JP2009185654A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control device capable of performing appropriate operation control by further improving the accuracy of acquisition / estimation of fuel properties.
An internal combustion engine (1) which is an object of the present invention is configured to be able to use a fuel (F) including a first component (F1) and a second component (F2). The first component (F1) and the second component (F2) can be independently supplied to the combustion stroke of the internal combustion engine (1), and the first component (F1) and the second component (F2) has different combustion characteristics. The internal combustion engine control device (2) of the present invention issues a fuel (F) injection command during execution of the fuel cut control, and acquires the combustion state of the fuel (F) by the injection during the fuel cut control. Further, the internal combustion engine control device (2) acquires the property of the fuel (F), that is, the concentration of the second component (F2) in the fuel (F) based on the combustion state thus acquired. .
[Selection] Figure 1

Description

  The present invention relates to an internal combustion engine control device, that is, a device that controls the operation of an internal combustion engine.

  Various internal combustion engines that can use a plurality of types of fuels and mixtures thereof have been proposed. In particular, in recent years, the application of petroleum alternative fuels (application of bioethanol to gasoline engines and application of biodiesel fuel to diesel engines) has been actively pursued for environmental measures and the like. In this case, in the same internal combustion engine, petroleum fuel and alternative fuel may be used alone, or a mixed fuel of this and petroleum fuel may be used.

  The mixing ratio of biofuel to gasoline and light oil (biofuel concentration) varies. For example, as for the ethanol-containing gasoline fuel used in so-called FFV (Flexible Fuel Vehicle), the main ones are “E3” whose ethanol concentration is 3%, “E85” whose concentration is 85%, and 100% ethanol fuel. “E100” is known, and the ethanol concentration has a wide range.

  This type of internal combustion engine is known to include a fuel property sensor (alcohol concentration sensor or the like) and to perform operation control based on the fuel property (alcohol concentration) detected by the fuel property sensor ( For example, a microfilm disclosed in Japanese Utility Model Application No. 60-79279 (Japanese Utility Model Application No. 61-194744), Japanese Patent Application Laid-Open No. 5-5446, Japanese Patent Application Laid-Open No. 2005-232997, etc.

In this type of internal combustion engine, the alcohol concentration in the alcohol-containing fuel is based on the average value of the air-fuel ratio feedback correction coefficient (which is obtained based on the output of the air-fuel ratio sensor provided in the exhaust gas passage). Are known (for example, JP-A-5-163992 and JP-A-2006-77683, etc.).
Microfilm of Japanese Utility Model No. 60-79279 (Japanese Utility Model Application No. 61-194744) Japanese Patent Laid-Open No. 5-5446 JP-A-2005-232997 Japanese Patent Laid-Open No. 5-163992 JP 2006-77683 A

  In general, different fuel types have different combustion characteristics. For example, for stoichiometric air-fuel ratio, gasoline is approximately 14.6 to 14.7, whereas ethanol is approximately 9.0. Also, the octane number of ethanol is much higher than gasoline (especially regular gasoline). Therefore, in order to properly control the operation of this type of internal combustion engine, it is important to accurately obtain the properties of the fuel used for the combustion stroke (the type of petroleum fuel / alternative fuel or the mixture ratio of both). is there.

  In this regard, the above-described fuel property sensor is generally not very accurate at present, and may deteriorate over time. In addition, in the estimation of the alcohol concentration based on the average value of the air-fuel ratio feedback correction coefficient as described above, a considerable error may occur due to individual differences or deterioration with time of various sensors, fuel injectors, and the like. (Hereinafter, this error is referred to as “mechanical / time-dependent error”). Therefore, in the conventional internal combustion engine of this type, there is a risk that problems such as deterioration in performance and deterioration of exhaust emission may occur due to mechanical and time-dependent errors in obtaining and estimating fuel properties.

  Specifically, for example, in a low alcohol (ethanol) concentration region in alcohol-containing gasoline, since the variation rate of the octane number accompanying the concentration change is large, the influence of an error in obtaining and estimating the fuel property (alcohol concentration) is large. Therefore, in such a region, there is a concern that abnormal combustion such as knocking or pre-ignition may occur due to a mechanical / time-dependent error in obtaining / estimating fuel properties.

  On the other hand, for example, when the combustion conditions (compression ratio and ignition timing) matched to gasoline not containing ethanol are controlled in FFV, the occurrence of abnormal combustion can be suppressed. However, with this, the improvement in thermal efficiency and output that should originally be obtained cannot be obtained.

  The present invention has been made to address such problems. That is, an object of the present invention is to provide an internal combustion engine control device that can perform appropriate operation control by further improving the accuracy of acquisition and estimation of fuel properties.

  The internal combustion engine that is the subject of the present invention is configured to be able to use a fuel containing a first component and a second component that can be independently subjected to combustion. The first component and the second component differ in at least one of combustion characteristics (theoretical air-fuel ratio, octane number, cetane number, etc.).

  The internal combustion engine control device (hereinafter, may be simply referred to as “control device”) of the present invention issues a fuel injection command during execution of fuel cut control, and the combustion state of the fuel by injection during the fuel cut control ( For example, engine speed fluctuation, heat generation amount, etc.) are acquired. The control device is configured to acquire the property of the fuel, that is, the concentration of the second component, based on the combustion state. Here, “fuel cut control” means that the fuel injection by the fuel injector is interrupted, and is executed when a predetermined operating condition is satisfied.

  (1) The control device according to one aspect of the present invention includes an injection command unit, a combustion state acquisition unit, and a fuel property acquisition unit. The “part” can also be referred to as “means” (for example, “injection command means”, etc.

  The injection command unit commands the fuel injection to the fuel injector during execution of the fuel cut control. The combustion state acquisition unit is configured to acquire the combustion state of the fuel injected during execution of the fuel cut control according to a command from the injection command unit. The fuel property acquisition unit acquires a fuel property corresponding to the concentration of the second component in the fuel based on the combustion state acquired by the combustion state acquisition unit.

  In such a configuration, fuel cut control is executed when the predetermined operating condition is satisfied. During the execution of the fuel cut control, the injection command section commands the fuel injection to the fuel injector. The injection command can be performed under appropriate conditions such that the injected fuel burns efficiently (completely) while preventing unnecessary output from being generated as much as possible during execution of the fuel cut control. For example, the injection command during execution of the fuel cut control can be made so that the injection amount (substantially lean side) is considerably smaller than that during normal fuel injection control.

  When the fuel is injected during execution of the fuel cut control according to a command from the injection command unit, the combustion state is acquired by the combustion state acquisition unit. This combustion state changes corresponding to the change in the fuel properties if other combustion conditions (fuel injection amount, etc.) are the same. Therefore, the fuel property is acquired by the fuel property acquisition unit based on the combustion state acquired by the combustion state acquisition unit. In the result of acquisition of the fuel property by the fuel property acquisition unit, the mechanical and temporal errors as described above are relatively small.

  Thus, according to this configuration, the fuel property can be acquired (estimated) with higher accuracy than before by acquiring the combustion state associated with fuel injection during execution of the fuel cut control. Therefore, according to the present invention, appropriate engine operation control according to the fuel property can be performed.

  (2) A control device according to another aspect of the present invention includes first and second fuel property acquisition units, an injection command unit, and a combustion state acquisition unit.

  The first fuel property acquisition unit acquires the fuel property based on the output of the air-fuel ratio sensor. The air-fuel ratio sensor is configured to generate the output based on the concentration of the gas component in the exhaust gas. The injection command unit and the combustion state acquisition unit are the same as described above. The second fuel property acquisition unit is configured to acquire the fuel property based on the combustion state acquired by the combustion state acquisition unit.

  In such a configuration, based on the output of the air-fuel ratio sensor (more specifically, the air-fuel ratio feedback correction coefficient and its average value acquired according to the output) by the first fuel property acquisition unit, The fuel properties are obtained relatively easily and with a relatively high accuracy compared to conventional alcohol concentration sensors. Of course, the result obtained by the first fuel property acquisition unit (hereinafter referred to as “first fuel property”) may include not only the above-described mechanical and time-dependent errors.

  By the way, when the said predetermined | prescribed driving | running condition is satisfy | filled, the above-mentioned fuel cut control is performed. Here, in the configuration of the present invention, during the execution of the fuel cut control, the injection command unit commands the fuel injector to inject the fuel (this injection command is also appropriately as described above. Can be done under conditions). The combustion state of the fuel injected during execution of the fuel cut control by this command is acquired by the combustion state acquisition unit. Based on the acquired combustion state, the second fuel property acquisition unit acquires the fuel property (this acquisition result is hereinafter referred to as “second fuel property”).

  As described above, the second fuel property is obtained (estimated) based on the combustion state associated with fuel injection during execution of the fuel cut control, and is as described above rather than the first fuel property. There are few mechanical and temporal errors. Therefore, according to the present invention, by using the second fuel property together with or instead of the first fuel property, appropriate engine operation control according to the fuel property can be performed better. .

  (3) The control apparatus having the configuration of (2) may further include a fuel system abnormality diagnosis unit. The fuel system abnormality diagnosis unit performs abnormality diagnosis of a fuel system (including a part of the various sensors and the fuel injector) based on a deviation between the first fuel property and the second fuel property. It is like that.

  In this configuration, as described above, the first fuel property is acquired by the first fuel property acquisition unit, and the second fuel property is acquired by the second fuel property acquisition unit. Based on these deviations, abnormality diagnosis of the fuel system is performed.

  As described above, the second fuel property has fewer mechanical and temporal errors as described above than the first fuel property. Therefore, the deviation between the first fuel property and the second fuel property can indicate an individual difference of the fuel system or a degree of deterioration with time. That is, occurrence of an abnormality due to deterioration with time of the fuel system or the like can be determined based on the deviation.

  Therefore, according to such a configuration, the abnormality diagnosis of the fuel system can be performed with better accuracy than in the case of only based on the change with time of the average value of the air-fuel ratio feedback correction coefficient.

  (4) The control device according to another aspect of the present invention includes a fuel property acquisition unit, an injection command unit, a combustion state acquisition unit, and a fuel property correction value acquisition unit.

  The fuel property acquisition unit acquires the fuel property based on the output of the air-fuel ratio sensor. The injection command unit and the combustion state acquisition unit are the same as described above. The fuel property correction value acquisition unit acquires the fuel property correction value based on the combustion state acquired by the combustion state acquisition unit.

  In such a configuration, the fuel property is acquired based on the output of the air-fuel ratio sensor. Further, when the predetermined operating condition is satisfied, the fuel cut control described above is executed. During the execution of the fuel cut control, the injection command unit commands the fuel injector to inject the fuel (this injection command can also be performed under appropriate conditions as described above).

  When the fuel is injected during execution of the fuel cut control according to a command from the injection command unit, the combustion state is acquired by the combustion state acquisition unit. This combustion state corresponds to the fuel property as described above. Therefore, based on the combustion state and the fuel property acquired by the fuel property acquisition unit, the correction value for the fuel property (or may be referred to as the “learning value” of the fuel property) is acquired. . Specifically, for example, a deviation between the fuel property acquired by the fuel property acquisition unit and the fuel property acquired based on the combustion state can be acquired as the correction value.

  Thus, according to this configuration, the fuel property is easily acquired based on the output of the air-fuel ratio sensor, and based on the combustion state accompanying fuel injection during execution of the fuel cut control, The correction value for the fuel property is acquired. Therefore, the fuel property can be easily obtained and estimated with higher accuracy than before. Therefore, according to the present invention, appropriate engine operation control corresponding to the fuel property can be easily performed.

  (5) The control apparatus having the configuration of (4) may further include a fuel system abnormality diagnosis unit. The fuel system abnormality diagnosis unit performs a fuel system abnormality diagnosis based on the correction value.

  In this configuration, the correction value for the fuel property is acquired by the fuel property correction value acquisition unit. Here, when a state change (deterioration with time or failure) occurs in the fuel system, the correction value also varies. Therefore, the correction value can indicate the degree of change in the state of the fuel system. Therefore, the abnormality diagnosis of the fuel system is performed based on this correction value.

  Therefore, according to such a configuration, the abnormality diagnosis of the fuel system can be performed with better accuracy than in the case of only based on the change with time of the average value of the air-fuel ratio feedback correction coefficient.

  (6) Each of the control devices may further include a compression ratio control unit. The compression ratio control unit is configured to increase the compression ratio at the time of injection during execution of the fuel cut control according to the command. For example, when the internal combustion engine is provided with a variable compression ratio mechanism, the compression ratio is set to the highest value in the variable range during injection during execution of the fuel cut control.

  In such a configuration, the compression ratio is set high when acquiring the combustion state associated with fuel injection during execution of the fuel cut control. Thereby, the compression end temperature rises and the injected fuel burns efficiently. That is, the fuel property in the fuel injection during execution of the fuel cut control can be favorably reflected in the acquisition result of the combustion state. Therefore, according to such a configuration, the accuracy of acquisition and estimation of the fuel property can be further improved.

  Hereinafter, embodiments of the present invention (embodiments that the applicant considers best at the time of filing of the present application) will be described with reference to the drawings.

  In addition, the description about the following embodiment is specific to the extent possible, merely an example of the embodiment of the present invention in order to satisfy the description requirement (description requirement / practicability requirement) of the specification required by law. It is only what is described in. Therefore, as will be described later, it is quite natural that the present invention is not limited to the specific configurations of the embodiments described below. Examples of modifications to an embodiment are listed together at the end, as they are inserted during the description of the embodiment, preventing understanding of a consistent description of the embodiment.

<Engine configuration>
FIG. 1 is a schematic configuration diagram showing an overall configuration of a system S (vehicle or the like) including an engine 1 and a control device 2 for controlling the engine 1. The engine 1 is configured to be able to change the compression ratio, as will be described later. Further, the engine 1 in the present embodiment is configured such that a plurality of types of fuel F having different theoretical air-fuel ratios and different octane numbers can be used. That is, the engine 1 in this embodiment is applied to FFV, and is configured to be able to use gasoline F1, ethanol F2, and a mixture thereof as fuel F.

  First, a schematic configuration of the engine 1 will be described. As shown in FIG. 1, the engine 1 includes a cylinder block 11, a cylinder head 12, a crankcase 13, a variable compression ratio mechanism 14, an intake system 15, an exhaust system 16, and a fuel supply system. 17.

<< Engine block >>
A cylinder bore 111 is formed in the cylinder block 11. The cylinder bore 111 is a substantially cylindrical through hole formed along the height direction of the engine 1 (a direction parallel to the cylinder center axis CA). Inside the cylinder bore 111, a piston 112 is accommodated so as to be capable of reciprocating along the cylinder center axis CA. A water jacket 113 that is a passage for cooling water is formed around the cylinder bore 111.

  The cylinder head 12 is joined to the upper end portion of the cylinder block 11 (the end portion on the top dead center side of the piston 112). The cylinder head 12 is fixed to the cylinder block 11 with a bolt or the like (not shown) so as not to move relative to the cylinder block 11.

  A recess is formed at the lower end of the cylinder head 12 (the portion facing the cylinder block 11). The concave portion is provided at a position corresponding to the upper end portion of the cylinder bore 111. A combustion chamber CC is formed by the space inside the recess and the space inside the cylinder bore 111 above the top surface of the piston 112 (on the cylinder head 12 side).

  An intake port 121 and an exhaust port 122 are formed in the cylinder head 12. These are gas passages communicating with the combustion chamber CC. In addition, the cylinder head 12 includes an intake valve 123, an exhaust valve 124, a variable intake valve timing device 125, and a variable exhaust valve timing device in order to control the communication state between the combustion chamber CC and the intake port 121 and the exhaust port 122. 126 is provided.

  The variable intake valve timing device 125 and the variable exhaust valve timing device 126 are configured to change the opening / closing timing of the intake valve 123 and the exhaust valve 124. The specific configurations of the variable intake valve timing device 125 and the variable exhaust valve timing device 126 are already well known and are irrelevant to the essential parts of the present invention, so that the description thereof is omitted herein. Yes.

  A spark plug 127 and an igniter 128 are also attached to the cylinder head 12. The spark plug 127 is arranged such that a spark generating electrode provided at the end thereof is exposed at the upper end of the combustion chamber CC. The igniter 128 includes an ignition coil that generates a high voltage to be applied to the spark generating electrode in the spark plug 127.

  A crankshaft 131 is rotatably supported in the crankcase 13. The crankshaft 131 is connected to the piston 112 via a connecting rod 132 so as to be rotationally driven based on reciprocal movement along the cylinder center axis CA of the piston 112.

<< Variable compression ratio mechanism >>
The variable compression ratio mechanism 14 of the present embodiment changes the clearance volume by moving the joined body of the cylinder block 11 and the cylinder head 12 relative to each other along the cylinder center axis CA with respect to the crankcase 13. Thus, the compression ratio can be changed. The variable compression ratio mechanism 14 has the same configuration as that described in Japanese Patent Application Laid-Open Nos. 2003-206871 and 2007-056837. Therefore, in this specification, detailed description of this mechanism will be omitted, and only an outline will be described.

  The variable compression ratio mechanism 14 includes a connection mechanism 141 and a drive mechanism 142. The coupling mechanism 141 is configured to couple the cylinder block 11 and the crankcase 13 so as to be movable relative to each other along the cylinder center axis CA. The drive mechanism 142 includes a drive unit such as a motor and a gear mechanism, and a detection unit such as an encoder that monitors the drive state (rotation angle of the motor, etc.) of the drive unit. The drive mechanism 142 moves the cylinder block 11 and the crankcase 13 relative to each other along the cylinder central axis CA in accordance with an operation signal from the control device 2, and the cylinder block 11 and the crankcase 13 generated by the relative movement. The information corresponding to the relative position is output to the control device 2. That is, the control device 2 and the variable compression ratio mechanism 14 are configured to control the compression ratio in the engine 1 by exchanging signals with each other.

<< Intake and exhaust system >>
The intake system 15 includes an intake passage 151. The intake passage 151 includes an intake manifold, a surge tank, and the like, and is connected to the intake port 121. A throttle valve 152 is interposed in the intake passage 151. The throttle valve 152 is configured to be rotationally driven by a throttle valve actuator 153 made of a DC motor.

  The exhaust system 16 includes an exhaust passage 161. The exhaust passage 161 includes an exhaust manifold and is connected to the exhaust port 122. A catalytic converter 162 is interposed in the exhaust passage 161. The catalytic converter 162 includes therein a three-way catalyst having an oxygen storage function, and is configured to be able to purify HC, CO, and NOx in the exhaust gas.

<< Fuel supply system >>
The fuel supply system 17 is configured to supply fuel into the combustion chamber CC by delivering the fuel F stored in the fuel tank 171 to the injector 172 and injecting the fuel F with the injector 172. ing. In the present embodiment, the injector 172 is configured and arranged so as to inject the fuel F directly into the combustion chamber CC. The fuel tank 171 and the injector 172 are connected by a delivery pipe 173.

<Control device>
The control device 2 of the present embodiment includes an injection command unit, a combustion state acquisition unit, a (first / second) fuel property acquisition unit, a fuel property correction value acquisition unit, a compression ratio control unit, and a fuel system abnormality diagnosis according to the present invention. The engine electronic control unit (hereinafter abbreviated as “ECU”) 210 is included. The ECU 210 includes a CPU 211, a ROM 212, a RAM 213, a backup RAM 214, an interface 215, and a bus 216. The CPU 211, ROM 212, RAM 213, backup RAM 214, and interface 215 are connected to each other via a bus 216.

  In the ROM 212, routines (programs) executed by the CPU 211, tables (lookup tables, maps), parameters, and the like are stored in advance. The RAM 213 is configured to temporarily store data as necessary when the routine is executed by the CPU 211. The backup RAM 214 is configured to store data when the routine is executed by the CPU 211 in a state where the power is turned on, and to retain the stored data even after the power is shut off.

  The interface 215 is electrically connected to various sensors described later and the above-described detection unit in the drive mechanism 142, and is configured to transmit signals from these to the CPU 211. Further, the interface 215 is electrically connected to the above-described drive unit in the drive mechanism 142, the variable intake valve timing device 125, the variable exhaust valve timing device 126, the throttle valve actuator 153, the injector 172, and the like. An operation signal for operating these operation units can be transmitted from the CPU 211 to these operation units. That is, the control device 2 receives signals from the above-described various sensors via the interface 215, and sends the above-described operation signals to each operation unit based on the calculation result of the CPU 211 corresponding to the signals. It is configured.

<< Various sensors >>
The system S includes an air flow meter 221, an intake air temperature sensor 222, a throttle position sensor 223, an intake cam position sensor 224, an exhaust cam position sensor 225, a crank position sensor 226, a coolant temperature sensor 227, an air-fuel ratio sensor 228, an in-cylinder pressure sensor 229. Various sensors such as a fuel level sensor 231, a fuel property sensor 232, an accelerator opening sensor 233, and the like are provided.

  The air flow meter 221 is configured to output a signal corresponding to an intake air flow rate Ga, which is a mass flow rate of intake air flowing through the intake passage 151 per unit time. The air flow meter 221 is a known hot-wire air flow meter, and outputs a voltage Vg corresponding to the intake air flow rate Ga as shown in FIG. 2A.

  The intake air temperature sensor 222 and the throttle position sensor 223 are mounted in the intake passage 151. The intake air temperature sensor 222 is configured to output a signal corresponding to the temperature of the intake air. The throttle position sensor 223 is configured to output a signal corresponding to the rotational phase of the throttle valve 152 (throttle valve opening TA).

  The intake cam position sensor 224 and the exhaust cam position sensor 225 are mounted on the cylinder head 12. The intake cam position sensor 224 outputs a waveform signal having a pulse corresponding to a rotation angle of an intake cam shaft (not shown) for reciprocating the intake valve 123 (included in the variable intake valve timing device 125). It is configured. Similarly, the exhaust cam position sensor 225 is also configured to output a waveform signal having a pulse corresponding to the rotation angle of an exhaust camshaft (not shown) (included in the variable exhaust valve timing device 126).

  The crank position sensor 226 is attached to the crankcase 13. The crank position sensor 226 is configured to output a waveform signal having a pulse corresponding to the rotation angle of the crankshaft 131. Specifically, the crank position sensor 226 outputs a signal having a narrow pulse every time the crankshaft 131 rotates 10 ° and a signal having a wide pulse every time the crankshaft 131 rotates 360 °. It is configured. That is, the engine speed Ne is acquired based on the output signal of the crank position sensor 226.

  The coolant temperature sensor 227 is attached to the cylinder block 11. The cooling water temperature sensor 227 is configured to output a signal corresponding to the temperature of the cooling water in the water jacket 113 in the cylinder block 11 (cooling water temperature Tw).

  The air-fuel ratio sensor 228 is mounted upstream of the catalytic converter 162 (side closer to the exhaust port 122) in the exhaust passage 161, and outputs a signal corresponding to the oxygen concentration of the exhaust gas passing through the exhaust passage 161. It is configured as follows. This air-fuel ratio sensor 228 is an electromotive force type (concentration cell type) oxygen concentration sensor, and as shown in FIG. 2B, afr0 (approximately 14.6) which is a theoretical air-fuel ratio in 100% gasoline fuel. An output value Voxs, which is a voltage that changes suddenly in the vicinity, is output. Specifically, the air-fuel ratio sensor 228 is leaner than Voxs_ref (approximately 0.5 [V]), afr0 when the air-fuel ratio afr in the fuel mixture supplied to the combustion chamber CC and used for combustion is afr0. In this case, Voxs_min (approximately 0.1 [V]) is output, and when richer than afr0, Voxs_max (approximately 0.9 [V]) is output.

  An in-cylinder pressure sensor 229 is attached to the cylinder block 11. The in-cylinder pressure sensor 229 is configured to generate an output corresponding to the gas pressure in the combustion chamber CC.

  A fuel level sensor 231 and a fuel property sensor 232 are attached to the fuel tank 171. The fuel level sensor 231 is configured to output a signal corresponding to the liquid level of the fuel F in the fuel tank 171. The fuel property sensor 232 is configured to output a signal corresponding to the concentration of ethanol F2 in the fuel F, such as an alcohol concentration sensor.

  The accelerator opening sensor 233 is configured to output a signal corresponding to the operation amount (accelerator opening ψ or accelerator operation amount Accp) of the accelerator pedal 241 operated by the driver. Further, an alarm device 242 is provided at a position that is easily visible by the driver. The alarm device 242 includes a warning indicator lamp and the like.

<Overview of operation>
In the system S of the present embodiment, the following processing (control) is performed by the control device 2 (ECU 210).

<< Fuel injection control >>
The theoretical air-fuel ratio of ethanol F2 is approximately 9.0, which is greatly different from the theoretical air-fuel ratio afr0 (approximately 14.6 to 14.7) of gasoline F1. The calorific value per unit mass is also greatly different between gasoline F1 and ethanol F2 (ethanol F2 is smaller). Therefore, the concentration of ethanol F2 in the fuel F (ethanol concentration Cf) is a parameter for setting the target air-fuel ratio afrt, in addition to the engine speed Ne, the throttle valve opening TA, and the like.

  The basic fuel injection amount Fbase is acquired based on the target air-fuel ratio set as described above, the intake air flow rate Ga, and the like. When a predetermined feedback control condition is not satisfied, such as when the air-fuel ratio sensor 228 is not warmed up immediately after the engine 1 is started, open loop control based on the basic fuel injection amount Fbase is performed (this In the open loop control, learning control based on a learning correction coefficient KG described later is performed).

  When the feedback control condition is satisfied after the air-fuel ratio sensor 228 is activated, the basic fuel injection amount Fbase is corrected based on the feedback correction coefficient FAF, so that the command fuel injection that is the actual fuel injection amount from the injector 172 is performed. A quantity Fi is acquired. This feedback correction coefficient FAF is acquired based on the output from the air-fuel ratio sensor 228. This feedback correction coefficient FAF varies around 1.0. That is, the average value FAFav of the feedback correction coefficient FAF is ideally approximately 1.0.

  Here, there are individual differences in the injector 172, the air flow meter 221, the air-fuel ratio sensor 228, etc. (The characteristics of the air flow meter 221 and the air-fuel ratio sensor 228 are shown in FIGS. 2A and 2B, and the output voltage change is linear. It is considered that the influence of individual differences is greater in the unfavorable air flow meter 221 and in the air-fuel ratio sensor 228 whose output voltage changes sharply in a narrow air-fuel ratio range.

  The average value FAFav of the feedback correction coefficient FAF may deviate from 1.0 (mechanical / time-dependent error) due to such individual differences or changes over time. In this case, the basic fuel injection amount Fbase before the feedback correction is shifted to the rich side or the lean side from the target air-fuel ratio. Such a deviation from the FAFav value “1.0” can be regarded as a steady (long-term) error in air-fuel ratio control. Therefore, the learning correction coefficient KG for the above-described open loop control is acquired based on the deviation from the FAFav value “1.0”.

  Further, the fuel cut control is executed under a predetermined operation condition such as a deceleration operation (accelerator pedal 241 return operation).

<< Fuel property acquisition >>
As described above, when the ethanol concentration Cf is different, the calorific value per unit mass of the fuel F is also different. Therefore, the combustion state of the fuel F can reflect the ethanol concentration Cf in the fuel F.

  Therefore, in the present embodiment, a small amount of fuel F is injected during fuel cut control (a constant amount regardless of the intake air flow rate Ga), and the combustion state of this fuel F (changes in engine speed Ne or heat in the engine 1). And the obtained result is used for obtaining the ethanol concentration Cf as the fuel property. Specifically, for example, the ethanol concentration Cf can be directly acquired based on the acquisition result of the combustion state. Alternatively, for example, the correction value ΔCf for the ethanol concentration Cf acquired based on the learning correction coefficient KG described above can be acquired based on the acquisition result of this combustion state.

  The fuel F injection amount during fuel cut control for obtaining (or correcting) the ethanol concentration Cf is considerably smaller than that during normal fuel injection control (the air-fuel ratio in the fuel mixture is considerably higher). (Lean side). This is because (1) the ethanol concentration Cf can be satisfactorily acquired regardless of the intake air flow rate Ga, and (2) the ethanol concentration Cf is reduced by suppressing the generation of unburned fuel in the injected fuel F. To further improve the acquisition accuracy, (2) To minimize fuel injection by minimizing the amount of fuel injection that is not necessary for fuel cut control as much as possible, and (4) Fuel cut control This is to prevent inadvertent torque generation as much as possible.

  The appropriate injection amount of the fuel F during fuel cut control and the relationship between the combustion state resulting from the injection of the injection amount and the ethanol concentration Cf may vary depending on the specifications of the engine 1 (the displacement, the shape of the cylinder bore 111, etc.). Therefore, it can be obtained in advance by experiments, computer simulations, or the like.

<< Compression ratio control >>
The compression ratio ε is controlled by driving the variable compression ratio mechanism 14 (drive mechanism 142) according to the operating conditions of the engine 1 (warm-up state, load state, etc. of each part). Here, ethanol F2 has a much higher octane number than gasoline F1, and the octane number of fuel F varies greatly depending on ethanol concentration Cf1. Therefore, the ethanol concentration Cf is also used as a parameter for controlling the compression ratio ε.

  Further, at the time of fuel injection during fuel cut control for obtaining (or correcting) the ethanol concentration Cf as described above, the compression ratio is set to the highest value in the variable range.

<Specific example of operation>
Next, a specific example of the operation of the control device 2 of the present embodiment shown in FIG. 1 will be described using a flowchart. In the following description of the flowchart, “step” is abbreviated as “S”. In the drawings, “step” is abbreviated as “S”.

<< Lubrication judgment >>
The CPU 211 executes the fuel supply determination routine 300 shown in FIG. 3 every time it detects the opening of the fuel lid (not shown) and the subsequent closing. In the fuel supply determination routine 300, when a different type of fuel F from the previous fuel supply is supplied this time, the fuel supply flag Xf is set (Xf = 1).

  First, in S310, the liquid level L1 of the fuel F in the fuel tank 171 at a certain time is acquired. Next, in S320, the timer tf is reset and counting of the timer tf is started. Subsequently, in S330, based on the output of the fuel property sensor 232, the alcohol concentration C1 in the fuel tank 171 (the error is larger than the ethanol concentration Cf acquired by the routine described later, but the fuel supply fuel in the previous time and this time) Is sufficient to determine whether the types of are different). After the count value of the timer tf reaches the predetermined value tf0 (S340 = Yes), the process proceeds to S350 and below.

  In S350, the liquid level L2 of the fuel F in the fuel tank 171 after the elapse of the predetermined time tf0 from the acquisition of the liquid level L1 in S310 is acquired. Next, in S360, the liquid level increase δL in the fuel tank 171 is acquired from the difference between L2 and L1. Subsequently, in S370, it is determined whether or not the liquid level increase δL is larger than a predetermined value δL0. The predetermined value δL0 is set to a value slightly larger than an error that may occur in the liquid level detection value by the fuel level sensor 231 while the predetermined time tf0 has elapsed when fuel is not supplied.

  When the liquid level rise δL in the fuel tank 171 is larger than the predetermined value δL0 (S370 = Yes), refueling has been performed (fuel F has been added to the fuel tank 171). Therefore, in this case, the process proceeds to S375, and it is determined whether or not the alcohol concentration detection value C1 for the current fuel supply obtained in S330 is the same as the previous detection value C0. That is, it is determined whether or not there has been a change (change) in fuel properties due to refueling. When the current detection value C1 is different from the previous detection value C0 (S375 = No), a change in fuel properties due to refueling is detected. Therefore, the process proceeds to S380, and the value of C0 is rewritten to the current detection value C1 in preparation for the next refueling. Thereafter, the process proceeds to S385, the refueling flag Xf is set, and this routine ends.

  On the other hand, when the liquid level rise δL in the fuel tank 171 is not larger than the predetermined value δL0 (S370 = No), it means that the fuel supply has not been performed. Therefore, in this case, the process proceeds to S390, the refueling flag Xf is reset (Xf = 0), and this routine ends. The same applies to the case where the fuel F is added to the fuel tank 171 (S370 = Yes) but the fuel property is not changed (S375 = Yes).

<< Alcohol concentration change judgment in injected fuel >>
The CPU 211 repeatedly executes the density change determination routine 400 shown in FIG. 4 at predetermined timings after turning on the ignition switch. In this routine 400, a predetermined period from when there is a fuel property change determination due to refueling (setting of the refueling flag Xf) until the fuel before refueling remaining in the injector 172 or the delivery pipe 173 is consumed. After waiting for the predetermined time, the density change flag Xc is set after the predetermined time has elapsed. This concentration change flag Xc is a flag indicating a change in the properties of the fuel F injected by the injector 172.

  First, in S410, it is determined whether or not the fuel supply flag Xf is set. If the refueling flag Xf is not set (S410 = No), the processing of the subsequent steps is skipped, and this routine is temporarily terminated. Hereinafter, the operation of this routine will be described assuming that the refueling flag Xf is set (S410 = Yes).

  In S420, it is determined whether or not the engine 1 has been started. Before the engine 1 is started (S420 = No), the processing of the subsequent steps is skipped, and this routine is temporarily terminated. When the engine 1 is started (S410 = Yes), the process proceeds after S430. When the process proceeds to S430 for the first time after the ignition switch is turned on (S430 = Yes), the count value of the timer tc is reset and the timer tc starts counting up. Thereafter, the determination in S430 is “No”, and the process proceeds from S430 to S450.

  In S450, it is determined whether or not the count value of the timer tc exceeds a predetermined value tc0. Before the count value of the timer tc exceeds the predetermined value tc0 (S430 = No), the process does not proceed after S460. That is, the standby until the predetermined time described above is executed by the processes of S430, S440, and S450.

  When the count value of the timer tc exceeds the predetermined value tc0 (S430 = Yes), the process proceeds to S460, the concentration change flag Xc is set, the process proceeds to S470, and the refueling flag Xf is reset. This routine is once terminated. Thereafter, the processing of S410 is always No, and all of the processing of this routine is substantially skipped until there is a change in fuel properties due to refueling.

<< Fuel injection control >>
The CPU 211 repeatedly executes the fuel injection control routine 500 shown in FIG. 5 at predetermined timings after the engine 1 is started.

  First, in S510, based on the intake air flow rate Ga, the engine speed Ne, and the table stored in the ROM 212, the in-cylinder intake air amount Mc that is the intake air amount of the cylinder that reaches the current intake stroke is determined. To be acquired. Next, in S515, based on the in-cylinder intake air amount Mc, the ethanol concentration Cf (the target air-fuel ratio afrt determined thereby), and the table stored in the ROM 212, the basic fuel in the cylinder is determined. The injection amount Fb is acquired.

  Subsequently, in S520, it is determined whether or not a predetermined feedback control condition is satisfied. In this specific example, it is assumed that the feedback control condition is not satisfied when the fuel cut control condition is satisfied. That is, the feedback control condition is not satisfied when the fuel cut control condition is satisfied such that the return operation of the accelerator pedal 241 is performed, or the engine speed Ne or the vehicle speed V is equal to or higher than a predetermined value. .

  If the feedback control condition is satisfied (S520 = Yes), the process proceeds to S530. In S530, as usual, the basic fuel injection amount Fb is corrected using the feedback correction coefficient FAF obtained based on the output of the air-fuel ratio sensor 228 and the learning correction value KG, so that the command fuel injection amount Fi in the cylinder is corrected. Is acquired. Thereafter, the process proceeds to S540, fuel injection corresponding to the command fuel injection amount Fi is performed in the cylinder, and this routine is temporarily ended.

  If the feedback control condition is not satisfied (S520 = No), the process proceeds to S550, and it is determined whether the fuel cut control condition is satisfied. If the fuel cut control condition is not satisfied (S550 = No), the process proceeds to S560, and the state of the density change flag Xc is checked.

  In the state where there is no change in the fuel property due to refueling and before warm-up after start-up, the concentration change flag Xc is not set (S560 = Yes). Therefore, in this case, in order to perform normal open-loop control, the process proceeds to S570, and the basic fuel injection amount Fb is corrected using the learning correction value KG, thereby obtaining the command fuel injection amount Fi in the cylinder. Is done. Thereafter, the process proceeds to S540, fuel injection corresponding to the commanded fuel injection amount Fi is performed, and this routine is temporarily ended.

  When the fuel property has been changed by refueling (concentration change flag Xc set: S560 = No) and the fuel property (ethanol concentration Cf by the fuel property acquisition routine 700 described later) is before acquisition, the learning correction value KG is set. If the normal open loop control used is performed, there is a possibility that problems such as misfire and abnormal combustion may occur. Therefore, in this case, the process proceeds to S575, and the basic fuel injection amount Fb is set as the command fuel injection amount Fi as it is (the ethanol concentration Cf that is the basis of the basic fuel injection amount Fb at this time will be described later) In addition, the detected value of the alcohol concentration C1 based on the output of the fuel property sensor 232 is provisionally used.) Thereafter, the process proceeds to S540, fuel injection corresponding to the commanded fuel injection amount Fi is performed, and this routine is temporarily ended.

  When the fuel cut control condition is satisfied (S550 = Yes), the process proceeds to S580, and it is determined whether or not a minute amount injection command for obtaining the ethanol concentration Cf is issued in the current stroke. (This command is issued after a predetermined period has elapsed since the first time that the concentration change flag Xc was set and the fuel cut control condition was satisfied). When this minute injection is performed (S580 = Yes), the process proceeds to S590, the predetermined amount F_LC is set as the command fuel injection amount Fi, and then the process proceeds to S540, where the command fuel injection amount Fi is set. Corresponding fuel injection is performed, and this routine is temporarily terminated.

  When the fuel cut control condition is satisfied (S550 = Yes), and the minute amount injection command for obtaining the ethanol concentration Cf is not issued in this process (S580 = No), the processing of S590 and S540 Is skipped, and this routine is terminated once. That is, fuel cut is executed as usual by skipping the fuel injection process of S540.

<< Compression ratio setting >>
The CPU 211 repeatedly executes the compression ratio setting routine 600 shown in FIG. 6 at every predetermined timing. First, in S610, it is determined whether or not a fuel cut control condition is satisfied.

  If the fuel cut control condition is not satisfied (S610 = No), the process proceeds to S620. In S620, parameters such as the cooling water temperature Tw, the intake air flow rate Ga, the ethanol concentration Cf (C1 as a provisional value in the case of acquisition before the fuel property acquisition routine 700 described later) are stored in the ROM 212. The compression ratio ε is determined based on the existing table. The drive mechanism 142 of the variable compression ratio mechanism 14 is driven based on the determined compression ratio ε, so that the compression ratio ε (mechanical compression ratio) of the engine 1 is adapted to the operating conditions and the fuel properties. Set to Thereafter, the process proceeds to S630, and after the set compression ratio ε is stored in the backup RAM 214, this routine is once ended.

  When the fuel cut control condition is satisfied (S610 = Yes), the process proceeds to S640, and it is determined whether or not the density change flag Xc is set. When the density change flag Xc is not set (S640 = No), a normal fuel cut control process is performed. In this case, it is not necessary to change the setting state of the compression ratio ε immediately before the fuel cut control. Therefore, the process proceeds to S650, the setting state of the compression ratio ε immediately before being stored in the backup RAM 214 is read, and after the setting state is maintained, this routine is once ended.

  When the fuel cut control condition is satisfied (S610 = Yes) and the concentration change flag Xc is set (S640 = Yes), a small amount of fuel F is injected to acquire the ethanol concentration Cf. Can be done. Therefore, in this case, the process proceeds to S660. In S660, the compression ratio ε is set to the maximum value εmax in the variable range by the variable compression ratio mechanism 14. Thereafter, this routine is temporarily terminated.

<< Fuel property acquisition >>
The CPU 211 repeatedly executes the fuel property acquisition routine 700 shown in FIG. 7 at every predetermined timing. First, in S710, it is determined whether or not the density change flag Xc is set. When the density change flag Xc is not set (S710 = No), the subsequent processing is skipped, and this routine is temporarily ended. Hereinafter, the operation of this routine will be described assuming that the density change flag Xc is set (S710 = Yes).

  Next, in S720, it is determined whether fuel injection for obtaining the ethanol concentration Cf during fuel cut control has been performed. If such fuel injection has not yet been performed (S720 = No), the process proceeds to S730. In S730, as described above, the detected value of the alcohol concentration C1 based on the output of the fuel property sensor 232 is set as the provisional ethanol concentration Cf, and this routine is temporarily ended.

  When the fuel injection for obtaining the ethanol concentration Cf during the fuel cut control is performed (S720 = Yes), the process proceeds to S740, and the fluctuation ΔNe of the engine speed Ne due to the fuel injection is determined by the crank position sensor 226. Is obtained based on the output of. Subsequently, the ethanol concentration Cf is acquired based on ΔNe and a table stored in the ROM 212. As described above, this table is created in advance based on the results of experiments, computer simulations, and the like. Thereafter, the obtained ethanol concentration Cf is stored in the backup RAM 214 (S760), the concentration change flag Xc is reset (S770), and this routine is temporarily terminated.

<< Actions and effects of this specific example >>
In this specific example, a small predetermined amount of fuel F is injected during fuel cut control, and the ethanol concentration Cf is directly acquired based on the fluctuation ΔNe of the engine speed Ne accompanying such injection.

  The ethanol concentration Cf obtained in this way is influenced by the above-described mechanical and time-dependent errors, that is, errors due to individual differences such as the injector 172, the air flow meter 221, the air-fuel ratio sensor 228, and deterioration over time. Is small (particularly compared to that obtained based on the learning correction factor KG). Therefore, according to this specific example, the ethanol concentration Cf is obtained (estimated) with higher accuracy than before, and proper operation control of the engine 1 (control of the compression ratio ε and ignition timing) according to the ethanol concentration Cf is performed. Can be done.

  Further, when such ethanol concentration Cf is obtained, sensors that require warm-up, such as the air-fuel ratio sensor 228, are not used. For this reason, as in the above-described specific example, the ethanol concentration Cf can be acquired at the time of fuel cut control that is performed first after restarting after refueling. Therefore, a more accurate ethanol concentration Cf can be acquired early.

  In this specific example, the fuel F injection amount during fuel cut control for obtaining the ethanol concentration Cf is set to be considerably smaller than that during normal fuel injection control.

  Thereby, since generation | occurrence | production of the unburned part in the injected fuel F is suppressed, the acquisition precision of ethanol concentration Cf improves. Further, since the amount of fuel injection that is not originally required for fuel cut control is reduced as much as possible, deterioration of fuel consumption is suppressed to a minimum. Furthermore, inadvertent torque generation during fuel cut control is suppressed as much as possible.

  In this specific example, at the time of fuel injection during fuel cut control for obtaining the ethanol concentration Cf, the compression ratio ε is set to the highest value in the variable range. As a result, the compression end temperature rises, so that the fuel F injected during the fuel cut control burns efficiently and without ignition by the igniter 128 and the spark plug 127.

  Therefore, according to the present specific example, the ethanol concentration Cf in the fuel F injected in a minute amount during execution of the fuel cut control can be favorably reflected in the acquisition result of the combustion state. Therefore, according to such a configuration, the accuracy of acquisition and estimation of the ethanol concentration Cf can be further improved.

  Next, another specific example obtained by modifying the above specific example will be described. In this specific example, the ethanol concentration Cf1 is acquired based on the learning correction coefficient KG. Further, a minute predetermined amount of fuel F is injected during fuel cut control, the combustion state of the fuel F is acquired, and a correction value ΔCf for the ethanol concentration Cf1 is acquired based on the acquisition result.

More specifically, the generation factor of the learning correction coefficient KG includes changes in fuel properties in addition to the above-described mechanical and time-dependent errors (individual differences such as the injector 172 and the air flow meter 221 and changes over time). That is, there is a change in the ethanol concentration Cf. This is because the theoretical air-fuel ratio differs between gasoline F1 and ethanol F2, so that the theoretical air-fuel ratio in fuel F also changes when the ethanol concentration Cf in fuel F changes. Therefore, in the learning correction coefficient KG, the factor (normal learning value) based on the mechanical and time-dependent error as described above is KGn, and the factor (fuel learning value) based on the fuel property change is KGf.
KG = KGn + KGf
It becomes.

  Therefore, the ethanol concentration Cf1 is acquired based on the fuel learning value KGf obtained by subtracting the normal learning value KGn from the learning correction coefficient KG. Note that the initial value of the normal learning value KGn can be acquired when a known property such as 100% gasoline is used as the fuel F. Thereafter, the normal learning value KGn can be updated as appropriate based on the FAFav deviation that occurs when the fuel property is not changed for a predetermined period.

  The ethanol concentration Cf1 obtained in this way is more accurate than the alcohol concentration detection value C1 obtained by the fuel property sensor 232. The average value FAFav of the feedback correction coefficient FAF and the learning correction coefficient KG are values that are acquired (used) for normal operation control of the engine 1 and are acquired specifically for acquiring the ethanol concentration Cf. Is not to be done. Therefore, acquisition of the ethanol concentration Cf1 can be performed relatively easily with a simple apparatus configuration.

  However, the ethanol concentration Cf1 obtained in this way includes the above-described mechanical and temporal errors. On the other hand, in the combustion state accompanying the minute fuel injection during fuel cut control as described above, the influence of such an error is relatively small. Therefore, in this specific example, the correction value ΔCf acquired based on the combustion state is used to correct the ethanol concentration Cf1 based on the learning correction coefficient KG, thereby obtaining a more accurate ethanol concentration Cf. This can be performed relatively simply with a simple apparatus configuration.

  Hereinafter, the operation in this example will be described with reference to a flowchart. Note that the fuel supply determination routine 200, the concentration change determination routine 400, the fuel injection control routine 500, and the compression ratio setting routine 600 in the first specific example described above are executed in the same manner in this specific example. The description in the first specific example described above is incorporated. That is, instead of the fuel property acquisition routine 700 in the first specific example described above, the following fuel property acquisition process specific to this specific example is executed.

<< Fuel property acquisition (1) >>
The CPU 211 repeatedly executes the first fuel property acquisition routine 800 shown in FIG. 8 at every predetermined timing.

  In this routine 800, after the average value FAFav of the feedback correction coefficient FAF is stabilized and the learning correction coefficient KG is updated, the ethanol concentration Cf1 is acquired based on the learning correction coefficient KG. Before acquisition of the ethanol concentration Cf1, the detected value of the alcohol concentration C1 by the fuel property sensor 232 is set as the provisional ethanol concentration Cf, as in the first specific example described above. However, when the ethanol concentration Cf2 is acquired before the ethanol concentration Cf1 is acquired, the ethanol concentration Cf2 is set as the ethanol concentration Cf. This ethanol concentration Cf2 is acquired based on the combustion state accompanying a small amount of fuel injection during fuel cut control, as in the first specific example described above (acquisition of ethanol concentration Cf2 will be described later). A two-fuel property acquisition routine 900). After the ethanol concentrations Cf1 and Cf2 are acquired, the deviation ΔCf between the two is set as a correction value for the ethanol concentration Cf1, so that the ethanol concentration Cf1 is corrected by this correction value ΔCf.

  Specifically, first, in S810, it is determined whether or not the density change flag Xc is set. When the density change flag Xc is not set (S810 = No), the subsequent processing is skipped, and this routine is temporarily ended. Hereinafter, the operation of this routine will be described assuming that the density change flag Xc is set (S810 = Yes).

  In S820, it is determined whether FAFav is stable (whether the fluctuation range within a predetermined period is within a predetermined range). When FAFav is not stable (S820 = No), the process proceeds to S830, and it is determined whether the ethanol concentration Cf2 has been acquired. When the ethanol concentration Cf2 has not been acquired (S830 = No), the detected value of the alcohol concentration C1 by the fuel property sensor 232 is set as the provisional ethanol concentration Cf, and this routine is temporarily terminated. On the other hand, when the ethanol concentration Cf2 has been acquired (S830 = Yes), this Cf2 is set as the ethanol concentration Cf, and this routine is once ended.

  When FAFav is stabilized (S820 = Yes), the process proceeds to S850, and the learning correction coefficient KG is acquired from the deviation between the current FAFav and the value “1.0”. Next, in S855, the fuel learning value KGf is acquired by subtracting the normal learning value KGn from the learning correction coefficient KG. Subsequently, in S860, the ethanol concentration Cf1 is acquired based on the fuel learning value KGf newly acquired this time and the table stored in the ROM 212.

  Subsequently, the process proceeds to S870, and it is determined whether or not the correction value ΔCf has been acquired. If it is before acquisition of the correction value ΔCf (S870 = No), Cf1 has been acquired, but Cf2 has not been acquired, as will be apparent from the operation description described later. Therefore, in this case, the process proceeds to S875, Cf1 is set as the provisional ethanol concentration Cf, and this routine is temporarily ended.

  On the other hand, if the correction value ΔCf has been acquired (S870 = Yes), the process proceeds to S880, and the value obtained by correcting Cf1 with ΔCf is set as the ethanol concentration Cf, and this set value is stored in the backup RAM 214 (S885). ) Subsequently, after the density change flag Xc is reset (S890), this routine is once ended. Thereafter, the determination in S810 is always “No”, and all processes in this routine are substantially skipped until the fuel property is changed by refueling.

<< Fuel property acquisition (2) >>
The CPU 211 repeatedly executes the second fuel property acquisition routine 900 shown in FIG. 9 at every predetermined timing. In this routine 900, as in the fuel property acquisition routine 700 in the first specific example described above, the ethanol concentration Cf2 is acquired by the micro fuel injection during the fuel cut control.

  First, in S910, it is determined whether or not the density change flag Xc is set. When the density change flag Xc is not set (S910 = No), the subsequent processing is skipped, and this routine is temporarily ended. Hereinafter, the operation of this routine will be described assuming that the density change flag Xc is set (S910 = Yes).

  Next, in S920, it is determined whether or not the ethanol concentration Cf2 has not been acquired. When the ethanol concentration Cf2 has been acquired (S920 = No), the subsequent processing is skipped, and this routine is temporarily ended. Hereinafter, it is assumed that the ethanol concentration Cf2 is not acquired (S920 = Yes).

  In S930, it is determined whether fuel injection for obtaining the ethanol concentration Cf during fuel cut control has been performed. When such fuel injection is performed (S930 = Yes), the process proceeds to S940, and the fluctuation ΔNe of the engine speed Ne due to the fuel injection is acquired. Subsequently, in S950, the ethanol concentration Cf2 is acquired based on ΔNe and the table stored in the ROM 212. Thereafter, this routine is temporarily terminated. When fuel injection for obtaining the ethanol concentration Cf during fuel cut control has not yet been performed (S930 = No), the processing of S940 and S950 is skipped, and this routine is temporarily terminated.

<< Fuel property acquisition (3) >>
The CPU 211 repeatedly executes the third fuel property acquisition routine 1000 shown in FIG. 10 at every predetermined timing. In this routine 1000, when the ethanol concentrations Cf1 and Cf2 have been acquired, the above-described correction value ΔCf is acquired. Further, abnormality determination of the fuel system is performed based on the correction value ΔCf.

  First, in S1010, it is determined whether or not the density change flag Xc is set. When the density change flag Xc is not set (S1010 = No), the subsequent processing is skipped, and this routine is temporarily ended. Hereinafter, the operation of this routine will be described assuming that the density change flag Xc is set (S1010 = Yes).

  Next, in S1020, it is determined whether or not the ethanol concentration Cf2 has not been acquired. When the ethanol concentration Cf2 has not been acquired (S1020 = No), the subsequent processing is skipped, and this routine is temporarily ended. Hereinafter, it is assumed that the ethanol concentration Cf2 has been acquired (S1020 = No).

  In S1030, it is determined whether or not ΔCf has not been acquired. If ΔCf has not been acquired (S1040 = Yes), the process proceeds to S1040. In S1040, ΔCf is acquired from the deviation between Cf1 and Cf2. Subsequently, the process proceeds to S1050, where it is determined whether or not the absolute value of ΔCf is smaller than a predetermined abnormality determination value Err. When the absolute value of ΔCf is smaller than the predetermined abnormality determination value Err (S1050 = Yes), this routine is temporarily ended. On the other hand, if the absolute value of ΔCf is greater than or equal to the predetermined abnormality determination value Err (S1050 = No), the process proceeds to S1060, abnormality notification using the alarm device 242 is performed, and this routine is temporarily ended.

  After acquisition of the correction value ΔCf, (1) the process of S1010 is “No” after acquisition / storage of the ethanol concentration Cf, and (2) the process of S1030 is “0” before acquisition / storage of the ethanol concentration Cf. No ", and this routine is finished once.

<List of examples of modification>
It should be noted that the above-described embodiments and specific examples thereof are merely examples of embodiments of the present invention that the applicant considered to be the best at the time of filing of the present application, as described above, The invention should not be limited by the above-described embodiment or the like. Therefore, it goes without saying that various modifications can be made to the above-described embodiments and the like within a range that does not change the essential part of the present invention.

  Hereinafter, some modifications will be exemplified. Here, in the following description of the modified example, components having the same configurations and functions as the components in the above-described embodiment are given the same name and the same reference numerals in the modified example. And And about description of the said component, description in the above-mentioned embodiment shall be suitably used in the range which is not inconsistent.

  However, it goes without saying that the modified examples are not limited to the following. The limited interpretation of the present invention based on the description of the above-described embodiment and the following modifications unfairly harms the interests of the applicant (especially rushing the application under the principle of prior application), but improperly imitates the imitator. It is good and not allowed.

  Further, it goes without saying that the matters described in the above-described embodiments (including specific examples) and the following modifications can be applied in appropriate combination within a technically consistent range.

  (1) The present invention is not limited to the device configuration disclosed in the above-described embodiment. The fuel used is not limited to gasoline or ethanol. For example, the present invention can be suitably applied to a diesel engine that can use biofuel. The number of cylinders, cylinder arrangement system (series, V type, horizontally opposed), and fuel injection system (port injection, in-cylinder direct injection) are also not particularly limited.

  The configuration of the variable compression ratio mechanism 14 is not limited to that of the above-described embodiment. For example, when the configuration of the engine 1 is such that the compression ratio can be changed by changing the distance between the upper surface of the piston 112 and the center of the crankshaft 131 (Japanese Utility Model Application No. 60-79279 (Japanese Utility Model Application No. 61- No. 194744), Japanese Patent Application Laid-Open No. 2004-156541, etc.).

  (2) The compression ratio control in the above-described embodiment is mainly for the mechanical compression ratio. Here, the “mechanical compression ratio” is a value obtained by dividing the sum of the gap volume (combustion chamber volume at the piston top dead center) and the piston stroke volume by the gap volume, and is a nominal compression ratio or a geometric compression ratio. Also called. On the other hand, the “actual compression ratio” is an effective compression ratio with respect to intake air, and is typically a value obtained by dividing the combustion chamber volume at the start of compression of intake air by the combustion chamber volume at the end of compression. .

  The application of the present invention is not limited to the engine 1 having a configuration that can change only the mechanical compression ratio. For example, the present invention can be similarly applied to a configuration in which the actual compression ratio can be changed by the variable intake valve timing device 125 and the variable exhaust valve timing device 126. In addition, the change of the actual compression ratio according to the operating condition is a combination of the change of the mechanical compression ratio by the variable compression ratio mechanism 14 and the change of the valve timing by the variable intake valve timing device 125 or the variable exhaust valve timing device 126. Can also be done. The present invention can be satisfactorily applied to such a case.

  (3) Further, the present invention is not limited to the operation modes described in the above specific examples.

  The minute fuel injection command for obtaining the ethanol concentration Cf or Cf2 may be performed a plurality of times. In this case, a plurality of acquired values of ethanol concentration Cf or Cf2 can be statistically processed (for example, averaged) as appropriate. Thereby, ethanol concentration Cf can be acquired more accurately.

  When acquiring the ethanol concentration Cf or Cf2, the heat generation amount may be used instead of ΔNe. In this case, the heat generation amount can be acquired using the in-cylinder pressure P acquired based on the output of the in-cylinder pressure sensor 229. For example, the heat generation rate dQ / dθ is calculated based on the in-cylinder pressure P taken at a small crank angle (several degrees CA or less, specifically 1 ° CA as an example) (θ is the crank angle). Can be obtained (see Japanese Patent Application Laid-Open No. 2007-120392, Japanese Patent Application Laid-Open No. 2007-231883, etc.).

  As control on the safe side to more reliably suppress the occurrence of abnormal combustion, it is based on the ethanol concentration Cf1 based on the learning correction coefficient KG (fuel learning value KGf) and the combustion state of the minute amount injected fuel during fuel cut control. The lower one of the ethanol concentration Cf2 may be set as the acquired value of the ethanol concentration Cf.

  An abnormality diagnosis can be performed based on the degree of change with time instead of or together with the absolute value of the correction value ΔCf.

  The fuel cut control is performed not only at the time of deceleration, but also when the engine speed Ne or the vehicle speed V becomes a predetermined value or more. However, it is most preferable that the micro fuel injection for obtaining the ethanol concentration Cf or Cf2 is performed at the time of deceleration.

  (4) Other modifications not specifically mentioned are naturally included in the technical scope of the present invention within the scope not changing the essential part of the present invention.

  Further, in each element constituting the means for solving the problems of the present invention, what is expressed in terms of function and function is the specific structure disclosed in the above-described embodiments and modifications, It includes any structure that can realize this action / function.

It is the schematic which shows the whole structure of a system containing an engine and the control apparatus concerning one Embodiment of this invention for controlling this. It is the graph which showed the relationship between the output voltage of the airflow meter shown by FIG. 1, and the measured intake air flow rate. 2 is a graph showing the relationship between the output voltage of the air-fuel ratio sensor shown in FIG. 1 and the air-fuel ratio of the fuel mixture. 3 is a flowchart showing a specific example of the operation (fuel supply determination) of the control device in the configuration shown in FIG. 1. 3 is a flowchart showing a specific example of the operation (density change determination) of the control device in the configuration shown in FIG. 1. 3 is a flowchart showing a specific example of the operation (fuel injection control) of the control device in the configuration shown in FIG. 1. 3 is a flowchart showing a specific example of the operation (compression ratio setting) of the control device in the configuration shown in FIG. 1. 2 is a flowchart showing a specific example of the operation (fuel property acquisition) of the control device in the configuration shown in FIG. 1. 6 is a flowchart showing another specific example of the operation (fuel property acquisition) of the control device in the configuration shown in FIG. 1. 6 is a flowchart showing another specific example of the operation (fuel property acquisition) of the control device in the configuration shown in FIG. 1. 6 is a flowchart showing another specific example of the operation (fuel property acquisition) of the control device in the configuration shown in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 11 ... Cylinder block 111 ... Cylinder bore 12 ... Cylinder head 121 ... Intake port 127 ... Spark plug 13 ... Crank case 131 ... Crankshaft 132 ... Connecting rod 14 ... Variable compression ratio mechanism 141 ... Connection mechanism 142 ... Drive mechanism 15 ... Intake System 151 ... Intake passage 152 ... Throttle valve 16 ... Exhaust system 161 ... Exhaust passage 162 ... Catalytic converter 17 ... Fuel supply system 171 ... Fuel tank 172 ... Injector 2 ... Control device 210 ... ECU 211 ... CPU
221 ... Air flow meter 227 ... Cooling water temperature sensor 228 ... Air-fuel ratio sensor 229 ... In-cylinder pressure sensor 231 ... Fuel level sensor 232 ... Fuel property sensor 233 ... Accelerator opening sensor 241 ... Accelerator pedal 242 ... Alarm device F ... Fuel F1 ... Gasoline F2 ... Ethanol CA ... Cylinder center axis CC ... Combustion chamber S ... System

Claims (6)

An internal combustion engine control device for controlling the operation of an internal combustion engine capable of using a fuel containing first and second components that have different combustion characteristics and can be independently subjected to combustion,
An injection command unit that commands fuel injection to the fuel injector during fuel cut control;
A combustion state acquisition unit that acquires a combustion state of the fuel injected during execution of the fuel cut control according to a command from the injection command unit;
A fuel property acquisition unit that acquires a fuel property corresponding to the concentration of the second component in the fuel based on the combustion state acquired by the combustion state acquisition unit;
An internal combustion engine control device comprising: An internal combustion engine control device for controlling the operation of an internal combustion engine capable of using a fuel containing first and second components that have different combustion characteristics and can be independently subjected to combustion,
A first fuel property acquisition unit that acquires a fuel property corresponding to the concentration of the second component in the fuel based on the output of the air-fuel ratio sensor that generates an output based on the concentration of the gas component in the exhaust gas;
An injection command unit that commands fuel injection to the fuel injector during fuel cut control;
A combustion state acquisition unit that acquires a combustion state of the fuel injected during execution of the fuel cut control according to a command from the injection command unit;
A second fuel property acquisition unit that acquires the fuel property based on the combustion state acquired by the combustion state acquisition unit;
An internal combustion engine control device comprising: The internal combustion engine control device according to claim 2,
A fuel system abnormality diagnosis unit that performs a fuel system abnormality diagnosis based on a deviation between the fuel property acquired by the first fuel property acquisition unit and the fuel property acquired by the second fuel property acquisition unit; An internal combustion engine control device further comprising: An internal combustion engine control device for controlling the operation of an internal combustion engine capable of using a fuel containing first and second components that have different combustion characteristics and can be independently subjected to combustion,
A fuel property acquisition unit that acquires a fuel property corresponding to the concentration of the second component in the fuel based on the output of the air-fuel ratio sensor that generates an output based on the concentration of the gas component in the exhaust gas;
An injection command unit that commands fuel injection to the fuel injector during fuel cut control;
A combustion state acquisition unit for acquiring a combustion state of the fuel injected during execution of the fuel cut control according to a command from the injection command unit;
A fuel property correction value acquisition unit that acquires the fuel property correction value based on the combustion state acquired by the combustion state acquisition unit;
An internal combustion engine control device comprising: The internal combustion engine control device according to claim 4,
An internal combustion engine control apparatus, further comprising a fuel system abnormality diagnosis unit that performs a fuel system abnormality diagnosis based on the correction value. The internal combustion engine control device according to any one of claims 1 to 5,
An internal combustion engine control device, further comprising a compression ratio control unit for increasing a compression ratio during injection during execution of the fuel cut control according to the command.

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