JP2009074496A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine estimating the alcohol concentration of fuel supplied to the internal combustion engine while suppressing manufacturing cost. <P>SOLUTION: A fuel pump 14 is an electric pump using a DC motor 14a as a power source, and the DC motor 14a is a brushless motor (commutatorless motor). A pump controller 17 is connected to the fuel pump 14, and an ECU 18 is connected to the controller 17. The ECU 18 and pump controller 17 detect a behavior of the fuel pump 14 corresponding to drive input to the DC motor 14a, and estimate the alcohol concentration of fuel based on the detected behavior of the fuel pump 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device that detects an alcohol concentration of fuel supplied to the internal combustion engine.

In recent years, an internal combustion engine capable of using various fuels (fossil fuel, alcohol fuel, fossil fuel and alcohol fuel mixed fuel) has been developed from the viewpoint of effective use of resources. In such an internal combustion engine, control according to the alcohol concentration of the fuel is required in order to improve drivability and suppress emission of harmful exhaust components. On the other hand, a technique for estimating the alcohol concentration of the fuel from the refractive index and dielectric constant of the fuel and controlling the internal combustion engine based on the result is known (for example, Patent Document 1).
Japanese Unexamined Patent Publication No. 5-19539

  However, since such a technique requires a sensor for detecting the refractive index and dielectric constant of the fuel, there is a concern about an increase in the manufacturing cost of the control device that controls the internal combustion engine.

  The present invention has been made to solve the above-mentioned problems, and it is a main object of the present invention to provide a control device for an internal combustion engine that estimates the alcohol concentration of fuel supplied to the internal combustion engine while reducing the manufacturing cost. It is what.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  According to the first aspect of the present invention, the fuel pump that supplies fuel to the internal combustion engine uses an electric motor as a power source. Then, the pump behavior corresponding to the drive input to the electric motor (the behavior of the fuel pump) is detected, and the alcohol concentration of the fuel supplied to the internal combustion engine is estimated based on the behavior. Here, the pump behavior corresponding to the drive input to the electric motor changes according to the alcohol concentration of the fuel. That is, the higher the alcohol concentration of the fuel, the higher the viscosity of the fuel. As a result, the viscous resistance due to the fuel increases in the fuel pump, and the pump behavior corresponding to the drive input to the electric motor changes accordingly.

  Therefore, the alcohol concentration of the fuel can be estimated from the pump behavior corresponding to the drive input to the electric motor as described above. Specifically, for example, when the relationship between the pump behavior corresponding to a predetermined drive input and the alcohol concentration of the fuel is known, the drive input (predetermined drive input) is input to the electric motor, and the corresponding ( By detecting the pump behavior (according thereto), the alcohol concentration of the fuel can be estimated from the detected value (pump behavior). In this case, the alcohol concentration of the fuel can be estimated without requiring a sensor for detecting the physical properties (refractive index, dielectric constant, etc.) of the fuel. That is, the manufacturing cost of the control device that estimates the alcohol concentration of the fuel can be reduced.

  In the invention according to claim 2, as the pump behavior, the rotation speed of the electric motor corresponding to the electric power supplied to the electric motor or its correlation value (hereinafter referred to as “supply electric power etc.”) is detected, and based on the rotation speed. Estimate the alcohol concentration of the fuel. Here, it is considered that the rotation speed of the electric motor changes according to the alcohol concentration of the fuel. That is, when the electric power supplied to the electric motor is the same, the higher the alcohol concentration of the fuel (the higher the viscous resistance due to the fuel), the lower the rotational speed of the electric motor. Therefore, the alcohol concentration of the fuel can be estimated based on the rotation speed of the electric motor corresponding to the electric power supplied to the electric motor as described above.

  By the way, in the invention described in claim 2, in order to accurately estimate the alcohol concentration of the fuel, the rotation speed of the motor is stabilized after maintaining the electric power supplied to the motor at a constant value. It is desirable to detect speed. On the other hand, as a control mode of the internal combustion engine, it is conceivable to control the amount of fuel discharged by the fuel pump in accordance with the operating state of the engine. In this case, during the period in which the electric power supplied to the electric motor is maintained at a constant value as described above, the amount of fuel discharged by the fuel pump (rotational speed of the electric motor) cannot be controlled according to the operating state of the internal combustion engine. As a result, the stability of the engine may be impaired.

  In this regard, according to the third aspect of the present invention, the electric motor is driven with a predetermined constant power during a starting period until a predetermined time elapses after the internal combustion engine is started. And the rotation speed of an electric motor is detected in the said starting period. During the start-up period of the internal combustion engine, it is considered that the change in the operating state of the engine is relatively small. For example, during the start-up period of the in-vehicle internal combustion engine, the rotational speed of the engine is controlled to the idle rotational speed. Therefore, even if the power supplied to the motor is maintained at a constant value during the start-up period of the internal combustion engine as described above, it can be said that the influence on the operating state of the engine is relatively small. Therefore, by detecting the rotational speed of the electric motor as described above, it is possible to accurately estimate the alcohol concentration of the fuel supplied to the engine while suppressing a decrease in the stability of the internal combustion engine.

  In the invention according to claim 4, as the pump behavior, the rate of change is detected with respect to the rotational speed of the same motor that changes as the power supplied to the motor increases or decreases, and the alcohol concentration of the fuel is determined based on the rate of change. presume. Here, when the power supplied to the motor is increased or decreased, the rotational speed of the motor changes accordingly. The rate of change of the rotational speed at this time changes according to the alcohol concentration of the fuel (viscosity resistance by the fuel). Specifically, the rate of change of the rotational speed decreases as the alcohol concentration of the fuel increases (as the viscosity of the fuel increases). Therefore, the alcohol concentration of the fuel can be estimated based on the rate of change of the rotational speed of the electric motor accompanying the increase or decrease of the electric power supplied to the electric motor as described above.

  In the second to fourth aspects of the invention, the alcohol concentration of the fuel is detected by detecting the rotational speed of the electric motor. Therefore, it is desirable to employ a brushless motor as the electric motor, as in the fifth aspect of the invention. According to the brushless motor, the angular position of the rotor can be detected from the waveform of the electromotive force generated in the motor, and the rotational speed of the electric motor can be calculated from the angular position. Thus, since the rotational speed of the electric motor can be detected without requiring a sensor, the manufacturing cost of the control device that detects the alcohol concentration of the fuel can be reduced.

  In the sixth aspect of the invention, as the pump behavior, the current value of the transient current flowing through the motor as the drive voltage of the motor increases is detected, and the alcohol concentration of the fuel is estimated based on the current value. Here, when the drive voltage of the electric motor is increased, the current flowing through the electric motor increases with the increase. The transient current flowing at this time changes according to the alcohol concentration of the fuel (viscosity resistance by the fuel). Specifically, the current value of the transient current increases as the alcohol concentration of the fuel increases (as the viscosity of the fuel increases). Therefore, the alcohol concentration of the fuel can be estimated based on the current value of the transient current that flows through the motor as the driving voltage of the motor increases as described above.

  Here, it is considered that the viscosity of the fuel changes according to not only the alcohol concentration of the fuel but also the temperature of the fuel. Therefore, as in the invention of claim 7, the temperature of the fuel supplied to the internal combustion engine is detected, and the alcohol of the fuel supplied to the internal combustion engine is detected based on the detected fuel temperature in addition to the pump behavior. It is desirable to detect the concentration. Thereby, the alcohol concentration of the fuel can be estimated with higher accuracy.

  In addition, the theoretical air-fuel ratio of alcohol fuel (ratio where alcohol fuel and air burn without excess) is lower than the theoretical air-fuel ratio of fossil fuel (ratio where fossil fuel and air burn without excess), and the octane number of alcohol Is higher than the octane number of gasoline. Therefore, in the invention according to claim 8, in the invention according to claims 1 to 7, the fuel injection amount into the intake passage or the cylinder of the internal combustion engine is calculated based on the estimated alcohol concentration of the fuel. Thereby, stability of an internal combustion engine can be improved and discharge | emission of the exhaust gas harmful | toxic component by an internal combustion engine can be suppressed.

  Note that the functions of the plurality of means provided in the present invention are realized by hardware resources whose functions are specified by the configuration itself, hardware resources whose functions are specified by a program, or a combination thereof. The functions of the plurality of means are not limited to those realized by hardware resources that are physically independent of each other. The present invention can be specified not only as an apparatus invention but also as a program invention, a recording medium recording the program, and a method invention.

  Hereinafter, a plurality of embodiments embodying the present invention will be described with reference to the drawings.

(First embodiment)
The first embodiment embodies the present invention as a fuel supply system for an in-vehicle internal combustion engine, and a detailed configuration thereof will be described below. First, the schematic configuration of this fuel supply system will be described with reference to FIG. In FIG. 1, the internal combustion engine 10 is a multi-cylinder (for example, four cylinders) internal combustion engine, but one of the cylinders is shown. Further, it is assumed that the internal combustion engine 10 can use various fuels (fossil fuel, alcohol fuel, fossil fuel and alcohol fuel mixed fuel). The internal combustion engine according to the present invention may be for a four-wheeled vehicle or a two-wheeled vehicle. The engine may be a single cylinder.

  An injector 12 for injecting fuel is provided in the intake passage 11 of each cylinder of the internal combustion engine 10. The fuel stored in the fuel tank 13 is supplied to the injector 12. Specifically, the fuel in the fuel tank 13 is pumped up by the fuel pump 14 and supplied to the delivery pipe 16 through the fuel filter 15, and the fuel in the delivery pipe 16 is supplied to the injector 12.

  The fuel pump 14 is an electric pump using a DC motor 14a as a power source, and the DC motor 14a is a brushless motor (non-commutator electric motor). A pump controller 17 is connected to the fuel pump 14, and an ECU 18 is connected to the controller 17. The pump controller 17 drives the DC motor 14 a under the control of the ECU 18. The ECU 18 is an electronic control unit mainly composed of a known microcomputer provided with a CPU, a memory and the like. The memory stores various programs and parameters, and the CPU controls each part of the engine system mainly composed of the internal combustion engine 10 by executing the programs stored in the memory.

  Specifically, the ECU 18 includes an intake pressure sensor 19 that detects a pressure (intake pressure) in the intake passage 11, a crank angle sensor 21 that detects a rotational angle position of the crankshaft 20 of the internal combustion engine 10, and a delivery pipe 16. Various sensors such as a fuel pressure sensor 22 for detecting a differential pressure between the fuel pressure and the intake pressure are connected. Then, the ECU 18 reads the detection values of the above-described sensors in order to adjust the actual fuel pressure in the delivery pipe 16 to the target value (target fuel pressure), and based on these detection values, the rotational speed (pump rotation) of the DC motor 14a. (Speed) is feedback controlled. Further, the ECU 18 sets a target value (target injection amount) of the fuel injection amount by the injector 12 based on the detection value of the sensor described above.

  Here, the theoretical air-fuel ratio of alcohol fuel is lower than the theoretical air-fuel ratio of fossil fuel, and the octane number of alcohol is higher than the octane number of gasoline. Therefore, for example, when the fuel injection amount control set for the fossil fuel is applied as it is to the internal combustion engine 10 supplied with the alcohol fuel, drivability deteriorates and the exhaust amount of harmful exhaust components increases. Conceivable.

  Therefore, in the present embodiment, the alcohol concentration of the fuel is detected, and based on the detected value, the fuel injection timing, the fuel injection amount, the ignition timing, the valve timing, the fuel cut condition, the knock determination condition, the cylinder determination condition, the stroke determination Conditions are calculated. In particular, the alcohol concentration of the fuel is estimated from the behavior of the fuel pump 14, focusing on the fact that the viscosity changes according to the alcohol concentration of the fuel and the behavior of the fuel pump 14 changes according to the viscosity. ing.

  Specifically, the relationship between the drive voltage (pump drive voltage) of the DC motor 14a and the rotation speed (pump rotation speed) of the DC motor 14a when the same voltage is applied is considered to change according to the alcohol concentration of the fuel. That is, the higher the alcohol concentration of the fuel, the greater the viscous resistance due to the fuel. As a result, when the pump drive voltage is the same, the higher the alcohol concentration of the fuel, the lower the pump rotation speed. Therefore, the pump rotation speed is detected in a state where a predetermined pump drive voltage is applied to the DC motor 14a, and the alcohol concentration of the fuel is determined based on the relationship between the pump drive voltage and the pump rotation speed. In this case, the pump rotation speed corresponds to “the behavior of the fuel pump”.

  Next, the alcohol concentration estimation process will be described in more detail with reference to FIG. FIG. 2 is a flowchart showing the flow of the alcohol concentration estimation program. This program is executed by the ECU 18 at a predetermined cycle (every predetermined crank angle or at a predetermined time cycle). In FIG. 2, it is assumed that the pump drive voltage is maintained at a constant voltage V <b> 1 during a period (starting period) from the start of the internal combustion engine 10 until the predetermined time K <b> 1 elapses (FIG. 3A). Timing t11-t13).

  In step S10 shown in FIG. 2, the ECU 18 determines whether or not the alcohol concentration of the fuel has not been detected. When it is detected that the alcohol concentration of the fuel has not been detected, the ECU 18 proceeds to the process of step S11. When it is detected that the alcohol concentration of the fuel has been detected, the ECU 18 ends the execution of this program.

  In step S11, the ECU 18 determines whether or not an elapsed time TD from the start of the internal combustion engine 10 is not less than a predetermined time K2 and not more than the predetermined time K1. Here, K2 is set as follows. That is, the pump rotational speed NP changes after the engine 10 is started due to the increase (0 [V] → V1 [V]) of the pump drive voltage VP accompanying the start of the internal combustion engine 10. K2 is set to detect the rotational speed NP in a state where the pump rotational speed NP is stable.

  If it is determined in step S11 that the elapsed time from the start of the internal combustion engine 10 is not less than the predetermined time K2 and not more than the predetermined time K1, the ECU 18 causes the pump controller 17 to detect the pump rotation speed NP in step S12. Specifically, the pump controller 17 detects the position of the rotor from the waveform of the electromotive force generated in the DC motor 14a. Then, the ECU 18 calculates the pump rotation speed NP based on the rotor position sequentially detected by the pump controller 17.

  In subsequent step S13, the ECU 18 estimates the alcohol concentration based on the pump rotation speed NP calculated in step S12. Specifically, the ECU 18 estimates the alcohol concentration of the fuel from the pump rotation speed NP based on a map showing the relationship between the pump rotation speed NP and the alcohol concentration of the fuel. Specifically, when the pump rotation speed NP is less than or equal to the threshold value N1, the fuel alcohol concentration is high. When the pump rotation speed NP is greater than the threshold value N1 and less than or equal to the threshold value N2, the fuel alcohol concentration is high. Is a medium concentration, it is estimated that the alcohol concentration of the fuel is low when the pump rotational speed NP is greater than the threshold value N2. Then, the ECU 18 ends this program.

  On the other hand, when it is determined in step S11 that the elapsed time from the start of the internal combustion engine 10 is shorter than the predetermined time K2 or longer than the predetermined time K1, the ECU 18 executes this program without executing steps S12 and S13. The execution of is terminated.

  Note that the relationship between the pump rotation speed and the alcohol concentration of the fuel when the pump drive voltage is V1 differs for each pump 14 due to individual differences of the fuel pump 14. Therefore, it is desirable to calibrate the threshold values N1 and N2 as follows at the time of factory shipment. That is, a reference fuel (a fuel whose viscosity is known) is injected into the fuel pump 14, and a reference power (a pump drive voltage whose relationship between the pump rotation speed and the alcohol concentration of the fuel is known, for example, V1) is supplied to the pump 14. After the supply, the pump rotation speed NP is measured. Then, the thresholds N1 and N2 are calibrated based on the measured value of the pump rotation speed NP. Thereby, the error concerning the alcohol concentration estimation of the fuel due to the individual difference of the fuel pump 14 can be reduced.

  Next, the operation of the fuel supply system will be described with reference to FIG. The graph shown in FIG. 3A shows the pump drive voltage VP. In FIG. 3B, the solid line graph indicates the pump rotation speed NP when a high alcohol concentration fuel is used, and the broken line graph indicates the pump rotation speed NP when a medium alcohol concentration fuel is used. The one-dot chain line graph shows the pump rotation speed NP when a low alcohol concentration fuel is used. In FIG. 3, it is assumed that the pump drive voltage VP is maintained at the voltage V1 in the start period (period from the start of the internal combustion engine 10 until the predetermined time K1 elapses: see timings t11 to t13). .

  At timing t11, the pump drive voltage VP increases from 0 [V] to V1 [V] as the internal combustion engine 10 is started. As a result, after the timing t11, the pump rotation speed NP increases. At the timing t12 when the predetermined time K2 has elapsed from the timing t11, the pump rotation speed NP is stabilized. The ECU 18 detects the pump rotation speed NP at a timing after the timing t12 of the starting period. When the pump rotation speed NP is less than or equal to the threshold value N1, it is estimated that the alcohol concentration of the fuel is high. When the pump rotation speed NP is greater than the threshold value N1 and less than or equal to the threshold value N2, the alcohol concentration of fuel is estimated to be medium. When the pump rotational speed NP is larger than the threshold value N2, it is estimated that the alcohol concentration of the fuel is low.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  A pump rotational speed corresponding to a predetermined pump driving voltage (V1 [V]) is detected, and the alcohol concentration of the fuel is estimated based on the rotational speed. According to this configuration, the alcohol concentration of the fuel can be estimated without requiring a sensor for detecting the physical properties (refractive index, dielectric constant, etc.) of the fuel. In addition, a system that feedback-controls the pump rotation speed as in the present embodiment requires a configuration that detects the rotation speed in the first place. That is, the alcohol concentration of the fuel can be estimated without adding new hardware. Thereby, the manufacturing cost of the system which estimates the alcohol concentration of fuel can be reduced. Moreover, it is advantageous for miniaturization of the system.

  In particular, the DC motor 14a is a brushless motor. In this case, the pump rotation speed can be detected based on the waveform of the electromotive force generated in the brushless motor. That is, the pump rotation speed can be detected without requiring a rotation angle sensor for detecting the rotation angle of the DC motor 14a. Thereby, the manufacturing cost of the system for estimating the alcohol concentration of the fuel can be further reduced. In addition, the system is more advantageous in downsizing.

  Further, the pump drive voltage is maintained at a constant voltage V1 during the starting period of the internal combustion engine 10 (see timings t11 to t13 in FIG. 3), and the pump rotation speed is detected during the starting period. Thereby, the rotation speed can be detected in a state where the pump rotation speed is stabilized. Further, during the start-up period of the internal combustion engine 10, the rotational speed of the engine 10 is controlled to the idle rotational speed. Therefore, even if the pump drive voltage is maintained at the constant voltage V1 during the start-up period of the internal combustion engine 10 as described above, the influence on the operating state of the engine 10 is relatively small. Thereby, the alcohol concentration of the fuel supplied to the engine 10 can be accurately estimated while suppressing a decrease in the stability of the internal combustion engine 10.

  Further, by detecting the pump rotation speed during the start-up period of the internal combustion engine 10, the alcohol concentration of the fuel can be estimated at an early stage from the rotation speed. Further, by detecting the pump rotation speed when the pump drive voltage is V1, thresholds N1 and N2 (the threshold value for determining the alcohol concentration from the pump rotation speed) as thresholds related to the pump rotation speed (thresholds N1 and N2) It is only necessary to set (store in a storage device such as a memory of the ECU 18). That is, it is not necessary to set the threshold value at a voltage other than the voltage V1.

  Further, the fuel injection amount or the like into the intake passage or the cylinder of the internal combustion engine 10 is calculated based on the estimated value of the alcohol concentration of the fuel. Thereby, the stability of the internal combustion engine 10 can be improved, and the exhaust of harmful exhaust components by the engine 10 can be suppressed.

(Second Embodiment)
The second embodiment is different from the first embodiment in the alcohol concentration estimation process. Each component of the second embodiment is substantially the same as the corresponding component of the first embodiment except for the alcohol concentration estimation program. Therefore, the same reference numerals as those of the corresponding components in the first embodiment are given to these components, and the description thereof is omitted.

  In the alcohol concentration estimation process of this embodiment, the alcohol concentration of the fuel is estimated from the current value of the transient current flowing through the DC motor 14a as the pump drive voltage increases. Specifically, when the pump drive voltage increase mode (voltage increase range, voltage value before and after the increase, rate of increase (range of increase per unit time)) is the same, the current value of the transient current is the alcohol content of the fuel. The higher the concentration (the higher the viscosity of the fuel), the greater. Therefore, the pump drive voltage is increased in a predetermined manner, the current value of the transient current flowing through the DC motor 14a is detected along with the increase, and the alcohol concentration of the fuel is estimated based on the detected value (current value). In this case, the current value of the transient current corresponds to “the behavior of the fuel pump”.

  First, the alcohol concentration estimation process of the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the flow of the alcohol concentration estimation program. This program is executed by the ECU 18 at a predetermined cycle (every predetermined crank angle or at a predetermined time cycle). In FIG. 4, it is assumed that the pump drive voltage increases from 0 [V] to V1 [V] with the start of the internal combustion engine 10 (see timing t21 in FIG. 5A).

  In step S20 shown in FIG. 4, the ECU 18 determines whether or not the alcohol concentration of the fuel has not been detected. When it is detected that the alcohol concentration of the fuel has not been detected, the ECU 18 proceeds to the processing of step S21. When it is detected that the alcohol concentration of the fuel has been detected, the ECU 18 ends the execution of this program.

  In step S21, the ECU 18 determines whether or not the elapsed time TD from the start of the internal combustion engine 10 is not less than the predetermined time K3 and not more than the predetermined time K4. Here, K3 and K4 are set as follows. That is, when the pump drive voltage VP increases (0 [V] → V1 [V]) as the internal combustion engine 10 starts, the pump rotational speed NP changes after the engine 10 is started. K3 and K4 are set so that the maximum value of the pump drive current IP in the transient state is included in the period “K3 ≦ TD ≦ K4”.

  If it is determined in step S21 that the elapsed time from the start of the internal combustion engine 10 is not less than the predetermined time K3 and not more than the predetermined time K4, the ECU 18 detects the pump drive current IP in step S22. Specifically, the ECU 18 acquires the pump drive current IP from the pump controller 17.

  In subsequent step S23, the ECU 18 calculates the alcohol concentration based on the acquired pump drive current IP. Specifically, the ECU 18 estimates the alcohol concentration of the fuel from the pump driving current IP calculated in step S22 based on a map showing the relationship between the pump driving current IP and the alcohol concentration of the fuel. Specifically, when the pump drive current IP is less than or equal to the threshold value I1, it is estimated that the alcohol concentration is high, and when the pump drive current IP is greater than the threshold value I1 and less than or equal to the threshold value I2, the alcohol concentration is medium. If the pump drive current IP is larger than the threshold value I2, it is estimated that the alcohol concentration is low. Then, the ECU 18 ends this program.

  The relationship between the current value of the transient current flowing in the transient state of the pump drive current IP and the alcohol concentration of the fuel accompanying the increase of the pump drive voltage VP from 0 [V] to V1 [V] is as follows. It differs for each pump 14 due to individual differences. Therefore, the threshold values I1 and I2 are preferably calibrated at the time of factory shipment as follows. That is, reference fuel (fuel whose viscosity is known) is injected into the fuel pump 14, the pump drive voltage VP is increased in a reference increase mode, and the current value of the transient current associated with the increase is measured. Then, the threshold values I1 and I2 are calibrated based on the current value of the transient current. Here, the reference increase mode is a pump drive voltage increase mode (for example, 0 [V] → V1 [V]) in which the relationship between the transient current and the alcohol concentration of the fuel is known.

  On the other hand, if it is determined in step S21 that the elapsed time from the start of the internal combustion engine 10 is shorter than the predetermined time K3 or longer than the predetermined time K4, the ECU 18 executes this program without executing steps S12 and S13. The execution of is terminated.

  Next, the operation of the fuel supply system will be described with reference to FIG. The graph shown in FIG. 5A shows the pump drive voltage VP. On the other hand, in FIG. 5 (b), the solid line graph shows the pump drive current IP when the high alcohol concentration fuel is used, and the broken line graph shows the pump drive current IP when the medium alcohol concentration fuel is used. The one-dot chain line graph shows the pump drive current IP when a low alcohol concentration fuel is used. In FIG. 5, it is assumed that the pump drive voltage increases from 0 [V] to V1 [V] as the internal combustion engine 10 is started.

  At timing t21, the pump drive voltage VP is controlled to the voltage V1 as the internal combustion engine 10 is started. As a result, the pump drive current IP varies after the timing t21. The ECU 18 detects the current value of the pump drive current IP in a period between a timing t22 when the predetermined time K3 has elapsed from the timing t21 and a timing t24 when the predetermined time K4 has elapsed from the timing t21. The predetermined times K3 and K4 are set so that the maximum value (see timing t23) of the pump drive current IP in the transient state is included in the period “K3 ≦ TD ≦ K4” as described above.

  When the pump drive current IP detected in this way is less than or equal to the threshold value I1, it is estimated that the alcohol concentration is high, and when the pump drive current IP is greater than the threshold value I1 and less than or equal to the threshold value I2, the alcohol concentration is medium. If the pump drive current IP is larger than the threshold value I2, it is estimated that the alcohol concentration is low.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  A current value of a transient current (the same current that flows in a transient state of the pump drive current) accompanying an increase in pump drive voltage is detected, and the alcohol concentration of the fuel is estimated based on the current value. According to this configuration, the alcohol concentration of the fuel can be estimated without requiring a sensor for detecting the physical properties (refractive index, dielectric constant, etc.) of the fuel. In addition, a system that feedback-controls the pump rotation speed as in the present embodiment requires a configuration that detects the rotation speed in the first place. That is, the alcohol concentration of the fuel can be estimated without adding new hardware. Thereby, the manufacturing cost of the system which estimates the alcohol concentration of fuel can be reduced. Moreover, it is advantageous for miniaturization of the system.

  Further, the pump drive voltage is increased in a predetermined manner (0 [V] → V1 [V]), and a current value of a transient current (the same current that flows in a transient state of the pump drive current) accompanying the increase is detected. It was. Therefore, as threshold values related to the transient current (threshold value for determining the alcohol concentration from the transient current), “pump drive voltage increase width = V1”, “pump drive voltage before increase = 0”, “after increase” Only threshold values I1 and I2 (see FIG. 5) in the case of “pump drive voltage = V1” need only be set (stored in a storage device such as a memory of ECU 18). That is, it is not necessary to set threshold values (threshold values corresponding to I1 and I2) other than when the above three conditions are satisfied.

  In addition, a relatively large current value (maximum value or a value in the vicinity thereof) is detected with respect to a transient current (the same current that flows in a transient state of the pump drive current) associated with an increase in pump drive voltage. Specifically, in FIG. 5, the transient current is detected when the elapsed time from the timing 21 is not less than the predetermined time K3 and not more than the predetermined time K4. Here, when the above-described transient current in the case where the pump drive voltage increases in the same manner is compared at the same timing (timing when the same time has elapsed from the pump drive voltage increase start timing) with different alcohol concentrations in the fuel, The difference is considered to be so large that the current value is compared at a timing when the current value shows a relatively large value. For example, according to FIG. 5, when comparing the transient current indicated by the solid line, the transient current indicated by the broken line, and the transient current indicated by the alternate long and short dash line, these current values of these transient currents are compared at timing t22 rather than at the timing t22. It can be seen that these differences are larger when comparing the transient currents. Therefore, by detecting a relatively large current value for the transient current as described above and detecting the alcohol concentration of the fuel based on the detected value (current value), the alcohol concentration of the fuel can be accurately detected. .

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In each of the above embodiments, it is determined which of the three ranges (high concentration, medium concentration, and low concentration) the alcohol concentration of the fuel is included in. However, the present invention is not limited to this, and it may be determined whether the alcohol concentration of the fuel is included in two or four or more ranges, or a numerical value (percentage or the like) indicating the alcohol concentration of the fuel is estimated. You may do it.

  In the first embodiment, when the pump drive voltage is V1, the pump rotation speed is detected only once. However, the present invention is not limited to this, and the pump rotation speed may be detected when the pump drive voltage is a voltage different from V1. Further, the pump rotation speed may be detected a plurality of times. In this case, for example, a provisional value of the alcohol concentration of the fuel is estimated from a plurality of pump rotation speeds corresponding to different pump driving voltages, and a final value (average value or the like) of the alcohol concentration of the fuel is calculated from the provisional value (alcohol concentration). ) Can be calculated. Also, the final value (average value, etc.) of the pump rotational speed is calculated from the detected values of a plurality of pump rotational speeds corresponding to the same pump drive voltage, and the alcohol concentration of the fuel is estimated from the final value (average value). it can. Thereby, the alcohol concentration of the fuel can be accurately estimated.

  In the second embodiment, the pump drive voltage is increased from 0 [V] to V1 [V], and the current value of the transient current (the same current that flows in the transient state of the pump drive current) associated with the increase is only once. It was made to detect. However, the present invention is not limited to this, and the pump drive voltage may be raised in a rising manner different from the above manner, and a transient current associated with the rising may be detected. Further, the current value of the transient current may be detected a plurality of times. For example, as shown in FIG. 6, the current value of the pump drive current may be detected a plurality of times (see timings t30 and t31) in the pump drive current detection period (timing t22 to t24). In this case, a maximum value or an average value of a plurality of detection values (current values) may be calculated, and the alcohol concentration of the fuel may be estimated based on the maximum value or the average value. Thereby, the alcohol concentration of the fuel can be accurately estimated.

  In the first embodiment, the pump rotation speed is detected during the start-up period of the internal combustion engine 10 (see FIG. 3). However, the pump rotation speed may be detected in a period other than the start period of the internal combustion engine 10 or in both periods (a start period of the internal combustion engine 10, a period other than the synchronization period). In the second embodiment, the transient current that flows as the pump drive voltage rises when the internal combustion engine 10 is started (the same current that flows in the transient state of the pump drive current) is detected. However, the pump drive voltage is increased at a timing other than the start of the internal combustion engine 10 or at both timings (at the start of the internal combustion engine 10 and at a timing other than the start), and a transient current associated with the increase is detected. Good.

  Further, the alcohol concentration estimation process may be performed in each trip, or may be performed in a predetermined trip, from the start to the stop of the internal combustion engine 10 as one trip of the vehicle. When the alcohol concentration estimation process is performed in a predetermined trip, that is, when the same process is not performed in each trip, the estimated value of the alcohol concentration is stored in a backup memory (EEPROM, RAM that is powered by a backup power source). You just have to. Here, the predetermined trip means a trip after a predetermined time has elapsed since the execution of the alcohol concentration estimation process, or a trip in which the internal combustion engine 10 is started for the first time after refueling.

  In the first embodiment, the alcohol concentration of the fuel is estimated based on the detected value of the pump rotation speed corresponding to the predetermined pump drive voltage. However, the present invention is not limited to this, and the alcohol concentration of the fuel may be estimated based on the detected value of the pump rotation speed corresponding to the power supplied to the fuel pump 14. Further, when duty control is performed on the power supplied to the DC motor 14a, the alcohol concentration of the fuel pump is determined based on the duty ratio of the drive input to the motor 14a and the detected value of the pump rotation speed corresponding to the duty ratio. You may make it estimate.

  In the second embodiment, the alcohol concentration of the fuel is estimated based on the mode of increase of the pump drive voltage and the current value of the same current (transient current) in the transient state of the pump drive current accompanying the increase. However, the present invention is not limited to this, and the alcohol concentration of the fuel may be estimated on the basis of the manner of increasing the power supplied to the fuel pump 14 and the current value of the transient current accompanying the increase. In addition, when duty control is performed on the power supplied to the DC motor 14a, the duty ratio of the drive input to the motor 14a is increased and the current value of the transient current of the pump drive current accompanying the increase is determined. Thus, the alcohol concentration of the fuel may be estimated.

  In the first embodiment, the rotational speed is detected when the pump rotational speed is stable (stable state: see timings t12 to t13 in FIG. 3). Specifically, the pump rotational speed was detected after a predetermined time K2 from the start of the internal combustion engine 10 had elapsed. However, the present invention is not limited to this, and the alcohol concentration of the fuel may be detected as follows. In other words, in a transient state accompanying an increase or decrease in the power supplied to the fuel pump 14 or its correlation value, the rate of change of the pump rotation speed decreases as the alcohol concentration of the fuel increases (the viscosity of the fuel increases). For example, in FIG. 3, the pump rotation speed increases as the pump drive voltage (correlation value) increases (see timings t11 to t12). Therefore, in the transient state of the pump rotation speed accompanying the increase or decrease of the pump drive voltage, the change rate of the rotation speed is detected, and the alcohol concentration of the fuel is estimated based on the increase rate and the increase / decrease mode of the pump drive voltage. Also good.

  In this case, as an increase / decrease mode of the pump drive voltage, the increase / decrease width (increase amount) of the pump drive voltage accompanying the start of the internal combustion engine 10 and the pump drive voltage before increase (steady voltage before increase: 0 [V]) And an increased pump drive voltage (steady voltage after increase: V1 [V]) may be detected. In addition, as this increase / decrease mode, you may include the increase / decrease rate of pump drive voltage (the increase / decrease amount of the pump drive voltage per unit time).

  -In the said 2nd Embodiment, the pump drive voltage was raised at a stretch. However, if the same current (transient current) in the transient state of the pump drive current accompanying an increase in the pump drive voltage becomes excessive, the fuel pump 14 (DC motor 14a) may break down. Therefore, the pump drive voltage may be increased stepwise as shown in FIG. 7 or gradually increased as shown in FIG. Thereby, the said transient current is suppressed and the failure of the fuel pump 14 can be suppressed.

  In each of the above embodiments, the brushless DC motor 14 a is employed as the power source of the fuel pump 14. However, the present invention is not limited to this, and a commutator motor may be employed as a power source for the fuel pump 14. In this case, the pump rotation speed is detected based on the detection value of a sensor (rotation angle sensor) that detects the rotation angle of the rotor of the commutator motor, and the alcohol concentration of the fuel is estimated in the same manner as in the first embodiment. Can do. Further, the alcohol concentration of the fuel can be estimated as in the second embodiment.

  In each of the above embodiments, the alcohol concentration of the fuel is estimated based on the behavior of the fuel pump 14 on the assumption that the viscosity of the fuel changes with the alcohol concentration. However, the viscosity of the fuel also changes at that temperature. Therefore, the alcohol concentration of the fuel may be estimated based on the temperature of the fuel in addition to the behavior of the fuel pump 14.

  In each of the above embodiments, the fuel injection timing, fuel injection amount, ignition timing, valve timing, fuel cut condition, knock determination condition, cylinder determination condition, stroke determination condition, etc. are variably set based on the detected value of the alcohol concentration. . However, the present invention is not limited to this, and based on the detected value of the alcohol concentration, information indicating the concentration (for example, information indicating whether the concentration is high, medium, or low, or a numerical value indicating the concentration (percentage, etc.)) is displayed. You may make it display on an apparatus (for example, lamps etc. which were provided in the instrument panel). As a result, the driver can be notified of the alcohol concentration in the internal combustion engine 10 and the alcohol concentration of the fuel supplied to the engine 10. Further, when the detected value of the alcohol concentration indicates the same concentration outside the specification of the internal combustion engine 10, that fact may be displayed on a display device (for example, lamps provided on the instrument panel). . This can warn that the alcohol concentration of the fuel is not suitable for the internal combustion engine 10. Further, when the vehicle includes a device that displays the travelable distance, for example, when the vehicle includes a navigation system and the system has a function of displaying the travelable distance of the vehicle, the above is based on the detected value of the alcohol concentration. The travelable distance may be calculated.

The figure which shows schematic structure of a fuel supply system. The flowchart which shows the flow of the alcohol concentration estimation program which concerns on 1st Embodiment. The timing chart which shows the action | operation of the fuel supply system which concerns on 1st Embodiment. The flowchart which shows the flow of the alcohol concentration estimation program which concerns on 2nd Embodiment. The timing chart which shows the action | operation of the fuel supply system which concerns on 2nd Embodiment. The timing chart which shows the action | operation of the fuel supply system which concerns on other embodiment. The timing chart which shows the action | operation of the fuel supply system which concerns on other embodiment. The timing chart which shows the action | operation of the fuel supply system which concerns on other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Intake passage, 12 ... Injector, 13 ... Fuel tank, 14 ... Fuel pump, 14a ... DC motor (electric motor), 15 ... Fuel filter, 16 ... Delivery pipe, 17 ... Pump controller (pump behavior detection) , ECU (pump behavior detection means, alcohol concentration estimation means, motor control means, temperature detection means, injection amount setting means), 19 ... intake pressure sensor, 20 ... crankshaft, 21 ... crank angle Sensor, 22 ... Fuel pressure sensor.

Claims (9)

A fuel pump that supplies fuel to the internal combustion engine uses an electric motor as a power source,
A pump behavior detecting means for detecting a pump behavior corresponding to a drive input to the electric motor;
Alcohol concentration estimation means for estimating the alcohol concentration of fuel supplied to the internal combustion engine based on the pump behavior detected by the pump behavior detection means;
A control device for an internal combustion engine, comprising: The pump behavior detecting means detects the rotational speed of the electric motor corresponding to the power supplied to the electric motor or a correlation value thereof as the pump behavior,
The control apparatus for an internal combustion engine according to claim 1, wherein the alcohol concentration estimation means estimates the alcohol concentration of fuel supplied to the internal combustion engine based on the rotational speed detected by the pump behavior detection means. Electric motor control means for driving the electric motor with a predetermined constant power in a starting period until a predetermined time elapses after starting the internal combustion engine;
The control apparatus for an internal combustion engine according to claim 2, wherein the pump behavior detecting means detects a rotation speed of the electric motor during the start period. The pump behavior detecting means detects the rate of change of the rotational speed of the motor that changes with the increase or decrease of the power supplied to the motor or its correlation value as the pump behavior,
2. The control device for an internal combustion engine according to claim 1, wherein the alcohol concentration estimation means estimates the alcohol concentration of fuel supplied to the internal combustion engine based on a rate of change in rotational speed detected by the pump behavior detection means. .   The control device for an internal combustion engine according to any one of claims 2 to 4, wherein the electric motor is a brushless motor. The pump behavior detecting means detects a current value of a transient current flowing in the electric motor as the driving voltage of the electric motor increases as the pump behavior,
The control apparatus for an internal combustion engine according to claim 1, wherein the alcohol concentration estimation means estimates the alcohol concentration of fuel supplied to the internal combustion engine based on the transient current detected by the pump behavior detection means. Temperature detecting means for detecting the temperature of the fuel supplied to the internal combustion engine;
The alcohol concentration estimating means detects the alcohol concentration of the fuel supplied to the internal combustion engine based on the temperature of the fuel detected by the temperature detecting means in addition to the pump behavior. The control apparatus for an internal combustion engine according to claim 1   8. The fuel injection device according to claim 1, further comprising an injection amount calculating unit that calculates a fuel injection amount into the intake passage or the cylinder of the internal combustion engine based on the alcohol concentration of the fuel estimated by the alcohol concentration estimating unit. The control apparatus for an internal combustion engine according to the item. When the fuel pump that supplies fuel to the internal combustion engine uses an electric motor as a power source,
Detecting the pump behavior corresponding to the drive input to the motor;
A method for estimating the alcohol concentration of a fuel, wherein the alcohol concentration of the fuel supplied to the internal combustion engine is estimated based on the detected pump behavior.

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