JP4962436B2 - Control device for in-vehicle internal combustion engine - Google Patents

Description

  The present invention relates to a control apparatus for an in-vehicle internal combustion engine that includes a plurality of banks and that can use an alcohol-containing fuel as a fuel, and that controls supply of fuel to each bank.

As one of in-vehicle internal combustion engines, there is known an internal combustion engine that can use an alcohol-containing fuel in which alcohol is mixed with gasoline at an arbitrary ratio (see, for example, Patent Document 1). Since alcohol has a carbon atom content different from that of normal fuel such as gasoline, in such an internal combustion engine, it is necessary to control the fuel injection amount in accordance with the type and concentration of alcohol contained in the fuel. For example, since ethanol has a smaller theoretical air-fuel ratio than gasoline, when using a mixed fuel containing this, the oxygen concentration in the exhaust discharged when gasoline is burned under that theoretical air-fuel ratio It is necessary to increase the fuel injection amount so as to be equivalent to And by performing correction | amendment of the fuel injection amount based on such alcohol concentration, the purification performance of the catalyst apparatus provided in the exhaust passage can fully be demonstrated, and deterioration of exhaust properties can be suppressed. become. Therefore, in such an internal combustion engine, it is effective to learn the alcohol concentration of the fuel based on the detection value of the air-fuel ratio sensor provided in the exhaust passage and to correct the fuel injection amount based on the learned value. .
JP-A-4-116234

  By the way, although the alcohol-containing fuel is used, the alcohol concentration is not always kept constant. For example, when a refueling operation is performed, the alcohol concentration of the fuel stored in the fuel tank changes, and as a result, the alcohol concentration of the fuel also changes during subsequent engine operation. However, even when the alcohol concentration of the fuel stored in the fuel tank changes in this way, if the alcohol concentration learning process is completed, the fuel injection amount can be corrected according to the alcohol concentration at that time. However, if the alcohol concentration recognized by the control device that controls fuel injection etc. is significantly different from the actual alcohol concentration after refueling, etc., the alcohol concentration learning process cannot catch up, and the alcohol concentration is not reached. The correct fuel injection amount cannot be corrected. For this reason, there is a concern about deterioration of drivability due to a sudden change in fuel properties, such as when the internal combustion engine is cold started, or when the combustion property itself is low in robustness, the fuel property changes beyond the combustion limit. Become so.

  On the other hand, as can be seen in the above-mentioned Patent Document 1, in recent years, the above-mentioned alcohol-containing fuel can also be used for an onboard internal combustion engine composed of a plurality of banks, such as a horizontally opposed internal combustion engine or a V-type internal combustion engine. Institutions tend to be adopted. However, even though such an internal combustion engine consisting of a plurality of banks, as in the case of the internal combustion engine found in the literature 1, the fuel supply mode for the plurality of banks is made common, so that it depends on the number of banks. In addition, the above-mentioned concerns due to changes in fuel properties are inevitable.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an on-vehicle device that can suitably suppress deterioration in drivability due to a change in fuel properties through control of fuel supply modes for a plurality of banks. An object of the present invention is to provide a control device for an internal combustion engine.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
According to the first aspect of the present invention, fuel supply devices respectively provided in the first and second banks of the in-vehicle internal combustion engine are connected in series to connect the fuel supplied from the fuel tank to the fuel in the first bank. A fuel supply mechanism for supplying fuel to the fuel supply device of the second bank via the supply device; and a permission state for permitting the fuel to return from the fuel supply device of the second bank to the fuel tank. A fuel recirculation switching mechanism that can be switched to a prohibited state and a first bank and a second bank detect an air-fuel ratio of an air-fuel mixture provided for combustion from the exhaust gas of each bank. During the period in which the difference between the air-fuel ratio detection means and the detected air-fuel ratio for each bank is less than the reference value, the fuel recirculation switching mechanism is controlled to be switched to the prohibited state, and the difference between the air-fuel ratios exceeds the reference value. Based on growing And summarized in that and a fuel recirculation control means for switching control of the fuel reflux switching mechanism in the allowed state Te.

  When the aforementioned alcohol-containing fuel is used, the concentration (fuel property) of alcohol contained in the fuel is usually reflected as it is in the detected air-fuel ratio. For this reason, for example, when the alcohol concentration of the fuel stored in the fuel tank is greatly different from the current concentration due to refueling, the fuel in the fuel tank and the fuel in the fuel supply device of each bank are actively used. If the air-fuel ratio is repeatedly circulated, the combustion state is suddenly changed due to an excessively large air-fuel ratio feedback correction amount, and drivability deteriorates. On the other hand, even if the alcohol concentration of the fuel stored in the fuel tank is greatly different from the current concentration due to refueling, if the above-mentioned circulation of the fuel is prohibited, it is connected to the fuel supply device of each bank. Since only the amount of fuel injected by the injected injectors is compensated in these fuel supply devices, the detected air-fuel ratio difference for each bank is small at the initial stage of engine start. In this case, the alcohol concentration of the fuel gradually increases as the fuel is supplied to the fuel supply devices of each bank. The rate of alcohol concentration increase is higher in the fuel supply device in the first bank located on the upstream side than in the fuel supply device in the second bank located on the downstream side. Therefore, the detected deviation of the air-fuel ratio for each bank increases beyond a certain value. For this reason, as in the above configuration, the detected air-fuel ratio difference for each bank is a reference value, for example, the alcohol concentration of the fuel in the fuel supply device of the first bank on the upstream side is the alcohol concentration of the fuel in the fuel tank. Based on the fact that the fuel recirculation switching mechanism is controlled to be in a prohibited state during a period that is less than the equivalent value of the air-fuel ratio for each bank when the concentration is close, and the air-fuel ratio deviation becomes larger than the reference value. If the fuel recirculation switching mechanism is controlled to be in a permitted state, each air-fuel ratio is averaged based on a value obtained by smoothing (averaging) the air-fuel ratio, for example, the detected average value of the air-fuel ratio for each bank. Even when fuel injection control that determines the fuel injection amount from the injector provided in the bank is performed, a rapid change in the air-fuel ratio feedback correction amount can be suppressed, and thus the driver Deterioration of utility also becomes possible to suppress.

  According to a second aspect of the present invention, in the control device for an on-vehicle internal combustion engine according to the first aspect, the fuel recirculation control means prior to the comparison between the detected air-fuel ratio difference for each bank and the reference value. The change in the property of the fuel in the fuel supply device of the second bank is monitored, and the difference between the detected air-fuel ratio for each bank and the reference are provided on the condition that the property of the fuel has changed more than a predetermined value. The gist is to start comparison with the value.

According to the above configuration, before the comparison between the air-fuel ratio difference for each bank and the allowable value, the change in the property of the fuel in the fuel supply device of the second bank located downstream is monitored. At this time, if a change in the fuel property in the fuel supply device of the second bank, for example, the alcohol concentration, exceeds a predetermined value due to a refueling operation or the like, the air-fuel ratio for each bank is determined on this condition. Comparison of the difference between the reference value and the reference value is started. On the contrary, the comparison is not started unless the property change exceeding the predetermined value occurs in the fuel in the fuel supply device of the second bank. Since the fuel supply device of the second bank is located downstream of the fuel supply path, the second bank
The change in the property of the fuel in the fuel supply device of the first bank occurs later than the change in the property of the fuel in the fuel supply device of the first bank located upstream thereof. For this reason, when the fuel property change occurs in the fuel supply device of the second bank, it can be estimated that the fuel property change occurs in the fuel supply path with a considerably high probability. Therefore, by using the change in the fuel property in the fuel supply device of the second bank as a reference, it becomes possible to capture such a change in the property of the fuel more reliably. As a result, the difference in air-fuel ratio for each bank and the reference value can be obtained. While avoiding unnecessary comparison with the above, it is possible to accurately perform the switching control of the fuel recirculation switching mechanism based on the comparison when necessary.

  According to a third aspect of the present invention, in the control device for an on-vehicle internal combustion engine according to the first aspect, the fuel recirculation control means prior to the comparison between the detected air-fuel ratio difference for each bank and the reference value. The change in the property of the fuel in the fuel supply device of the first bank is monitored, and the difference between the detected air-fuel ratio for each bank and the reference are provided on the condition that the property of the fuel has changed more than a predetermined value. The gist is to start comparison with the value.

  Here, instead of the change in the fuel property in the fuel supply device in the second bank, the difference in the air-fuel ratio for each bank is based on the change in the fuel property in the fuel supply device in the first bank located upstream thereof. And comparison with the reference value is started. The fuel supply device of the first bank is a portion that changes its fuel properties at an earlier stage when the fuel property in the fuel tank, for example, the alcohol concentration, changes due to a refueling operation or the like. In other words, it can be said that it is a part that is more sensitive to changes in fuel properties. Therefore, by using the change in the fuel property in the fuel supply device of the first bank as a reference, it becomes possible to catch the change in the fuel property at an earlier stage. The switching control of the fuel recirculation switching mechanism is efficiently realized in such a way that the execution of the comparison with the value is promoted.

  According to a fourth aspect of the present invention, in the control device for an on-vehicle internal combustion engine according to the second or third aspect, the fuel recirculation control means is configured to perform the fuel recirculation when a change in the fuel property does not exceed a predetermined value. The gist is to switch the switching mechanism to the permission state.

  Even if a refueling operation is performed, there may be a case where there is no change in fuel properties, for example, fuel with an alcohol concentration equivalent to that before refueling is refueled. In such a case, since it is difficult for the internal combustion engine to change from the operating state before the refueling operation, there is no concern about the influence on the engine operation due to the refueling operation. In this regard, according to the above-described configuration, the fuel recirculation switching mechanism is controlled to be switched to the permitted state when there is little change in the fuel property in the fuel supply device of the second bank or the fuel supply device of the first bank. Reflux is allowed. In this case, since the change in the fuel property in the fuel supply device of each bank is small in the first place, there is no concern that the drivability will be deteriorated without executing the control according to the first aspect.

  According to a fifth aspect of the present invention, in the control device for an on-vehicle internal combustion engine according to any one of the first to fourth aspects, the fuel recirculation control means is autonomous in the properties of the fuel in which the temperature at the start of the on-vehicle internal combustion engine is used. The gist is to switch the fuel recirculation switching mechanism to the permission state unconditionally when the temperature is above the proper temperature at which operation is possible.

  In general, fuel containing alcohol tends to have a drastic deterioration in drivability due to the deterioration of the air-fuel ratio as the engine is cold, and conversely, if the fuel and engine temperature are above the appropriate temperature, the influence on the air-fuel ratio will not be affected. It tends to be reduced. For this reason, as described above, even if the recirculation of the fuel is permitted on the condition that the temperature at the start of the internal combustion engine is equal to or higher than the proper temperature at which the autonomous operation can be performed, the air-fuel ratio deteriorates and the drivability deteriorates. As a result, the vehicle can be started smoothly as an in-vehicle internal combustion engine.

  According to a sixth aspect of the present invention, in the control device for an on-vehicle internal combustion engine according to the first to fifth aspects, the fuel recirculation switching mechanism is a pressure regulator provided at a terminal portion of the fuel supply device of the second bank. The fuel tank supplies the fuel supplied to the fuel supply device of the first bank through a high-pressure return pipe that recirculates the fuel in the fuel supply device to the fuel tank via a fuel pressure switching valve that is an on-off valve. And a low pressure return pipe that branches and recirculates, and the fuel recirculation control means controls the fuel recirculation switching mechanism to the prohibited state by opening the fuel pressure switching valve and closes the fuel pressure switching valve. The gist is to switch the fuel recirculation switching mechanism to the permitted state as a valve state.

  According to this configuration, when the above-described fuel recirculation switching mechanism is switched through the fuel recirculation control means, the pressure regulator provided at the terminal portion of the fuel supply device of the second bank is used, that is, each bank Smooth fuel recirculation switching using the pressure of the fuel supplied to the fuel supply device can be realized.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS.
FIG. 1 mainly shows the schematic configuration of an eight-cylinder on-vehicle internal combustion engine having a V-type cylinder arrangement and its fuel supply system. As shown in FIG. 1, the internal combustion engine is provided with a right delivery pipe 14R and a left delivery pipe 14L as fuel supply devices corresponding to the right and left banks as the first bank and the second bank, respectively. It has been. Four injectors 16 are connected to these delivery pipes 14R and 14L corresponding to the respective cylinders. This internal combustion engine is a flexible fuel internal combustion engine that can use a mixed fuel in which ethanol (ethyl alcohol) is mixed with gasoline as a fuel. Incidentally, the ethanol concentration (alcohol concentration) of the mixed fuel usually differs depending on the ethanol concentration of the fuel remaining in the fuel tank 11 and the ethanol concentration of the fuel newly injected into the fuel tank 11 by the refueling operation. . Specifically, the concentration changes within a range of 0% (gasoline only) to 85%.

Here, the configuration of the fuel supply system of the internal combustion engine will be described.
A fuel pump 12 provided in the fuel tank 11 is connected to one delivery pipe 14R by a main pipe 13. In addition, the other delivery pipe 14L connected in series by the one delivery pipe 14R and the communication pipe 15 has a fuel pressure in each of the delivery pipes 14R and 14L, that is, a fuel injection pressure P for adjusting to a high pressure. A high pressure regulating valve (high pressure regulator) 21 is provided, and a high pressure return pipe 17 is connected through the high pressure regulating valve 21.

  Further, a low pressure return pipe 18 is connected to the main pipe 13 at a portion located in the vicinity of the fuel tank 11. The low pressure return pipe 18 is provided with a low pressure regulating valve (low pressure regulator) 22 for adjusting the fuel pressure in each delivery pipe 14R, 14L to a low pressure. The valve opening pressure PL of the low pressure regulating valve 22 is set lower than the valve opening pressure PH of the high pressure regulating valve 21 (PL <PH).

  On the other hand, the low-pressure return pipe 18 is provided with a fuel pressure switching valve 23 composed of an on-off valve, and the fuel in the main pipe 13 can flow into the low-pressure return pipe 18 according to the valve position of the fuel pressure switching valve 23. And the state where inflow is impossible.

That is, when the fuel pressure switching valve 23 is closed, fuel cannot flow into the low-pressure return pipe 18 from the main pipe 13, so that all the fuel discharged from the fuel pump 12 to the main pipe 13 is delivered to each delivery pipe. 14R and 14L are pumped. When the fuel pressure in the delivery pipes 14R and 14L becomes higher than the valve opening pressure PH of the high pressure regulating valve 21, the high pressure regulating valve 21 is opened so that the fuel is returned to the fuel tank 11 through the high pressure return pipe 17. become. As a result, the fuel injection pressure P is maintained at substantially the same pressure as the valve opening pressure PH of the high pressure regulating valve 21.

  On the other hand, when the fuel pressure switching valve 23 is opened, fuel flows from the main pipe 13 into the low pressure return pipe 18. The low pressure regulating valve 22 is opened before the fuel pressure in the delivery pipes 14R, 14L rises and the high pressure regulating valve 21 is opened, and part of the fuel is not pumped to the delivery pipes 14R, 14L. The fuel tank 11 is returned to the fuel tank 11 through the low pressure return pipe 18. As a result, the fuel injection pressure P is maintained at substantially the same pressure as the valve opening pressure PL of the low pressure regulating valve 22.

  Thus, in the fuel supply system according to the present embodiment, the fuel injection pressure P can be changed to a different pressure by switching the valve position of the fuel pressure switching valve 23. Basically, the fuel pressure switching valve 23 is driven so as to be in the open state during a period from when the engine is started until the predetermined condition is satisfied, and when the predetermined condition is satisfied, the fuel pressure switching valve 23 is closed. It is driven to become a state.

  The internal combustion engine is provided with various sensors for detecting various information including the engine operating state. For example, an engine rotation speed sensor 42 for detecting the rotation speed, that is, the engine rotation speed NE is provided in the vicinity of the crankshaft (not shown). The intake pipe (not shown) is provided with an intake air amount sensor 43 that detects an intake air amount GA. Further, a water jacket (not shown) of the cylinder block is provided with a coolant temperature sensor 44 for detecting the engine coolant temperature THW. The engine coolant temperature THW has a correlation with the engine temperature and the fuel temperature, and is used as an alternative value thereof. Also, a fuel pressure sensor 45 that detects fuel pressure (fuel injection pressure P) is provided on one of the delivery pipes 14R and 14L. In addition, the fuel tank 11 is provided with a fuel amount sensor 46 for detecting the fuel amount FL therein.

  In this embodiment, an exhaust pipe is also provided for each bank. A right bank three-way catalyst 32R is provided in the right bank exhaust pipe 31R corresponding to the right bank, and a right bank air-fuel ratio sensor 47R is provided upstream thereof. Similarly, a left bank three-way catalyst 32L is provided in the left bank exhaust pipe 31L, and a left bank air-fuel ratio sensor 47L is provided upstream thereof. Of these, the right bank air-fuel ratio sensor 47R outputs a signal that continuously changes in accordance with the air-fuel ratio DOR of the air-fuel mixture subjected to combustion in the right bank each time. Further, the left bank air-fuel ratio sensor 47L outputs a signal that continuously changes in accordance with the air-fuel ratio DOL of the air-fuel mixture provided for the respective combustion in the left bank. Incidentally, the ethanol concentration of the fuel in the right delivery pipe 14R and the left delivery pipe 14L is not always constant, and the fuel properties change depending on the refueling operation or the like. For this reason, in the present embodiment, the fuel property in the delivery pipe 14R and the delivery pipe 14L, that is, the ethanol concentration (alcohol concentration) for each bank is calculated from the detection signals of the air-fuel ratio sensors 47R and 47L. . The air-fuel ratio sensors 47R and 47L cannot detect the air-fuel ratios DOR and DOL with high accuracy when the element temperature is lower than a predetermined activation temperature. For this reason, the air-fuel ratio sensors 47R and 47L have built-in heaters for heating the element to raise the element temperature to the activation temperature when the exhaust temperature and the outside air temperature are low.

All the detection signals of the various sensors 42 to 47 are taken into the electronic control unit 41 of the internal combustion engine. The electronic control device 41 includes a storage unit 41a that stores and holds various control programs, calculation maps, data calculated when various controls are executed, and the like. In addition to the ROM and RAM, the storage unit 41a stores the memory by power supply from a battery (not shown) even when engine operation is stopped, in other words, when power supply to the electronic control device 41 is stopped. It includes a backup RAM that holds the contents. The electronic control device 41 drives the injector 16, the fuel pressure switching valve 23, and the like based on the detection signals of various sensors including these sensors 42 to 47, so that the fuel injection amount, the fuel injection pressure, the fuel circulation mode, etc. Control related to fuel injection is executed.

  Next, an outline of the fuel supply control executed in the present embodiment will be described with reference to FIGS. 2 and 3 together with a transition example of the ethanol concentration of the fuel in each part accompanying the start of the on-vehicle internal combustion engine described above.

  First, in FIG. 2, FIG. 2 (a) shows a change in ethanol concentration in the right delivery pipe 14R, FIG. 2 (b) shows a change in ethanol concentration in the left delivery pipe 14L, and FIG. Changes in the ethanol concentration of fuel injected from the injector 16 in accordance with changes in the ethanol concentration in the left and right delivery pipes are shown. Here, the fuel remaining in the fuel tank 11 and the fuel supply path is a fuel having an ethanol concentration of 0% (fuel E0), and the newly supplied fuel is a fuel having an ethanol concentration of 85% (fuel E85). And

  Under this assumption, first, when the internal combustion engine is started by turning on the ignition switch, the fuel stored in the left and right delivery pipes is injected from the injector 16. When the fuel is injected from the injector 16 in this way, the fuel is reduced by the amount injected from the left and right delivery pipes, so that the fuel E85 is supplied from the fuel tank 11 so as to compensate for this decrease. At this time, in the present embodiment, as is clear from FIG. 1, the fuel E85 is supplied from the fuel tank 11 to the left delivery pipe L via the right delivery pipe 14R by the fuel pump 12. As a result, the fuel E85 is mixed with the fuel E0 remaining in the delivery pipes 14R, 14L, and the ethanol concentration of the fuel in the delivery pipes 14R, 14L gradually changes from E0 to E85. At this time, the fuel supplied to the left delivery pipe 14L located on the downstream side is a mixture of the fuel E0 stored in the right delivery pipe 14R located on the upstream side and the newly supplied fuel E85. It has been made fuel. Further, as described above, during the period from when the engine is started until the predetermined condition is satisfied, the fuel pressure switching valve 23 is maintained in the open state, and the fuel from the delivery pipes 14R and 14L via the high pressure return pipe 17 is maintained. Circulation is limited.

  Here, in the present embodiment, the period during which the fuel pressure switching valve 23 is opened after the engine is started is the ethanol concentration deviation (condition 1) of the fuel in the left delivery pipe 14L and between the left and right delivery pipes 14L, 14R. It is determined based on the difference in ethanol concentration of fuel (condition 2).

More specifically, under the above condition 1, as shown in FIG. 2 (b), the ethanol concentration of the fuel in the left delivery pipe 14L at the time of engine low temperature start is higher than the concentration change reference value α1 at low temperature due to the refueling operation. That is, whether or not the fuel concentration in the left delivery pipe 14L has actually changed from the fuel E0 before refueling to the reference value α1 or more is monitored. The temperature at engine starting is judged by whether it exceeds a predetermined temperature as a suitable temperature value T ₀ (for example 34 ° C.), if the optimum temperature value T ₀ or less, the engine is cold start As a result, the change in the ethanol concentration is monitored based on the reference value α1.

On the other hand, under the above condition 2, the difference (difference value) between the ethanol concentration β1 of the fuel in the right delivery pipe 14R shown in FIG. 2A and the ethanol concentration β2 of the fuel in the left delivery pipe 14L shown in FIG. It is monitored whether or not) is equal to or greater than the reference value β. That is, when the fuel pressure switching valve 23 is opened, the circulation of fuel through the high pressure return pipe 17 is restricted, so that the fuel in the right delivery pipe 14R takes priority over the fuel in the left delivery pipe 14L. The fuel is mixed. For this reason, when the mixing of the fuel proceeds to some extent, the ethanol concentration of the fuel in the right delivery pipe 14R on the upstream side increases as shown in FIGS. 2 (a) and 2 (b). The difference between the fuel concentration in the left delivery pipe 14L on the downstream side and the ethanol concentration gradually increases. When the difference is equal to or greater than the reference value β, it is determined that the ethanol concentration in the right delivery pipe 14R has approached the ethanol concentration of the fuel in the fuel tank 11.

  When these conditions 1 and 2 are satisfied, the fuel pressure switching valve 23 is closed, and fuel circulation through the high-pressure return pipe 17 is allowed. When the fuel circulation is allowed in this way, the fuel in the right and left delivery pipes 14R, 14L is replaced with the fuel after refueling in the fuel tank 11 as the fuel pressure increases, so that the right and left delivery pipes 14R, The difference in the ethanol concentration of the fuel between 14L is eliminated. After that, the ethanol concentration of the fuel in both delivery pipes 14R, 14L rapidly changes to the ethanol concentration E85 after refueling.

  As described above, when the engine is started after the refueling operation, the ethanol concentration of the fuel in the right and left delivery pipes 14R, 14L shows different transitions, but the fuel pressure switching valve is passed through the above conditions 1 and 2. By switching control of the valve 23 from the open state to the closed state, the ethanol concentration of the fuel injected from the injector 16 also changes on average in the manner shown in FIG.

  FIG. 3 shows, as a comparative example, the ethanol concentrations in the delivery pipes 14R and 14L or the injectors when the fuel pressure switching valve 23 is closed at the same time as the engine start without being limited by the conditions 1 and 2 described above. 16 shows the transition of the ethanol concentration of the fuel injected through 16 in correspondence with FIG.

  Now, when the fuel pressure switching valve 23 is closed as the engine starts, the fuel is circulated through the high-pressure return pipe 17 as the pressure of the fuel supplied from the fuel tank 11 rises, and fueling is performed. Mixing of the fuel before and after refueling is performed abruptly. Due to such rapid mixing of the fuel, as shown in FIGS. 3 (a) and 3 (b), the ethanol concentration of the fuel in both delivery pipes 14R and 14L also suddenly changes from E0 (0%) to E85 (85%), Along with this sudden change in ethanol concentration, the time delay td as shown in FIG. 3 (c) is found in the learning of the ethanol concentration (alcohol concentration) described at the beginning, that is, the recognition of the ethanol concentration of the fuel injected from the injector 16. It comes to occur. For this reason, the fuel injection control according to the actual fuel property cannot be executed, and drivability is deteriorated due to a rapid change in the air-fuel ratio feedback correction amount. In this regard, in the present embodiment, as illustrated in FIG. 2, the fuel pressure switching valve 23 is maintained in the open state until the above conditions 1 and 2 are satisfied. An abrupt change in the correction amount is suppressed, and hence deterioration in drivability is also suppressed.

Next, details of the fuel supply and fuel injection control of the present embodiment executed by the electronic control unit 41 based on this background will be described with reference to FIGS.
First, the procedure for calculating the fuel injection amount injected from the injector 16 will be described with reference to the flowchart of FIG. The series of processing shown in this flowchart is repeatedly executed by the electronic control device 41 with a predetermined period.

  As shown in FIG. 4, in this series of processing, first, the basic fuel injection amount QBASE is calculated based on the engine rotational speed NE and the engine load calculated from the engine rotational speed NE and the intake air amount GA. (Step S200).

  Next, it is determined by the air-fuel ratio sensors 47L and 47R whether or not the air-fuel ratios DOL and DOR of the air-fuel mixture provided for each combustion in each bank can be detected (step S201). As described above, the air-fuel ratio sensors 47L and 47R cannot detect the air-fuel ratios DOL and DOR with high accuracy when the element temperature is lower than the predetermined activation temperature. When the element temperature is equal to or higher than the predetermined activation temperature, it is determined that the air-fuel ratios DOL and DOR can be detected by the air-fuel ratio sensors 47L and 47R.

  If it is determined that the air-fuel ratios DOL and DOR of both banks can be detected (step S201: YES), the left bank air-fuel ratio feedback correction is performed based on the values detected by the air-fuel ratio sensors 47L and 47R. A coefficient FAFL and a right bank air-fuel ratio feedback correction coefficient FAFR are calculated. The air-fuel ratio feedback correction coefficients FAFL and FAFR corresponding to these left and right banks are temporary values between the oxygen concentration of exhaust gas discharged when gasoline is burned under its stoichiometric air-fuel ratio and the oxygen concentration of actual exhaust gas. This is to compensate for the large discrepancy.

  When the air-fuel ratio feedback correction coefficients FAFL and FAFR for each of the left and right banks are thus calculated (step S203), it is next determined whether or not an execution condition for air-fuel ratio learning is satisfied (step S204). As the execution condition, for example, the vehicle is not accelerated or decelerated, the internal combustion engine is in a steady operation state, and a value obtained by subtracting “1.0” from the feedback correction coefficients FAFL and FAFR for each of the left and right banks. For example, the state where the absolute value is larger than the reference value continues for a predetermined period.

  Here, if it is determined that the execution condition of the air-fuel ratio learning is satisfied (step S204: YES), the average value FAFAVE of the left bank air-fuel ratio feedback correction coefficient FAFL in a predetermined period set in advance and the right bank empty An average value FAFAVER of the fuel ratio feedback correction coefficient FAFR is calculated (step S205).

  Then, the value obtained by subtracting “1.0” from the average values FAFAVE and FAFOVER of the feedback correction coefficients for the left and right banks, respectively, is added to the current air-fuel ratio learning value KG. Calculated as values KGL and KGR (step S206). The air-fuel ratio learned values KGL and KGR for the left and right banks calculated in this way are stored in the backup RAM of the storage unit 41a as the air-fuel ratio learned values corresponding to the left and right banks. As the air-fuel ratio learning value is updated, the feedback correction coefficients FAFL and FAFR for each of the left and right banks are set to “1.0” which is the initial value.

  Next, the air-fuel ratio learning values KGL and KGR for the left and right banks, and the ethanol concentration learning values KALCL and KALCR for the left and right banks obtained through the ethanol concentration learning processing routine shown in FIG. 5 are read from the backup RAM of the storage unit 41a ( Step S207).

  On the other hand, when the air-fuel ratio sensors 47L and 47R determine that the air-fuel ratios DOL and DOR cannot be detected (step S201: NO), the air-fuel ratio feedback correction coefficients FAFL and FAFR for each of the left and right banks are “1.0. (Step S202), the air-fuel ratio learned values KGL and KGR for the left and right banks and the ethanol concentration learned values KALCL and KALCR for the left and right banks are read (step S207). Even when it is determined that the execution condition for air-fuel ratio learning is not satisfied (step S204: NO), the air-fuel ratio learning values KGR and KGL for the left and right banks, and the ethanol concentration learning value KALCL for the left and right banks, Each KALCR is read (step S207).

  Next, the air-fuel ratio learning values KGL and KGR calculated for the left and right banks and the ethanol concentration learning values KALCL and KALCR, the air-fuel ratio feedback correction coefficient FAFL, The average value of FAFR is calculated. By this averaging process, the air-fuel ratio learning average value KGa, the ethanol concentration learning average value KALCa, and the air-fuel ratio feedback correction coefficient average value FAFa are calculated (step S208).

  Finally, the air-fuel ratio learning average value KGa, the ethanol concentration learning average value KALCa, and the air-fuel ratio feedback correction coefficient average value FAFa calculated by the averaging process are added, and the added value and the basic fuel injection amount QBASE are calculated. The integrated value is calculated as the final fuel injection amount QFIN (step S209).

When the final fuel injection amount QFIN is calculated in this way, this series of processing is once ended.
Actually, the fuel injection time TAU, that is, the valve opening time of the injector 16 is calculated based on the final fuel injection amount QFIN calculated through the fuel injection amount calculation processing and the fuel injection pressure P detected by the fuel pressure sensor 45. Is done. Then, the electronic control unit 41 opens the injector 16 based on the fuel injection time TAU. As a result, an amount of fuel corresponding to the final fuel injection amount QFIN is injected from the injector 16.

  Incidentally, as described above, the flexible fuel internal combustion engine according to the present embodiment uses a mixed fuel containing ethanol having a theoretical air / fuel ratio smaller than that of gasoline. It is necessary to correct the fuel injection amount so that it becomes equal to the oxygen concentration of the exhaust gas discharged when burned. And by performing correction | amendment of such fuel injection amount, the purification performance of the catalyst apparatus provided in the exhaust passage can fully be exhibited, and it becomes possible to suppress the deterioration of exhaust property.

  Therefore, in the present embodiment, the ethanol concentration of the fuel is estimated based on the detection values of the air-fuel ratio sensors 47R and 47L provided in the exhaust passage, and the value to be corrected is learned, and the above steps S208 and S209 are performed. As in this process, the fuel injection amount is corrected based on the learned value. In addition, the final fuel injection amount QFIN is obtained by using the average value of the learning values of the left and right banks so as to suppress the variation in the air-fuel ratio between the left and right banks caused by the divergence of ethanol fuel in the left and right delivery pipes. Yes. Even if the ethanol concentration of the fuel in one delivery pipe suddenly changes, such an averaging process can suppress a sudden change in the final fuel injection amount QFIN.

Hereinafter, the ethanol concentration learning process will be described with reference to FIGS. 5 and 6.
FIG. 5 is a flowchart showing a processing procedure of the ethanol concentration learning process. A series of processing shown in this flowchart is also repeatedly executed by the electronic control device 41 with a predetermined cycle. Note that during the execution of the ethanol concentration learning process, the execution of the air-fuel ratio learning process (steps S203 to S207) in the fuel injection amount calculation process is prohibited. This ethanol concentration learning process is executed separately for the left and right banks.

  As shown in FIG. 5, in this series of processing, first, after the refueling operation is performed, it is determined whether or not the learning of the ethanol concentrations ALCL and ALCR for each of the left and right banks has not been completed (step). S300). Specifically, when the refueling operation flag XF is set to “ON”, it is determined that the learning of the ethanol concentrations ALCL and ALCR for each of the left and right banks has not been completed after the refueling operation. This refueling operation flag XF is set to “ON” when the fuel amount FL in the fuel tank 11 increases by a predetermined amount or more, and thereafter, when the learning of the ethanol concentrations ALCL and ALCR for each of the left and right banks is completed, that is, It is set to “OFF” when the concentration to be learned reaches a stable concentration.

When it is determined that the refueling operation flag XF is “OFF” (step S300: NO), this series of processes is temporarily terminated.
On the other hand, if it is determined that the refueling operation has been performed (step S300: YES), it is next determined whether or not the ethanol concentration learning execution condition is satisfied (step S301). Here, in both the left and right banks, when the following condition (A) and condition (B) are satisfied, it is determined that the ethanol concentration learning execution condition is satisfied.

(Condition A) Left bank air-fuel ratio sensor 47L and right bank air-fuel ratio sensor 47R are activated (Condition b) Absolute value of left bank air-fuel ratio feedback correction coefficient FAFL ≠ 1.0
Absolute value of right bank air-fuel ratio feedback correction coefficient FAFR ≠ 1.0
Here, when it is determined that the ethanol concentration learning execution condition is not satisfied (step S301: NO), this series of processes is temporarily terminated.

  On the other hand, when it is determined that the ethanol concentration learning execution condition is satisfied (step S301: YES), for example, based on the detection results of the air-fuel ratio sensors 47L and 47R when a fixed amount of fuel is injected in the left and right banks. Air-fuel ratio feedback correction coefficients FAFL and FAFR corresponding to the left and right banks are calculated. Deviations ΔFAFL and ΔFAFR between these values and the initial values (= 1.0) of the air-fuel ratio feedback correction coefficients FAFL and FAFR are calculated. Based on these deviations ΔFAFL and ΔFAFR, ethanol concentrations ALCL and ALCR in the left and right delivery pipes are estimated (step S302).

  That is, as shown in FIG. 6A, in the case of engine start immediately after refueling, deviations ΔFAFL and ΔFAFR between the left and right bank feedback correction coefficients FAFL and FAFR calculated after refueling and their initial values (= 1.0). Depends on the ethanol concentration. Therefore, the ethanol concentrations ALCL and ALCR of the fuel can be estimated based on the deviations ΔFAFL and ΔFAFR of the air-fuel ratio feedback correction coefficients FAFL and FAFR of the left and right banks.

  Thereafter, the ethanol concentration learning values KALCL and KALCR for each of the left and right banks, which are correction values corresponding to the estimated ethanol concentrations ALCL and ALCR, are calculated through the calculation map shown in FIG. 6B (step S303). These calculation maps are created in advance based on results obtained through experiments and the like, and are stored in the ROM of the storage unit 41a. Further, the left bank ethanol concentration learned value KALCL and the right bank ethanol concentration learned value KALCR calculated in this way are stored in the backup RAM of the storage unit 41a.

  Note that the right delivery pipe 14R and the left delivery pipe 14L located downstream of the right delivery pipe have different fuel mixing conditions for engine start immediately after refueling, and therefore are calculated based on the detection result of the air-fuel ratio sensor 47R. The right bank air-fuel ratio feedback correction coefficient FAFR is different from the left bank air-fuel ratio feedback correction coefficient FAFL. As a result, in the ethanol concentration learning process described above, the difference between the calculated learning values between the left and right banks is correlated with the actual difference in fuel ethanol concentration between the left and right delivery pipes.

FIG. 7 shows the fuel pressure for controlling the opening and closing of the fuel pressure switching valve 23 under the conditions 1 and 2 described with reference to FIG. 2 while performing the calculation of the fuel injection amount and the learning of the ethanol concentration. It is a flowchart which shows the control procedure about switching valve opening / closing control, and hereafter, the detail of the fuel supply control by the control apparatus of this Embodiment is demonstrated with reference to this FIG. A series of processing shown in this flowchart is executed by the electronic control device 41 every time the engine is started.

  As shown in FIG. 7, at the time of this control, it is first determined whether or not the above-described refueling operation flag XF is set to “ON” as a determination as to whether or not the engine has been started for the first time after refueling ( Step S500). In this determination process, when the engine start operation is performed while the flag XF is “ON”, it is determined that the refueling operation is performed while the engine is stopped.

  If it is determined that the refueling operation flag XF is set to “OFF” through this process (step S500: NO), a process for closing the fuel pressure switching valve 23 is then performed (step S510). Thereafter, the learned values KALCL and KALCR for the left and right banks of fuel, which are correction values used for calculating the fuel injection amount, are set to the values KALCL0 and KALCR0 learned for each left and right banks during the previous engine operation ( Step S511), this process is terminated.

On the other hand, if it is determined that the refueling flag XF is set to "ON" (step S500: YES), again in a higher than suitable temperature value T ₀ at engine starting, further the engine temperature is above It is determined whether or not the engine has been started (step S501). Specifically, the engine coolant temperature THW as an alternative value of the temperature of the fuel remaining in the delivery pipe is detected by the coolant temperature sensor 44, engine temperature and fuel on the basis of that the temperature is above the optimum temperature value T ₀ It is determined that the temperature is in an appropriate temperature state.

When it is determined through this process that the engine is restarted in a state higher than the optimum temperature value T ₀ at the time of engine start (step S501: YES), a process for closing the fuel pressure switching valve 23 is executed as it is ( Step S506), this process is terminated.

On the other hand, if the engine temperature is determined that it is the appropriate temperature value _{T 0} or less (step S501: NO), First processing is executed to open the fuel pressure switching valve 23 (step S502). The difference between the left bank ethanol concentration learned value KALCL after fuel refueling and the left bank starting learned value KALCL0 learned during the previous engine operation is equal to or greater than the reference value α1 (FIG. 2) of the concentration change at low temperatures described above. Is determined (step S503a). By this determination processing, it is determined whether or not fuel having an ethanol concentration different from that before refueling has been supplied by the refueling operation, and whether or not the ethanol concentration in the left delivery pipe 14L has actually changed.

  When it is determined that the difference between the left bank ethanol concentration learned value KALCL after fuel refueling and the left bank start learned value KALCL0 is less than the aforementioned low temperature concentration change reference value α1 (FIG. 2). (Step S503a: NO), this determination process is repeated until the time Ts1 elapses (Steps S503a and S503b). This time Ts1 is a necessary measurement time for detecting a change in the ethanol concentration in the left delivery pipe 14L only through fuel injection by the injector 16 when the fuel pressure switching valve 23 is in the open state after the engine is started. When the property (concentration) changes due to fuel supply, the minimum time required for measuring the change is set.

That is, even if the necessary measurement time Ts1 has elapsed, the difference between the left bank ethanol concentration learning value KALCL after fuel supply and the left bank starting learning value KALCL0 learned during the previous engine operation is less than the reference value α1. If it is determined that there is (step S503b: YES), it is determined that there is no significant change in the ethanol concentration of the fuel supplied. In this case, the same processing as in the case where the engine has not been started for the first time after the refueling operation is performed, and this processing is terminated. That is, the fuel pressure switching valve 23 is closed (step S510), and then the ethanol concentration learning values KALCL and KALCR of the left and right banks of the fuel, which are correction values used for calculating the fuel injection amount, are learned during the previous engine operation. Learning value KA at start of left and right banks
LCL0 and KALCR0 are set (step S511).

  On the other hand, the difference between the left bank ethanol concentration learned value KALCL after fueling through the processing of steps S503a and S503b and the learned value KALCL0 learned during the previous engine operation is equal to or higher than the concentration change reference value α1 at low temperature. If it is determined (step S503a: YES), it is determined that the ethanol concentration of the fuel has changed to an extent that affects the combustion.

  When such a determination is made, the ethanol concentration learning values KALCL and KALCR in the left and right banks are first set to the starting learning values KALCL0 and KALCR0 once learned for the left and right banks during the previous engine operation (step S504). Then, until it is determined that the difference between the left bank ethanol concentration learning value KALCL and the right bank ethanol concentration learning value KALCR is equal to or greater than the reference value β (FIG. 2), the ethanol concentration learning illustrated in FIG. The process is repeated (steps S505a and S505b). After such processing, when it is determined that the difference between the left bank ethanol concentration learned value KALCL and the right bank ethanol concentration learned value KALCR is equal to or greater than the previous reference value β (FIG. 2) (step S505a: YES) ), It is estimated that the ethanol concentration of the fuel in the right delivery pipe 14R approaches the actual ethanol concentration, that is, the ethanol concentration of the fuel in the fueled fuel tank 11. At this time, the fuel pressure switching valve 23 is driven to close (step S506), and this series of processing ends.

  FIG. 8 shows an example of an operation example associated with such fuel pressure switching valve opening / closing control. In FIG. 8, the ethanol concentration of the fuel to be newly supplied is higher than the ethanol concentration ALC of the fuel remaining in the fuel tank 11, and the operation of each part is performed when the engine is restarted at a low temperature. It shows the ethanol concentration transition.

As shown in FIG. 8, a refueling operation is performed at timing t1 while the internal combustion engine is stopped (FIG. 8 (a)), and then the ignition switch is turned ON at timing t2, and the internal combustion engine is operated. Is restarted (FIG. 8B). At this time, since the engine temperature (cooling water temperature) is equal to or lower than the appropriate temperature value T ₀ , the fuel pressure switching valve 23 is opened, and the recirculation of fuel through the high pressure return pipe 17 is limited (FIG. 8 (c)).

  When the internal combustion engine is restarted in this state, the fuel newly supplied into the left and right delivery pipes 14L and 14R as fuel is injected by the injector 16 is gradually supplied through the main pipe 13 and before the fuel supply. And the newly supplied fuel are mixed, the ethanol concentration in the fuel gradually increases from the right delivery pipe 14R located upstream to the left delivery pipe 14L located downstream.

  Thereafter, assuming that the ethanol concentration of the fuel in the left delivery pipe 14L reaches a concentration equal to or higher than the reference value α1 before the elapse of the time Ts1 at timing t3 (FIG. 8D), between the left and right banks. Is started to be monitored, and the fuel pressure switching valve 23 is driven to close at a timing t4 when the difference reaches the reference value β (FIGS. 8E and 8C). . As described above, the timing at which the deviation of the ethanol concentration learning value reaches the reference value β is the time when the fuel concentration in the fuel tank 11 is increased to the ethanol concentration of the fuel in the fuel tank 11 through the previous fuel injection by the injector 16. This is the time when it is determined that the ethanol concentration of the fuel is approaching, and at this point, the following restrictions on fuel recirculation are released, and large variations on the air-fuel ratio and the like are alleviated.

When the fuel pressure switching valve 23 is closed in this way, newly supplied fuel is recirculated into the fuel tank 11 through the high-pressure return pipe 17 as the fuel pressure increases.
By this recirculation, the ethanol concentration of the fuel in the fuel supply path becomes uniform, and thereafter, stable fuel injection that does not cause air-fuel ratio variation or the like is continued according to the uniform ethanol concentration ( FIG. 8 (f)).

As described above, according to the control apparatus for an on-vehicle internal combustion engine according to the present embodiment, the following effects can be obtained.
(1) In the above embodiment, the ethanol concentration learning value KALCL for each left and right bank estimated from the detection values of the air-fuel ratio sensors 47L and 47R corresponding to the left and right banks after the electronic control unit 41 detects the refueling operation. In addition, the fuel in the left and right delivery pipes is restricted from being returned to the fuel tank 11 through the high-pressure return pipe 17 until the difference between KALCR and the reference value β is exceeded. For this reason, the fuel before the refueling operation remaining in the left and right delivery pipes 14L and 14R and the main pipe 13, that is, the fuel whose learning value of ethanol concentration has already been set and the refueled fuel are gradually mixed. Thus, the fuel injected from the injector 16 can be gradually changed from the ethanol concentration before the refueling operation to the ethanol concentration changed by the refueling operation. Therefore, fuel injection can be performed while avoiding a large divergence between the ethanol concentration recognized through ethanol concentration learning and the actual ethanol concentration, and the deterioration of the air-fuel ratio due to this divergence can be avoided. Can be suppressed. That is, it is possible to suitably suppress the deterioration of drivability during the period.

  (2) As a condition for canceling the restriction of recirculation, the difference between the ethanol learning values KALLR and KALCR for each of the left and right banks is equal to or greater than the reference value β, that is, the ethanol concentration of the fuel in the right delivery pipe 14R located upstream is the fuel tank. 11 was determined to be equal to or more than an index value for judging that the fuel concentration in the fuel was close to the ethanol concentration. For this reason, the continuity of the air-fuel ratio change from the state before the release of the recirculation restriction can be smoothly maintained, and the drivability after that time can be well maintained.

  (3) In relation to the above (1) and (2), ethanol concentration learning is performed while monitoring changes in the properties of the fuel in the left and right delivery pipes 14L and 14R even in a region where drivability cannot be ensured conventionally. Can be implemented. In other words, the ethanol concentration learning area can be expanded.

(4) When the engine is started after refueling, the fuel pressure switching valve 23 is closed to allow the fuel to recirculate after the overall concentration deviation of the fuel in the fuel supply path is reduced. As a result, conventionally, as a condition for ensuring drivability, the engine temperature has been required to exceed an appropriate temperature value T ₀ (34 ° C.). However, this condition is extended to a low temperature region of 0 ° C. or higher, for example. In addition, the learning speed for ethanol concentration learning can be accelerated.

  (5) The final fuel injection amount QFIN is calculated based on the average value of the learning values calculated for the left and right banks. As a result, the change in the ethanol concentration for each of the left and right banks is averaged, and the variation in the final fuel injection amount QFIN accompanying the sudden change in the fuel properties, and hence the deterioration of the air-fuel ratio can be suppressed.

(6) Prior to the comparison between the difference between the ethanol concentration learning values for the left and right delivery pipes 14L and 14R and the reference value β, the change in the ethanol concentration learning value of the fuel in the left delivery pipe 14L located downstream is first monitored. It was decided. At this time, if a change in the ethanol concentration learning value in the left delivery pipe 14L that is greater than or equal to the reference value α1 occurs due to a refueling operation or the like, the ethanol for the left and right delivery pipes 14L and 14R is separated on this condition The comparison between the deviation of the concentration learning value and the reference value β was started. For this reason, it becomes possible to capture the change in the properties of the fuel more reliably, and it is necessary while avoiding unnecessary comparison between the difference in the ethanol concentration learning value between the left and right delivery pipes 14R and 14L and the reference value β. Sometimes, the switching control of the fuel pressure switching valve 23 based on the comparison can be performed with high accuracy.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the low temperature concentration change reference value α1 is used as the reference value for determining whether or not the ethanol concentration of the fuel in the left delivery pipe 14L at the time of engine low temperature start has changed due to the refueling operation. Using. Not limited thereto, using a reference value α2, as shown by a broken line in earlier shown in FIG. 2 (b) as the value of monitoring the change in concentration at high temperatures when the engine temperature is in the optimum temperature value T ₀ or more, the engine temperature even if it exceeds proper temperature value T ₀ monitors the change in the fuel properties of the left delivery pipe 14L, it is also possible to perform a reflux restriction process in accordance with a change in the fuel property in the left delivery pipe.

That is, as shown in FIG. 9, when it is determined that an engine restart at higher than engine start a suitable temperature value T ₀ (step S501: YES), passed necessary measurement time Ts2 at high temperature Whether the difference between the ethanol concentration learning value KALCL in the left bank after fueling and the starting learning value KALCL0 in the left bank learned during previous engine operation is equal to or higher than the concentration change reference value α2 at high temperature Is determined (steps S520a and S520b). By this determination processing, whether or not fuel having an ethanol concentration different from that before refueling was supplied by the refueling operation even when the fuel temperature and the engine temperature were at appropriate temperatures, and the ethanol concentration in the left delivery pipe 14L actually changed. A determination is made whether or not. On the other hand, even if the necessary measurement time Ts2 has elapsed, it is determined that the difference between the left bank learned value KALC after fueling and the left bank starting learned value KALCL0 learned during the previous engine operation is lower than the reference value α2. If it is determined (step S520a: NO), the fuel temperature and the engine temperature are in an appropriate temperature state, and the ethanol concentration of the fuel that has been refueled and the ethanol concentration of the fuel before the refueling operation are substantially the same fuel. Thus, the same processing as that in the case where the engine is not started for the first time after the refueling operation (step S500: NO) is performed. That is, after the fuel pressure switching valve 23 is closed, the learned values KALCL and KALCR of the left and right banks of fuel, which are correction values used for calculating the fuel injection amount, are values learned during the previous engine operation. The starting learning values KALCL0 and KALCR0 are set (step S511), and a series of processing ends. On the other hand, when it is determined that the difference between the left bank ethanol concentration learned value KALCL after fuel supply and the left bank ethanol concentration learned value KALCL0 learned during the previous engine operation is equal to or greater than the reference value α2. (Step S520a: YES), it is estimated that the fuel temperature and the engine temperature are in the proper temperature state, and the fuel for which the refueling operation has been performed is different from the ethanol concentration before fuel refueling. For this reason, the process of closing the fuel pressure switching valve 23 is executed (step S521), and the learning values KALCL and KALCR of the left and right banks are set to the concentration learning initial value KALCI, which is the initial value (step S522). Here, the concentration learning initial value KALCI is the lowest of the low concentration learning value and the ethanol concentration ALC set when the ethanol concentration ALC is the lowest among the concentration learning values learned through the ethanol concentration learning process (that is, 0%). It is an average value with the high concentration learning value set when it is high (85%). When the density learning value initialization process is executed in this way, this series of processes is terminated.

According to this modification, even when the engine temperature exceeds the appropriate temperature value T ₀ , the change in the fuel property in the left delivery pipe 14L is monitored by the concentration change reference value α2 at a high temperature, and the fuel property When the change is so significant that the influence on the air-fuel ratio is concerned, the fuel flow recirculation restriction process is performed in the same manner as when the engine temperature is low. Thereby, the deterioration of the dryness resulting from the change of a fuel property can be suppressed more suitably.

In the above embodiment or the above modified example, when the engine is started for the first time after the refueling operation and the engine water temperature is restarted in a state higher than the appropriate temperature value T ₀ at the time of starting the engine, the fuel pressure The process of closing the switching valve 23 is executed, and the left and right delivery pipes 1 through the high pressure return pipe 17.
4L, but be prohibited to limit that fuel 14R is returned to the fuel tank 11, the engine water temperature is even higher than the engine startup suitable temperature value T _0, the right and left delivery pipe 14L, the 14R You may make it restrict | limit that a fuel is returned to the fuel tank 11. FIG.

  In the above embodiment, after the refueling operation, if it is not the first engine start time, the restriction process is not executed, but if a refueling operation is detected, it is determined whether or not the engine start time. Regardless, the fuel pressure switching valve 23 may be opened to restrict the fuel in the left and right delivery pipes 14L, 14R from being returned to the fuel tank 11 through the high pressure return pipe 17. That is, the refueling operation is not limited to when the engine is stopped, and may be executed while the engine is operating. Therefore, the restriction process may be started not when the engine is started but when the refueling operation is detected.

  In the above embodiment, when it is detected that the refueling operation has been performed at the time of restarting the engine, the delivery pipe 14R, through the high pressure return pipe 17 is opened by opening the fuel pressure switching valve 23 provided in the low pressure return pipe 18. The 14 L fuel is restricted from being returned to the fuel tank 11, and a certain amount of fuel before the refueling operation is left in the delivery pipes 14 R, 14 L and the main pipe 13. Not limited to this, the discharge pressure of the fuel pump 12 is made smaller than when no refueling operation is detected, so that the fuel in the delivery pipes 14R, 14L is restricted from being returned to the fuel tank 11. Good.

  In the above embodiment, when the refueling operation flag XF is set to “ON”, it is determined that the refueling operation has been performed while the engine is stopped. However, the present invention is not limited to this. When the difference between the left bank ethanol concentration learned value KALCL and the left bank start learned value KALCL0 is higher than the low temperature concentration change reference value α1, it is determined that the refueling operation has been performed. May be. Further, a detecting means for detecting opening / closing operation of the lid of the fuel filler opening may be provided, and the presence / absence of the refueling operation may be determined based on opening / closing of the lid. Furthermore, a means for detecting an operation of inserting the fuel gun into the fuel filler port may be provided, and the presence or absence of the fueling operation may be determined based on the presence or absence of the insertion.

  In the above embodiment, it is detected that the fuel property changes based on the difference between the left bank ethanol concentration learned value KALCL and the left bank start-up learned value KALCL0 (condition 1). In addition to this, in order to detect a change in fuel properties early and efficiently, a difference between the right bank ethanol concentration learned value KALCR and the right bank starting learned value KALCR0 may be used as an alternative value.

  In the above embodiment, the final fuel injection amount QFIN is calculated based on the average value of the learning values of the left and right banks. However, the present invention is not limited to this, and based on the learning values calculated for the left and right banks, The final fuel injection amount QFIN may be calculated for each bank. In this case, the value of the reference value β used to determine the difference between the ethanol concentration learning values in the left and right delivery pipes 14L and 14R may be changed according to the calculated final fuel injection amount QFIN. .

  In the above embodiment, the learning values KALCL, KALCLR, and KALCL0 based on the estimated ethanol concentration value are used as the judgment values for the fuel recirculation control that controls the open / close state of the fuel pressure switching valve 23 in the conditions 1 and 2. Not limited to this, in performing fuel recirculation control based on the fuel properties in the left and right delivery pipes 14L and 14R, the air-fuel ratio learning values KGL and KGR, the air-fuel ratio feedback correction coefficients FAFL and FAFR for each left and right bank, or these The fuel injection correction amount based on the above may be used as a judgment value for fuel recirculation control. That is, in short, during a period in which the deviation of the air-fuel ratio detected separately for the plurality of banks is less than the reference value (β equivalent value), the fuel is prohibited from recirculating through the high-pressure return pipe 17, and the air-fuel ratio What is necessary is just to permit the return of the fuel through the high-pressure return pipe 17 when the deviation exceeds the reference value.

  In the above-described embodiment, the fuel flow recirculation control means is required to satisfy the conditions 1 and 2. However, the present invention is not limited to this. It may be a requirement. In other words, the fuel recirculation may be controlled based only on the change in the value indicating the fuel property for the left and right banks.

  In the above embodiment, the fuel recirculation switching mechanism is embodied in the fuel pressure switching valve 23 that can be opened and closed. However, the present invention is not limited to this, and any fuel recirculation switching mechanism may be used as long as it can prohibit or permit fuel recirculation by controlling the flow resistance of the fuel supply path.

  In the above embodiment, the air-fuel ratio detection means is embodied by the air-fuel ratio sensors 47L and 47R. However, the present invention is not limited to this, for example, oxygen recirculation control based on the change in fuel properties for the left and right banks. A configuration may be used in which a change in fuel property for each left and right bank is estimated using a concentration sensor or the like.

  In the above embodiment, the ethanol concentration of the mixed fuel differs each time depending on the ethanol concentration of the fuel remaining in the fuel tank 11 and the ethanol concentration of the fuel injected into the fuel tank 11 by the refueling operation. Although it is assumed that it varies within the range of 0% (gasoline only) to 85%, for example, even when using a mixed fuel in which the ethanol concentration varies from 0% to 100% (ethanol only) The present invention can be embodied in the form according to the embodiment.

  In the above embodiment, the alcohol mixed with gasoline is ethanol, but is not limited to this, and may be methanol, isopropyl ethanol, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic and block diagram which mainly show the structure of the fuel supply system about one Embodiment of the control apparatus of the vehicle-mounted internal combustion engine concerning this invention. (A)-(c) is a graph which shows the ethanol concentration transition of the fuel inject | poured from the change of the ethanol concentration in a right-and-left delivery pipe, and the injector 16. FIG. (A)-(c) is a graph which shows the ethanol concentration transition of the fuel injected from the injector 16 and the change of the ethanol concentration in a right-and-left delivery pipe as a comparative example of FIG. The flowchart which shows the process sequence about the fuel injection amount calculation process by the embodiment. The flowchart which shows the process sequence about the ethanol concentration learning process by the embodiment. (A) is a graph which shows the relationship between the variation | change_quantity of an air fuel ratio feedback correction coefficient, and the ethanol concentration of a fuel. (B) is a graph showing the relationship between the ethanol concentration of the fuel and the ethanol concentration learning value. The flowchart which shows the control procedure about the fuel pressure switching valve opening / closing control by the embodiment. The timing chart which shows the operation example accompanying the fuel pressure switching valve opening / closing control of the embodiment. The flowchart which shows the control procedure about the modification of the fuel pressure switching valve opening / closing control by the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Fuel tank, 12 ... Fuel pump, 13 ... Main piping, 14R ... Right delivery pipe, 14L ... Left delivery pipe, 15 ... Communication pipe, 16 ... Injector, 17 ... High pressure return piping, 18 ... Low pressure return piping, 21 ... High pressure regulator, 22 ... Low pressure regulator, 23 ... Fuel pressure switching valve (open / close valve), 31L ... Exhaust pipe for left bank, 31R ...
Exhaust pipe for right bank, 32L ... three-way catalyst for left bank, 32R ... three-way catalyst for right bank, 41 ... electronic control unit, 41a ... storage unit, 42 ... engine speed sensor, 43 ... intake air amount sensor, 44 ... cooling water temperature sensor, 45 ... fuel pressure sensor, 46 ... fuel amount sensor, 47R ... right bank air-fuel ratio sensor, 47L ... left bank air-fuel ratio sensor.

Claims (6)

A fuel supply device provided in each of the first and second banks of the in-vehicle internal combustion engine is connected in series to connect the fuel supplied from the fuel tank to the second bank via the fuel supply device of the first bank. A fuel supply mechanism for supplying to the fuel supply device of
A fuel recirculation switching mechanism capable of switching between a permitted state permitting fuel recirculation from the fuel supply device of the second bank to the fuel tank and a prohibited state prohibiting recirculation of the fuel;
Air-fuel ratio detecting means for detecting the air-fuel ratio of the air-fuel mixture provided for combustion from the exhaust gas of each bank in the first bank and the second bank;
During the period in which the detected air-fuel ratio difference for each bank is less than the reference value, the fuel recirculation switching mechanism is controlled to be switched to the prohibited state, and the difference in the air-fuel ratio becomes larger than the reference value. Fuel recirculation control means for switching and controlling the fuel recirculation switching mechanism to the permitted state;
A control device for an on-vehicle internal combustion engine comprising: The fuel recirculation control means monitors the change in the property of the fuel in the fuel supply device of the second bank prior to the comparison between the detected air-fuel ratio difference for each bank and the reference value. 2. The control device for an on-vehicle internal combustion engine according to claim 1, wherein the comparison between the detected divergence of the air-fuel ratio for each bank and the reference value is started on the condition that a predetermined change or more occurs. The fuel recirculation control means monitors the change in the property of the fuel in the fuel supply device of the first bank prior to the comparison between the detected air-fuel ratio difference for each bank and the reference value, and the property of the fuel 2. The control device for an on-vehicle internal combustion engine according to claim 1, wherein the comparison between the detected divergence of the air-fuel ratio for each bank and the reference value is started on the condition that a predetermined change or more occurs. The on-vehicle internal combustion engine control device according to claim 2 or 3, wherein the fuel recirculation control means switches the fuel recirculation switching mechanism to the permitted state when a change of a predetermined value or more has not occurred in the property of the fuel. The fuel recirculation control means unconditionally switches the fuel recirculation switching mechanism to the permitted state when the temperature at the start of the in-vehicle internal combustion engine is equal to or higher than an appropriate temperature at which autonomous operation is possible in the properties of the fuel used. The on-vehicle internal combustion engine control device according to any one of claims 1 to 4. The fuel recirculation switching mechanism includes a high-pressure return pipe that recirculates fuel in the fuel supply device to the fuel tank via a pressure regulator provided at a terminal portion of the fuel supply device of the second bank, and an open / close valve. A low-pressure return pipe that branches and recirculates fuel supplied to the fuel supply device of the first bank to the fuel tank via a fuel pressure switching valve, and the fuel recirculation control means includes the fuel pressure switching valve. The fuel recirculation switching mechanism is controlled to be switched to the prohibited state with the valve open state, and the fuel recirculation switching mechanism is switched to the permission state while the fuel pressure switching valve is closed. The control device for the on-vehicle internal combustion engine according to the item.

Images