JP2009191650A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of a lean difference in an air-fuel ratio by a shortage of delivery capacity of a fuel pump in a high rotation-high load area, even when using fuel of the high alcohol concentration. <P>SOLUTION: An alcohol concentration sensor 37 is arranged for detecting the alcohol concentration of the fuel supplied to a fuel injection valve 21 by the fuel pump 31 from a fuel tank 30. The stoichiometric air-fuel ratio of the fuel reduces as the alcohol concentration of the fuel increases, and since there is the relationship of increasing a fuel injection quantity required for controlling the actual air-fuel ratio in the stoichiometric air-fuel ratio, the fuel injection quantity is increasingly corrected in response to the alcohol concentration of the fuel so as to increase the fuel injection quantity as the alcohol concentration of the fuel detected by the alcohol concentration sensor 37 increases. The suction air volume is limiting by limiting throttle opening in response to the alcohol concentration of the fuel so that fuel consumption per unit time of an engine 11 does not exceed maximum delivery capacity of the fuel pump 3 by a quantity increase correction of this fuel injection quantity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

In recent years, demands for automobiles equipped with engines (internal combustion engines) that can use gasoline, alcohol, and mixed fuels of both as fuels have increased due to social demands such as reducing CO ₂ emissions and using alternative fuels for oil. is doing. In such an automobile, when fuel having a different alcohol concentration from the previous time is supplied to the fuel tank, the alcohol concentration of the fuel in the fuel tank changes. Since the theoretical air-fuel ratio differs between gasoline and alcohol, if the alcohol concentration of the fuel changes, the theoretical air-fuel ratio of the fuel also changes. Therefore, the fuel injection amount (actual air-fuel ratio) depends on the alcohol concentration of the fuel (theoretical air-fuel ratio). ) Need to be changed.

Therefore, as described in Patent Document 1 (Japanese Patent Laid-Open No. 3-85347), the alcohol concentration of the fuel is detected by an alcohol concentration sensor, and the fuel injection amount is corrected according to the detected value. Or, as described in Patent Document 2 (JP 2005-48625 A), Patent Document 3 (JP 2007-9903 A), and Patent Document 4 (JP 2007-146831 A), Some have estimated the alcohol concentration of fuel based on the output of an air-fuel ratio sensor for detecting the air-fuel ratio of exhaust gas, and corrected the fuel injection amount in accordance with the estimated value.
JP-A-3-85347 JP-A-2005-48625 JP 2007-9903 A JP 2007-146831 A

  Incidentally, since the theoretical air-fuel ratio of alcohol is smaller than the theoretical air-fuel ratio of gasoline, the higher the alcohol concentration of the fuel, the smaller the theoretical air-fuel ratio of the fuel, and it is necessary to increase the fuel injection amount. For this reason, when using fuel with a high alcohol concentration, a fuel pump that supplies fuel to the fuel injection valve with fuel consumption per unit time in a high rotation / high load region where fuel consumption per unit time increases. The maximum required discharge capacity (maximum discharge flow rate) may be exceeded (see Fig. 2), and as a result, the required injection required to control the actual air-fuel ratio to the stoichiometric air-fuel ratio in the high rotation and high load range. There is a possibility that an amount of fuel cannot be injected, the actual air-fuel ratio shifts to the lean side, and exhaust emission deteriorates.

  As a countermeasure, it is conceivable to change to a fuel pump with a large maximum discharge capacity so that a fuel amount corresponding to the required injection amount can be injected even in a high rotation / high load region when using 100% alcohol fuel. This increases the size and cost of the fuel pump, and cannot meet the demands for downsizing and cost reduction, which are important technical issues in recent years.

  The present invention has been made in view of such circumstances. Therefore, even when a fuel with a high alcohol concentration is used, the object of the present invention is to reduce the air-fuel ratio due to insufficient discharge capacity of the fuel pump in a high rotation / high load region. An object of the present invention is to provide a control device for an internal combustion engine that can prevent the occurrence of lean deviation and deterioration of exhaust emission, and can avoid an increase in size and cost of a fuel pump.

  In order to achieve the above object, an invention according to claim 1 is provided with a fuel pump for supplying fuel in a fuel tank to a fuel injection valve, and an internal combustion engine capable of using a mixed fuel of gasoline and alcohol as fuel. The control device includes alcohol concentration determination means for detecting or estimating the alcohol concentration of the fuel, and control means for correcting the fuel injection amount of the fuel injection valve based on the alcohol concentration detected or estimated by the alcohol concentration determination means. The output of the internal combustion engine is limited in accordance with the alcohol concentration so that the fuel consumption per unit time of the internal combustion engine does not exceed the maximum discharge capacity of the fuel pump.

  In this configuration, since the output of the internal combustion engine is limited according to the alcohol concentration of the fuel so that the fuel consumption per unit time of the internal combustion engine does not exceed the maximum discharge capacity of the fuel pump, a fuel with a high alcohol concentration is used. Even in this case, it is possible to prevent the output of the internal combustion engine from being controlled beyond the range in which the required amount of fuel can be injected (the range in which the actual air-fuel ratio can be controlled to the stoichiometric air-fuel ratio). It is possible to prevent an air-fuel ratio lean shift and exhaust emission deterioration due to insufficient discharge capability of the fuel pump in the region, and to avoid an increase in size and cost of the fuel pump.

  Here, when the output of the internal combustion engine is limited so that the fuel consumption amount per unit time of the internal combustion engine does not exceed the maximum discharge capacity of the fuel pump, for example, the detection is performed by the alcohol concentration determination means as in claim 2. Alternatively, the intake air amount of the internal combustion engine may be limited according to the estimated alcohol concentration of the fuel. In this case, the intake air amount is limited by restricting intake system control parameters such as throttle opening, variable valve control amount (valve timing, valve lift amount, working angle), turbocharger supercharging pressure, and the like. . If the intake air amount is limited in the high-speed / high-load region where the fuel consumption per unit time of the internal combustion engine increases, the fuel injection amount required to control the actual air-fuel ratio to the stoichiometric air-fuel ratio is reduced. And the increase in the rotational speed of the internal combustion engine can be suppressed, so that an increase in fuel consumption per unit time of the internal combustion engine can be suppressed in the region of high rotation and high load, It is possible to prevent an air-fuel ratio lean shift and exhaust emission deterioration due to insufficient pump discharge capacity.

  In addition, the present invention may limit the rotational speed of the internal combustion engine according to the alcohol concentration of the fuel. As a method for limiting the rotational speed of the internal combustion engine, for example, a reduced-cylinder operation that cuts (stops) fuel injection in some cylinders may be performed, or the ignition timing, variable valve control amount, and the like may be controlled in the torque decreasing direction. Even if the rotation speed of the internal combustion engine is limited, the fuel consumption per unit time of the internal combustion engine can be limited.

  Further, as in claim 3, the present invention is applied to a system including throttle opening control means for controlling the throttle opening in accordance with the required torque set based on the accelerator opening or the like to control the intake air amount. In this case, the required torque may be limited according to the alcohol concentration of the fuel detected or estimated by the alcohol concentration determination means. If the required torque is limited, the throttle opening is limited accordingly, and the intake air amount is limited.

  When the required torque is not limited according to the alcohol concentration of the fuel, the required throttle opening (base target throttle opening) calculated from the required torque is limited according to the alcohol concentration of the fuel to finally open the target throttle. In this method, the intake air amount can be limited according to the alcohol concentration of the fuel.

  Further, as the alcohol concentration determination means, an alcohol concentration sensor for detecting the alcohol concentration of the fuel may be used as in claim 4, or the air-fuel ratio feedback control state (feedback correction amount, The alcohol concentration of the fuel may be estimated based on at least one of an air-fuel ratio deviation amount, torque fluctuation, and rotational speed fluctuation. If the alcohol concentration sensor is used, there is an advantage that the alcohol concentration of the fuel can be accurately detected. On the other hand, if the alcohol concentration of the fuel is estimated based on the air-fuel ratio feedback control state or the like, the alcohol concentration sensor becomes unnecessary. Therefore, there is an advantage that the cost can be reduced accordingly.

  Further, as described in claim 6, from the start of the internal combustion engine until the detection or estimation of the alcohol concentration by the alcohol concentration determination means is completed, the output of the internal combustion engine is limited by a provisional limit value at a predetermined alcohol concentration. You may do it. Here, the predetermined alcohol concentration that is tentatively set may be set to the highest alcohol concentration or an alcohol concentration close to the alcohol concentration of the fuel that is likely to be used (fuel distributed in the market). Preferably, for example, as in claims 8 and 9, it is conceivable to set the predetermined alcohol concentration to 85% or 100%. In this way, the output of the internal combustion engine is sufficiently limited even before the detection or estimation of the alcohol concentration is completed after the start of the internal combustion engine, so that the lean deviation of the air-fuel ratio due to insufficient discharge capacity of the fuel pump or exhaust emission Can be prevented from deteriorating.

  The alcohol concentration data detected or estimated during the previous operation is stored in a rewritable non-volatile memory such as a backup RAM (a rewritable storage means for retaining stored data even when the internal combustion engine is stopped). Until the detection or estimation of the alcohol concentration is completed after the engine is started, the output of the internal combustion engine may be limited using the previous alcohol concentration data stored in the nonvolatile memory.

  At this time, for example, a switch for detecting whether the internal combustion engine is stopped or not is based on, for example, whether there is an increase in the remaining amount of fuel measured by a fuel fuel gauge, or detecting whether the fuel cap is opened or closed. If refueling is detected while the internal combustion engine is stopped, the previous alcohol concentration stored data stored in the non-volatile memory is discarded at the time of subsequent startup, and the alcohol concentration is detected. Alternatively, until the estimation is completed, the output of the internal combustion engine may be limited by using the alcohol concentration of the fuel that is likely to be used as the provisional alcohol concentration, or the alcohol concentration that is the highest or close thereto. good.

  According to another aspect of the present invention, there is provided an abnormality diagnosing unit for determining whether or not the alcohol concentration determining unit is abnormal, and when the abnormality of the alcohol concentration determining unit is detected, the limit value at the predetermined alcohol concentration is used. The output may be limited. In this way, even when a fuel with a high alcohol concentration is used when an abnormality occurs in the alcohol concentration determination means, it is possible to prevent the lean deviation of the air-fuel ratio and the deterioration of exhaust emission due to insufficient discharge capacity of the fuel pump.

  It should be noted that the present invention takes into account the fact that the higher the alcohol concentration of the fuel, the smaller the theoretical air-fuel ratio of the fuel and the greater the fuel injection amount required to control the actual air-fuel ratio to the stoichiometric air-fuel ratio. Thus, the upper limit of the output of the internal combustion engine may be limited as the alcohol concentration of the fuel detected or estimated by the alcohol concentration determination means increases. In this way, even when fuel with a high alcohol concentration is used, the output of the internal combustion engine can be limited so that the fuel consumption per unit time of the internal combustion engine does not exceed the maximum discharge capacity of the fuel pump. .

Hereinafter, an embodiment in which the best mode for carrying out the present invention is applied to an intake port injection type internal combustion engine will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.

  An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake manifold 20 for introducing air into each cylinder of the engine 11 is provided in the surge tank 18. A fuel injection valve 21 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 20 of each cylinder. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of the ignition plug 22 of each cylinder.

  On the other hand, the exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying gas is provided.

  A cooling water temperature sensor 26 that detects the cooling water temperature and a knock sensor 29 that detects knocking are attached to the cylinder block of the engine 11. A crank angle sensor 28 that outputs a pulse signal every time the crankshaft 27 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 27. Based on the output signal of the crank angle sensor 28, the crank angle and engine The rotation speed is detected.

  The engine 11 can use any of gasoline, alcohol such as ethanol and methanol, and alcohol mixed fuel obtained by mixing alcohol with gasoline as fuel, and any of these gasoline, alcohol, and alcohol mixed fuel can be used in the fuel tank 30. To refuel. A fuel pump 31 that pumps up fuel is provided in the fuel tank 30. The fuel discharged from the fuel pump 31 is sent to the delivery pipe 33 through the fuel pipe 32 and is distributed from the delivery pipe 33 to the fuel injection valve 21 of each cylinder. A fuel filter 34 and a pressure regulator 35 are connected in the vicinity of the fuel pump 31 in the fuel pipe 32, and the discharge pressure of the fuel pump 31 is regulated to a predetermined pressure by the pressure regulator 35, and surplus fuel exceeding that pressure The minute amount is returned into the fuel tank 30 by the fuel return pipe 36.

  Further, an alcohol concentration sensor 37 (alcohol concentration determination means) that detects the alcohol concentration of the fuel stored in the fuel tank 30 is installed in the fuel tank 30. Thus, if the alcohol concentration sensor 37 is installed in the fuel tank 30, there is an advantage that fuel leakage from the alcohol concentration sensor 37 to the outside can be prevented when the alcohol concentration sensor 37 fails. However, the alcohol concentration sensor 37 is installed. The location is not limited to the inside of the fuel tank 30, and the alcohol concentration sensor 37 may be installed in the fuel pipe 32 or the delivery pipe 33. In short, the point is appropriately in the fuel supply path from the fuel tank 30 to the fuel injection valve 21. The alcohol concentration sensor 37 may be installed at the position.

  The outputs of the various sensors described above are input to a control circuit (hereinafter referred to as “ECU”) 38. The ECU 38 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 21 according to the engine operating state and the like. The ignition timing of the spark plug 22 is controlled.

  At that time, considering that there is a relationship that the higher the alcohol concentration of the fuel, the lower the theoretical air-fuel ratio of the fuel, and the more fuel injection amount is required to control the actual air-fuel ratio to the theoretical air-fuel ratio. The ECU 38 executes a fuel injection control program (not shown) so that the fuel injection amount increases as the alcohol concentration of the fuel detected by the alcohol concentration sensor 37 increases, according to the alcohol concentration of the fuel. Correct the injection amount to increase.

  In general, the alcohol-mixed fuel specification engine 11 is manufactured by modifying a gasoline-specific engine. However, in order to reduce the cost, the number of parts common to the gasoline-specific engine is increased. The fuel pump 31 of the engine 11 of the specification is almost the same as that of the gasoline engine. For this reason, as shown in FIG. 2, the maximum discharge capacity (maximum discharge flow rate) of the fuel pump 31 is that the fuel injection valve 21 supplies fuel corresponding to the maximum fuel consumption when using 100% gasoline (alcohol concentration 0%). Designed to be able to supply.

  As described above, since the fuel injection amount necessary for controlling the actual air-fuel ratio to the stoichiometric air-fuel ratio increases as the alcohol concentration of the fuel increases, when using fuel with a high alcohol concentration, In a high rotation / high load region where fuel consumption per unit time increases, the fuel consumption per unit time may exceed the maximum discharge capacity (maximum discharge flow rate) of the fuel pump 31, and as a result, In the high speed / high load range, it becomes impossible to inject fuel for the required injection amount required to control the actual air-fuel ratio to the stoichiometric air-fuel ratio, and the actual air-fuel ratio shifts to the lean side and exhaust emissions may deteriorate. There is sex.

  Therefore, in the present embodiment, by executing the programs of FIGS. 3 and 4, the fuel consumption per unit time of the engine 11 depends on the alcohol concentration of the fuel so that it does not exceed the maximum discharge capacity of the fuel pump 31. By restricting the throttle opening and restricting the intake air amount, the output of the engine 11 is restricted according to the alcohol concentration of the fuel. Hereinafter, the processing contents of each program of FIGS. 3 and 4 will be described.

[Target throttle opening setting program]
The target throttle opening setting program of FIG. 3 is repeatedly executed by the ECU 38 at a predetermined cycle during engine operation, and serves as a control means in the claims. When this program is started, first, in step 101, the outputs of various sensors such as the crank angle sensor 28 and the air flow meter 14 are read, and the engine such as the current engine speed, intake air amount, charging efficiency, accelerator opening, etc. Detect the operating state.

  Thereafter, the process proceeds to step 102, where the required throttle opening (base target throttle opening) is calculated from a map or the like based on the current accelerator opening and the required torque from the auto cruise control system or the like. Thereafter, the process proceeds to step 103, the output of the alcohol concentration sensor 37 is read to detect the alcohol concentration of the fuel, and then the process proceeds to step 104, where an alcohol concentration throttle opening limit value calculation program of FIG. A throttle opening limit value corresponding to the alcohol concentration of the fuel is calculated.

  Thereafter, the routine proceeds to step 105, where the required throttle opening degree according to the accelerator opening degree and the throttle opening limit value according to the alcohol concentration are compared, and the smaller one is set as the final target throttle opening degree. Accordingly, in a region where the required throttle opening exceeds the throttle opening limit value, the throttle opening limit value becomes the final target throttle opening, and the actual throttle opening is limited so as not to exceed the throttle opening limit value. If a throttle opening limit value other than alcohol concentration is set, the minimum throttle opening is set as the final target throttle opening among all the throttle opening limit values and the required throttle opening. Just do it.

[Alcohol concentration throttle opening limit value calculation program]
The alcohol concentration throttle opening limit value calculation program shown in FIG. 4 is a subroutine executed in step 104 of the target throttle opening setting program shown in FIG. When this program is started, first, in step 201, it is determined whether or not the alcohol concentration sensor 37 is functioning normally based on the diagnosis result of the self-diagnosis function (abnormality diagnosis means) installed in the ECU 38.

  The abnormality diagnosis method for the alcohol concentration sensor 37 is, for example, determining whether there is an abnormality based on whether or not the output voltage of the alcohol concentration sensor 37 is out of the voltage range corresponding to the alcohol concentration of 0% to 100%, It is determined whether there is an abnormality based on whether the output fluctuation amount (the fluctuation amount of the detected value) of the alcohol concentration sensor 37 during operation exceeds the abnormality determination value, or the air-fuel ratio feedback control state, torque fluctuation, rotation The alcohol concentration of the fuel is estimated based on the speed fluctuation or the like, and whether or not there is an abnormality is determined based on whether or not the difference between the estimated value of the alcohol concentration and the detection value of the alcohol concentration sensor 37 exceeds the abnormality determination value. Anyway.

  If it is determined in step 201 that the alcohol concentration sensor 37 is abnormal, the process proceeds to step 205, where the throttle opening limit value when the alcohol concentration sensor is abnormal is stored in a non-volatile memory such as a ROM of the ECU 38. Set to. The throttle opening limit value when the alcohol concentration sensor is abnormal is set to the highest alcohol concentration or the alcohol concentration close to the alcohol concentration of fuel that may be used (fuel distributed in the market) For example, the alcohol concentration is set to 85% or 100%.

  On the other hand, if it is determined in step 201 that the alcohol concentration sensor 37 is functioning normally, the process proceeds to step 202 to determine whether or not the alcohol concentration sensor 37 has already detected the alcohol concentration. If the detection of the alcohol concentration has not been completed yet, the routine proceeds to step 204, where the throttle opening limit value when the alcohol concentration is not detected is set to a predetermined value stored in a nonvolatile memory such as the ROM of the ECU 38. The throttle opening limit value when the alcohol concentration is not detected is the fuel that may be used (the fuel that is distributed in the market) in the same manner as the throttle opening limit value when the alcohol concentration sensor is abnormal in step 205. The alcohol concentration is set to the highest alcohol concentration or an alcohol concentration close thereto, for example, the alcohol concentration is set to 85% or 100%.

  On the other hand, if it is determined in step 202 that the alcohol concentration has been detected, the process proceeds to step 203, where the alcohol consumption is controlled so that the fuel consumption per unit time of the engine 11 does not exceed the maximum discharge capacity of the fuel pump 31. A throttle opening limit value is calculated by a map or the like according to the alcohol concentration detected by the concentration sensor 37. Thus, after the alcohol concentration is detected, the throttle opening limit value is set so that the throttle opening (intake air amount) decreases as the alcohol concentration of the fuel increases.

  According to the present embodiment described above, the throttle opening is made according to the alcohol concentration of the fuel detected by the alcohol concentration sensor 37 so that the fuel consumption per unit time of the engine 11 does not exceed the maximum discharge capacity of the fuel pump 31. Since the throttle opening (intake air amount) is limited in accordance with the alcohol concentration of the fuel by setting the degree limit value, the output of the engine 11 is the required injection amount even when fuel with a high alcohol concentration is used. Can be prevented from exceeding the region where fuel can be injected (the region where the actual air-fuel ratio can be controlled to the theoretical air-fuel ratio), and the discharge capacity of the fuel pump 31 is insufficient in the high-speed / high-load region As a result, it is possible to prevent the air-fuel ratio lean shift and the exhaust emission from deteriorating, and the increase in size and cost of the fuel pump 31 can be avoided.

  Further, in this embodiment, the throttle opening limit when the alcohol concentration is not detected is tentatively set until the detection of the alcohol concentration by the alcohol concentration sensor 37 is completed from the start of the engine by the processing of step 202 → 204 in FIG. Since the throttle opening (intake air amount) is limited using the value, the throttle opening (intake air amount) can be limited even before the detection of the alcohol concentration is completed after the engine is started. Therefore, it is possible to prevent the lean deviation of the air-fuel ratio and the deterioration of exhaust emission due to the insufficient discharge capacity of 31.

  Further, in the present embodiment, when the abnormality of the alcohol concentration sensor 37 occurs, the throttle opening (intake air amount) is set by using the throttle opening limit value when the alcohol concentration sensor is abnormal, by the processing of step 201 → 205 in FIG. Since the restriction is made, the throttle opening (intake air amount) can be restricted even when an abnormality occurs in the alcohol concentration sensor 37, and the lean deviation of the air-fuel ratio or the deterioration of exhaust emission due to the insufficient discharge capacity of the fuel pump 31. Can be prevented.

  In this embodiment, the throttle opening is limited as a means for limiting the intake air amount. However, in addition to the throttle opening, a variable valve control amount (valve timing, valve lift amount, working angle), excess The intake air amount may be limited by limiting the control parameters of the intake system such as the supercharging pressure of the feeder.

  In addition, the present invention may limit the engine speed according to the alcohol concentration of the fuel. As a method for limiting the engine speed, for example, a reduced-cylinder operation that cuts (stops) fuel injection of some cylinders may be performed, or the ignition timing, the variable valve control amount, and the like may be controlled in the torque decreasing direction. Even if the engine speed is limited, the fuel consumption per unit time of the engine 11 can be limited.

  In this embodiment, the required throttle opening (base target throttle opening) set according to the accelerator opening, the required torque from the auto cruise control system, etc. by the target throttle opening setting program of FIG. The final target throttle opening is set by limiting the throttle opening limit value according to the alcohol concentration of the vehicle, but the required torque from the accelerator opening and the auto cruise control system is limited according to the alcohol concentration of the fuel. However, the final target throttle opening may be set based on the limited required torque, and in this case, the same effect as in the present embodiment can be obtained.

  In this embodiment, the alcohol concentration of the fuel is detected by the alcohol concentration sensor 37, but at least the air-fuel ratio feedback control state (feedback correction amount, air-fuel ratio deviation amount, etc.), torque fluctuation, and rotational speed fluctuation are at least. The alcohol concentration of the fuel may be estimated based on one. This eliminates the need for an alcohol concentration sensor, so that there is an advantage that the cost can be reduced accordingly.

  As described above, the higher the alcohol concentration of the fuel, the smaller the theoretical air-fuel ratio of the fuel, and the fuel injection amount necessary to control the actual air-fuel ratio to the theoretical air-fuel ratio increases. As the estimated alcohol concentration of the fuel increases, the upper limit of the engine output (intake air amount, etc.) is limited so that the fuel consumption per unit time of the engine 11 even when a fuel with a high alcohol concentration is used. Therefore, the engine output can be limited so that the maximum discharge capacity of the fuel pump 31 is not exceeded.

  In addition, the present invention stores alcohol concentration data detected or estimated during the previous operation in a rewritable nonvolatile memory such as a backup RAM (a rewritable storage means for holding stored data even when the engine is stopped). Until the detection or estimation of the alcohol concentration is completed after the engine is started, the engine output (intake air amount or the like) may be limited using the previous alcohol concentration data stored in the nonvolatile memory.

  At this time, the presence or absence of refueling while the engine is stopped is determined by, for example, the presence or absence of an increase in the remaining amount of fuel measured by a fuel fuel gauge, or a switch for detecting opening and closing of a fuel cap that opens and closes the fuel filler port of the fuel tank 30 If it is determined by a signal or the like and refueling is detected while the engine is stopped, the previous alcohol concentration stored data stored in the non-volatile memory is discarded at the time of subsequent startup, and the alcohol concentration is detected or estimated. Until completion, limit the engine output (intake air volume, etc.) using the highest alcohol concentration or the alcohol concentration close to it as the provisional alcohol concentration among the alcohol concentrations of fuel that may be used. Also good.

  In addition, the present invention is not limited to the intake port injection type engine as shown in FIG. 1, but includes an in-cylinder injection type engine, and both an intake port injection fuel injection valve and an in-cylinder injection fuel injection valve. It can also be applied to dual-injection engines.

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a fuel consumption characteristic view explaining the relationship between the alcohol concentration of the fuel, the engine rotation speed, the maximum fuel consumption, and the maximum discharge capacity (maximum discharge flow rate) of the fuel pump. It is a flowchart which shows the flow of a process of the target throttle opening setting program. It is a flowchart which shows the flow of a process of the alcohol concentration throttle opening restriction value calculation program.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter, 15 ... Motor, 16 ... Throttle valve, 17 ... Throttle opening sensor, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 24 ... exhaust gas sensor, 25 ... catalyst, 28 ... crank angle sensor, 30 ... fuel tank, 31 ... fuel pump, 34 ... fuel filter, 35 ... pressure regulator, 37 ... alcohol concentration sensor (alcohol concentration determination means), 38 ... ECU (Control means, abnormality diagnosis means, throttle opening control means)

Claims (10)

In a control device for an internal combustion engine that includes a fuel pump that supplies fuel in a fuel tank to a fuel injection valve and that can use a mixed fuel of gasoline and alcohol as fuel,
Alcohol concentration determination means for detecting or estimating the alcohol concentration of the fuel;
Control means for correcting the fuel injection amount of the fuel injection valve based on the alcohol concentration of the fuel detected or estimated by the alcohol concentration determination means,
The control means limits the output of the internal combustion engine according to the alcohol concentration so that the fuel consumption per unit time of the internal combustion engine does not exceed the maximum discharge capacity of the fuel pump. apparatus.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the control means limits an intake air amount of the internal combustion engine in accordance with the alcohol concentration of the fuel detected or estimated by the alcohol concentration determination means. Throttle opening control means for controlling the throttle opening according to the required torque set based on the accelerator opening etc. to control the intake air amount,
The control device for an internal combustion engine according to claim 1 or 2, wherein the control means limits the required torque in accordance with the alcohol concentration of the fuel detected or estimated by the alcohol concentration determination means.   The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the alcohol concentration determination means includes an alcohol concentration sensor that detects an alcohol concentration of fuel.   4. The internal combustion engine according to claim 1, wherein the alcohol concentration determination unit estimates the alcohol concentration of the fuel based on at least one of an air-fuel ratio feedback control state, torque fluctuation, and rotation speed fluctuation. Engine control device.   The control means limits the output of the internal combustion engine with a limit value at a predetermined alcohol concentration tentatively set from the start of the internal combustion engine until the detection or estimation of the alcohol concentration by the alcohol concentration determination means is completed. The control device for an internal combustion engine according to any one of claims 1 to 5. An abnormality diagnosing unit for determining whether or not the alcohol concentration determining unit is abnormal;
7. The control unit according to claim 1, wherein the control unit limits the output of the internal combustion engine with a limit value at a predetermined alcohol concentration when an abnormality of the alcohol concentration determination unit is detected by the abnormality diagnosis unit. The control apparatus of the internal combustion engine in any one.   The control apparatus for an internal combustion engine according to claim 6 or 7, wherein the predetermined alcohol concentration is 85%.   The control apparatus for an internal combustion engine according to claim 6 or 7, wherein the predetermined alcohol concentration is 100%. In a control device for an internal combustion engine that includes a fuel pump that supplies fuel in a fuel tank to a fuel injection valve and that can use a mixed fuel of gasoline and alcohol as fuel,
Alcohol concentration determination means for detecting or estimating the alcohol concentration of the fuel;
Control means for correcting the fuel injection amount of the fuel injection valve based on the alcohol concentration of the fuel detected or estimated by the alcohol concentration determination means,
The control device of the internal combustion engine, wherein the control means restricts the upper limit of the output of the internal combustion engine to be lower as the alcohol concentration of the fuel detected or estimated by the alcohol concentration determination means becomes higher.

Images