JP2010242676A - Alcohol-mixed fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly reproduce an alcohol concentration in fuel actually supplied to an engine from the alcohol concentration in the fuel detected by one sensor, and to make the amount of fuel injection appropriate. <P>SOLUTION: At a predetermined time with a fuel flow rate as a shaft, an output O1 of the concentration sensor is sampled, and the sampled value is stored. Next, when the integration value of a momentary flow rate reaches the set amount of fuel KFCONST, an output O2 of the concentration sensor is sampled again, and the sampled value is similarly stored. Such sampling of the alcohol concentration detected by the concentration sensor is repeatedly performed and sampled data are time-sequentially stored. Then, with respect to the sampled and detected alcohol concentration, interpolation calculation using the fuel quantity until fuel with the alcohol concentration detected by the concentration sensor is injected, that is, the amount of a delay KFFSDLY, and the set amount of fuel KFCONST setting a sampling cycle is performed, thereby calculating a reproduced alcohol concentration. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an alcohol-mixed fuel injection control device that corrects a fuel injection amount injected from a fuel injection valve based on an alcohol concentration in fuel.

  In recent years, in vehicles such as automobiles, a system using a mixed fuel obtained by adding alcohol to a conventional fuel such as gasoline has attracted attention from the viewpoints of resource saving and pollution reduction. In an engine using this alcohol-mixed fuel, in order to maintain the air-fuel ratio appropriately, it is necessary to accurately grasp the alcohol concentration in the fuel and determine the fuel injection amount.

  For example, in Patent Document 1, the fuel injection amount is corrected by a correction constant based on the output signal of the alcohol sensor, and when the temperature of the alcohol mixed fuel reaches a predetermined temperature or higher corresponding to the alcohol concentration, the fuel injection amount is set. A technique for stabilizing the air-fuel ratio by fixing a correction constant to be corrected to a predetermined value is disclosed.

  In Patent Document 2, alcohol concentration sensors are respectively provided in an upstream fuel passage and a downstream fuel passage of an injector (fuel injection valve), and a pipe length and an alcohol concentration between the injector and the alcohol concentration sensor are provided. A technique is disclosed that enables appropriate control by calculating the actual alcohol concentration of the fuel supplied to the engine based on the alcohol concentration detected by the sensor.

  Furthermore, in Patent Document 3, when a change in fuel properties is detected, the limit of fuel injection control is canceled to enable injection amount correction beyond an allowable range, without using an alcohol concentration sensor. A technique for optimizing fuel injection control is disclosed.

Japanese Patent Laid-Open No. 4-86342 JP-A-4-116244 JP 2003-120363 A

  However, in the technique disclosed in Patent Document 1, since the fuel injection amount is corrected using the output of the alcohol concentration sensor installed in the fuel pipe as it is, it may differ from the alcohol concentration of the fuel actually injected from the injector. There is no guarantee that the air-fuel ratio will be controlled to an appropriate value.

  In that respect, the technique disclosed in Patent Document 2 can reflect the alcohol concentration of the fuel that is actually injected into the fuel injection amount, but two alcohol concentration sensors are required, and there are only restrictions on the outfitting. Instead, it becomes a factor of cost increase.

  Moreover, in the technique disclosed in Patent Document 3, a change in the alcohol concentration in the fuel is detected by the fact that there has been refueling based on opening and closing of the fuel filler lid. For this reason, when the alcohol concentration in the piping changes due to separation of the alcohol in the fuel tank or piping at a low temperature or the like, it is difficult to cope with it only by not using the alcohol concentration sensor.

  The present invention has been made in view of the above circumstances, and accurately reproduces the alcohol concentration of the fuel actually supplied to the engine from the alcohol concentration of the fuel detected by one sensor to optimize the fuel injection amount. It is an object of the present invention to provide an alcohol-mixed fuel injection control device that can perform the above-described operation.

  In order to achieve the above object, an alcohol mixed fuel injection control apparatus according to the present invention includes a fuel tank that stores alcohol mixed fuel, a fuel pump that discharges fuel in the fuel tank, and a fuel that extends from the fuel pump to a fuel injection valve. Alcohol mixing that provides a concentration sensor for detecting the alcohol concentration in the fuel at a desired position in the fuel supply system including the piping, and corrects the fuel injection amount injected from the fuel injection valve based on the alcohol concentration in the fuel In the fuel injection control device, a fuel flow rate calculation unit that calculates the flow rate of the alcohol mixed fuel, and a detection that samples the alcohol detected concentration by the concentration sensor at a sampling period set based on the fuel flow rate calculated by the fuel flow rate calculation unit Alcohol sampling sampled by the concentration sampling unit and the detected concentration sampling unit. Reproduced alcohol concentration calculation that calculates a reproduced alcohol concentration that reproduces the alcohol concentration of the fuel injected from the fuel injection valve based on the concentration and the delay amount of fuel transportation between the concentration sensor and the fuel injection valve And a section.

  According to the present invention, the alcohol concentration of the fuel actually supplied to the engine can be accurately reproduced from the alcohol concentration of the fuel detected by one sensor, and the fuel injection amount is optimized while suppressing an increase in cost. can do.

Configuration diagram of fuel supply system Explanatory diagram showing concentration behavior change of alcohol concentration Block diagram showing alcohol concentration estimation / reproduction function Explanatory diagram showing the reproduction logic of alcohol concentration change Flowchart of reproduction alcohol concentration calculation processing

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a fuel supply system of an engine operated using an alcohol mixed fuel. The fuel supply system includes a fuel tank 1, a fuel pump 2, a pressure regulator 3, a fuel pipe 4, a concentration sensor 5, and an injector 6 (fuel injection valve). FIG. 1 shows an example of a four-cylinder engine, and shows four injectors 6 corresponding to each cylinder.

  The fuel tank 1 stores an alcohol mixed fuel obtained by mixing gasoline and alcohol such as ethanol at a predetermined ratio. The alcohol mixed fuel in the fuel tank 1 is boosted to a predetermined pressure by the fuel pump 2 and regulated to a prescribed injection pressure by the pressure regulator 3. The fuel (alcohol mixed fuel) adjusted to the prescribed fuel pressure is supplied to the injector 6 through the fuel pipe 4. The injector 6 is driven by the valve opening time (injection pulse width) calculated by the engine control unit (ECU) 10 and injects a fuel amount corresponding to the target air-fuel ratio.

  The ECU 10 is configured around a microcomputer and executes engine control such as fuel injection control and ignition timing control. The ECU 10 receives signals from various sensors that detect operating conditions such as the concentration sensor 5, the crank angle sensor 7, and the intake air amount sensor 8, and based on these signals, the fuel injection amount (injection pulse width), The engine control amount such as the ignition timing is calculated, and drive signals for various actuators including the injector 6 are output.

  In addition, as the concentration sensor 5 for detecting the alcohol concentration in the fuel, a resistance type sensor using a change in conductivity of the alcohol mixed fuel, a capacitance type sensor using a change in dielectric constant, and a change in refractive index are used. A known sensor such as an optical sensor can be used.

  The fuel injection amount injected from the injector 6 is calculated by a function of the ECU 10 as an injection amount calculation unit. That is, the ECU 10 determines the basic fuel injection amount (basic injection pulse width) Tp (Tp) based on the engine speed Ne based on the signal from the crank angle sensor 7 and the intake air amount Q based on the signal from the intake air amount sensor 8. = K × Q / Ne; K is a constant) is corrected by various correction amounts to calculate the fuel injection amount.

For example, as shown in the following equation (1), the basic injection pulse width Tp is changed to a correction coefficient α for air-fuel ratio feedback control, a correction coefficient COEF for various increase corrections, and a correction related to fuel properties according to the alcohol concentration of fuel. Correction is made by the coefficient Kal, the correction amount Ts related to the drive voltage of the injector 6, and the injection pulse width Ti of the drive signal for the injector 6 is calculated.
Ti = Tp × Kal × COEF × α + Ts (1)

  At this time, the ECU 10 does not set the correction coefficient Kal using the alcohol concentration detected by the concentration sensor 5 as it is as the correction coefficient Kal based on the alcohol concentration of the fuel, but instead of setting the correction coefficient Kal from the alcohol detected concentration by the concentration sensor 5. The alcohol concentration of the fuel is estimated and reproduced, the correction coefficient Kal is set using the reproduced alcohol concentration, and the injection pulse width Ti is calculated.

  That is, the concentration sensor 5 is interposed at a desired position of the fuel supply system (a predetermined position of the fuel pipe 4 between the pressure regulator 3 and the injector 6 in FIG. 1). For this reason, the alcohol concentration detected by the concentration sensor 5 is the alcohol concentration of the fuel at the sensor mounting position. For example, alcohol separation in the fuel tank 1 at a low temperature, alcohol only (or gasoline only) When the alcohol concentration in the fuel changes due to replenishment or the like, the alcohol detection concentration of the concentration sensor 5 does not necessarily match the alcohol concentration of the fuel actually injected from the injector 6. This is because the alcohol concentration of the actual fuel injected by the injector 6 does not change until all the fuel in the pipe from the concentration sensor 5 to the injector 6 is consumed.

  FIG. 2 shows the change in concentration behavior when the alcohol concentration in the fuel changes, in relation to the fuel flow rate (the integrated value of the fuel that is injected and consumed from the injector 6). In FIG. 2, the concentration obtained by back-calculating the alcohol concentration of the fuel injected from the injector 6 from the change in the air-fuel ratio with respect to the alcohol detected concentration by the concentration sensor 5 indicated by the thin solid line is indicated by the bold solid line. From FIG. 2, it can be seen that there is a delay from when the alcohol concentration change of the fuel in the fuel pipe 4 is detected by the concentration sensor 5 to when the alcohol concentration of the fuel actually injected from the injector 6 changes. .

  At this time, if the alcohol detected concentration by the concentration sensor 5 is shifted by a flow rate corresponding to the pipe volume of the fuel pipe 4 from the concentration sensor 5 to the injector 6, the result becomes as shown by a broken line in FIG. It becomes close to the density change form calculated backward from the change. That is, if the fuel flow rate is taken as a reference, it can be seen that the delay concentration obtained by delaying the concentration by the concentration sensor 5 in the fuel flow direction is substantially similar to the actual concentration change form.

  Therefore, the alcohol concentration measured by the concentration sensor 5 is reproduced with a delay according to the consumed fuel flow rate to reproduce the concentration change, whereby an accurate concentration change that matches the actual behavior of the engine can be grasped. For this reason, as shown in FIG. 3, the ECU 10 functions as a function of estimating and reproducing the alcohol concentration of the fuel actually injected from the injector 6 as a fuel flow rate calculation unit 11, a detected concentration sampling unit 12, and a reproduction alcohol concentration calculation unit. 13 is provided.

  The fuel flow rate calculation unit 11 calculates the flow rate of the alcohol mixed fuel flowing in the fuel pipe 4 in order to sample the alcohol detected concentration of the concentration sensor 5 with reference to the fuel flow rate. The fuel flow rate in the fuel pipe 4 can be calculated from the fuel injection amount of the injector 6, and the fuel flow rate (instantaneous flow rate) qf per unit time flowing in the fuel pipe 4 from the injection pulse width Ti for each injection cycle is obtained. calculate.

  The detected concentration sampling unit 12 samples the alcohol detected concentration data from the concentration sensor 5 at a sampling period based on the fuel flow rate calculated by the fuel flow rate calculating unit 11, and stores and stores the data in time series. Specifically, the instantaneous flow rate qf is integrated for each alcohol concentration estimation / reproduction processing cycle, and when the flow integrated value reaches a preset set fuel amount KFCCONST, the alcohol detection concentration is sampled. The detected concentration is stored in time series.

  For example, as shown in FIG. 4, the output O1 of the concentration sensor 5 is sampled at a predetermined time point with the fuel flow rate as an axis, and the sampled value is stored. Next, the instantaneous flow rate qf is integrated, and when the integrated flow rate reaches the set fuel amount KFCCONST, the output O2 of the concentration sensor 5 is sampled again, and the sampling value is stored in the same manner. The sampling of the alcohol detection concentration by the concentration sensor 5 is repeated, and the sampled data is stored in time series.

  The reproduction alcohol concentration calculation unit 13 performs a reproduction process on the alcohol detection concentration sampled by the detection concentration sampling unit 12 based on the fuel transport delay amount between the concentration sensor 5 and the injector 6. The alcohol concentration (reproduced alcohol concentration) detn obtained by this reproduction process indicates the alcohol concentration of the fuel injected from the injector 6, and a correction coefficient Kal for calculating the fuel injection amount from the reproduced alcohol concentration detn is set.

  Specifically, first, a fuel amount corresponding to the volume of the fuel pipe 4 from the concentration sensor 5 to the injector 6 is set as a fuel reference delay amount KFFSDLY with respect to the alcohol detected concentration of the concentration sensor 5. This delay amount KFFSDLY is stored in advance in the memory of the ECU 10 as a control constant uniquely determined from the configuration of the fuel supply system of each engine.

  The reproduced alcohol concentration detn may be obtained by reproducing the alcohol detected concentration stored in the detected concentration sampling unit 12 in accordance with the sampling cycle based on the set fuel amount KFCCONST. It will change. Accordingly, the reproduction alcohol concentration calculation unit 13 performs an interpolation calculation based on the fuel amount until the fuel whose alcohol concentration is detected by the concentration sensor 5 is injected, that is, the delay amount KFFSDLY, and the set fuel amount KFCCONST that determines the sampling period. This is executed for each estimation / reproduction processing cycle to calculate the reproduction alcohol concentration detn.

That is, as shown in FIG. 4, if the concentration data obtained by shifting the output values O1 and O2 of the concentration sensor 5 sampled for each set fuel amount KFCCONST by the delay amount KFFSDLY in the fuel axis direction are S1 and S2, the concentration data For the difference between S1 and the concentration data S2, the reproduced alcohol concentration detn is calculated by interpolation calculation proportional to the amount of fuel consumed. Specifically, when the calculation cycle of the interpolation calculation is Δt, the reproduced alcohol concentration detn is calculated by the interpolation calculation according to the following equation (2).
detn = detn (−1) − {(S1−S2) / KFCCONST × qf × Δt} (2)
However, detn (-1): Reproduced alcohol concentration before the calculation cycle

  From the reproduced alcohol concentration detn, a fuel property correction coefficient Kal for calculating the injection pulse width Ti is set. The correction coefficient Kal is set using, for example, a map with the reproduced alcohol concentration detn as an axis, and the higher the reproduced alcohol concentration detn is, the more the difference in calorific value between gasoline and alcohol is corrected to optimize the air-fuel ratio. The value of the correction coefficient Kal is increased.

  Then, as described in the above equation (1), the basic injection pulse width Tp is corrected by various correction amounts including the correction coefficient Kal, and the injection pulse width Ti of the drive signal for the injector 6 is calculated. Thereby, even if the alcohol concentration in the fuel pipe 4 changes, the alcohol concentration of the fuel actually injected from the injector 6 can be accurately grasped, and can be appropriately reflected in the fuel injection amount.

  Next, the program processing for calculating the reproduced alcohol concentration in the ECU 10 will be described with reference to the flowchart of FIG.

  The program process of FIG. 5 is a process executed every predetermined time period Δt (for example, Δt = 16 msec). First, in the first step P1, the fuel flow rate per unit time is determined from the current injection pulse width of the injector 6. (Instantaneous flow rate) qf is calculated. Next, the process proceeds to Step P2, where the instantaneous flow rate qf is integrated to calculate the integrated flow rate value.

  In the subsequent step P3, the flow rate integrated value is compared with a preset set fuel amount KFCCONST. If the integrated flow value <KFCCONST, the process proceeds to step P7. If the integrated flow value ≥KFCCONST, the alcohol detection concentration of the concentration sensor 5 is stored in time series for each set fuel amount KFCCONST after step P4. The process of storing and storing in the array M of the past storage density is performed.

  That is, the data of the array element M [j] storing and storing the alcohol concentration detected in the past in step P4 is sequentially shifted backward (M [j] → M [j + 1]), and the latest in step P5. Is stored and stored in the first array element M [0]. In step P6, the integrated flow rate is reset to 0, and the process proceeds to step P7.

In step P7, the element number i of the past storage concentration array is determined as the time series number of the alcohol concentration storage value corresponding to the delay amount KFFSDLY. This element number i is calculated by the following equation (3) using the delay amount KFFSDLY and the set fuel amount KFCCONST.
i = KFFSDLY / KFCCONST (3)

  Next, proceeding to step P8, the past storage density stored in the array element M [i] of the element number i is stored in S1, and the array element M [i-1] of the element number (i-1) is stored. The past storage density is S2. In step P9, the current reproduced alcohol concentration detn is calculated from the past stored concentrations S1 and S2 using the above-described equation (2), and the process is exited.

  As described above, in the present embodiment, the concentration sensor 5 detects the delay in transportation of the fuel in the fuel pipe from the concentration sensor 5 that detects the alcohol concentration in the fuel to the injector 6 that injects the fuel. The alcohol concentration of the fuel that is actually injected is accurately reproduced using the alcohol concentration.

  Thereby, even if the alcohol concentration of the fuel in the pipe changes, it can be appropriately reflected in the fuel injection amount, and the optimum air-fuel ratio can be maintained. In addition, a plurality of concentration sensors 5 can be installed at a desired position in the fuel supply system without using a plurality of sensors, avoiding restrictions on the outfitting and suppressing an increase in cost.

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Fuel pump 4 Fuel piping 5 Concentration sensor 6 Injector 10 Engine control unit 11 Fuel flow rate calculation part 12 Detection density | concentration sampling part 13 Reproduction alcohol concentration calculation part KFFSDLY Delay amount Kal Correction coefficient detn Reproduction alcohol concentration

Claims (4)

The alcohol concentration in the fuel at a desired position in the fuel supply system including a fuel tank for storing the alcohol-mixed fuel, a fuel pump for discharging the fuel in the fuel tank, and a fuel pipe extending from the fuel pump to the fuel injection valve In an alcohol mixed fuel injection control device that provides a concentration sensor for detecting the fuel and corrects the fuel injection amount injected from the fuel injection valve based on the alcohol concentration in the fuel,
A fuel flow rate calculation unit for calculating the flow rate of the alcohol mixed fuel;
A detection concentration sampling unit that samples the alcohol detection concentration by the concentration sensor at a sampling period set based on the fuel flow rate calculated by the fuel flow rate calculation unit;
Based on the detected alcohol concentration sampled by the detected concentration sampling unit and the amount of delay in fuel transportation between the concentration sensor and the fuel injector, the alcohol concentration of the fuel injected from the fuel injector is reproduced. An alcohol mixed fuel injection control apparatus comprising: a reproduction alcohol concentration calculation unit that calculates a reproduction alcohol concentration.   2. The alcohol mixed fuel injection control device according to claim 1, wherein the fuel flow rate calculation unit calculates a fuel flow rate based on the fuel injection amount. The detected concentration sampling unit stores the alcohol detected concentration for each sampling period in time series,
3. The alcohol-mixed fuel injection according to claim 1, wherein the reproduction alcohol concentration calculation unit calculates the reproduction alcohol concentration based on a stored value of an alcohol detection concentration of a time series number corresponding to the delay amount. Control device.   The reproduction alcohol concentration calculation unit uses the amount of fuel corresponding to the pipe volume of the fuel pipe from the concentration sensor to the fuel injection valve as the delay amount, and the amount of fuel corresponding to the pipe volume and the sampling rate for each sampling period. 4. The alcohol mixed fuel injection control device according to claim 3, wherein the time series number is determined based on an integrated value of the fuel flow rate.

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