JP4325573B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to fuel injection control for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine that uses GTL (Gas To Liquid) fuel as fuel.

  In recent years, GTL fuel has been developed as one of alternative fuels in diesel engines. This GTL fuel is a fuel mainly composed of saturated hydrocarbons (paraffinic hydrocarbons) synthesized from natural gas using a catalyst. It is colorless and odorless, does not contain sulfur and aroma, and has a high cetane number. It can be used for other diesel engines. It also has the function of reducing harmful substances such as carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter from the exhaust gas. Development is currently underway as an alternative fuel.

JP 2004-108231 A

  By the way, when GTL fuel is spread in the market, the properties of GTL fuel may change depending on the region or the like, and it may happen that desired performance cannot be exhibited constantly.

  As a conventional technique corresponding to the change in fuel properties, there is a method for correcting the fuel injection amount according to the oxygen content of the fuel as disclosed in Patent Document 1. However, this prior art is premised on the use of a fuel containing oxygen, and cannot be directly applied to the fuel injection control of an internal combustion engine premised on the use of the GTL fuel targeted by the present invention.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel injection control device for an internal combustion engine that uses a GTL fuel and can obtain a certain performance even when the properties of the GTL fuel change.

  In order to achieve the above object, one aspect of the present invention is a fuel injection control device for an internal combustion engine that uses GTL fuel, a fuel density detection means for detecting the density of the GTL fuel, and the detected density. And a fuel injection amount correcting means for correcting the fuel injection amount in accordance with the calculated heat generation amount.

  In the case of GTL fuel, if the density of the fuel is known, the calorific value of the fuel can be calculated relatively easily and accurately based on the density. Therefore, with the above configuration, the fuel injection amount can be corrected in accordance with the actual heat generation amount of the fuel, and a constant performance can be obtained even when the heat generation amount of the fuel changes.

  Preferably, the calorific value calculation means calculates an average C number of the GTL fuel based on the detected density of the GTL fuel, and calculates a calorific value of the GTL fuel based on the calculated average C number. To do.

GTL fuel can be represented almost in its molecular configuration in the form of C _n H _{2n + 2} . According to the above configuration, since the average C number of the fuel is calculated based on the density of the fuel, the average molecular configuration of the GTL fuel can be determined and the calorific value can be calculated relatively easily.

  Preferably, the apparatus further includes transparency detecting means for detecting transparency of the GTL fuel, and fuel determining means for determining whether or not the fuel supplied is GTL fuel according to the detected transparency.

  Since GTL fuel does not contain sulfur, it is almost colorless and transparent. Therefore, as in the above configuration, it is possible to determine whether or not the fuel is a GTL fuel by detecting the transparency of the fuel. According to this configuration, even when fuel other than the GTL fuel is erroneously refueled, the fact can be clearly detected. For example, fuel injection control can be switched or a warning can be given to the user.

  According to the present invention, in an internal combustion engine using GTL fuel, an excellent effect is obtained that a certain performance can be obtained even when the properties of the GTL fuel change.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the present embodiment, the internal combustion engine is a diesel engine, particularly a common rail diesel engine. However, the present invention may be applicable to other types of engines such as gasoline engines.

  FIG. 1 shows a fuel injection control device for an internal combustion engine according to this embodiment. In the figure, the diesel engine 1 has four in-line cylinders, but there is no particular limitation on the number of cylinders and the cylinder arrangement form. Fuel consisting of GTL fuel is injected from a fuel injection valve (injector) 2 into the combustion chamber of each cylinder. Each fuel injection valve 2 is connected to a common rail 3, and fuel is supplied to the common rail 3 from a high-pressure fuel pump 4. The fuel stored in the fuel tank 6 is supplied to the high-pressure fuel pump 4 by a feed pump 15. The high-pressure fuel pump 4 is operated and controlled by an electronic control unit (ECU) 5 as a control means so that the fuel pressure in the common rail 3 becomes a predetermined pressure corresponding to the engine operating state. In order to achieve the feedback control of the fuel pressure, the common rail 3 is provided with a fuel pressure sensor 42, and an output signal of the fuel pressure sensor 42 is sent to the ECU 5. The fuel pressure in the common rail 3 corresponds to the fuel injection pressure injected from the fuel injection valve 2. Each fuel injection valve 2 has its valve opening timing and valve opening time controlled by the ECU 5 in accordance with the engine operating state.

  Further, an intake branch pipe is connected to each cylinder of the diesel engine 1, and each intake branch pipe is connected to an intake pipe 8 via an intake manifold 7. A compressor 10 of a turbocharger 9 is provided in the middle of the intake pipe 8, and air sucked from an air cleaner 12 is sent to the compressor 10 after passing through an air flow meter 11. The air flow meter 11 outputs an output signal corresponding to the amount of air flowing therethrough to the ECU 5, and the ECU 5 calculates the intake air amount based on the output signal of the air flow meter 11. An intercooler 13 is installed on the downstream side of the compressor 10, and an intake throttle valve 14 is provided on the downstream side of the intercooler 13. The intake throttle valve 14 includes driving means such as a rotary solenoid, and the opening degree is controlled by the ECU 5 according to the operating state of the diesel engine 1.

  Further, an exhaust branch pipe is connected to each cylinder of the diesel engine 1, each exhaust branch pipe is connected to an exhaust manifold 17, the exhaust manifold 17 is connected to a turbine 18 of the turbocharger 9, and the turbine 18 is exhausted. Connected to tube 19. In the present embodiment, the exhaust branch pipe, the exhaust manifold 17, the turbine 18, and the exhaust pipe 19 constitute an exhaust passage. In the present embodiment, the turbine 18 is of a variable capacity type, and the opening degree of the variable vane inside thereof is controlled by the ECU 5 according to the operating state of the diesel engine 1. However, the turbine 18 may not be a variable capacity type.

  The exhaust gas of the diesel engine 1 flows from the exhaust manifold 17 through the turbine 18 of the turbocharger 9 to the exhaust pipe 19, and at this time, the turbine 18 drives the compressor 10. As a result, the intake air is boosted by the compressor 10, becomes supercharged air, flows through the intake pipe 8, and is supplied to the combustion chamber of each cylinder via the intake manifold 7. By changing the opening degree of the variable vane of the turbine 18, the flow rate of the exhaust gas flowing through the turbine 18 can be changed and the supercharging pressure can be changed relatively rapidly. A waste gate device for exhaust bypass (not shown) is also provided, and the waste gate valve of the waste gate device is controlled to open and close by the ECU 5 to limit the supercharging pressure within a predetermined value.

  The intake manifold 7 and the exhaust manifold 17 are connected by an exhaust gas recirculation pipe 28, and an exhaust gas recirculation control valve (hereinafter abbreviated as EGR valve) 29 is provided in the exhaust gas recirculation pipe 28. The opening degree of the EGR valve 29 is controlled by the ECU 5 according to the operating state of the diesel engine 1, and the exhaust gas having a flow rate corresponding to the opening degree of the EGR valve 29 is recirculated from the exhaust manifold 17 to the intake manifold 7. The EGR valve 29 can employ a linear solenoid drive type or the like. An exhaust gas recirculation pipe 28 upstream of the EGR valve 29 is provided with an EGR cooler 39 for cooling the recirculated exhaust gas.

  The ECU 5 is composed of a digital computer, and includes a ROM (Read On Memory), a RAM (Random Access Memory), a CPU (Central Processor Unit), an input port, and an output port that are connected to each other via a bidirectional bus. Various controls such as quantity control are executed.

  For such control, an input signal from the air flow meter 11 is input to the input port of the ECU 5, and an input signal from the rotation speed sensor 30 and an input signal from the accelerator opening sensor 31 are input to the input port of the ECU 5. The The rotational speed sensor 30 outputs an output signal corresponding to the rotational speed of the diesel engine 1 to the ECU 5, and the ECU 5 calculates the engine rotational speed from this output signal. The accelerator opening sensor 31 outputs to the ECU 5 an output signal corresponding to the depression amount of the accelerator pedal, that is, the accelerator opening. An input signal from the atmospheric pressure sensor 20 and an input signal from the water temperature sensor 21 are input to the input port of the ECU 5. The atmospheric pressure sensor 20 outputs an output signal corresponding to the atmospheric pressure to the ECU 5, and the water temperature sensor 21 outputs an output signal corresponding to the engine cooling water temperature to the ECU 5.

  In particular, in the present embodiment, a density detection sensor 22 that detects the density of the actual GTL fuel used for injection is provided. As the density detection sensor 22, a sensor that utilizes the fact that the wave velocity in the fuel changes according to the change in the fuel density, such as a light reflection type, a light transmission type, and an ultrasonic type can be adopted. The density detection sensor 22 of this embodiment employs an ultrasonic type. The density detection sensor 22 introduces the fuel in the fuel tank 6 through the fuel introduction passage 24, detects the density of the fuel, and outputs an output signal corresponding to the density to the ECU 5. The density detection sensor 22 is connected to an intake passage (intake manifold 7 or intake pipe 8) on the downstream side of the intake throttle valve 14 through a negative pressure introduction passage 25, and sucks up fuel by using the introduced intake negative pressure. It has become. The fuel introduction passage 24 and the negative pressure introduction passage 25 are provided with electromagnetic valves 26 and 27, respectively. These electromagnetic valves 26 and 27 are normally open, and are opened in response to an off signal output from the ECU. It is closed according to the ON signal that is output.

  As shown in detail in FIG. 2, the density detection sensor 22 includes a casing 31 that stores the sucked-up fuel, a heat insulating material or an air layer 32 that is provided on the inner surface of the casing 31 and keeps the stored fuel, and A heater (panel heater) 33 that is affixed to the inner surface of the heat insulating material and heats the stored fuel, a temperature sensor 34 that detects the temperature of the stored fuel, and an ultrasonic wave that applies ultrasonic waves to the stored fuel A vibrator 35 and a linear piezoelectric element 36 that is disposed opposite to the ultrasonic vibrator 35 and detects ultrasonic waves transmitted through the fuel are provided. The heater 33 and the ultrasonic transducer 35 are turned on / off in response to an on / off signal output from the ECU, the temperature sensor 34 outputs an output signal corresponding to the fuel temperature to the ECU 5, and the piezoelectric element 36 corresponds to the detected ultrasonic wave. The output signal is output to the ECU 5. The ultrasonic transducer 35 and the piezoelectric element 36 are arranged near the top in the casing 31. The fuel introduction passage 24 is formed by the fuel introduction pipe 37 and is connected to the bottom of the casing 31. The inlet end 24a of the fuel introduction passage 24 can be disposed in the fuel tank 6 and at a position slightly lower than the liquid level FL when the fuel is full. The negative pressure introduction passage 25 is formed by a negative pressure introduction pipe 38 and is connected to the top of the casing 31. The operations of the density detection sensor 22 and the electromagnetic valves 26 and 27 will be described later.

  As described above, when using such a GTL fuel, the properties of the GTL fuel may change depending on the region and the like, and it may not be possible to achieve a desired performance. Therefore, in the present embodiment, the problem is solved by calculating the actual heat generation amount of the GTL fuel and correcting the fuel injection amount in accordance with the calculated heat generation amount.

  The reason why the fuel injection amount can be corrected is that the heat generation amount of the GTL fuel can be calculated by a relatively simple device and method. In other words, light oil, which is a common diesel fuel, is a method of distilling from heavy oil, so it contains sulfur and aroma. To control fuel properties, change the distillation characteristics or change the cetane number with additives, etc. There is no choice but to change. There are legal regulations regarding distillation characteristics, cetane number and sulfur content, and the fuel itself varies greatly depending on the origin of heavy oil. At present, the standard fuel is prepared for each engine destination country, and engine adaptation (mapping, control constant setting, etc.) is being implemented. In other words, it is very difficult to detect the properties of the fuel that is commonly used at present due to the large number and complexity of the fuel-containing components using equipment such as a vehicle equipped with an engine. . Conversely, a very expensive analyzer and a long measurement time are required to make this detectable, which is not realistic. For these reasons, it is extremely difficult to calculate the actual amount of heat generated by the fuel. Therefore, there is no choice but to apply for each country or region where the heat generated by the fuel is different. It was very complicated and at the same time was a big obstacle to the standardization. The same applies to gasoline fuel.

  On the other hand, in the case of GTL fuel, it is a production method that synthesizes from natural gas using a catalyst, and since it is a relatively pure fuel that does not contain sulfur or aroma, it is easy to identify components, unlike light oil and gasoline. It is. Therefore, as will be understood later, the calorific value can be calculated by a relatively simple device and method, and the fuel injection amount can be corrected based on the calorific value. According to this, it becomes unnecessary to carry out the adaptation for each country and each region where the heat generation amount of the fuel is different, and the control can be uniformly performed using the same control constant. In addition, control accuracy can be improved and standardization can be promoted.

Here, the GTL fuel is a fuel centered on a saturated hydrocarbon (paraffinic hydrocarbon), and its molecular configuration can be substantially expressed in the form of C _n H _{2n + 2} . The hydrocarbon bond length can be controlled, and the degree of freedom in fuel design is high. There is no polarity.

  Next, the content of the fuel injection control according to the present embodiment will be described with reference to FIGS. FIG. 4 is a flowchart regarding a processing routine for calculating and learning the actual heat generation amount of the GTL fuel, and FIG. 5 is a processing routine for correcting the fuel injection amount according to the calculated actual heat generation amount of the GTL fuel. It is a flowchart regarding.

  First, the process shown in FIG. 4 will be described. This process is executed by the ECU 5.

  In the first step S101, it is determined whether or not the engine is starting. Here, when the start operation is performed by the user, for example, when the ignition switch or the starter is turned on, the determination is yes, otherwise the determination is no and the process is terminated. The reason for determining whether or not to start the engine is substantially to determine whether or not the fuel tank 6 has been refueled. That is, since the engine is normally stopped at the time of refueling, it is possible to indirectly determine the presence or absence of refueling without using a special sensor or the like by detecting that the engine has been started after the stop. In addition to this method, for example, the presence or absence of fuel supply can be determined by a method of detecting by a sensor that the cap of the fuel tank 6 has been released. Thus, in this embodiment, the oil supply determination means which determines the presence or absence of oil supply is provided.

  If it is determined in step S101 that the engine is starting (step S101: YES), the process proceeds to step S102, and the previous heat generation amount Hu_pre already stored in the memory (RAM) of the ECU 5 is acquired. The previous heat generation amount Hu_pre is a value learned in step S108 when the past processing is executed. In step S102, the fuel change flag is further turned off and initialized.

  In the next step S103, the actual fuel density is detected by the density detection sensor 22. This density detection is performed by the following method.

  Referring to FIG. 2, in the initial state, solenoid valves 26 and 27 are off, that is, in a valve open state. Since the engine is started, the intake negative pressure in the intake passage is introduced into the casing 31 through the negative pressure introduction passage 25. Due to this negative pressure, the fuel in the fuel tank 6 is sucked into the casing 31 through the fuel introduction passage 24. While the fuel is accumulated in the casing 31, the ultrasonic transducer 35 is turned on and continues to emit ultrasonic waves. When the fuel is almost filled in the casing 31, an ultrasonic wave corresponding to that case is detected by the piezoelectric element 36. At this time, the electromagnetic valves 26 and 27 are turned on and closed. As a result, the fuel is confined in the casing 31. Next, the heater 33 is turned on, and the fuel in the casing 31 is heated. When the fuel temperature detected by the temperature sensor 34 reaches a predetermined value (for example, 40 ° C.), the heater 33 is turned off and the heating of the fuel is ended. The reason why the fuel is set to a predetermined temperature in this way is to make the temperature condition regarding the fuel density constant. Simultaneously with the end of this heating, ultrasonic waves are detected by the linear piezoelectric element 36, and the ECU 5 calculates the fuel density based on the signal output from the piezoelectric element 36. This calculation is performed by a map or arithmetic expression set and stored in advance. This completes the detection of the fuel density. Thereafter, during engine operation, the electromagnetic valves 26 and 27 are turned on and maintained in a closed state, thereby preventing fuel from flowing into the intake passage from the casing 31 through the negative pressure introduction passage 25. When the engine is stopped (for example, when the ignition switch is turned off by the user), the electromagnetic valves 26 and 27 are turned off and opened. When this happens, the fuel falls from the casing 31 by gravity and returns to the fuel tank 6 through the fuel introduction passage 24.

  After the fuel density is detected in this way, the process proceeds to step S104, and atmospheric pressure correction is performed on the detected density. This atmospheric pressure correction is performed based on the actual atmospheric pressure detected by the atmospheric pressure sensor 20. The reason for performing the atmospheric pressure correction in this way is to make the pressure condition related to the fuel density uniform. Thus, the fuel density ρ1 after atmospheric pressure correction is obtained here.

  In the next step S105, the actual average C number of fuel is calculated. For this calculation, the map shown in FIG. 3 is used. This map is created in advance by experiments or the like and stored in the memory (ROM) of the ECU 5. In this map, the relationship between the fuel density and the average C number is input, and the ECU 5 determines the average C number corresponding to the fuel density ρ1 after atmospheric pressure correction obtained in the previous step S104 from the map. In this embodiment, the average C number corresponding to the actual fuel density ρ1 is 15, the density of the reference fuel used for adaptation is ρ0, and the average C number corresponding to this is 17.

  The map in FIG. 3 is very close to the correlation between density and average C number in saturated hydrocarbons (paraffinic hydrocarbons), and as can be seen, the correlation between density and average C number is strong. Saturated hydrocarbons are also not polar. Therefore, the average C number can be easily and accurately determined from the density. On the other hand, in the case of light oil, since there is a sulfur content and polycyclic aromatics, such a strong correlation does not occur, and thus the average C number cannot be easily calculated from the density.

In the next step S106, the weight ratio of C and H in the fuel is calculated. In the previous step S105, it was found that the average C number of the actual fuel is 15. Therefore, it is estimated that the average numerator contained in the fuel is C ₁₅ H ₃₂ . The weight per unit mol of C ₁₅ H ₃₂ is 12.01 g / mol for C and 1.008 g / mol for H.
C ₁₅ H ₃₂ = 12.01 * 15 + 1.008 * 32 = 180.15 + 32.256 = 212.406 g / mol
Therefore, when the weight ratio for each of C and H is expressed in weight%,
C weight% = 180.15 / 212.406 = 0.8481
H weight% = 32.256 / 212.406 = 0.1519
It becomes.

  In the next step S107, the heat generation amount Hu of the fuel is calculated. Each weight ratio calculated in step S106 is equal to the weight ratio per kg of fuel. Therefore, if the calorific value constants for C and H are A and B, the calorific value (low calorific value) Hu per kg of fuel can be calculated by the following equation.

Hu = 0.8481A + 0.1519B (MJ / kg)
Here, in many liquid fuels, the binding energy of elemental bonds is smaller than the reaction energy, so that the binding energy can generally be omitted. Therefore, the calorific value of the compound fuel or mixture thereof can be approximately calculated by taking the sum according to the calorific element content ratio of the constituent elements. In the case of GTL fuel, the above formula is simple, but in the case of light oil, the formula is as follows.

Hu = AC + B (HO-8) + DS-EW (MJ / kg)
Here, C, H, O, S, and W are the weights of carbon, hydrogen, oxygen, sulfur, and moisture per kg of fuel, respectively, and A, B, D, and E are calorific value constants. However, in the liquid fuel, the moisture is almost 0 and the oxygen is 1-2%. Since GTL fuel does not contain sulfur, S = 0, and this formula is simplified to Hu = AC + BH, and the calorific value can be easily calculated. That is, the correction of the fuel injection amount based on the calorific value of the fuel in the present invention is practically possible because of the GTL fuel.

  After the fuel heat generation amount Hu is calculated in this way, the process proceeds to step S108, where the heat generation amount Hu is compared with the previous heat generation amount Hu_pre, and it is determined whether the heat generation amount Hu is equal to the previous heat generation amount Hu_pre. When it is determined that the calorific value Hu is equal to the previous calorific value Hu_pre (step S108: YES), it can be estimated that refueling has not been performed or equivalent fuel has been refueled, so the processing is terminated as it is. When it is determined that the heat generation amount Hu is different from the previous heat generation amount Hu_pre (step S108: NO), it can be estimated that a different fuel has been refueled, so the routine proceeds to step S109 where the fuel change flag is turned on and the current heat generation amount Hu. Is updated and stored in the RAM as the previous heat generation amount Hu_pre, and the process is terminated.

  Next, the process shown in FIG. 5 will be described. This process is executed by the ECU 5 for each fuel injection cycle.

  In the first step S201, detection values detected by the various sensors, that is, engine parameters are acquired. The engine parameters include the engine rotation speed Ne based on the output signal of the crank sensor 30, the accelerator opening Ac based on the output signal of the accelerator opening sensor 31, the atmospheric pressure based on the output signals of the atmospheric pressure sensor 20 and the water temperature sensor 21, respectively. And the engine cooling water temperature and the like, and in particular, the calorific value Hu calculated by the processing.

  In the next step S202, a basic basic injection amount Qb is calculated based on the acquired engine parameters (in this embodiment, the engine speed Ne and the accelerator opening Ac). That is, in the memory (ROM) of the ECU 5, a map of the basic injection amount Qb associated with the engine speed Ne and the accelerator opening degree Ac is stored in advance. Then, the ECU 5 calculates a basic injection amount Qb from the acquired engine rotation speed Ne and accelerator opening degree Ac with reference to a map.

  In the next step S203, the calculated basic injection amount Qb is corrected based on engine parameters excluding the heat generation amount Hu. The value thus obtained is referred to as a basic corrected injection amount Qbc. Similarly, the injection timing and the number of injections are set based on the engine parameters. In the present embodiment, a plurality of fuel injections may be executed during one injection cycle depending on the engine operating state at that time. For example, two pilot injections and one main injection are executed, or each one pilot injection, main injection, and post injection are executed. The number of such fuel injections is set here, and simultaneously the injection timing of each fuel injection is set.

  In the next step S204, it is determined whether or not the fuel change flag is turned on by the processing of FIG. When the fuel change flag is turned on (step S204: YES), in the next step S205, the heat generation amount correction coefficient α is calculated by the equation: α = Hu0 / Hu.

Here, Hu0 is the calorific value of the fuel used for adaptation, that is, the basic calorific value as a base. As described above, in this embodiment, the GTL fuel used for adaptation has a density ρ0 and a C number of 17. In this case, the same manner, the average molecule contained in the fuel is estimated to be _C 17 _{H 36,} weight per unit mol of the _C 17 _{H 36} is
C ₁₇ H ₃₆ = 12.01 * 17 + 1.008 * 36 = 204.17 + 36.288 = 240.458 g / mol
The weight ratio for each of C and H is expressed in weight%.
C weight% = 204.17 / 240.458 = 0.8491
H wt% = 36.288 / 240.458 = 0.1509
Therefore, the basic heating value (low heating value) Hu0 per kg of fuel is
Hu0 = 0.8491A + 0.1509B (MJ / kg)
It becomes. After all, the calorific value correction coefficient α is
α = Hu0 / Hu = (0.8491A + 0.1509B) / (0.8481A + 0.1519B)
It becomes.

  Thereafter, in step S207, the final injection amount Qfnl to be injected is calculated by the formula: Qfnl = α * Qbc, and correction of the fuel injection amount based on the heat generation amount of the fuel is executed. According to this, when the fuel currently in use has a higher calorific value than the reference fuel used for adaptation, the fuel injection amount is corrected to the decrease side, and conversely, the fuel currently in use is used for adaptation. In the case where the calorific value is lower than the reference fuel obtained, the fuel injection amount is corrected to the increase side. Thus, according to the actual fuel, the fuel injection amount is corrected so that a performance equivalent to that at the time of adaptation can be obtained, and a constant engine performance can be obtained stably.

  In the next step S208, fuel injection is performed, that is, an amount of fuel equal to the final injection amount Qfnl is injected simultaneously with the arrival of the injection timing set in step S203. Here, the final injection amount Qfnl is the total amount of injection in one injection cycle. When multiple injections are performed, the final injection amount Qfnl is shared by each injection, and the injection amount of each injection is set. Is done. At the same time as the injection timing of each injection comes, the corresponding injection amount is injected.

  On the other hand, if the fuel change flag is not turned on (that is, is turned off) in step S204 (step S204: NO), the heat generation amount correction coefficient α is calculated by the formula: α = Hu0 / Hu_pre in the next step S206. In step S207, the final injection amount Qfnl is calculated by the formula: Qfnl = α * Qbc, and in the next step S208, an amount of fuel equal to the final injection amount Qfnl is injected. As can be seen from this, when there is a fuel change or refueling accompanied by a change in the heat generation amount of the fuel (step S204: YES), the heat generation amount correction coefficient α or the correction amount is also changed accordingly. When there is no change or refueling of the fuel that accompanies a change in the heat generation amount of the fuel (step S204: NO), the heat generation amount correction coefficient α or the correction amount is the same as before. Although the correction here is performed by multiplication of the correction coefficient α, it may be performed by other operations such as addition.

  As described above, according to the present embodiment, even when the properties of the GTL fuel change according to the region or the like and the heat generation amount thereof changes, the fuel injection amount is corrected according to the heat generation amount. It is possible to stably obtain the performance of Further, since the amount of heat generated by the fuel can be obtained simply by detecting the density of the fuel, the calculation of the amount of heat generated, and hence the correction of the fuel injection amount, can be performed by a relatively simple device and method. This is a merit peculiar to GTL fuel. It is not necessary to perform the adaptation for each country or region having a different amount of heat generated from the fuel, and the control can be uniformly performed using the same control constant, and the adaptation is greatly simplified. In addition, control accuracy can be improved and standardization can be promoted.

  By the way, at the time of fuel supply, it is also conceivable that the user supplies fuel other than GTL fuel by mistake. In this case, it is not preferable to perform the fuel injection control as described above based on GTL fuel, and it is preferable to inform the user of the fact of misfueling. For this reason, in this embodiment, the transparency detection means for detecting the transparency of the GTL fuel, and the fuel discrimination means for determining whether or not the supplied fuel is GTL fuel according to the detected transparency. ing.

  As described above, since GTL fuel does not contain sulfur, it is more colorless and transparent than light oil. Therefore, in the present embodiment, it is determined whether or not the fuel is a GTL fuel by detecting the transparency of the fuel. In order to detect this transparency, a single sensor may be provided. However, in the embodiment described here, a light reflection type or a light transmission type is used for the density detection sensor 22, and the transparency is detected simultaneously. We are trying to make it common.

  Hereinafter, based on FIG. 6, the content of this fuel discrimination | determination process is demonstrated. This control is performed by the ECU 5.

  First, in step S301, it is determined whether or not the engine is starting. This is for substantially determining the presence or absence of refueling, as in step S101 of FIG. If it is not at the time of engine start, the process is terminated. In step S <b> 302, the actual fuel transparency CL is detected by the density detection sensor 22.

  In the next step S303, the detected transparency CL is compared with a predetermined value CL1, and it is determined whether or not the transparency CL is greater than or equal to the predetermined value CL1. Here, the maximum transparency value at which the fuel cannot be regarded as a GTL fuel is set as the predetermined value CL1. That is, when the transparency CL is equal to or greater than the predetermined value CL1, it means that the fuel is so transparent that the fuel can be regarded as a GTL fuel, and conversely, when the transparency CL is less than the predetermined value CL1, This means that the transparency of the fuel is so low that it cannot be regarded as a GTL fuel. In this way, it is determined whether or not the supplied fuel is GTL fuel.

  When the transparency CL is equal to or greater than the predetermined value CL1 (step S303: YES), the fuel is regarded as a GTL fuel, and the process proceeds to step S304 where the fuel injection control for the GTL fuel as described above is performed.

  On the other hand, when the transparency CL is less than the predetermined value CL1 (step S303: NO), the fuel is regarded as a fuel other than the GTL fuel. In the present embodiment, since it is a diesel engine, there is a high possibility that light oil fuel has been misfueled. Therefore, the fuel injection control for light oil fuel is performed here according to the light oil fuel program and map stored in advance in the ECU 5. In step S306, a warning lamp is turned on to inform the user of the fact of misfueling.

  Thus, even when fuel other than GTL fuel is misfueled, the fact can be clearly detected. When such erroneous fueling occurs, the fuel injection control is switched from GTL fuel to light oil fuel, so that failsafe is achieved. Moreover, the fact can be surely notified to the user.

  As can be seen from the above description, in the present embodiment, the fuel density detection means is constituted by the density detection sensor 22, and the heat generation amount calculation means is constituted by a portion that executes steps S <b> 105 to S <b> 107 of the ECU 5, thereby correcting fuel injection amount. The means is constituted by a part that executes steps S205, S206, and S207 of the ECU 5, the transparency detecting means is constituted by a light reflection type or light transmission type density detection sensor 22, and the fuel discrimination means is a part that executes step S303 of the ECU 5. Consists of.

The present invention can employ various other embodiments. For example, the map in FIG. 3 can be replaced with an arithmetic expression. Each numerical value shown in the embodiment is merely an example, and can take an arbitrary value. In the above embodiment, the molecular configuration of the GTL fuel is close to the shape of C _n H _{2n + 2} . However, GTL fuels other than this molecular structure can be assumed, and in this case, there is a possibility that it can be dealt with by standardization of the C / H ratio.

It is a schematic block diagram of the fuel-injection control apparatus of the internal combustion engine which concerns on this embodiment. It is sectional drawing of a density detection sensor. It is a map for calculating | requiring an average C number from a fuel density. It is a flowchart regarding the calorific value calculation routine of GTL fuel. 6 is a flowchart relating to a fuel injection amount correction routine. It is a flowchart in connection with a fuel discrimination | determination process.

Explanation of symbols

1 Diesel engine 5 Electronic control unit (ECU)
22 Density detection sensor 22
Heat generation of Hu GTL fuel this time
Hu_pre GTL fuel's previous calorific value α Calorific value correction coefficient Qbc Basic corrected post-injection amount Qfnl Final injection amount ρ0 Density of fuel used for adaptation ρ1 Actual fuel density CL Actual fuel transparency

Claims (3)

A fuel injection control device for an internal combustion engine that uses GTL fuel,
Fuel density detecting means for detecting the density of the GTL fuel under a constant temperature condition ;
Means for performing atmospheric pressure correction to make the pressure condition constant for the detected density;
A calorific value calculating means for calculating the calorific value of the GTL fuel based on the density after atmospheric pressure correction ;
A fuel injection control device for an internal combustion engine, comprising: fuel injection amount correction means for correcting the fuel injection amount in accordance with the calculated heat generation amount. The calorific value calculation means calculates an average C number of the GTL fuel based on the density after the atmospheric pressure correction, and calculates a calorific value of the GTL fuel based on the calculated average C number. The fuel injection control device for an internal combustion engine according to claim 1. The calorific value calculation means calculates the weight ratio of C and H in the fuel based on the calculated average C number, and calculates the calorific value per unit weight of the GTL fuel based on the calculated weight ratio. The fuel injection control device for an internal combustion engine according to claim 2, wherein:

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