JP2010060463A - Method for detecting fuel composition and engine combustion controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimally control combustion in an engine by measuring the content of oxygen containing functional group in fuel in real time with engine driving. <P>SOLUTION: Liquid fuel is irradiated with electromagnetic wave of a frequency of several 10 GHz to several THz, and electromagnetic wave absorptance by the oxygen containing functional group contained in the liquid fuel is measured, thereby estimating the content of oxygen containing functional group in the liquid fuel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for detecting the composition of fuel supplied to an engine and an engine combustion control device for controlling combustion conditions of the engine in accordance with the detected value.

  Gasoline or light oil used as a fuel for automobiles is a mixture of hydrocarbons (HC) of various molecular weights, and the composition varies depending on the production area of crude oil, the refining method and the like. In addition, the combustion situation varies depending on the fuel composition, and the amount of HC in the exhaust gas may vary greatly.

  For example, a light fuel with a large amount of low molecular weight HC tends to evaporate, and a heavy fuel with a large amount of high molecular weight HC hardly evaporates. Therefore, when light fuel is burned with a fuel supply amount corresponding to heavy fuel, the amount of fuel actually used for combustion becomes excessive, and the amount of HC in the exhaust gas increases. Therefore, for example, Japanese Patent Laid-Open No. 2000-064878 discloses a control device for an internal combustion engine that detects whether the fuel is light or heavy using a fuel property sensor and controls the fuel supply amount according to the combustion property. Proposed.

  This publication describes a fuel property sensor that detects the amount of combustion ions generated after combustion and outputs a large value when the fuel is heavy and outputs a small value when the fuel is light.

  In recent years, fuel mixed with alcohol, which is a biofuel, has been used. The evaporation temperature varies depending on the amount of alcohol mixed, and the 90% distillation temperature (T90) decreases as the amount of alcohol mixed increases. Then, it becomes difficult to adjust the temperature of the nozzle part of the fuel injection valve to T90 or less, and there arises a problem that the amount of deposit attached to the nozzle part increases and the fuel injection quantity decreases.

Japanese Patent Laid-Open No. 2005-232997 proposes a fuel injection control method in which the alcohol concentration in the fuel is detected and the fuel injection pressure is increased in accordance with the detected value. According to this method, it is possible to suppress deposits from adhering to the nozzle part of the fuel injection valve. This publication describes the use of a capacitance-type alcohol concentration sensor as means for detecting the alcohol concentration.
JP 2000-0664878 JP 2005-232997 A

  In recent years, the use of plant-derived biofuels has been increasing as a means of suppressing global warming. However, biofuels may contain fatty acids such as oleic acid in addition to alcohol, and it is difficult to detect these with an alcohol concentration sensor or the like. Even if alcohol is used, if the hydroxyl group changes to an aldehyde group or a carboxyl group by oxidation, this cannot be detected by the alcohol concentration sensor.

  Biofuel also contains intramolecular oxygen that is not contained in fossil fuels, and oxidation begins in the fuel tank when the number of days has elapsed since refueling, and the fuel properties change. However, it has been difficult for conventional engine combustion control devices to cope with fuel properties that change every moment.

  The present invention has been made in view of such circumstances, and makes it possible to measure the content of oxygen-containing functional groups in fuel in real time with engine drive, thereby enabling optimal control of combustion in the engine. This is a problem to be solved.

  A feature of the fuel composition detection method of the present invention that solves the above problems is that the liquid fuel is irradiated with an electromagnetic wave having a frequency of several tens of GHz to several THz, and an electromagnetic wave absorption rate by an oxygen-containing functional group contained in the liquid fuel is measured. It is to estimate the content of oxygen-containing functional groups in the liquid fuel.

The engine combustion control device of the present invention is characterized by an irradiation device that irradiates liquid fuel with electromagnetic waves having a frequency of several tens of GHz to several THz, a light receiving device that receives electromagnetic waves transmitted through the liquid fuel, and the liquid fuel is burned. A combustion variable device that varies the combustion conditions of the engine, and a control device that controls the combustion variable device;
The control device measures the electromagnetic wave absorption rate by the oxygen-containing functional group contained in the liquid fuel from the signal of the light receiving device to estimate the content of the oxygen-containing functional group in the liquid fuel, and includes the estimated oxygen-containing functional group content The variable combustion device is controlled based on the quantity.

  In the fuel composition detection method and the engine combustion control device of the present invention, the liquid fuel is irradiated with electromagnetic waves (hereinafter referred to as terahertz waves) having a frequency of several tens of GHz to several THz. Terahertz waves have both the properties of radio waves and light, and have both straightness and transparency. Further, it is also included in the category of infrared rays, and absorption spectra corresponding to various functional groups can be obtained by scanning the frequency and irradiating the fuel in the same manner as in the infrared spectroscopic analysis. Infrared rays have low sensitivity to organic substances having 8 to 16 or more carbon atoms, whereas terahertz waves have high sensitivity to high molecular weight substances such as oleic acid (carbon number: 18), and can be detected with high accuracy.

  According to the engine combustion control apparatus of the present invention, the content of the oxygen-containing functional group in the fuel can be detected with high accuracy, and the fuel injection amount, the fuel injection timing, the EGR rate, or the like can be controlled according to the value. Therefore, the combustion of the engine can be optimally controlled in accordance with the properties of the supplied fuel, and effects such as a reduction in the amount of HC in the exhaust gas, a reduction in fuel consumption, and high efficiency combustion can be obtained.

  In the present invention, a terahertz wave having a frequency of several tens of GHz to several THz is used. Since each fingerprint spectrum of an oxygen-containing functional group such as a hydroxyl group, an aldehyde group, or a carboxyl group is in the terahertz region, each group can be clearly separated and detected. When the frequency is lower than this range, the detection accuracy of the oxygen-containing functional group decreases. Further, if the frequency is higher than this range, it becomes difficult for the liquid fuel to pass through, and the detection accuracy also decreases.

  Examples of the liquid fuel include gasoline mixed with biofuel, light oil mixed with biofuel, kerosene mixed with biofuel, and the like.

  Examples of the oxygen-containing functional group include a hydroxyl group, an aldehyde group, an ether group, and a carboxyl group.

  When the liquid fuel is irradiated with terahertz waves, if only the presence or absence of a kind of oxygen-containing functional group is to be measured, a single wavelength terahertz wave may be irradiated. However, it is necessary to estimate the content of oxygen-containing functional groups, and since there are various oxygen-containing functional groups contained in biofuel, it is preferable to measure by irradiating terahertz waves of multiple types of wavelengths, It is desirable to measure the absorption spectrum while scanning while changing the frequency. The amount of the oxygen-containing functional group can be estimated from a comparison with the absorption spectrum specific to the reference substance.

  An engine combustion control device of the present invention controls an irradiation device that irradiates terahertz waves, a light receiving device that receives terahertz waves that have passed through liquid fuel, a combustion variable device that varies combustion conditions of the engine, and a combustion variable device And a control device.

  As an irradiation apparatus for irradiating terahertz waves, an apparatus that generates terahertz waves using a femtosecond laser, a semiconductor laser, laser plasma, or the like, a magnetron, or the like can be used. As the light receiving device, a photoconductive switch, a pyroelectric element, an EO detection method, a Schottky barrier diode, or the like can be used.

  The irradiation device and the light receiving device are arranged so as to sandwich the liquid fuel. For example, it can arrange | position so that it may mutually oppose so that a liquid fuel may be pinched | interposed into the mutually opposing side wall of a fuel tank. Alternatively, a pair of windows that can transmit a terahertz wave may be provided on the common rail or the fuel pipe so as to face each other, and the irradiation device and the light receiving device may be disposed outside the windows. Since the detection accuracy improves as the amount of liquid fuel existing between the irradiation device and the light receiving device increases, it is desirable to provide a fuel tank that can increase the distance between the irradiation device and the light receiving device.

  Examples of the combustion variable device that changes the combustion condition of the engine include a fuel injection device and an EGR device. And a control apparatus controls a combustion variable apparatus, and if it is a motor vehicle, it is desirable to use ECU.

  The control device estimates the content of the oxygen-containing functional group in the liquid fuel by measuring the electromagnetic wave absorption rate by the oxygen-containing functional group contained in the liquid fuel from the signal of the light receiving device, and based on the content of the oxygen-containing functional group To control the combustion variable device.

  For example, if the combustion variable device is a fuel injection device, if the oxygen-containing functional group content is higher than a predetermined value, the fuel injection amount is set higher than the predetermined value, and the oxygen-containing functional group content is lower than the predetermined value. The fuel injection amount is controlled to be less than a predetermined value. Alternatively, when the content of the oxygen-containing functional group is larger than the predetermined value, the fuel injection interval is made shorter than the predetermined value, and when the content of the oxygen-containing functional group is less than the predetermined value, the fuel injection interval is made longer than the predetermined value. To control. By controlling in this way, engine combustion is optimized, and effects such as reduction of the amount of HC in the exhaust gas and high-efficiency combustion can be obtained.

  If the combustion variable device is an EGR device, if the content of the oxygen-containing functional group is larger than a predetermined value, the combustion easily occurs and smoke is reduced, so the EGR amount is increased from the predetermined value. By controlling in this way, fuel consumption can be reduced.

  Hereinafter, the present invention will be described specifically by way of examples.

Example 1
FIG. 1 shows the configuration of the engine combustion control apparatus of this embodiment. A fuel tank 1 contains a mixed fuel 10 of biofuel and gasoline. The mixed fuel 10 in the fuel tank 1 is pressurized by the common rail 3 through the common rail pump 2 and supplied from the common rail 3 to the injector 5 provided in the engine 4. The injector 5 is driven by an injector driver 50 controlled by a signal from the ECU 100 and intermittently injects the mixed fuel 10 into the cylinder of the engine 4.

  On the left and right side walls of the fuel tank 1, a transmitter 6 that oscillates terahertz waves and a receiver 7 that receives terahertz waves oscillated from the transmitter 6 and transmitted through the mixed fuel 10 are disposed. The transmitter 6 is controlled by the ECU 100, and a signal from the receiver 7 is input to the ECU 100.

  FIG. 2 shows the control contents of the ECU 100. The process is started when the engine 4 is started. First, in step 101, the ECU 100 oscillates a terahertz wave from the transmitter 6 and scans in the frequency range of 0.3 THz to 3 THz. In step 102, the absorption rate of the hydroxyl group, aldehyde group and carboxyl group contained in the mixed fuel 10 and the reference absorption rate derived from gasoline are calculated from the signal of the receiver 7.

  If the calculation is performed manually, an absorption spectrum as shown in FIG. 3 is created from the signal from the receiver 7. In this absorption spectrum, since each of a hydroxyl group, an aldehyde group, a carboxyl group, and a gasoline-derived group has a peak at a specific frequency, the peak height from the baseline is the absorption rate.

  In step 103, the content of hydroxyl group, aldehyde group, and carboxyl group in the mixed fuel 10 is estimated from the reference absorption rate derived from gasoline and each measured absorption rate.

  In step 104, the oxygen content ratio in the mixed fuel 10 is calculated from the content of each group as a function of the content concentration of each group.

  That is, as shown in FIG. 4, the oxygen content in the mixed fuel 10 increases as the proportion of the oxygen-containing functional group increases, but the degree varies depending on the type of the oxygen-containing functional group. However, since the relationship between the type of oxygen-containing functional group and the degree of increase in the oxygen content ratio is known in advance, the oxygen content ratio in the mixed fuel 10 is expressed as a function of the content concentration of each functional group.

  In step 105, referring to engine map data as shown in FIG. 5, the fuel injection amount is determined from the value of the oxygen content ratio. Based on the determined value, the ECU 100 drives the injector driver 50 in step 106.

  In step 107, the actual fuel injection amount is calculated from the drive time of the injector driver 50. If the fuel injection amount has not reached the determined value, the process returns to step 106. When the fuel injection amount reaches the determined value, after the drive of the injector driver 50 is stopped, the process proceeds to step 108 and it is checked whether or not the engine 4 is stopped. If the engine 4 is still driven, the process returns to step 101.

  That is, according to the engine combustion control apparatus of the present embodiment, the property of the mixed fuel 10 is always investigated while the engine 4 is being driven, and the oxygen-containing functional groups contained in the mixed fuel 10 supplied to the engine 4 are checked. Since the fuel injection amount is appropriately adjusted according to the content, the engine 4 always performs optimum combustion. Therefore, effects such as reduction of the amount of HC in the exhaust gas and high efficiency combustion can be obtained.

(Example 2)
In the engine combustion control apparatus of this embodiment, as shown in FIG. 6, the engine 4 includes an EGR 8, and the ECU 100 controls the injector driver 50 and also controls the EGR rate by the EGR 8. Other configurations are the same as those of the first embodiment.

  In the present embodiment, control is performed in the same manner as in the first embodiment except that the contents of steps 105 and 106 are different. That is, in step 105 shown in FIG. 7, the fuel injection amount is determined from the oxygen content ratio value, and map data is referred to as shown in FIG. 8, and the EGR rate is determined from the oxygen content ratio value.

  In step 106, the drive of the injector driver 50 is controlled, and the EGR 8 is controlled so as to achieve the determined EGR rate.

  Therefore, according to the engine combustion control apparatus of the present embodiment, in addition to the effects of the first embodiment, the EGR rate can be optimally controlled, so that the fuel efficiency is improved.

  The fuel composition detection method of the present invention can be used not only for an engine combustion control device but also for detecting the concentration of biofuel in the fuel and detecting the degree of oxidation of the biofuel.

1 is a block diagram of an engine combustion control device according to an embodiment of the present invention. It is a flowchart which shows the control content in the engine combustion control apparatus which concerns on one Example of this invention. It is a diagram which shows an example of the absorption spectrum of a terahertz wave. It is a graph which shows the relationship between the oxygen content rate in a fuel, and the ratio of each oxygen containing functional group. It is a graph which shows the relationship between the oxygen content rate in a fuel, and the amount of fuel injection. It is a block diagram of the engine combustion control apparatus which concerns on 2nd Example of this invention. It is a flowchart which shows the control content in the engine combustion control apparatus which concerns on 2nd Example of this invention. It is a graph which shows the relationship between the oxygen content rate in a fuel, and an EGR rate.

Explanation of symbols

1: Fuel tank 2: Common rail pump 3: Common rail 4: Engine 5: Injector 6: Transmitter (irradiation device)
7: Receiver (light receiving device) 8: EGR 10: Fuel mixture
50: Injector driver 100: ECU (control unit)

Claims (4)

  The liquid fuel is irradiated with an electromagnetic wave having a frequency of several tens of GHz to several THz, and the content of the oxygen-containing functional group in the liquid fuel is measured by measuring the electromagnetic wave absorption rate by the oxygen-containing functional group contained in the liquid fuel. A fuel composition detection method characterized by estimating. An irradiation device that irradiates an electromagnetic wave having a frequency of several tens of GHz to several THz to a liquid fuel, a light receiving device that receives the electromagnetic wave transmitted through the liquid fuel, and a variable combustion that varies a combustion condition of an engine in which the liquid fuel is burned A control device for controlling the combustion variable device,
The control device estimates the content of the oxygen-containing functional group in the liquid fuel by measuring the electromagnetic wave absorption rate by the oxygen-containing functional group contained in the liquid fuel from the signal of the light receiving device, and the estimated An engine combustion control device that controls the combustion variable device based on the content of an oxygen-containing functional group.   The engine combustion control device according to claim 2, wherein the combustion variable device is a fuel injection device, and the control device controls at least one of a fuel injection amount and a fuel injection interval based on a content of the oxygen-containing functional group.   The engine combustion control device according to claim 2, wherein the combustion variable device is an EGR device, and the control device controls an EGR rate based on a content of the oxygen-containing functional group.

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