration learning is large, and the execution of the ethanol concentration learning control can be prohibited. On the other hand, for example, even if the amount of blow-by gas to be refluxed GB is large, if the intake amount GA is large and the contribution P is less than or equal to the determination value TP, it is determined that the influence of the blow-by gas on the ethanol concentration learning is small. The ethanol concentration learning control can be executed. Accordingly, it is possible to increase learning opportunities while maintaining the accuracy of alcohol concentration learning.

  (2) When the ethanol concentration learning is performed, the mechanical PCV valve 36 that is difficult to perform drive control suitable for the ethanol concentration learning, such as reducing the blow-by gas amount GB returned to the intake passage 22 less than usual, is provided in the internal combustion engine 10. Even if it is installed in the engine, the amount of blow-by gas that is recirculated is estimated based on the pressure in the intake passage related to the driving mode of the PCV valve, so the ethanol concentration learning control is executed according to the valve opening of the PCV valve. Therefore, it is possible to increase learning opportunities while maintaining the accuracy of alcohol concentration learning.

(Second Embodiment)
A second embodiment in which the internal combustion engine control apparatus according to the present invention is embodied as an internal combustion engine electronic control apparatus capable of using an alcohol-mixed fuel in which alcohol and gasoline are mixed is described below with reference to FIGS. To explain. Note that the internal combustion engine 10, its peripheral members, the configuration of the electronic control device 60, and the air-fuel ratio feedback control executed by the electronic control device 60 in the present embodiment are the first implementation shown in FIGS. 1 and 2. It is the same as the form.

  In the electronic control unit 60 of the internal combustion engine 10 in the present embodiment, blow-by gas recirculated from the crank chamber 40 to the intake passage 22 with respect to the intake air amount GA sucked into the intake passage 22 as in the first embodiment described above. The contribution P, which is the ratio of the amount GB, is calculated, and the alcohol concentration learning control is executed on condition that the contribution P is equal to or less than the determination value TP. Here, in the first embodiment described above, the recirculated blow-by gas amount GB is estimated based on the pressure PM in the intake passage. A predetermined value is used as the determination value TP.

  On the other hand, in the present embodiment, the pressure in the intake passage 22 is estimated based on the throttle opening TA, which is the opening of the throttle valve 26, and the engine rotational speed NE, which is the rotational speed of the crankshaft 42. The blow-by gas amount GB to be recirculated is estimated on the basis of the pressure in the intake passage 22 to be recirculated. As for the determination value TP, the determination value TP is set according to the degree of fuel dilution of the engine oil that is the lubricating oil of the internal combustion engine 10. The following description will be made in detail with a focus on differences from the first embodiment.

  FIG. 7 is a flowchart showing a processing procedure of ethanol concentration learning control corresponding to alcohol concentration learning control, and a series of processing shown in this flowchart is repeatedly executed by the electronic control device 60 with a predetermined period.

  As shown in FIG. 7, in this series of processing, first, as in the first embodiment described above, it is determined whether or not the ethanol concentration learning execution condition is satisfied (step S410). When it is determined that the ethanol concentration learning execution condition is not satisfied (step S410: NO), this series of processes is temporarily terminated. On the other hand, if it is determined that the execution condition for the ethanol concentration learning is satisfied (step S410: YES), the contribution calculation process shown in FIG. 8 is executed (step S420). This execution condition is the same as that in the first embodiment.

  As shown in FIG. 8, the contribution degree calculation process starts with the intake air amount GA output from the air flow meter 54 (FIG. 1), the throttle opening degree TA output from the throttle opening degree sensor 53, and the engine speed. The engine speed NE output from the sensor 51 is acquired (step S510). Then, a blow-by gas amount GB that is recirculated is estimated based on the throttle opening degree TA and the engine speed NE (step S520).

  Here, with respect to the throttle opening TA, as the throttle opening TA increases, the amount of air flowing into the intake passage 22 increases, so the pressure in the intake passage 22 increases. As for the engine speed NE, the amount of air flowing from the intake passage 22 into the combustion chamber 12 increases as the engine speed NE increases, so the pressure in the intake passage 22 decreases. Therefore, the pressure in the intake passage 22 can be estimated based on the throttle opening degree TA and the engine speed NE.

  In step S520, the pressure in the intake passage 22 estimated based on the throttle opening degree TA and the engine rotational speed NE is used as “pressure PM” in the graph of FIG. The blow-by gas amount GB to be estimated is estimated.

  Using the blow-by gas amount GB estimated based on the pressure PM in the graph shown in FIG. 6, as shown in FIG. 8, the blow-by gas recirculated with respect to the intake amount GA sucked into the intake passage 22. A ratio (GB / GA) of the amount GB is calculated, and the calculated value is input as the contribution degree P (step S530). Then, the process proceeds to step S430 of the process shown in FIG.

Next, as shown in FIG. 7, a determination value TP is set according to the degree of fuel dilution of engine oil, which is lubricating oil (step S430).
The amount of unburned fuel that evaporates from the engine oil increases and decreases according to the degree of dilution of the engine oil by the unburned fuel, and further, the amount of unburned fuel contained in the blow-by gas that flows back into the intake passage 22 also increases and decreases. To do.

  Therefore, in the present embodiment, as a method of setting the determination value TP, when the degree of dilution is large, it is estimated that the amount of fuel in the blow-by gas recirculated into the intake passage 22 is large. Is set to a smaller value. Specifically, for example, “0.1” is set as the minimum value of the determination value TP. Further, when the dilution degree is small, it is estimated that the amount of fuel in the blow-by gas recirculated into the intake passage 22 is small, so the determination value TP is set larger. Specifically, for example, “0.2” is set as the maximum value of the determination value TP. By setting the determination value TP in this way, when the contribution P exceeds the determination value TP, it is determined that the influence of blow-by gas on the alcohol concentration learning control is large.

  As for the method for determining the degree of dilution, whether or not the previous engine operation was diluted with engine oil fuel every time the internal combustion engine 10 was stopped, that is, a short-term engine operation in a low temperature state. If it is affirmative, the dilution degree counter is incremented by “1”. On the other hand, if the engine cooling water temperature THW increases to some extent during the operation of the internal combustion engine 10, the fuel mixed in the engine oil evaporates and the dilution of the engine oil with the fuel is reduced. Then, it is determined whether the engine coolant temperature THW has increased to some extent. If the result is affirmative, the dilution degree counter is decreased by “1”. Such a dilution degree counter is a value indicating the degree of dilution of the engine oil by the fuel in the internal combustion engine 10.

  Then, as shown in FIG. 7, it is determined whether or not the contribution P calculated in the previous contribution calculation process (FIG. 8) is equal to or less than the determination value TP set as described above (step S440). ), When it is determined that the contribution degree P exceeds the determination value TP (step S440: NO), this series of processes is temporarily ended.

  On the other hand, when it is determined that the contribution P is equal to or less than the determination value TP (step S440: YES), the air-fuel ratio feedback control (FIG. 2) is calculated from the feedback correction value FAF, as in the first embodiment described above. Based on the learned air-fuel ratio value FG, the ethanol concentration ALC of the mixed fuel of the internal combustion engine 10 is learned (step S450).

Thus, when the ethanol concentration ALC of the mixed fuel of the internal combustion engine 10 is learned, a series of processing is completed.
According to the present embodiment described above, the following effects can be obtained in addition to the effects (1) and (2) in the first embodiment.

  (3) When the degree of dilution of the engine oil, which is the lubricating oil in the internal combustion engine 10, with the fuel is large, it is estimated that the amount of fuel in the blow-by gas recirculated into the intake passage is large, so the determination value TP is made smaller. It is possible to maintain the accuracy of alcohol concentration learning by setting. Further, when the degree of dilution is small, it is estimated that the amount of fuel in the blow-by gas recirculated into the intake passage 22 is also small. Therefore, the determination value TP is set larger to further increase the chance of learning the alcohol concentration. Making it possible. By setting the determination value TP in this way, it is possible to increase learning opportunities while appropriately maintaining the accuracy of alcohol concentration learning.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
In the second embodiment, the determination value TP related to the contribution degree P is set according to the fuel dilution degree of the engine oil that is the lubricating oil of the internal combustion engine 10 in step S430 in FIG. Alternatively, or in addition thereto, the determination value TP may be set according to the temperature of the engine oil. As a method for setting the determination value TP, for example, when the temperature of the engine oil is high, it is estimated that the amount of fuel in the blow-by gas recirculated into the intake passage is large, so the determination value TP is set smaller. Maintain the accuracy of alcohol concentration learning. Further, when the engine oil temperature is low, it is estimated that the amount of fuel in the blow-by gas that is recirculated into the intake passage is also small. Therefore, the determination value TP is set larger to further increase the chance of learning the alcohol concentration. Like that. Specifically, for example, a range of “0.1 to 0.2” can be set as the determination value TP. As described above, by setting the determination value, it is possible to increase learning opportunities while appropriately maintaining the accuracy of alcohol concentration learning. In the first and second embodiments, the engine cooling water temperature THW detected from the water temperature sensor 56 has a correlation with the temperature of the engine oil. Therefore, in this embodiment, the engine cooling water temperature THW is substituted for the temperature of the engine oil. It may be used as a value, or a separate sensor may be provided in the oil pan in the crank chamber, and the temperature of the engine oil may be directly detected by the sensor.

  In the first and second embodiments, the blow-by gas amount GB returned to the intake passage 22 is estimated based on the graph as shown in FIG. 6, but as shown in FIG. The amount of blow-by gas to be recirculated may be estimated based on a graph created based on a value corresponding to the pressure in the intake passage and a value corresponding to the amount of blow-by gas to be recirculated. Good.

  In the first and second embodiments, the feedback correction value FAF is calculated in the air-fuel ratio feedback control, and the fuel in the internal combustion engine 10 is calculated based on the air-fuel ratio learning value FG calculated from the feedback correction value FAF. The ethanol concentration ALC is learned. However, the ethanol concentration ALC may be learned based on a value other than the air-fuel ratio learned value FG calculated from the feedback correction value FAF, or directly to the feedback correction value FAF. Based on this, the ethanol concentration ALC may be learned. In addition, air-fuel ratio feedback control is performed based on the output value of the oxygen concentration sensor whose output value changes greatly with the stoichiometric air-fuel ratio as a boundary, so that the stoichiometric air-fuel ratio is obtained. The ethanol concentration ALC may be learned by calculating the fuel ratio.

  In the first and second embodiments, the internal combustion engine 10 uses a mixed fuel in which ethanol is mixed. However, for example, a mixed fuel in which alcohol such as methanol or isopropyl alcohol is mixed is used. Also good.

  The internal combustion engine 10 in the first and second embodiments is a flow rate adjusting valve that adjusts the flow rate of blow-by gas that is recirculated from the crank chamber 40 to the intake passage 22, by the differential pressure between the crank chamber 40 and the intake passage 22. The mechanical PCV valve 36 that is driven to recirculate an amount of blow-by gas according to the operating state of the internal combustion engine 10 is provided. However, the flow rate adjusting valve according to the present invention is not limited to this, and An electronically controlled PCV valve or the like may be employed as long as the valve opening is adjusted according to the differential pressure between the chamber and the intake passage.

The block diagram which shows the schematic structure about the control apparatus of the internal combustion engine concerning the 1st Embodiment of this invention. The flowchart which shows the process sequence of the air fuel ratio feedback control in the embodiment. The graph which shows the output characteristic of an air fuel ratio sensor. The flowchart which shows the process sequence of the ethanol concentration learning control in the embodiment. The flowchart which shows the process sequence of the contribution calculation process in the embodiment. The graph which shows the relationship between the pressure in the intake passage in the same embodiment, and the amount of blow-by gas recirculated to an intake passage. The flowchart which shows the process sequence of ethanol concentration learning control in 2nd Embodiment. The flowchart which shows the process sequence of the contribution calculation process in the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder block, 12 ... Combustion chamber, 14 ... Fuel injection valve, 16 ... Spark plug, 18 ... Exhaust passage, 20 ... Catalyst device, 22 ... Intake passage, 24 ... Throttle motor, 26 ... Throttle valve 28 ... Surge tank, 30 ... Blow-by gas reduction device, 32 ... Introduction passage, 34 ... PCV passage, 36 ... PCV valve, 40 ... Crank chamber, 42 ... Crankshaft, 44 ... Accelerator pedal, 51 ... Engine speed sensor, 52 ... Accelerator sensor, 53 ... Throttle opening sensor, 54 ... Air flow meter, 55 ... Pressure sensor, 56 ... Water temperature sensor, 57 ... Air-fuel ratio sensor, 60 ... Electronic control device.

Claims (6)

Alcohol mixed fuel that is a mixture of alcohol and gasoline can be used.
A blow-by gas recirculation passage provided so that blow-by gas recirculates from the crank chamber to the intake passage;
A flow rate adjusting valve that is provided in the middle of the blow-by gas recirculation passage and adjusts the flow rate of the blow-by gas to be recirculated according to the pressure difference between the intake passage and the crank chamber;
Applied to an internal combustion engine provided with an air-fuel ratio sensor provided in an exhaust passage and outputting a value corresponding to an air-fuel ratio according to an exhaust component,
A control device that performs air-fuel ratio feedback control performed based on an output value of the air-fuel ratio sensor and alcohol concentration learning control that learns alcohol concentration of the fuel of the engine based on the air-fuel ratio feedback control,
A contribution that is a ratio of the amount of the blow-by gas to be recirculated with respect to the intake amount sucked into the intake passage is calculated, and the alcohol concentration learning control is executed on condition that the contribution is equal to or less than a determination value. A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 1,
The engine further includes a throttle opening sensor that outputs an opening of a throttle valve provided in the intake passage,
The control apparatus for an internal combustion engine, wherein the amount of blow-by gas to be recirculated is estimated based on an output value of the throttle opening sensor. The control apparatus for an internal combustion engine according to claim 1 or 2,
The engine further includes an engine rotation speed sensor that outputs a rotation speed of an output shaft of the engine,
The control apparatus for an internal combustion engine, wherein the amount of blow-by gas to be recirculated is estimated based on an output value of the engine rotation speed sensor. The control device for an internal combustion engine according to any one of claims 1 to 3,
The control value for the internal combustion engine, wherein the determination value is set according to a degree of dilution of the lubricating oil by the fuel in the engine. The control device for an internal combustion engine according to any one of claims 1 to 4,
The control value for the internal combustion engine, wherein the determination value is set according to a temperature of lubricating oil in the engine. The control apparatus for an internal combustion engine according to any one of claims 1 to 5,
The control apparatus for an internal combustion engine, wherein the flow rate adjustment valve is a mechanical PCV valve that is driven by a differential pressure between the intake passage and the crank chamber to recirculate an amount of blow-by gas corresponding to an engine operating state. .

Images