JP2010138825A - Method for determining fuel composition and fuel composition determining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine a blend ratio of a composite fuel to be used without causing increase in cost, using various sensors of means for detecting operating states of existing engines generally used in engine operation control, as to an engine using the composite fuel. <P>SOLUTION: A method for determining fuel composition is performed by a fuel composition determining device 1 mounted on a control system of the engine using the composite fuel, which detects output signals from predetermined engine operating state detecting means 11, 12, 13, and 14 to perform engine control depending on an operating state of the engine. In the method, knocking is intentionally generated by adding a predetermined operation at ignition timing, a knocking detecting means 15 detects the knocking and the ignition timing at that time, and based on the detected knocking generation ignition timing and the operating state of the engine, the blend ratio of the composite fuel to be used is determined by a predetermined system using difference of each octane value of fuels blended in the composite fuel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention supplies a “mixed fuel” obtained by mixing approximately two types of fuels having different octane numbers, such as LPG (liquefied petroleum gas) fuel mainly composed of propane and butane and oxygen-containing hydrocarbon fuel. The present invention relates to a fuel composition determination method and a fuel composition determination device in an engine (hereinafter referred to as “mixed fuel engine”) mounted on an LPG engine or FFV (flexible fail vehicle).

  LPG supplied to the LPG engine is a mixed fuel mainly composed of propane and butane, and the composition ratio thereof generally varies depending on the region, manufacturer, season of manufacture, and the like. Propane has a higher octane number and a lower density per unit volume than butane. Therefore, when the fuel components of LPG are different, the optimum ignition timing and fuel injection amount important for engine operation control are also affected.

  However, in a conventional LPG engine mounted on a vehicle, control based on the ignition timing and fuel injection amount optimized for the composition ratio of propane and butane used is not executed, and a standard predetermined These settings are usually made on the premise of the ratio. Therefore, when LPG with a composition ratio different from the assumed standard product is used, the vehicle will be driven with room for improvement in the fuel efficiency and exhaust gas performance of the vehicle, resulting in deterioration of these performances. It was connected.

  In an LPG engine that injects LPG into the intake pipe or intake port in a liquid state, the LPG is maintained at a pressure equal to or higher than the vapor pressure using a booster such as a pump in order to keep the LPG inside the injector in a liquid state. There is a need. However, the target pressure for increasing the pressure needs to be set to a sufficiently high target pressure in case the LPG mainly composed of propane having the highest vapor pressure is supplied to the engine. The work of the booster device increases and the fuel consumption deteriorates. For this reason, it is necessary to estimate the vapor pressure of the LPG used by determining the fuel composition, and to set it to the minimum target fuel pressure.

  On the other hand, as described in JP-A-61-275555 and JP-A-2004-324509, the LPG injection control device detects the fuel temperature and gas-phase fuel pressure in the fuel tank storing the LPG. Based on this, it is common to determine the fuel composition by obtaining the composition ratio of propane and butane of the LPG used by using a predetermined data table or the like, and to correct the reference fuel injection amount, the reference ignition timing, etc. Has been done.

  However, in order to carry out such a fuel composition determination method, it is necessary to newly provide a pressure sensor and a temperature sensor in the fuel tank. Since such a pressure sensor is a relatively expensive component, There is a problem that the cost of the system cannot be avoided.

  In addition, in an engine that uses gasoline mixed with ethanol or ethanol that has a higher octane ratio than gasoline, such as an engine mounted on a FFV (flexible fail car), if the mixing ratio of gasoline and ethanol is different, Since the calorific value changes, it is necessary to change the fuel injection amount, and the ignition timing can be set to an optimum condition by utilizing the high octane characteristic of ethanol.

  Therefore, conventional spark ignition engines have a wide range of autoignition characteristics (characteristics such as octane number and cetane number) to determine normal combustion and knock limit ignition with mixed fuel. Means for estimating self-ignitability of the mixed fuel based on the timing, and estimating self-ignitability of the fuel to be judged based on the self-ignitability of the mixed fuel, the self-ignitability of the reference fuel, and the ratio It is presented in Japanese Patent Application Laid-Open No. 2008-223567.

The means for determining self-ignitability presented in this gazette is a means for calculating the mixing ratio of two types of fuels having greatly different octane numbers based on the knocking judgment result as presented in JP-A-2005-2914. Compared to the above, it has the advantage of being able to determine a wide range of self-ignitability, but the fuel to be judged in the main tank is injected from the fuel injection valve, and the self-ignitability stored in the sub tank is known. Since the reference fuel is injected from the fuel injection valve, not only is extra equipment necessary, but it is not practical.
JP-A 61-275555 JP 2004-324509 A JP 2008-223567 A JP 2005-2914 A

  The present invention is intended to solve the above-described problems, and is a mixed fuel engine that supplies a mixed fuel obtained by mixing mainly two types of fuels having different octane numbers, such as an LPG engine or an engine mounted on an FFV. Therefore, it is an object of the present invention to make it possible to determine the fuel composition of a mixture to be used without increasing costs by using existing sensors that are normally used for engine operation control.

  Accordingly, the present invention provides a fuel composition determination method in a mixed fuel engine having an engine control system that executes engine control in accordance with an engine operating state using detection values from various operating state detecting means attached to a predetermined position. The knocking ignition timing obtained by detecting the knocking state intentionally generated by performing control to change the ignition timing of the engine by the knock detection means and the detected value by the engine operating state detection means It is characterized in that the composition ratio of the mixed fuel used is obtained by the judging means using the fact that the octane number is different depending on the estimated engine operating state and the mixed ratio of the mixed fuel.

  LPG with a lot of propane components has a high octane number, so the ignition timing for knocking is on the advance side, and for LPG with a lot of butane components, the ignition timing on the knocking state is on the retard side. Since the ratio of propane and butane can be estimated in reverse, based on the ignition timing that was knocked by intentionally changing the ignition timing and the engine operating status at that time, the existing engine operating status It becomes possible to determine the fuel composition of the used LPG using various sensors as detection means.

  Further, in gasoline mixed with ethanol, as in the case described above, when the amount of ethanol is large, the octane number is high, and the ignition timing at which the engine is knocked is advanced, so that the fuel mixture ratio can be determined.

  In this case, as the determination means, the mixed fuel to be used is applied by applying the ignition timing information at the time of the knocking state and the engine operation state information at that time to the fuel composition determination reference information prepared in advance. By estimating the fuel composition, it is easy to make a highly accurate determination with a simple procedure.

  In the fuel composition determination method described above, the operation of the ignition timing can cause knocking relatively easily if the ignition timing is gradually advanced during high load operation of the engine. This makes it easy to accurately determine the fuel composition.

  Further, in the above fuel composition determination method, in addition to the knock detection means, the engine operating state detection means is an engine speed detection means, an engine load estimation means, an intake air temperature detection means, and a cooling water temperature detection means. In this case, the fuel composition of the LPG can be determined by using various sensors that are existing engine operation state detection means generally attached to the mixed fuel engine.

  Furthermore, a fuel composition determination device for determining a fuel composition of a mixed fuel to be used by being disposed in a control system for a mixed fuel engine provided with the above-described engine operating state detecting means and knock detecting means, comprising the above-mentioned mixed fuel engine A fuel composition determination apparatus for a mixed fuel engine, in which a control program for carrying out the fuel composition determination method is stored, the fuel composition determination described above can be achieved simply by disposing it in the system. The method can be easily realized.

  In this case, if the fuel composition determination device of the mixed fuel engine also serves as an engine control device and performs an operation of switching to engine control suitable for the determined fuel composition, Accurate engine control can be executed according to the fuel composition.

  According to the present invention for determining the fuel composition of the used mixed fuel from the ignition timing of the knocking state using the difference in octane number of the mixed fuel, according to the present invention, the existing sensors normally used for engine operation control are used. Thus, the fuel composition of the mixed fuel to be used can be determined without increasing the cost.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a fuel composition determination of an engine that supplies a mixed fuel obtained by mixing mainly two types of fuels having different octane numbers, such as LPG fuel or a mixed fuel of gasoline and oxygen-containing hydrocarbon fuel. FIG. 1 is a functional block diagram for explaining the configuration and operation of a fuel composition determination apparatus 1 that is a main body of the method, and the present invention is usually used for engine operation control in a vehicle equipped with a mixed fuel engine. The purpose is to accurately detect the fuel composition of the mixed fuel to be used in an inexpensive system without adding new sensors by using various sensors that are the existing seven stages of engine operating state detection. It is.

  The fuel composition determination device 1 of the present embodiment may be configured so that a normal engine control device that controls fuel injection and ignition timing of a mixed fuel engine also functions, and additional dedicated hardware is added. If the contents of the functional block diagram of FIG. 1 are functionally executed by the installed control program without any problems, it will be more advantageous in terms of cost.

  The fuel composition determination apparatus 1 includes engine speed detection means 11 for detecting engine speed, engine load detection means 12 for detecting engine load, and engine intake air temperature. Are connected to an output signal line extending from sensors of the intake air temperature detecting means 13 for detecting the engine air and the coolant temperature detecting means 14 for detecting the engine coolant temperature, and each output signal (data) is input. It is like that.

  The fuel composition determination apparatus 1 is connected to an output signal line from a knock detection means 15 for detecting a knocking state during fuel combustion in the dual fuel mixture engine, and receives a knocking detection signal. ing. As this knock detection means 15, an acceleration detection type knock sensor, an ion current detection device for detecting ions generated during fuel combustion, an in-cylinder pressure sensor, or the like may be used. On the other hand, the engine load detection means 12 uses a throttle sensor used in the throttle body, a pressure sensor provided in the intake manifold, an air flow meter signal provided between intakes, and an estimation method from the engine speed. be able to.

  Further, the fuel composition determination device 1 is functionally provided with an engine operating state estimation means 30 and a fuel composition determination means 10, and a fuel composition determination reference database 20 created in advance is stored in the storage means. Yes. Then, the engine operation estimation means 30 estimates the engine operation state based on each sensor signal indicating the engine operation state, and determines the fuel composition from the knocking occurrence ignition timing when the knocking state is detected and the engine operation state at that time. The fuel composition determination means 10 determines the fuel composition of the used LPG by checking the information from the reference database 20 for use.

  As an example of the fuel composition determination database 20 to be stored, for example, a plurality of maps showing the relationship between the knocking occurrence ignition timing and the fuel composition obtained experimentally in advance may be stored for each engine operating state. It is done. In addition, two types of maps are stored for each engine engine operating condition: the fuel with the highest octane number and the fuel that is less likely to knock, and the fuel that has the lowest octane number and the subject to knocking. It is also possible to minimize the amount of map data by proportionally interpolating these fuels.

  Next, the present embodiment will be described in detail with reference to the flowchart of FIG. 2 as an example of the fuel composition determination method performed by the fuel composition determination apparatus 1.

  When the determination of the fuel composition is started, first, the control system is operated so as to gradually advance the ignition timing by detecting the engine high load operation state (A1), or the ignition timing is gradually increased from the knocking state. The knocking generation ignition timing is detected from the knocking detection signal detected by the knock detection means 15 (A2), and the engine speed detection means 11 is operated. Engine operating state information estimated by the engine operating state estimating unit 30 from engine speed, engine load, intake air temperature, and cooling water temperature data by the engine load detecting unit 12, the intake air temperature detecting unit 13, and the cooling water temperature detecting unit 14. The fuel composition obtained from the fuel composition judgment reference database 20 by the fuel composition judgment means 10 By collating the titration, reference information, it determines to estimate the fuel composition of the mixed fuel to be used (A3). Further, based on this determination result, the ignition timing control and the fuel injection control are switched according to the composition of the mixed fuel to be used.

  The reason why the fuel composition of the mixed fuel is determined in such a procedure is as follows. That is, LPG with a high propane component generally has a high octane number, so the ignition timing at which knocking occurs is advanced, whereas LPG with a high butane component has a knocking because butane has a lower octane number than propane. This is because it is known that the ignition timing is retarded. In general, ethanol-mixed gasoline with a large amount of ethanol has a high octane number, so that the ignition timing at which knocking occurs is advanced, whereas gasoline has a lower octane number than ethanol, so ethanol mixed with a large amount of gasoline. This is because gasoline is known to have a retarded ignition timing at which knocking occurs.

  Therefore, by intentionally generating the knocking state as described above, such a phenomenon can be clearly discriminated, and the mixture ratio of the mixed fuel can be estimated in reverse from the ignition timing at which the knocking state is reached. It is. As a result, the ignition timing control and fuel injection control can be switched to the control corresponding to the determined fuel composition of the mixed fuel, and as a result, the potential of fuel consumption and exhaust gas performance possessed by the used fuel can be effectively extracted. It will be possible.

  In addition, when implementing the fuel composition determination method of the above-described procedure, existing sensors for detecting the engine operating state can be used as they are, so there is no need to add new sensors. Since it can be implemented simply by adding it to an electronic control unit that is an engine control device, it is possible to realize a system that performs accurate control according to the composition of the LPG used at a relatively low cost. .

  As described above, various types of sensors, which are existing engine operating state detection means normally used for engine operation control according to the present invention, for a mixed fuel engine that supplies a mixed fuel in which fuels having different octane numbers are mixed with each other. It is possible to determine the fuel composition of the mixed fuel to be used without increasing the cost.

The functional block diagram which shows embodiment of this invention. The flowchart for demonstrating operation | movement of the fuel composition determination apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel composition determination means, 11 Engine speed detection means, 12 Engine load detection means, 13 Intake air temperature detection means, 14 Cooling water temperature detection means, 15 Knock detection means, 20 Fuel composition determination reference database, 30 Engine operating state Estimating means

Claims (8)

  It has an engine control system that executes engine control in accordance with the engine operating state using detection values from various engine operating state detecting means attached at predetermined positions, and supplies mixed fuel in which fuels having different octane numbers are mixed with each other An engine operating state estimated from a knocking occurrence ignition timing obtained by detecting a knocking state intentionally generated by a knock detecting means and a detected value by the engine operating state detecting means And determining the mixing ratio of the fuel used by the determining means using the fact that the octane number varies depending on the mixing ratio mixed in the supplied mixed fuel. .   Mixing used by the determination means applying the ignition timing information when the knocking state occurs and the engine operation state information when the knocking state occurs to the fuel composition determination reference information prepared in advance. 2. The fuel composition determination method for a mixed fuel engine according to claim 1, wherein the fuel composition of the fuel is estimated.   3. The method of determining a fuel composition in a mixed fuel engine according to claim 1, wherein the intentional knocking generation means gradually increases the ignition timing when the engine is operating at a high load.   The intentional knocking generating means and the knocking detecting means operate the engine with the ignition timing set in advance for the fuel having the highest octane number, and knocking is performed by gradually retarding the ignition timing during high load operation. 3. The method for determining a fuel composition in a mixed fuel engine according to claim 1 or 2, wherein the operating condition that subsides is detected.   The engine operating state at the time of the occurrence of the intentional knocking is such that when the vehicle starts, the transmission gear ratio is lowered so that the engine speed is low and the engine load is high. 2. A method for determining a fuel composition in a mixed fuel engine described in 2.   4. The mixed fuel engine according to claim 1, wherein the engine operating state detecting means is an engine speed detecting means, an engine load estimating means, an intake air temperature detecting means, and a cooling water temperature detecting means. Fuel composition determination method.   A fuel composition determination device arranged in a control system for a mixed fuel engine provided with the engine operating state detection means and the knock detection means to determine the fuel composition of the LPG used, A fuel composition determination apparatus for a mixed fuel engine, wherein a control program for executing the described fuel composition determination method for a mixed fuel engine is stored.   6. The fuel composition determination apparatus for a mixed fuel engine according to claim 5, wherein the fuel composition determination apparatus for the mixed fuel engine according to claim 5, wherein the operation is switched to engine control adapted to the determined fuel composition while also serving as an engine control apparatus.

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