JP4992851B2 - Fuel property determination device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel property determination apparatus in an internal combustion engine that determines the property of fuel used in the internal combustion engine while the internal combustion engine is being driven.

  In a general engine (internal combustion engine), fuel is injected into an intake port or a combustion chamber and mixed with air. This mixture is compressed during the compression stroke of the piston, and then sparked to explode, and combustion gas (exhaust gas) Gas) is discharged to the outside and purified. In this case, the basic fuel injection amount is set so that the air-fuel ratio becomes a predetermined value (theoretical air-fuel ratio = stoichiometric) with respect to the intake air amount, and this basic fuel injection amount is set to the engine cooling water temperature, the intake air temperature, the engine speed, The fuel injection amount is set by correcting the throttle opening and accelerator opening.

  However, the types of fuel supplied to the engine include fuels having different properties from heavy to light, and such fuels have different boiling points and different evaporation amounts at a predetermined temperature. For this reason, when fuel having different properties is added after the engine is stopped, the air-fuel ratio at the time of engine start varies, which affects the rotation and deteriorates the startability. Therefore, conventionally, when the engine is started, the fuel amount is slightly increased and injected to ensure startability. After the air-fuel ratio sensor provided in the exhaust system is activated, the detection result of the air-fuel ratio sensor Based on this, feedback control is performed so that the air-fuel ratio of the internal combustion engine becomes the target air-fuel ratio.

  In addition, as what determines the fuel property of an internal combustion engine, there exists a thing described in the following patent document 1, for example. The fuel property acquisition device for an internal combustion engine described in Patent Document 1 forces the in-cylinder injection ratio for a predetermined period while maintaining the total injection amount at the basic fuel injection amount when the engine is in a steady operation state. The exhaust air / fuel ratio disturbance that occurs immediately after the in-cylinder injection ratio is changed to “1” is determined as the degree of fuel heaviness. Utilizing this dependence, the fuel's severity (fuel properties) is acquired.

JP 2006-161788 A

  However, when air-fuel ratio feedback control is performed, the air-fuel ratio sensor is used to start air-fuel ratio feedback control after the engine is started and the air-fuel ratio sensor is activated. That is, the air-fuel ratio sensor before activation does not function as a sensor for detecting the air-fuel ratio, and air-fuel ratio feedback control becomes difficult from immediately after engine startup until before the air-fuel ratio sensor is activated. Therefore, as described above, while the air-fuel ratio feedback control cannot be performed, the fuel injection amount is slightly increased so that the engine does not misfire, and hydrocarbons (NOx) increase. Fuel consumption will deteriorate.

  Further, in the fuel property acquisition device for an internal combustion engine described in Patent Document 1 described above, the degree of fuel heavyness (fuel) is obtained by utilizing the disturbance of the exhaust air / fuel ratio that occurs immediately after the in-cylinder injection ratio is changed. Property). For this reason, sufficient detection accuracy cannot be ensured until the air-fuel ratio sensor is activated, and the fuel property cannot be determined with high accuracy.

  An object of the present invention is to provide a fuel property determination apparatus for an internal combustion engine that can solve such a problem and enables highly accurate fuel property determination.

In order to solve the above-described problems and achieve the object, a fuel property determination apparatus for an internal combustion engine according to the present invention includes a first fuel injection valve capable of injecting fuel into an intake port of the internal combustion engine, and a combustion chamber of the internal combustion engine. An internal combustion engine comprising: a second fuel injection valve capable of injecting fuel; and a fuel injection control means capable of changing a fuel injection ratio between the first fuel injection valve and the second fuel injection valve in accordance with an operating state of the internal combustion engine. In the engine, when the entire fuel injection amount is made constant by the fuel injection control means and the fuel injection ratio of the second fuel injection valve is changed to gradually increase, the change in the operation amount with respect to the internal combustion engine or the internal combustion engine It is characterized in that it is determined that the fuel is heavy fuel when the change in the control amount in is greater than a preset threshold value.

  In the fuel property determination apparatus for an internal combustion engine according to the present invention, when the fuel injection control unit changes the fuel injection ratio of the second fuel injection valve so as to gradually increase, the change rate of the manipulated variable or the control amount It is characterized in that it is determined that the fuel is heavy when the rate of change is greater than a preset threshold value.

  In the fuel property determination apparatus for an internal combustion engine according to the present invention, when the fuel injection control unit changes the fuel injection ratio of the second fuel injection valve to gradually increase, the operation amount or the control amount is preset. It is characterized in that it is determined that the fuel is heavy fuel when the elapsed time to reach the predetermined determination operation amount or the predetermined determination control amount is shorter than a predetermined threshold value.

The fuel property determination apparatus for an internal combustion engine according to the present invention includes a first fuel injection valve capable of injecting fuel into an intake port of the internal combustion engine, and a second fuel injection valve capable of injecting fuel into a combustion chamber of the internal combustion engine. , in the internal combustion engine and a said internal combustion engine fuel injection ratio capable of changing the fuel injection control means of the first fuel injection valve according to the operating state and the second fuel injection valve, the whole of the fuel by the fuel injection control means When the fuel injection ratio of the second fuel injection valve is changed to be increased by a constant amount while the injection amount is constant, an equilibrium value of an operation amount for the internal combustion engine or an equilibrium value of a control amount for the internal combustion engine is preset. It is characterized in that it is determined that the fuel is heavy when it is greater than the threshold value.

  In the fuel property determination apparatus for an internal combustion engine according to the present invention, the manipulated variable is an ignition timing in the internal combustion engine.

  In the fuel property determination apparatus for an internal combustion engine according to the present invention, the control amount is an engine rotational speed or an output torque of the internal combustion engine.

  The fuel property determination apparatus for an internal combustion engine according to the present invention is characterized in that the property determination of the fuel used is executed when the internal combustion engine is started.

  The fuel property determination apparatus for an internal combustion engine according to the present invention is characterized in that when the air-fuel ratio sensor provided in the exhaust system of the internal combustion engine is not warmed up, the property determination of the fuel used is executed.

According to the fuel property determination apparatus for an internal combustion engine of the present invention, the first fuel injection valve capable of injecting fuel into the intake port and the second fuel injection valve capable of injecting fuel into the combustion chamber are provided, and the fuel injection control means When the overall fuel injection amount is constant and the fuel injection ratio of the second fuel injection valve is changed so as to gradually increase, the change in the operation amount for the internal combustion engine or the change in the control amount in the internal combustion engine is greater than a preset threshold value. When it is large, it is judged as heavy fuel. Further, according to the fuel property determination apparatus for an internal combustion engine of the present invention, when the fuel injection ratio of the second fuel injection valve is changed to be increased by a certain amount by the fuel injection control means, the equilibrium value or the control amount of the manipulated variable. Is determined to be heavy fuel when the equilibrium value is greater than a preset threshold value.

  Therefore, the properties of the fuel used can be determined with high accuracy by considering the vaporization state of the fuel injected into the intake port and the fuel injected into the combustion chamber and the vaporization properties of the heavy fuel and the light fuel. Can do.

  Embodiments of a fuel property determination apparatus for an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this Example.

  1 is a schematic configuration diagram of an engine to which a fuel property determination apparatus for an internal combustion engine according to a first embodiment of the present invention is applied. FIG. 2 is a schematic configuration diagram illustrating a fuel system in the internal combustion engine of the first embodiment. FIG. 4 is a flowchart showing fuel property determination control of the fuel property determination device in the internal combustion engine of the first embodiment, and FIG. 4 is a time chart showing fuel property determination control of the fuel property determination device in the internal combustion engine of the first embodiment.

  In the first embodiment, an in-line four-cylinder gasoline engine having a port injection type fuel injection device and an in-cylinder injection type fuel injection device is applied as the internal combustion engine. In this engine, as shown in FIG. 1, a cylinder head 12 is fastened on a cylinder block 11, and pistons 14 are fitted to a plurality of cylinder bores 13 formed on the cylinder block 11 so as to freely move up and down. Yes. A crankcase 15 is fastened to the lower part of the cylinder block 11, and a crankshaft 16 is rotatably supported in the crankcase 15. Each piston 14 is connected to the crankshaft 16 via a connecting rod 17. Has been.

  The combustion chamber 18 is constituted by the wall surface of the cylinder bore 13 in the cylinder block 11, the lower surface of the cylinder head 12, and the top surface of the piston 14, and the combustion chamber 18 has a high central portion at the upper portion (lower surface of the cylinder head 12). It has a pent roof shape that is slanted. An intake port 19 and an exhaust port 20 are formed on the upper portion of the combustion chamber 18, that is, the lower surface of the cylinder head 12, and the intake valve 19 and the exhaust valve 20 are opposed to the intake port 19 and the exhaust port 20. The lower end portions of 22 are respectively positioned. The intake valve 21 and the exhaust valve 22 are supported by the cylinder head 12 so as to be movable in the axial direction, and are urged and supported in a direction (upward in FIG. 1) for closing the intake port 19 and the exhaust port 20. ing. An intake cam shaft 23 and an exhaust cam shaft 24 are rotatably supported on the cylinder head 12, and the intake cam and the exhaust cam are in contact with upper ends of the intake valve 21 and the exhaust valve 22.

  Although not shown, the crankshaft sprocket fixed to the crankshaft 16 and the camshaft sprockets respectively fixed to the intake camshaft 23 and the exhaust camshaft 24 are wound with endless timing chains. The crankshaft 16, the intake camshaft 23, and the exhaust camshaft 24 can be interlocked.

  Accordingly, when the intake camshaft 23 and the exhaust camshaft 24 rotate in synchronization with the crankshaft 16, the intake cam and the exhaust cam move up and down the intake valve 21 and the exhaust valve 22 at a predetermined timing. The exhaust port 20 can be opened and closed to allow the intake port 19 and the combustion chamber 18 to communicate with the combustion chamber 18 and the exhaust port 20. In this case, the intake camshaft 23 and the exhaust camshaft 24 are set to rotate once (360 degrees) while the crankshaft 16 rotates twice (720 degrees). Therefore, the engine performs four strokes of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke while the crankshaft 16 rotates twice. At this time, the intake camshaft 23 and the exhaust camshaft 24 rotate once. Will be.

  The valve mechanism of the engine is a variable intake valve timing mechanism (VVT: Variable Valve Timing-intelligent) 25 that controls the intake valve 21 and the exhaust valve 22 at an optimal opening / closing timing according to the operating state. The intake variable valve mechanism 25 is configured by providing a VVT controller 26 at the shaft end of the intake camshaft 23, and the hydraulic pressure from the oil control valve 27 is supplied to an advance chamber and a retard chamber (not shown) of the VVT controller 26. By acting on this, the phase of the intake camshaft 23 with respect to the cam sprocket can be changed, and the opening / closing timing of the intake valve 21 can be advanced or retarded. In this case, the intake variable valve mechanism 25 advances or retards the opening / closing timing while keeping the operating angle (opening period) of the intake valve 21 constant. The intake camshaft 23 is provided with a cam position sensor 28 for detecting the rotational phase.

  A surge tank 30 is connected to the intake port 19 via an intake manifold 29, and an intake pipe 31 is connected to the surge tank 30. An air cleaner 32 is attached to an air intake port of the intake pipe 31. . An electronic throttle device 34 having a throttle valve 33 is provided on the downstream side of the air cleaner 32. The intake pipe 31 is provided with a bypass passage 35 that bypasses the throttle valve 33, and an idle speed control valve 36 is provided in the bypass passage 35.

  An exhaust pipe 38 is connected to the exhaust port 20 via an exhaust manifold 37, and the exhaust pipe 38 has a three-way catalyst 39 for purifying harmful substances contained in the exhaust gas and a NOx occlusion reduction type catalyst 40. Is installed. The three-way catalyst 39 simultaneously purifies HC, CO, and NOx contained in the exhaust gas by an oxidation-reduction reaction when the air-fuel ratio (exhaust air-fuel ratio) is stoichiometric. The NOx occlusion reduction type catalyst 40 is in a rich combustion region or stoichiometric combustion region where the NOx contained in the exhaust gas is temporarily stored when the air-fuel ratio (exhaust air-fuel ratio) is lean, and the oxygen concentration in the exhaust gas is reduced. Sometimes, the stored NOx is released and NOx is reduced by the added fuel as a reducing agent.

  An exhaust gas recirculation passage (EGR passage) 41 is provided between the downstream side of the surge tank 30 in the intake pipe 31 and the upstream side of the three-way catalyst 39 in the exhaust pipe 38. Are provided with an exhaust gas recirculation control valve (EGR valve) 42 and an exhaust gas recirculation cooler (EGR cooler) 43. Further, an EGR gas temperature sensor 44 that detects the temperature of the EGR gas is provided on the intake pipe 31 side of the EGR passage 41 from the EGR valve 42.

  The cylinder head 12 is equipped with a first injector (first fuel injection valve) 45 for injecting fuel into the intake port 19 and a second injector (second fuel injection valve) for injecting fuel directly into the combustion chamber 18. 46 is attached. A plurality of first injectors 45 are provided in the intake manifold 29 corresponding to each intake port 19, and fuel can be injected from the intake port 19 toward the combustion chamber 18 when the intake valve 21 is opened. A plurality of second injectors 46 are provided in the cylinder head 12 corresponding to the respective intake ports 19, are located on the respective intake ports 19 side, and the tip end is inclined downward at a predetermined angle (shown horizontally in FIG. 1). Is arranged).

  In the in-line four-cylinder gasoline engine of this embodiment, as shown in FIGS. 1 and 2, a low-pressure fuel supply system 47 that transfers low-pressure fuel to the first injector 45, and a high-pressure fuel that branches off from the low-pressure fuel supply system 47 Has a high-pressure fuel supply system 48 for transferring the fuel to the second injector 46. Therefore, the low-pressure fuel supply system 47 boosts the fuel to a predetermined low pressure and transfers the fuel to the first injector 45, and the first injector 45 injects the low-pressure fuel into the intake port 19. On the other hand, the high-pressure fuel supply system 48 boosts the low-pressure fuel to a predetermined high pressure and transfers it to the second injector 46, and the second injector 46 injects the high-pressure fuel into the combustion chamber 18.

  That is, in the low pressure fuel supply system 47, a fuel pump 49 for storing fuel is provided with a feed pump 50, and a low pressure fuel supply pipe 51 is connected to the feed pump 50. The two low-pressure fuel branch pipes 51 a and 51 b are branched, and one low-pressure fuel branch pipe 51 a is connected to the first delivery pipe 52. The feed pump 50 is an electric low-pressure fuel pump that pressurizes the fuel in the fuel tank 49 to a predetermined pressure (low pressure) and discharges the fuel to the low-pressure fuel supply pipe 51. In addition, four first injectors 45 are attached to the first delivery pipe 52 in series. A low pressure fuel return pipe 53 is branched from the low pressure fuel supply pipe 51, and a regulator 54 is attached to the low pressure fuel return pipe 53. Therefore, when the fuel pressure in the low pressure fuel supply system 47 becomes higher than a predetermined pressure, a part of the low pressure fuel discharged from the feed pump 50 is returned to the fuel tank 49 through the low pressure fuel return pipe 53 and the regulator 54, The pressure of the fuel in the low pressure fuel supply system 47, that is, the first delivery pipe 52 can be maintained at a predetermined low pressure.

  On the other hand, in the high pressure fuel supply system 48, a high pressure fuel pump 55 is connected to a low pressure fuel branch pipe 51 b branched from the low pressure fuel supply pipe 51 in the low pressure fuel supply system 47. The high pressure fuel pump 55 is connected to a second delivery pipe 57 via a high pressure fuel supply pipe 56, and a high pressure fuel check valve 58 is attached to the high pressure fuel supply pipe 56. The high-pressure fuel pump 55 is driven by the rotation of the exhaust camshaft 24 of the engine, pressurizes the low-pressure fuel in the low-pressure fuel supply pipe 51 in the low-pressure fuel supply system 47 to a predetermined pressure to obtain high-pressure fuel, and supplies the high-pressure fuel. This is a metering type high-pressure fuel pump for supplying the second delivery pipe 57 through a pipe 56. The high pressure fuel check valve 58 is for preventing the high pressure fuel supplied to the second delivery pipe 57 by the high pressure fuel pump 55 from flowing back to the low pressure fuel supply system 47.

  In the high-pressure pump 55, a plunger 102 is movably supported by a cylindrical casing 101, and a pressure chamber 103 for pressurizing fuel is formed by the casing 101 and the plunger 102. The plunger 102 is biased and supported by a spring 104 in a direction in which the pressure chamber 103 expands (downward in FIG. 2). A drive cam 24a is formed on the exhaust camshaft 24, and the lower end portion of the plunger 102 is always in contact. When the exhaust camshaft 24 rotates, the plunger 102 is moved up and down by the drive cam 24a, and the pressure chamber 103 is moved. Can be enlarged or reduced.

  A suction port 105 communicating with the low pressure fuel branch pipe 51 b is formed in the upper part of the casing 101, and a discharge port 106 communicating with the pressure chamber 103 and the high pressure fuel supply pipe 56 is formed. In this case, the discharge port 106 is connected to the high-pressure fuel supply pipe 56 via the high-pressure fuel check valve 58. Further, an electromagnetic spill valve 107 as a metering valve for opening and closing the suction port 105 is supported on the upper portion of the casing 101 so as to be movable up and down. The electromagnetic spill valve 107 is urged and supported in a direction to open the suction port 105 by the urging spring 108, and is lifted by energizing the electromagnetic solenoid 109 to close the suction port 105.

  Therefore, when the exhaust camshaft 24 is rotated and the plunger 102 is lowered by the drive cam 104 in a state where the suction port 105 is opened by the electromagnetic spill valve 107, the low-pressure fuel in the low-pressure fuel branch pipe 51b in the low-pressure fuel supply system 47. Can be sucked into the pressure chamber 103 from the suction port 105. When the exhaust camshaft 24 rotates and the plunger 102 is raised by the drive cam 24a, when the electromagnetic solenoid 109 is energized to raise the electromagnetic spill valve 107, the electromagnetic spill valve 107 closes the suction port 105. After the low pressure fuel in the pressure chamber 103 is pressurized to a predetermined pressure, the high pressure fuel in the high pressure fuel supply system 48 is opened by opening the high pressure fuel check valve 58 from the discharge port 106. It can be discharged to the supply pipe 56.

  In this case, the timing for closing the suction port 105 by the electromagnetic spill valve 107 is adjusted by controlling the energization timing to the electromagnetic solenoid 109 according to the high pressure fuel pressure in the second delivery pipe 57, and the high pressure fuel supply pipe The amount of fuel discharged to the 56 side can be adjusted. The electromagnetic spill valve 107 is a so-called normally open spill valve. When the electromagnetic solenoid 109 is not energized, the electromagnetic spill valve 107 is supported by the urging spring 108 so that the suction port 105 is opened. The low-pressure fuel in the branch pipe 51 b can flow to the high-pressure fuel supply pipe 56 side through the suction port 105, the pressure chamber 103, and the discharge port 106. For this reason, even when the electromagnetic solenoid 109 fails, the suction port 105 is maintained in an open state, thereby suppressing fuel supply failure and fuel system damage to a minimum.

  The second delivery pipe 57 is connected to a fuel tank 49 via a high-pressure fuel return pipe 59, and a relief valve 60 is attached to the high-pressure fuel return pipe 59. Therefore, the pressure of the fuel supplied to the second delivery pipe 57 by the high-pressure pump 55 can be kept constant by the relief valve 60, and when the fuel pressure becomes higher than a predetermined pressure, the excess fuel is increased in pressure. It can be returned to the fuel tank 49 via the fuel return pipe 59. In this case, since the fuel pressure in the second delivery pipe 57 is affected by the opening pressure of the relief valve 60, the opening pressure of the relief valve 60 is set according to the fuel injection pressure required by the second injector 46. Must be set.

  The cylinder head 12 is provided with a spark plug 61 that is located above the combustion chamber 18 and ignites the air-fuel mixture.

  As shown in FIG. 1, an electronic control unit (ECU) 71 is mounted on the vehicle. The ECU 71 includes fuel injection timings of the injectors 45 and 46, ignition timing of the spark plug 61, and high-pressure fuel pump 55. It is possible to control the discharge amount, etc., and the fuel injection amount and fuel based on the detected intake air amount, intake air temperature, throttle opening, accelerator opening, engine speed, cooling water temperature, fuel pressure and other engine operating conditions The injection pressure, fuel injection timing, ignition timing, etc. are determined.

  That is, an air flow sensor 72 and an intake air temperature sensor 73 are mounted on the upstream side of the intake pipe 31, and the measured intake air amount and intake air temperature are output to the ECU 71. The electronic throttle device 34 is provided with a throttle position sensor 74, and the accelerator pedal is provided with an accelerator position sensor 75, which outputs the current throttle opening and accelerator opening to the ECU 71. The crankshaft 16 is provided with a crank angle sensor 76 and outputs the detected crank angle to the ECU 71. The ECU 71 discriminates an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke in each cylinder based on the crank angle, and an engine. Calculate the number of revolutions. The cylinder block 11 is provided with a water temperature sensor 77 and outputs the detected engine cooling water temperature to the ECU 71. The cylinder block 11 is provided with a knock sensor 78 and outputs a detected knocking signal to the ECU 71.

An air-fuel ratio (A / F) sensor 79 is provided upstream of the three-way catalyst 39 in the exhaust pipe 38, and an oxygen (O ₂ ) sensor 80 is provided downstream of the three-way catalyst 39. The A / F sensor 79 and the O ₂ sensor 80 detect the exhaust air / fuel ratio (oxygen amount) of the exhaust gas exhausted from the combustion chamber 18 through the exhaust port 20 and the exhaust manifold 37 to the exhaust pipe 38, and the detected exhaust air is detected. The fuel ratio is output to the ECU 71. The ECU 71 corrects the fuel injection amount by feeding back the exhaust air-fuel ratio detected by the A / F sensor 79 and the O ₂ sensor 80 and comparing it with the target air-fuel ratio set according to the engine operating state. In this case, the A / F sensor 79 is provided with a heater (not shown) for warming it up, and the ECU 71 heats the A / F sensor 79 with this heater when the engine is cold started. , Enabling early activation. The second delivery pipe 57 that communicates with the second injector 55 is provided with a fuel pressure sensor 81 (see FIG. 2) that detects high-pressure fuel pressure, and outputs the detected fuel pressure to the ECU 71.

  Since the in-line four-cylinder engine of this embodiment has the low pressure fuel supply system 47 and the port injection type first injector 45, the high pressure fuel supply system 48 and the in-cylinder injection type second injector 46, The fuel supply systems 47 and 48 and the injectors 45 and 46 are selectively used according to the engine operating state. Generally, the high pressure fuel supply system 48 and the in-cylinder injection type second injector 46 are used in the low load operation region of the engine, and the low pressure fuel supply system 47 and the port injection type are used in the medium / high load operation region of the engine. The first injector 45, the high-pressure fuel supply system 48, and the in-cylinder second injector 46 are used in combination.

  The ECU 71 can control the intake variable valve mechanism 25 based on the engine operating state. That is, when the temperature is low, the engine is started, the engine is idle, or the load is light, the exhaust gas blows back into the intake port 19 or the combustion chamber 18 by eliminating the overlap between the exhaust valve 22 closing timing and the intake valve 21 opening timing. Reduce the amount to enable stable combustion and improved fuel efficiency. Further, at the time of medium load, by increasing the overlap, the internal EGR rate is increased to improve the exhaust gas purification efficiency, and the pumping loss is reduced to improve the fuel consumption. Further, at the time of high-load low-medium rotation, the closing timing of the intake valve 21 is advanced, thereby reducing the amount of intake air that blows back to the intake port 19 and improving the volume efficiency. At the time of high load and high rotation, the closing timing of the intake valve 21 is retarded in accordance with the rotation speed, so that the timing is adjusted to the inertial force of the intake air and the volume efficiency is improved.

  By the way, the types of fuel supplied to the engine generally include fuels having different properties from heavy to light. Such fuels have different boiling points and have different evaporation amounts at a predetermined temperature. For this reason, if fuels having different properties are added after the engine is stopped, the air-fuel ratio at the time of starting the engine varies, affecting the rotation and reducing the startability. In this embodiment, although the air-fuel ratio sensor 79 is provided in the exhaust system, the air-fuel ratio sensor 79 has not yet been activated immediately after starting, and air-fuel ratio feedback control is difficult.

  Therefore, in the internal combustion engine of the first embodiment, the first injector 45 of the port injection type and the second injector 46 of the in-cylinder injection type are provided, and the ECU 71 as the fuel injection control means The fuel injection ratio of the injector 45 and the second injector 46 can be changed, and in particular, a fuel property determination device capable of determining the fuel property at the time of cold start of the engine is mounted. This fuel property determination device is used when the fuel injection ratio of the second injector 46 is gradually increased so that the change in the operation amount for the engine or the change in the control amount in the engine is greater than a preset threshold value. Judged to be quality fuel.

  In the fuel property determination apparatus according to the first embodiment, when the ECU 71 changes the fuel injection rate of the second injector 46 so as to gradually increase, the heavy fuel is used when the change rate of the control amount is greater than a preset threshold value. Judge that there is. In this case, the control amount is the engine speed (engine speed).

  In the fuel property determination apparatus according to the first embodiment, the property determination of the used fuel is executed when the engine is started. That is, when the air-fuel ratio sensor 79 is inactive (not warmed up), the property determination of the used fuel is executed.

  In the first embodiment, the ECU 71 has the function of the fuel property determination device.

  Here, the control for determining the fuel property used in the engine by the fuel property determination device in the internal combustion engine of the first embodiment will be described based on the flowchart of FIG.

  In the fuel property determination control in the fuel property determination device in the internal combustion engine of the present embodiment, as shown in FIG. 3, in step S11, the ECU 71 determines whether or not the precondition is satisfied. It is determined whether the set reference engine speed is exceeded. If it is determined that the engine speed Ne does not exceed the reference engine speed, the process proceeds to step S19. If it is determined that the engine speed Ne exceeds the reference engine speed, the engine has already started. The process proceeds to step S12.

  In step S12, the ECU 71 sets the fuel injection ratio of the first injector 45 and the second injector 46 in time series, that is, sets the fuel injection ratio of the first injector 45 to “1”, and the fuel injection of the second injector 46. A fuel injection amount control map for decreasing the fuel injection ratio of the first injector 45 and increasing the fuel injection ratio of the second injector 46 from the ratio “0” is created based on the current engine operating state. Or select from stored ones.

  In step S13, the ECU 71 resets the time determined so far and starts counting again. Subsequently, in step S14, the ECU 71 changes the fuel injection ratio (fuel injection amount) of the first injector 45 and the second injector 46, reflecting the fuel ratio set by the fuel injection amount control map. In step S15, the ECU 71 stores the history of the engine speed Ne when the fuel injection ratios of the first injector 45 and the second injector 46 are gradually changed, and in step S16, the injectors 45, 46 are stored. It is determined whether or not an elapsed time after changing the fuel injection ratio has exceeded a preset specified time. Here, if it is determined that the elapsed time since the change of the fuel injection ratio of each injector 45, 46 has not passed the specified time, the process returns to step S14 to continue this process. On the other hand, if it is determined that the elapsed time since the change of the fuel injection ratio of each injector 45, 46 has passed the specified time, the process after the change of the fuel injection ratio of each injector 45, 46 is determined in step S17. The engine speed change rate during the period until the specified time elapses is calculated.

  In step S18, the ECU 71 determines the property of the currently used fuel, that is, whether it is heavy fuel or light fuel, based on the engine speed change rate calculated in step S17. When the fuel property is determined, in step S19, the ECU 71 reflects the determined fuel property in the fuel injection control.

  Here, the fuel property determination method based on the engine speed change rate will be described based on the time chart of FIG.

  When the low pressure fuel is injected into the intake port 19 by the first injector 45 and when the high pressure fuel is injected into the combustion chamber 18 by the second injector 46, the high pressure fuel is injected into the combustion chamber 18 by the second injector 46. Is less affected by differences in fuel properties. That is, when the low pressure fuel is injected into the intake port 19 by the first injector 45, the intake port 19 is low in pressure and low in temperature, and the injection flow velocity is low. It adheres easily and the entire amount of injected fuel is difficult to be introduced into the combustion chamber 18. On the other hand, when high-pressure fuel is injected into the combustion chamber 18 by the second injector 46, the combustion chamber 18 is high-pressure and high-temperature, and the injection flow velocity is high. Evaporates easily. In addition, heavy fuel and light fuel are less likely to evaporate under the same temperature condition. In this embodiment, the fuel property is determined using such characteristics.

As shown in FIG. 4, for example, at the engine start time t ₀ , the port fuel injection ratio of the first injector 45 is set to “1”, the in-cylinder fuel injection ratio of the second injector 46 is set to “0”, and the time at t _1, while reducing the port fuel injection ratio of the first injector 45 gradually increases the in-cylinder fuel injection ratio of the second injector 46. At this time, in-cylinder injection has a larger fuel evaporation rate than port injection, so even if the overall fuel injection amount is constant without increasing, the amount of fuel injection into the cylinder increases, causing engine rotation. The number increases. In-cylinder fuel injection is less affected by the difference in fuel properties than port fuel injection, and heavy fuel is less likely to evaporate than light fuel. Therefore, heavy fuel that is injected into the intake port 19 is less likely to evaporate. Since the quality fuel is easily injected into the combustion chamber 18 and evaporates, the engine speed is more likely to increase when the fuel is heavy fuel than when the fuel is light fuel.

Therefore, engine speed variation per prescribed time from time t ₁ to time t ₂ will be larger variation ΔNe2 the definitive heavy fuel than the change amount ΔNe1 in light fuel. In other words, since the engine speed change rate for heavy fuel is larger than the engine speed change rate for light fuel, the difference between the engine speed change rate for light fuel and the engine speed change rate for heavy fuel By setting a threshold value for determination, it is possible to determine whether the fuel being used is light fuel or heavy fuel.

When the specified time elapses and time t ₂ is reached, the port fuel injection ratio of the first injector 45 is returned to “1” and the in-cylinder fuel injection ratio of the second injector 46 is changed to “1” by time t _3. Return to "0".

  As described above, in the fuel property determination apparatus for the internal combustion engine according to the first embodiment, the first injector 45 capable of injecting fuel into the intake port 19 and the second injector 46 capable of injecting fuel into the combustion chamber 18 are provided. When the ECU 71 makes it possible to change the fuel injection ratio of the first injector 45 and the second injector 46 according to the operating state of the engine, and the ECU 71 changes the fuel injection ratio of the second injector 46 so as to gradually increase. When the engine speed change rate is larger than a preset threshold value, it is determined that the fuel is heavy fuel.

  Therefore, when the fuel injection ratio of the second injector 46 is changed to increase with time, the intake port 19 is determined to be heavy fuel when the engine speed change rate is larger than the threshold value. By considering the vaporization state of the injected fuel and the fuel injected into the combustion chamber 18 and the vaporization properties of the heavy fuel and the light fuel, the properties of the fuel used can be determined with high accuracy.

  Further, in the fuel property determination apparatus for the internal combustion engine of the first embodiment, the entire fuel injection amount is made constant and the fuel injection ratio of the second injector 46 is changed to gradually increase, while the fuel injection of the first injector 45 is changed. When the ratio is changed to be small, it is determined that the fuel is heavy fuel when the engine speed change rate is larger than the threshold value. Therefore, by gradually changing the fuel injection ratio, there is no sudden engine speed fluctuation, so that the driver does not feel uncomfortable.

  In the fuel property determination apparatus for the internal combustion engine according to the first embodiment, the control amount is the engine speed (engine speed), and the fuel property is determined based on the engine speed change rate. Therefore, the fuel property determination can be performed using the already installed crank angle sensor 76, and the cost can be reduced.

  Further, in the fuel property determination device for the internal combustion engine of the first embodiment, the property determination of the fuel used is executed when the engine is started. In particular, when the air-fuel ratio sensor 79 is inactive, the property determination of the fuel used is executed. Accordingly, the fuel property is determined before the air-fuel ratio feedback control by the air-fuel ratio sensor 79 is performed, the fuel injection amount at the time of starting can be set according to the fuel property, and it is necessary to inject surplus fuel. Thus, fuel consumption can be improved and exhaust purification characteristics can be improved.

  FIG. 5 is a flowchart showing the fuel property determination control of the fuel property determination device in the internal combustion engine according to the second embodiment of the present invention, and FIG. 6 shows the fuel property determination control of the fuel property determination device in the internal combustion engine of the second embodiment. It is a time chart. The overall configuration of the internal combustion engine fuel property determination apparatus according to the present embodiment is substantially the same as that of the first embodiment described above, and will be described with reference to FIG. 1 and has the same functions as those described in this embodiment. The members having the same reference numerals are denoted by the same reference numerals and redundant description is omitted.

  In the fuel property determination device for an internal combustion engine according to the second embodiment, as shown in FIG. 1, when the ECU 71 changes the fuel injection ratio of the second injector 46 so as to gradually increase, the change rate of the operation amount is set in advance. It is determined that the fuel is heavy when it is greater than the threshold value. In this case, the manipulated variable is the ignition timing of the engine. The ECU 71 performs feedback control of the ignition timing. When the fuel injection ratio of each of the injectors 45 and 46 is changed, the engine speed changes, and the feedback operation amount of the ignition timing, that is, the ignition timing also changes. . Therefore, the fuel property is determined based on the change rate of the ignition timing.

  Here, the control for determining the fuel property used in the engine by the fuel property determination device in the internal combustion engine of the second embodiment will be described based on the flowchart of FIG.

  In the fuel property determination control in the fuel property determination device in the internal combustion engine of the present embodiment, as shown in FIG. 5, in step S21, the ECU 71 determines whether or not the precondition is satisfied. It is determined whether the set reference engine speed is exceeded. If it is determined that the engine speed Ne does not exceed the reference engine speed, the process proceeds to step S29. If it is determined that the engine speed Ne exceeds the reference engine speed, the engine has already started. The process proceeds to step S22.

  In step S22, the ECU 71 sets the fuel injection ratio of the first injector 45 and the second injector 46 in time series, that is, sets the fuel injection ratio of the first injector 45 to “1” and the fuel injection of the second injector 46. A fuel injection amount control map for decreasing the fuel injection ratio of the first injector 45 and increasing the fuel injection ratio of the second injector 46 from the ratio “0” is created based on the current engine operating state. Or select from stored ones.

  In step S23, the ECU 71 resets the time determined so far and starts counting again. Subsequently, in step S24, the ECU 71 reflects the fuel ratio set by the fuel injection amount control map, and changes the fuel injection ratio (fuel injection amount) of the first injector 45 and the second injector 46. In step S25, the ECU 71 stores a history of ignition timing when the fuel injection ratios of the first injector 45 and the second injector 46 are gradually changed, and in step S26, the fuel of each injector 45, 46 is stored. It is determined whether an elapsed time after changing the injection ratio has passed a preset specified time. Here, if it is determined that the elapsed time after changing the fuel injection ratio of each injector 45, 46 has not passed the specified time, the process returns to step S24 to continue this process. On the other hand, if it is determined that the elapsed time since the change of the fuel injection ratio of each injector 45, 46 has passed the specified time, the process after the change of the fuel injection ratio of each injector 45, 46 in step S27. The ignition timing change rate in a period until the specified time elapses is calculated.

  In step S28, the ECU 71 determines the property of the currently used fuel, that is, whether it is heavy fuel or light fuel, based on the ignition timing change rate calculated in step S27. When the fuel property is determined, in step S29, the ECU 71 reflects the determined fuel property in the fuel injection control.

  Here, a fuel property determination method based on the ignition timing change rate will be described based on the time chart of FIG.

As shown in FIG. 6, for example, at the engine start time t ₀ , the port fuel injection ratio of the first injector 45 is set to “1”, the in-cylinder fuel injection ratio of the second injector 46 is set to “0”, and the time at t _1, while reducing the port fuel injection ratio of the first injector 45 gradually increases the in-cylinder fuel injection ratio of the second injector 46. At this time, in-cylinder injection has a larger fuel evaporation rate than port injection, so even if the overall fuel injection amount is constant without increasing, the amount of fuel injection into the cylinder increases, causing engine rotation. The number increases and the ignition timing is retarded. In-cylinder fuel injection is less affected by the difference in fuel properties than port fuel injection, and heavy fuel is less likely to evaporate than light fuel. Therefore, heavy fuel that is injected into the intake port 19 is less likely to evaporate. Since the quality fuel is easily injected into the combustion chamber 18 and evaporates, the ignition timing is more likely to be retarded when the fuel is a heavy fuel than when the fuel is a light fuel.

Therefore, the ignition timing retard amount per specified time from time t ₁ to time t ₂ is larger in the retard amount in the heavy fuel than in the light fuel. In other words, since the ignition timing change rate for heavy fuel is larger than the ignition timing change rate for light fuel, the determination is made between the ignition timing change rate for light fuel and the ignition timing change rate for heavy fuel. It is possible to determine whether the fuel being used is light fuel or heavy fuel.

When the specified time elapses and time t ₂ is reached, the port fuel injection ratio of the first injector 45 is returned to “1” and the in-cylinder fuel injection ratio of the second injector 46 is changed to “1” by time t _3. Return to "0".

  As described above, in the fuel property determination apparatus for the internal combustion engine according to the second embodiment, the first injector 45 capable of injecting fuel into the intake port 19 and the second injector 46 capable of injecting fuel into the combustion chamber 18 are provided. The ECU 71 can change the fuel injection ratio between the first injector 45 and the second injector 46 in accordance with the operating state of the engine. When the ECU 71 changes the fuel injection ratio of the second injector 46 so as to increase, When the time change rate is larger than a preset threshold value, it is determined that the fuel is heavy fuel.

  Therefore, by considering the vaporization state of the fuel injected into the intake port 19 and the fuel injected into the combustion chamber 18 and the vaporization properties of the heavy fuel and the light fuel, the properties of the fuel used can be accurately determined. Can be determined.

  In the fuel property determination apparatus for the internal combustion engine according to the second embodiment, the entire fuel injection amount is made constant and the fuel injection ratio of the second injector 46 is changed to gradually increase, while the fuel injection of the first injector 45 is changed. When the ratio is changed to be small, it is determined that the fuel is heavy when the ignition timing change rate is larger than the threshold value. Therefore, by gradually changing the fuel injection ratio, there is no sudden engine speed fluctuation, so that the driver does not feel uncomfortable.

  In the fuel property determination apparatus for an internal combustion engine according to the second embodiment, the control amount is set to the ignition timing (ignition timing feedback manipulated variable), and the fuel property is determined based on the ignition timing change rate. Therefore, the fuel property determination can be performed using the ignition timing feedback manipulated variable already used in the control, and the cost can be reduced.

  FIG. 6 is a flowchart showing the fuel property determination control of the fuel property determination device in the internal combustion engine according to the third embodiment of the present invention. The overall configuration of the internal combustion engine fuel property determination apparatus according to the present embodiment is substantially the same as that of the first embodiment described above, and will be described with reference to FIG. 1 and has the same functions as those described in this embodiment. The members having the same reference numerals are denoted by the same reference numerals and redundant description is omitted.

  In the fuel property determination device for an internal combustion engine according to the third embodiment, as shown in FIG. 1, when the ECU 71 changes the fuel injection ratio of the second injector 46 so as to gradually increase, the change rate of the control amount is set in advance. It is determined that the fuel is heavy when it is greater than the threshold value. In this case, the control amount is the output torque. When the ECU 71 changes the fuel injection ratio of the injectors 45 and 46, the engine speed changes and the output torque also changes. Therefore, the fuel property is determined based on the change amount or change rate of the output torque.

  Here, the control for determining the fuel property used in the engine by the fuel property determination device in the internal combustion engine of the third embodiment will be described based on the flowchart of FIG.

  In the fuel property determination control in the fuel property determination device for the internal combustion engine of the present embodiment, as shown in FIG. 7, in step S31, the ECU 71 determines whether or not the precondition is satisfied. If it is determined that the precondition is not satisfied, the process proceeds to step S40. If it is determined that the precondition is satisfied, it is determined that the engine has already been started, and the process proceeds to step S32.

  In step S32, the ECU 71 sets the fuel injection ratio of the first injector 45 and the second injector 46 in time series, that is, sets the fuel injection ratio of the first injector 45 to “1” and the fuel injection of the second injector 46. A fuel injection amount control map for decreasing the fuel injection ratio of the first injector 45 and increasing the fuel injection ratio of the second injector 46 from the ratio “0” is created based on the current engine operating state. Or select from stored ones.

  In step S33, the ECU 71 resets the time determined so far and starts counting again. Subsequently, in step S34, the ECU 71 reflects the fuel ratio set by the fuel injection amount control map, and changes the fuel injection ratio (fuel injection amount) of the first injector 45 and the second injector 46. In step S35, the ECU 71 estimates the output torque of the engine when the fuel injection ratios of the first injector 45 and the second injector 46 are gradually changed, and in step S36, the output torque history is stored. In step S37, it is determined whether or not an elapsed time after changing the fuel injection ratio of each of the injectors 45 and 46 has passed a preset specified time. In this case, the output torque of the engine may be estimated based on the crank angle detected by the crank angle sensor 76 or may be estimated based on the in-cylinder pressure detected by the in-cylinder pressure sensor provided with the in-cylinder pressure sensor.

  If it is determined in step S37 that the elapsed time since the fuel injection ratios of the injectors 45 and 46 have not changed exceeds the specified time, the process returns to step S34 and the process is continued. On the other hand, if it is determined that the elapsed time since the change of the fuel injection ratio of each injector 45, 46 has passed the specified time, the process after the change of the fuel injection ratio of each injector 45, 46 in step S38. The amount of change in output torque (or rate of change in output torque) during the period until the specified time elapses is calculated.

  In step S39, the ECU 71 determines the property of the currently used fuel, that is, whether it is heavy fuel or light fuel, based on the ignition timing change rate calculated in step S38. When the fuel property is determined, in step S40, the ECU 71 reflects the determined fuel property in the fuel injection control.

  That is, the amount of change in the output torque per specified time is larger in the heavy fuel than in the light fuel. In other words, since the rate of change in output torque for heavy fuel is larger than the amount of change in output torque for light fuel, the rate of change of output torque for light fuel and the rate of change of output torque for heavy fuel By setting a threshold value for determination, it is possible to determine whether the fuel being used is light fuel or heavy fuel.

  As described above, in the fuel property determination apparatus for the internal combustion engine according to the third embodiment, the first injector 45 capable of injecting fuel into the intake port 19 and the second injector 46 capable of injecting fuel into the combustion chamber 18 are provided. The ECU 71 can change the fuel injection ratio between the first injector 45 and the second injector 46 in accordance with the operating state of the engine, and the ECU 71 changes the engine injection ratio so that the fuel injection ratio of the second injector 46 increases. It is determined that the fuel is heavy fuel when the amount of change (rate of change) of the output torque is greater than a preset threshold value.

  Therefore, by considering the vaporization state of the fuel injected into the intake port 19 and the fuel injected into the combustion chamber 18 and the vaporization properties of the heavy fuel and the light fuel, the properties of the fuel used can be accurately determined. Can be determined.

  In the fuel property determination apparatus for the internal combustion engine according to the third embodiment, the entire fuel injection amount is made constant, and the fuel injection ratio of the second injector 46 is changed to gradually increase, while the fuel injection of the first injector 45 is changed. When the ratio is changed to be small, it is determined that the fuel is heavy fuel when the change amount of the output torque is larger than the threshold value. Therefore, by gradually changing the fuel injection ratio, there is no sudden engine speed fluctuation, so that the driver does not feel uncomfortable.

  Further, in the fuel property determination device for the internal combustion engine of the third embodiment, the control amount is the output torque, and the fuel property is determined based on the change amount of the output torque. Therefore, the fuel property determination can be performed using the output torque already used in the control, and the cost can be reduced.

  FIG. 8 is a flowchart showing the fuel property determination control of the fuel property determination device in the internal combustion engine according to the fourth embodiment of the present invention, and FIG. 9 shows the fuel property determination control of the fuel property determination device in the internal combustion engine of the fourth embodiment. It is a time chart. The overall configuration of the internal combustion engine fuel property determination apparatus according to the present embodiment is substantially the same as that of the first embodiment described above, and will be described with reference to FIG. 1 and has the same functions as those described in this embodiment. The members having the same reference numerals are denoted by the same reference numerals and redundant description is omitted.

  In the fuel property determination device for an internal combustion engine according to the fourth embodiment, as shown in FIG. 1, when the ECU 71 changes the fuel injection ratio of the second injector 46 so as to gradually increase, the determination control in which the control amount is set in advance is performed. When the elapsed time to reach the amount is shorter than a preset threshold, it is determined that the fuel is heavy. In this case, the control amount is the engine speed and the arrival time. Since the engine speed fluctuates when the fuel injection ratio of each injector 45, 46 is changed, the ECU 71 determines the fuel property based on the arrival time of the engine speed up to a predetermined determination engine speed. To do.

  Here, the control for determining the fuel property used in the engine by the fuel property determination device in the internal combustion engine of the fourth embodiment will be described based on the flowchart of FIG.

  In the fuel property determination control in the fuel property determination device for the internal combustion engine of the present embodiment, as shown in FIG. 8, in step S41, the ECU 71 determines whether or not the precondition is satisfied. Here, if it is determined that the precondition is not satisfied, the process proceeds to step S49, and if it is determined that the precondition is satisfied, it is determined that the engine has already been started and the process proceeds to step S42.

  In step S42, the ECU 71 sets the fuel injection ratio of the first injector 45 and the second injector 46 in time series, that is, sets the fuel injection ratio of the first injector 45 to “1”, and the fuel injection of the second injector 46. A fuel injection amount control map for decreasing the fuel injection ratio of the first injector 45 and increasing the fuel injection ratio of the second injector 46 from the ratio “0” is created based on the current engine operating state. Or select from stored ones.

  In step S43, the ECU 71 resets the time determined so far and starts counting again. Subsequently, in step S44, the ECU 71 changes the fuel injection ratio (fuel injection amount) of the first injector 45 and the second injector 46, reflecting the fuel ratio set by the fuel injection amount control map. In step S45, the ECU 71 gradually changes the fuel injection ratios of the first injector 45 and the second injector 46 until the determination value (determination engine speed) and the engine speed reach the determination value. The elapsed time is saved, and it is determined in step S46 whether the determination is completed, that is, whether the engine speed has reached the determination value. Here, if it is determined that the engine speed after changing the fuel injection ratio of each of the injectors 45 and 46 has not reached the determination value, the process returns to step S44 to continue this process. On the other hand, if it is determined that the engine speed after changing the fuel injection ratio of each injector 45, 46 has reached the determination value, the engine is changed after changing the fuel injection ratio of each injector 45, 46 in step S47. The arrival period until the rotation speed reaches the determination value is stored.

  In step S48, the ECU 71 changes the fuel injection ratio of each injector 45, 46 stored in step S47 to the currently used fuel based on the arrival period until the engine speed reaches the determination value. Characteristics, that is, whether the fuel is heavy or light. When the fuel property is determined, in step S49, the ECU 71 reflects the determined fuel property in the fuel injection control.

  Here, the fuel property determination method based on the arrival period until the engine speed reaches the determination value will be described based on the time chart of FIG.

As shown in FIG. 9, for example, at the engine start time t ₀ , the port fuel injection ratio of the first injector 45 is set to “1”, the in-cylinder fuel injection ratio of the second injector 46 is set to “0”, and the time at t _1, while reducing the port fuel injection ratio of the first injector 45 gradually increases the in-cylinder fuel injection ratio of the second injector 46. At this time, in-cylinder injection has a larger fuel evaporation rate than port injection, so even if the overall fuel injection amount is constant without increasing, the amount of fuel injection into the cylinder increases, causing engine rotation. The number increases. In-cylinder fuel injection is less affected by the difference in fuel properties than port fuel injection, and heavy fuel is less likely to evaporate than light fuel. Therefore, heavy fuel that is injected into the intake port 19 is less likely to evaporate. Since the quality fuel is easily injected into the combustion chamber 18 and evaporates, the engine speed is more likely to increase when the fuel is heavy fuel than when the fuel is light fuel.

Therefore, the arrival time from the time t ₁ until the engine speed reaches the prescribed engine speed, shorter towards the arrival time t ₂ in the heavy fuel from the arrival time t ₄ in light fuel. That is, the determination during a period from the direction of the rotation speed of the change amount in the heavy fuel from the amount of change of the engine speed is increased in the light fuel, and the arrival time t ₄ of the light fuel and the arrival time t ₂ of the heavy fuel By setting a threshold value for, it is possible to determine whether the fuel being used is light fuel or heavy fuel.

When the engine speed reaches the specified value, the port fuel injection ratio of the first injector 45 is returned to “1” by the time t ₃ or t ₅ and the in-cylinder fuel injection ratio of the second injector 46 is changed to “ Return to "0".

  As described above, in the fuel property determination apparatus for the internal combustion engine according to the fourth embodiment, the first injector 45 capable of injecting fuel into the intake port 19 and the second injector 46 capable of injecting fuel into the combustion chamber 18 are provided. The ECU 71 can change the fuel injection ratio between the first injector 45 and the second injector 46 in accordance with the operating state of the engine, and the ECU 71 changes the engine injection ratio so that the fuel injection ratio of the second injector 46 increases. When the arrival time at which the rotational speed rises to a preset determination value is shorter than a preset threshold value, it is determined that the fuel is heavy fuel.

  Therefore, by considering the vaporization state of the fuel injected into the intake port 19 and the fuel injected into the combustion chamber 18 and the vaporization properties of the heavy fuel and the light fuel, the properties of the fuel used can be accurately determined. Can be determined.

  FIG. 10 is a flowchart showing the fuel property determination control of the fuel property determination device in the internal combustion engine according to the fifth embodiment of the present invention. The overall configuration of the internal combustion engine fuel property determination apparatus according to the present embodiment is substantially the same as that of the first embodiment described above, and will be described with reference to FIG. 1 and has the same functions as those described in this embodiment. The members having the same reference numerals are denoted by the same reference numerals and redundant description is omitted.

  In the fuel property determination device for an internal combustion engine according to the fifth embodiment, as shown in FIG. 1, when the ECU 71 changes the fuel injection ratio of the second injector 46 so as to gradually increase, the determination operation with the operation amount set in advance is performed. When the elapsed time to reach the amount is shorter than a preset threshold, it is determined that the fuel is heavy. In this case, the manipulated variable is the ignition timing and the arrival time. When the fuel injection ratios of the injectors 45 and 46 are changed, the ECU 71 changes the engine speed, and also changes the feedback operation amount of the ignition timing, that is, the ignition timing. Therefore, the fuel property is determined based on the arrival time until the ignition timing is set in advance to the determined ignition timing.

  Here, the control for determining the fuel property used in the engine by the fuel property determination device in the internal combustion engine of the fifth embodiment will be described based on the flowchart of FIG.

  In the fuel property determination control in the fuel property determination device in the internal combustion engine of the present embodiment, as shown in FIG. 10, in step S51, the ECU 71 determines whether or not the precondition is satisfied. If it is determined that the precondition is not satisfied, the process proceeds to step S59. If it is determined that the precondition is satisfied, the engine is determined to have already started and the process proceeds to step S52.

  In step S52, the ECU 71 sets the fuel injection ratio of the first injector 45 and the second injector 46 in time series, that is, sets the fuel injection ratio of the first injector 45 to “1”, and the fuel injection of the second injector 46. A fuel injection amount control map for decreasing the fuel injection ratio of the first injector 45 and increasing the fuel injection ratio of the second injector 46 from the ratio “0” is created based on the current engine operating state. Or select from stored ones.

  In step S53, the ECU 71 resets the time determined so far and starts counting again. Subsequently, in step S54, the ECU 71 changes the fuel injection ratio (fuel injection amount) of the first injector 45 and the second injector 46, reflecting the fuel ratio set by the fuel injection amount control map. In step S55, when the ECU 71 gradually changes the fuel injection ratio of the first injector 45 and the second injector 46, the elapsed time until the determination value (determination ignition timing) and the ignition timing reach the determination value. In step S56, it is determined whether the determination is completed, that is, whether the ignition timing has reached a determination value. Here, if it is determined that the ignition timing after changing the fuel injection ratios of the injectors 45 and 46 has not reached the determination value, the process returns to step S54 to continue this process. On the other hand, if it is determined that the ignition timing after changing the fuel injection ratios of the injectors 45 and 46 has reached the determination value, the ignition timing is changed after the fuel injection ratios of the injectors 45 and 46 are changed in step S57. Stores the arrival period until the determination value is reached.

  In step S58, the ECU 71 changes the fuel injection ratio of each injector 45, 46 stored in step S57, and then determines the fuel currently used based on the arrival period until the ignition timing reaches the determination value. The property, that is, whether it is heavy fuel or light fuel is determined. When the fuel property is determined, in step S59, the ECU 71 reflects the determined fuel property in the fuel injection control.

  That is, the arrival time until the ignition timing reaches the specified ignition timing is shorter for the heavy fuel than for the light fuel. In other words, since the amount of change in the ignition timing for heavy fuel is greater than the amount of change in the ignition timing for light fuel, a threshold for determination is set between the arrival time of light fuel and the arrival time of heavy fuel. By setting, it can be determined whether the fuel being used is a light fuel or a heavy fuel.

  As described above, in the fuel property determination apparatus for the internal combustion engine according to the fifth embodiment, the first injector 45 capable of injecting fuel into the intake port 19 and the second injector 46 capable of injecting fuel into the combustion chamber 18 are provided. The ECU 71 can change the fuel injection ratio between the first injector 45 and the second injector 46 in accordance with the operating state of the engine. When the ECU 71 changes the fuel injection ratio of the second injector 46 so as to increase, It is determined that the fuel is heavy when the arrival time at which the timing rises to a predetermined determination value is shorter than a predetermined threshold.

  Therefore, by considering the vaporization state of the fuel injected into the intake port 19 and the fuel injected into the combustion chamber 18 and the vaporization properties of the heavy fuel and the light fuel, the properties of the fuel used can be accurately determined. Can be determined.

  FIG. 11 is a flowchart showing the fuel property determination control of the fuel property determination device in the internal combustion engine according to the sixth embodiment of the present invention. The overall configuration of the internal combustion engine fuel property determination apparatus according to the present embodiment is substantially the same as that of the first embodiment described above, and will be described with reference to FIG. 1 and has the same functions as those described in this embodiment. The members having the same reference numerals are denoted by the same reference numerals and redundant description is omitted.

  In the fuel property determination device for an internal combustion engine according to the sixth embodiment, as shown in FIG. 1, when the ECU 71 changes the fuel injection ratio of the second injector 46 so as to gradually increase, the determination control in which the control amount is set in advance is performed. When the elapsed time to reach the amount is shorter than a preset threshold, it is determined that the fuel is heavy. In this case, the controlled variable is the output torque and the arrival time. When the fuel injection ratios of the injectors 45 and 46 are changed, the ECU 71 changes the engine speed and the output torque. Therefore, the fuel property is determined based on the arrival time until the output torque reaches the predetermined determination output torque.

  Here, the control for determining the fuel property used in the engine by the fuel property determination device in the internal combustion engine of the sixth embodiment will be described based on the flowchart of FIG.

  In the fuel property determination control in the fuel property determination device for the internal combustion engine of the present embodiment, as shown in FIG. 11, in step S61, the ECU 71 determines whether or not the precondition is satisfied. Here, if it is determined that the precondition is not satisfied, the process proceeds to step S70. If it is determined that the precondition is satisfied, it is determined that the engine has already been started, and the process proceeds to step S62.

  In step S62, the ECU 71 sets the fuel injection ratio of the first injector 45 and the second injector 46 in time series, that is, sets the fuel injection ratio of the first injector 45 to “1” and the fuel injection ratio of the second injector 46. A fuel injection amount control map for decreasing the fuel injection ratio of the first injector 45 and increasing the fuel injection ratio of the second injector 46 from the ratio “0” is created based on the current engine operating state. Or select from stored ones.

  In step S63, the ECU 71 resets the time determined so far and starts counting again. Subsequently, in step S64, the ECU 71 changes the fuel injection ratio (fuel injection amount) of the first injector 45 and the second injector 46, reflecting the fuel ratio set by the fuel injection amount control map. In step S65, the ECU 71 estimates the output torque of the engine when the fuel injection ratios of the first injector 45 and the second injector 46 are gradually changed. In step S66, the output torque determination value (determination) Output torque) and the elapsed time until the output torque reaches the determination value are stored, and in step S67, determination is completed, that is, it is determined whether the output torque has reached the determination value. If it is determined that the output torque after changing the fuel injection ratios of the injectors 45 and 46 has not reached the determination value, the process returns to step S64 to continue this process. On the other hand, if it is determined that the output torque after changing the fuel injection ratio of each injector 45, 46 has reached the determination value, the output torque is changed after the fuel injection ratio of each injector 45, 46 is changed in step S68. Stores the arrival period until the determination value is reached.

  In step S69, the ECU 71 changes the fuel injection ratio of each injector 45, 46 stored in step S68, and then determines the fuel currently used based on the arrival period until the output torque reaches the determination value. The property, that is, whether it is heavy fuel or light fuel is determined. When the fuel property is determined, in step S70, the ECU 71 reflects the determined fuel property in the fuel injection control.

  That is, the arrival time until the output torque reaches the specified output torque is shorter for the heavy fuel than for the light fuel. In other words, since the change amount of the output torque in the heavy fuel is larger than the change amount of the output torque in the light fuel, a threshold for determination is set between the arrival time of the light fuel and the arrival time of the heavy fuel. By setting, it can be determined whether the fuel being used is a light fuel or a heavy fuel.

  As described above, in the fuel property determination apparatus for the internal combustion engine according to the sixth embodiment, the first injector 45 capable of injecting fuel into the intake port 19 and the second injector 46 capable of injecting fuel into the combustion chamber 18 are provided. The ECU 71 can change the fuel injection ratio between the first injector 45 and the second injector 46 in accordance with the operating state of the engine, and the ECU 71 outputs an output when the fuel injection ratio of the second injector 46 is increased. When the arrival time for the torque to rise to a preset judgment value is shorter than a preset threshold, the heavy fuel is judged.

  Therefore, by considering the vaporization state of the fuel injected into the intake port 19 and the fuel injected into the combustion chamber 18 and the vaporization properties of the heavy fuel and the light fuel, the properties of the fuel used can be accurately determined. Can be determined.

  FIG. 12 is a time chart showing fuel property determination control of the fuel property determination device in the internal combustion engine according to the seventh embodiment of the present invention. The overall configuration of the internal combustion engine fuel property determination apparatus according to the present embodiment is substantially the same as that of the first embodiment described above, and will be described with reference to FIG. 1 and has the same functions as those described in this embodiment. The members having the same reference numerals are denoted by the same reference numerals and redundant description is omitted.

  In the fuel property determination apparatus for an internal combustion engine according to the seventh embodiment, as shown in FIG. 1, when the ECU 71 changes the fuel injection ratio of the second injector 46 so as to increase by a certain amount, the control value equilibrium value is set in advance. It is determined that the fuel is heavy when it is greater than the set threshold. In this case, the control amount is the engine speed (engine speed). The ECU 71 determines the fuel property based on the equilibrium value of the engine speed because the engine speed fluctuates when the fuel injection ratios of the injectors 45 and 46 are changed.

  Here, the control for determining the fuel property used in the engine by the fuel property determination device in the internal combustion engine of the seventh embodiment will be described based on the time chart of FIG.

In the fuel property determination control in the fuel property determination device in an internal combustion engine of the present embodiment, as shown in FIG. 12, for example, at startup t ₀ of the engine, the port fuel injection ratio of the first injector 45 is set to "1" The in-cylinder fuel injection ratio of the second injector 46 is set to “0”, and the port fuel injection ratio of the first injector 45 is decreased by a certain ratio at time t ₁ while the in-cylinder fuel injection ratio of the second injector 46 is decreased. Is increased by a certain percentage. At this time, the in-cylinder injection has a larger fuel evaporation rate than the port injection, so even if the overall fuel injection amount is constant without increasing, the fuel injection amount into the cylinder increases by a certain amount. The engine speed increases by a certain amount. In-cylinder fuel injection is less affected by the difference in fuel properties than port fuel injection, and heavy fuel is less likely to evaporate than light fuel. Therefore, heavy fuel that is injected into the intake port 19 is less likely to evaporate. Since the quality fuel is easily injected into the combustion chamber 18 and evaporates, the engine speed is more likely to increase when the fuel is heavy fuel than when the fuel is light fuel.

Therefore, the engine speed of the equilibrium value per specified time from the time t ₁ to time t _2, the larger the equilibrium value definitive heavy fuel than the equilibrium value in light fuel. That is, by setting a threshold value for determination between the equilibrium value of the engine speed of light fuel and the equilibrium value of the engine speed of heavy fuel, it is determined whether the fuel being used is light fuel or heavy fuel. It can be determined whether the fuel is a quality fuel.

Incidentally, when the specified time arrives to the time t ₂ has elapsed, the port fuel injection ratio of the first injector 45 with return to "1", returning cylinder fuel injection ratio of the second injector 46 to "0".

  Thus, in the fuel property determination apparatus for an internal combustion engine according to the seventh embodiment, the first injector 45 capable of injecting fuel into the intake port 19 and the second injector 46 capable of injecting fuel into the combustion chamber 18 are provided. The ECU 71 can change the fuel injection ratio between the first injector 45 and the second injector 46 in accordance with the operating state of the engine, and the ECU 71 changes the engine injection ratio so that the fuel injection ratio of the second injector 46 increases. When the equilibrium value of the rotational speed is larger than a preset threshold value, it is determined that the fuel is heavy fuel.

  Therefore, by considering the vaporization state of the fuel injected into the intake port 19 and the fuel injected into the combustion chamber 18 and the vaporization properties of the heavy fuel and the light fuel, the properties of the fuel used can be accurately determined. Can be determined.

  In the fuel property determination apparatus for an internal combustion engine according to the seventh embodiment, the overall fuel injection amount is made constant, and the fuel injection ratio of the second injector 46 is changed so as to increase by a fixed amount at a time, while the first injector 45 When the fuel injection ratio of the engine is changed so as to decrease by a certain amount at a time, it is determined that the fuel is heavy fuel when the equilibrium value of the engine speed is larger than the threshold value. Therefore, by changing the fuel injection ratio by a certain amount at a time, the determination period can be shortened, and quick fuel property determination can be made.

  In the above-described embodiment, when the fuel injection ratio of the second injector (second fuel injection valve) 46 is changed so as to increase, the change in the operation amount or control amount for the engine (internal combustion engine) is larger than the threshold value. Is judged to be heavy fuel. In this case, the ignition timing is applied as the manipulated variable, and the engine speed (engine rotational speed) and the output torque are applied as the controlled variable. However, the present invention is not limited to these. For example, an intake air amount, an in-cylinder pressure, or the like may be applied as the control amount. Specifically, the amount of change in the manipulated variable or the controlled variable, the rate of change, the arrival time until the determination value, and the like are applied, but this combination is not limited to each embodiment.

  As described above, the fuel property determination apparatus for an internal combustion engine according to the present invention determines the fuel property based on the change in the operation amount or the control amount with respect to the internal combustion engine when the in-cylinder fuel injection ratio is changed. It enables highly accurate fuel property determination, and is useful for any internal combustion engine.

1 is a schematic configuration diagram of an engine to which a fuel property determination device for an internal combustion engine according to a first embodiment of the present invention is applied. FIG. 1 is a schematic configuration diagram showing a fuel system in an internal combustion engine of Embodiment 1. FIG. 3 is a flowchart illustrating fuel property determination control of the fuel property determination device in the internal combustion engine according to the first embodiment. 3 is a time chart showing fuel property determination control of the fuel property determination device in the internal combustion engine of the first embodiment. It is a flowchart showing the fuel property determination control of the fuel property determination apparatus in the internal combustion engine which concerns on Example 2 of this invention. 6 is a time chart showing fuel property determination control of a fuel property determination device in an internal combustion engine according to a second embodiment. It is a flowchart showing the fuel property determination control of the fuel property determination apparatus in the internal combustion engine which concerns on Example 3 of this invention. It is a flowchart showing the fuel property determination control of the fuel property determination apparatus in the internal combustion engine which concerns on Example 4 of this invention. 6 is a time chart showing fuel property determination control of a fuel property determination device in an internal combustion engine according to a fourth embodiment. It is a flowchart showing the fuel property determination control of the fuel property determination apparatus in the internal combustion engine which concerns on Example 5 of this invention. It is a flowchart showing the fuel property determination control of the fuel property determination apparatus in the internal combustion engine which concerns on Example 6 of this invention. It is a time chart showing the fuel property determination control of the fuel property determination apparatus in the internal combustion engine which concerns on Example 7 of this invention.

Explanation of symbols

18 Combustion chamber 19 Intake port 20 Exhaust port 21 Intake valve 22 Exhaust valve 45 First injector (first fuel injection valve)
46 Second injector (second fuel injection valve)
47 Low-pressure fuel supply system 48 High-pressure fuel supply system 61 Spark plug 71 Electronic control unit, ECU (fuel injection control means)

Claims (8)

A first fuel injection valve capable of injecting fuel into an intake port of the internal combustion engine;
A second fuel injection valve capable of injecting fuel into the combustion chamber of the internal combustion engine;
An internal combustion engine comprising fuel injection control means capable of changing a fuel injection ratio between the first fuel injection valve and the second fuel injection valve in accordance with an operating state of the internal combustion engine.
When the fuel injection control means changes the fuel injection ratio of the second fuel injection valve to be gradually increased while keeping the total fuel injection amount constant , the change in the operation amount with respect to the internal combustion engine or the control amount in the internal combustion engine It is determined that the fuel is heavy when the change in is greater than a preset threshold value.
A fuel property determination apparatus for an internal combustion engine.   When the change rate of the manipulated variable or the change rate of the control amount is greater than a preset threshold when the fuel injection control means changes the fuel injection rate of the second fuel injection valve to gradually increase. 2. The fuel property determining apparatus for an internal combustion engine according to claim 1, wherein the fuel property determining apparatus determines that the fuel is heavy.   When the fuel injection control unit changes the fuel injection ratio of the second fuel injection valve so as to gradually increase, the operation amount or the control amount is a predetermined determination operation amount or a predetermined determination control amount. 2. The fuel property determination apparatus for an internal combustion engine according to claim 1, wherein the fuel property determination unit determines that the fuel is heavy fuel when an elapsed time to reach a value is shorter than a preset threshold value. A first fuel injection valve capable of injecting fuel into an intake port of the internal combustion engine;
A second fuel injection valve capable of injecting fuel into the combustion chamber of the internal combustion engine;
An internal combustion engine comprising fuel injection control means capable of changing a fuel injection ratio between the first fuel injection valve and the second fuel injection valve in accordance with an operating state of the internal combustion engine.
When the total fuel injection amount is made constant by the fuel injection control means and the fuel injection ratio of the second fuel injection valve is changed to be increased by a constant amount, the equilibrium value of the operation amount for the internal combustion engine or the internal combustion engine It is determined that the fuel is heavy when the equilibrium value of the control amount is greater than a preset threshold value.
A fuel property determination apparatus for an internal combustion engine.   5. The fuel property determination apparatus for an internal combustion engine according to claim 1, wherein the manipulated variable is an ignition timing in the internal combustion engine.   5. The fuel property determination apparatus for an internal combustion engine according to claim 1, wherein the control amount is an engine rotation speed or an output torque of the internal combustion engine.   The fuel property determination apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the fuel property determination is performed when the internal combustion engine is started.   The internal combustion engine according to any one of claims 1 to 7, wherein a property determination of the fuel used is executed when an air-fuel ratio sensor provided in an exhaust system of the internal combustion engine is not warmed up. Fuel property determination device.

Images