JP4243383B2 - Fuel evaporation characteristic detection device and control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel evaporation characteristic detection device that detects the fuel evaporation characteristic of an internal combustion engine and a control device that controls the internal combustion engine in accordance with the detected evaporation characteristic.
[0002]
[Prior art]
As a parameter representing the fuel evaporation characteristics of an internal combustion engine, the Reid Vaper Pressure measured at a temperature of 37.8 ° C. when the ratio of the fuel quantity in the gas state to the fuel quantity in the liquid state is 4: 1. It has been known.
[0003]
The air-fuel ratio control of the air-fuel mixture supplied to the internal combustion engine is performed by controlling the fuel supply amount according to the engine operating state. Even if the fuel amount injected into the intake pipe is the same, the fuel evaporation characteristic As a result, the actual air-fuel ratio changes. Therefore, it is desirable to detect the evaporation characteristics of the fuel used during engine operation, particularly during warm-up operation.
For this purpose, a wide-range air-fuel ratio sensor that detects the air-fuel ratio based on the oxygen concentration in the exhaust gas is provided in the engine exhaust system, and the detected air-fuel ratio during the warm-up operation of the engine and the reference value are compared. A technique for determining the level of the reed vapor pressure is known.
[0004]
[Problems to be solved by the invention]
However, in the above conventional method, since the determination is made from the exhaust gas, the determination accuracy is low and cannot be used for air-fuel ratio control of the engine.
The present invention has been made paying attention to this point, and more suitable for the operation of the internal combustion engine in accordance with the detected fuel evaporation characteristic and the fuel evaporation characteristic detection device capable of accurately detecting the evaporation characteristic of the fuel in use. It is an object of the present invention to provide a control device that can be controlled.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention provides a fuel evaporation characteristic detecting device for detecting an evaporation characteristic of fuel supplied to an internal combustion engine, an in-cylinder pressure detecting means for detecting an in-cylinder pressure of the engine, An indicated mean effective pressure calculating means for calculating an indicated mean effective pressure from the detected in-cylinder pressure; a characteristic detecting means for detecting an evaporation characteristic of the fuel based on the indicated mean effective pressure calculated by the indicated mean effective pressure calculating means; The characteristic detection means calculates a standard deviation and an average value for a predetermined number of data of the indicated mean effective pressure during the warm-up operation of the engine, and divides the standard deviation by the average value. A variation rate is calculated, and an evaporation characteristic of the fuel is detected according to the variation rate.
[0006]
According to this configuration, the indicated mean effective pressure is calculated from the detected in-cylinder pressure, and the fuel evaporation characteristic is detected based on the indicated mean effective pressure. Therefore, the fuel evaporation characteristic is detected more accurately than in the past. be able to. Further, since the fuel evaporation characteristic is detected according to the fluctuation rate of the indicated mean effective pressure during the warm-up operation, a highly accurate evaporation characteristic can be obtained.
[0007]
According to a second aspect of the present invention, there is provided a control device for controlling an amount of fuel supplied to an internal combustion engine and an ignition timing. The indicated mean effective pressure calculating means for calculating the characteristic, the characteristic detecting means for detecting the evaporation characteristic of the fuel based on the indicated mean effective pressure calculated by the indicated mean effective pressure calculating means, and the characteristic detecting means Correction means for correcting at least one of the fuel supply amount and the ignition timing in accordance with the fuel evaporation characteristic, and the characteristic detection means has a predetermined number of the indicated mean effective pressure during the warm-up operation of the engine . standard deviation and the average value of the data, especially in that the calculated variation rate by the standard deviation is divided by the said average value, detects the evaporation characteristics of the fuel in accordance with the fluctuation rate To.
[0008]
According to this configuration, the indicated mean effective pressure is calculated from the detected in-cylinder pressure, the fuel evaporation characteristic is detected based on the indicated mean effective pressure, and the fuel supply amount and the ignition timing are determined according to the detected evaporation characteristic. Since at least one of these is corrected, the fuel supply amount and / or the ignition timing suitable for the fuel evaporation characteristics can be set, and fuel waste, deterioration of exhaust gas characteristics, and / or reduction of engine output can be prevented. Can do. Further, since the fuel evaporation characteristic is detected according to the fluctuation rate of the indicated mean effective pressure during the warm-up operation, a highly accurate evaporation characteristic can be obtained and finer correction can be made.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is an overall configuration diagram of an internal combustion engine (hereinafter referred to as “engine”) and its control device including a fuel evaporation characteristic detection device according to a first embodiment of the present invention. A throttle valve 3 is arranged in the middle of the pipe 2. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3, and an electric signal corresponding to the opening of the throttle valve 3 is output to output an engine control electronic control unit (hereinafter referred to as “ECU”) 5. To supply.
[0010]
The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). At the same time, it is electrically connected to the ECU 5 and the valve opening time of the fuel injection valve 6 is controlled by a signal from the ECU 5.
[0011]
On the other hand, an intake pipe absolute pressure (PBA) sensor 7 is provided immediately downstream of the throttle valve 3, and the absolute pressure signal converted into an electric signal by the absolute pressure sensor 7 is supplied to the ECU 5. Further, an intake air temperature (TA) sensor 8 is attached downstream thereof, detects the intake air temperature TA, outputs a corresponding electric signal, and supplies it to the ECU 5.
[0012]
An engine water temperature (TW) sensor 9 mounted on the main body of the engine 1 is composed of a thermistor or the like, detects the engine water temperature (cooling water temperature) TW, outputs a corresponding temperature signal, and supplies it to the ECU 5.
A crank angle position sensor 10 that detects a rotation angle of a crankshaft (not shown) of the engine 1 is provided, and a signal corresponding to the rotation angle of the crankshaft is supplied to the ECU 5. The crank angle position sensor 10 is a cylinder discrimination sensor that outputs a signal pulse (hereinafter referred to as “CYL signal pulse”) at a predetermined crank angle position of a specific cylinder of the engine 1, and a top dead center (TDC) at the start of the intake stroke of each cylinder. ) With a constant crank angle period (for example, a period of 1 to 30 degrees) shorter than the TDC sensor and a TDC sensor that outputs a TDC signal pulse at a crank angle position before a predetermined crank angle (every crank angle of 180 degrees in a four-cylinder engine). It consists of a CRK sensor that generates one pulse (hereinafter referred to as “CRK signal pulse”), and a CYL signal pulse, a TDC signal pulse, and a CRK signal pulse are supplied to the ECU 5. These signal pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of the engine speed NE.
[0013]
An in-cylinder pressure sensor 11 is provided as in-cylinder pressure detecting means for detecting the in-cylinder pressure PCYL of each cylinder of the engine 1, and the detection signal is supplied to the ECU 5 via a charge amplifier 12 having an amplification and integration function. . Since the output of the in-cylinder pressure sensor 11 is proportional to the rate of change (differential value) of the in-cylinder pressure, the in-cylinder pressure PCYL is obtained by integrating this.
[0014]
A spark plug 20 provided in each cylinder of the engine 1 is connected to the ECU 5, and its operation is controlled by the ECU 5.
The exhaust pipe 13 is provided with a three-way catalyst 16 for purifying exhaust gas, and a proportional air-fuel ratio sensor 14 (hereinafter referred to as “LAF sensor 14”) is mounted on the upstream side of the three-way catalyst 16. ing. The LAF sensor 14 outputs an electrical signal that is substantially proportional to the oxygen concentration (air-fuel ratio) in the exhaust gas and supplies it to the ECU 5.
[0015]
The ECU 5 shapes an input signal waveform from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, and the like, and a central processing circuit (hereinafter referred to as “CPU”). 5b), various calculation programs executed by the CPU 5b, tables and maps used in the calculation programs, storage means 5c for storing calculation results, etc., driving signals are supplied to the fuel injection valve 6, spark plug 20, etc. Output circuit 5d and the like.
[0016]
The CPU 5b determines various engine operating states based on the various engine parameter signals described above, and synchronizes with the TDC signal pulse based on the following equation (1) according to the determined engine operating states. The fuel injection time TOUT of the fuel injection valve 6 that is opened is calculated.
TOUT = TI × KRVP × KCMD × KLAF × K1 + K2 (1)
Here, TI is the basic fuel injection time of the fuel injection valve 6 and is determined by searching a TI map set according to the engine speed NE and the intake pipe absolute pressure PBA. The TI map is set so that the air-fuel ratio of the air-fuel mixture supplied to the engine is substantially the stoichiometric air-fuel ratio in the operating state corresponding to the engine speed NE and the intake pipe absolute pressure PBA on the map.
[0017]
KRVP is a fuel characteristic correction coefficient that is set according to the determination result of determining whether the reed vapor pressure RVP is high or low during the warm-up operation of the engine 1.
KCMD is a target air-fuel ratio coefficient, and is set according to engine operating parameters such as the engine speed NE, the intake pipe absolute pressure PBA, and the engine water temperature TW. The target air-fuel ratio coefficient KCMD is proportional to the reciprocal of the air-fuel ratio A / F, that is, the fuel-air ratio F / A, and takes a value of 1.0 when the stoichiometric air-fuel ratio is used.
[0018]
KLAF is an air-fuel ratio correction coefficient calculated by PID control so that the detected equivalent ratio KACT calculated from the detection value of the LAF sensor 14 matches the target equivalent ratio KCMD.
K1 and K2 are other correction coefficients and correction variables that are calculated according to various engine parameter signals, respectively, and are predetermined values that can optimize various characteristics such as fuel efficiency characteristics and engine acceleration characteristics according to engine operating conditions. To be determined.
[0019]
The CPU 5b further calculates the ignition timing IG by the following equation (2) according to the engine operating state. The ignition timing IG is calculated as an advance amount with respect to the top dead center.
IG = IGMAP + IGRVP (2)
Here, IGMAP is a basic ignition timing determined by searching an IG map set according to the engine speed NE and the intake pipe absolute pressure PBA, and IGRVP is set according to the level of the reed vapor pressure RVP. Correction term.
[0020]
The CPU 5b supplies the fuel injection valve 6 with a drive signal for opening the fuel injection valve 6 based on the fuel injection time TOUT obtained as described above, and an ignition signal for driving the spark plug 20 based on the ignition timing IG. Is supplied to the spark plug 20.
[0021]
FIG. 2 is a flowchart of processing for detecting the lead vapor pressure RVP and calculating the correction coefficient KRVP for the fuel injection time TOUT and the correction term IGRVP for the ignition timing IG according to the detected lead vapor pressure RVP. This processing is performed in the CPU 5b. It is executed at regular intervals or in synchronization with the generation of TDC signal pulses.
[0022]
In step S11, it is determined whether or not the engine 1 is warming up. If the engine 1 is not warming up, the correction coefficient KRVP is set to 1.0 and the correction term IGRVP is set to 0 (step S20). This process is terminated.
When the engine is warming up, the cylinder pressure PCYL detected by the cylinder pressure sensor 11 is read (step S12), and the indicated mean effective pressure PMI is calculated from the cylinder pressure PCYL (step S13). Specifically, the data obtained by sampling the in-cylinder pressure PCYL at every predetermined crank angle (for example, 1 degree) is integrated during the compression stroke and the explosion stroke of the cylinder, and the indicated average is calculated according to the integrated value thus obtained. An effective pressure PMI is calculated.
[0023]
Next, it is determined whether or not the calculated indicated mean effective pressure PMI is higher than the predetermined pressure PMIB (step S14). If PMI> PMIB, it is determined that the fuel has a high reed vapor pressure RVP (step S15). The correction coefficient KRVP is set to a predetermined coefficient value KRVP1 smaller than 1, and the correction term IGRVP is set to a negative predetermined value IGRVP1 (step S16). As a result, the fuel supply amount is corrected to decrease, and the ignition timing IG is corrected in the retard direction.
[0024]
On the other hand, if PMI ≦ PMIB in step S14, it is determined that the fuel is low in reed vapor pressure RVP (step S17), the correction coefficient KRVP is set to a predetermined coefficient value KRVP2 greater than 1, and the correction term IGRVP is set to The positive predetermined value IGRVP2 is set (step S18). As a result, the fuel supply amount is corrected to increase, and the ignition timing IG is corrected in the advance direction.
[0025]
The predetermined pressure PMIB is set to the indicated mean effective pressure PMI corresponding to fuel having an average reed vapor pressure.
In the subsequent step S19, the learning value KRVPAVE of the correction coefficient KRVP and the learning value IGRVP of the correction term IGRVP are calculated by the following equations (3) and (4).
KRVPAVE = A × KRVP + (1−A) × KRVPAVE (3)
IGRVPAVE = A × IGRVP + (1−A) × IGRVPAVE (4)
[0026]
Here, KRVPAVE and IGRVPAVE on the right side are the previous values of the learning values, and A is an annealing coefficient set to a value between 0 and 1. The learned values KRVPAVE and IGRVPAVE are stored in a backup RAM that retains the stored contents even when the ignition switch is turned off, and are used as initial values at the start of the next warm-up operation.
[0027]
As described above, in the present embodiment, the indicated mean effective pressure PMI is calculated from the detected in-cylinder pressure PCYL, and the lead vapor pressure RVP of the fuel in use is determined based on the indicated mean effective pressure PMI. It is possible to make a more accurate determination than Further, by correcting the fuel injection amount and the ignition timing according to the determination result thus obtained, it is possible to control the fuel injection amount and the ignition timing suitable for the evaporation characteristics of the fuel in use. As a result, waste of fuel during warm-up operation and deterioration of exhaust gas characteristics can be prevented, and good engine output can be obtained.
[0028]
In this embodiment, step S13 in FIG. 2 corresponds to the indicated mean effective pressure calculating means, steps S14, S15 and S17 in the figure correspond to the characteristic detecting means, and steps S16 and S18 correspond to the correcting means.
[0029]
(Second Embodiment)
In the first embodiment, the reed vapor pressure RVP is determined directly from the indicated mean effective pressure PMI. However, in this embodiment, the fluctuation rate RDPMI of the indicated mean effective pressure PMI is calculated by the process of FIG. The lead vapor pressure RVP is calculated according to the fluctuation rate RDPMI, and the fuel injection amount and the ignition timing are corrected according to the calculated lead vapor pressure RVP. Except for the RVP detection correction process shown in FIG. 3, the process is the same as that of the first embodiment.
[0030]
Steps S21 to S23 and S31 in FIG. 3 are the same processes as steps S11 to S13 and S20 in FIG. 2, respectively.
In step S24, it is determined whether or not the up-counter n set to “0” has become 100 or more when the ignition switch is turned on. Initially, since n <100, the process proceeds to step S25, where the counter n is incremented by 1, then the correction coefficient KVRP is set to 1.0, and the correction term IGRVP is set to 0 (step S26). The process ends. In this way, the detected value of the indicated mean effective pressure PMI is stored in the storage means until n = 100.
[0031]
When n ≧ 100 in step S24, the PMI fluctuation is expressed by the following equation using 100 detected values of the indicated mean effective pressure PMI stored in the storage means (or 100 new detected values when n is greater than 100). A rate RDPMI is calculated (step S27).
RDPMI = σPMI / PMIAVE
[0032]
Here, σPMI is a standard deviation of 100 PMI values, and PMIAVE is an average value of 100 PMI values.
In the subsequent step S28, the RVP table shown in FIG. 4A is retrieved according to the PMI fluctuation rate RDPMI, and the lead vapor pressure RVP of the fuel in use is calculated. The RVP table is set so that the RVP value decreases as the fluctuation rate RDPMI increases. This is because as the reed vapor pressure RVP is lower, the actual air-fuel ratio is shifted in the lean direction, so that the fluctuation rate RDPMI tends to increase.
[0033]
In step S29, the KRVP table shown in FIG. 4B and the IGRVP table shown in FIG. 4C are retrieved according to the lead vapor pressure RVP, and the correction coefficient KRVP and the correction term IGRVP are calculated. The KRVP table is set so that the correction coefficient KRVP decreases as the reed vapor pressure RVP increases, and the IGRVP table is set so that the correction term IGRVP decreases as the reed vapor pressure RVP increases. In each table, when the reed vapor pressure RVP is an average value RVP0 (= 11 psi (pound / square inch)), it is set so as to be an uncorrected value (KRVP = 1.0, IGRVP = 0). Has been. The standard for automotive gasoline in the United States stipulates three grades of grades of lead vapor pressure RVP: a grade lower than 9 psi, a grade lower than 11 psi, and a grade lower than 13 psi. The pressure RVPH is 13 psi.
[0034]
In the subsequent step S30, the correction coefficient KRVP and the learning values KRVPAVE and IGRVPAVE of the correction term IGRVP are calculated by the above equations (3) and (4), and this process ends.
As described above, in the present embodiment, the reed vapor pressure RVP is detected according to the PMI fluctuation rate RDPMI, so that the reed vapor pressure RVP can be obtained with higher accuracy than in the first embodiment. Further, by using this value to correct the fuel injection amount and the ignition timing, finer correction can be made.
[0035]
In this embodiment, step S23 in FIG. 3 corresponds to the indicated mean effective pressure calculating means, steps S27 and S28 in the figure correspond to the characteristic detecting means, and step S29 corresponds to the correcting means.
The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, both the fuel injection amount and the ignition timing are corrected according to the detected lead vapor pressure RVP, but only one of them may be corrected.
[0036]
【The invention's effect】
As described above in detail, according to the first aspect of the present invention, the indicated mean effective pressure is calculated from the detected in-cylinder pressure, and the fuel evaporation characteristics are detected based on the indicated mean effective pressure. Compared with this, the fuel evaporation characteristic can be detected with higher accuracy. Further, since the fuel evaporation characteristic is detected according to the fluctuation rate of the indicated mean effective pressure during the warm-up operation, a highly accurate evaporation characteristic can be obtained.
[0037]
According to the second aspect of the invention, the indicated mean effective pressure is calculated from the detected in-cylinder pressure, the fuel evaporation characteristic is detected based on the indicated mean effective pressure, and the detected evaporation characteristic is determined in accordance with the detected evaporation characteristic. Since at least one of the fuel supply amount and the ignition timing is corrected, the fuel supply amount and / or the ignition timing suitable for the evaporation characteristics of the fuel can be set, and the fuel is wasted, the exhaust gas characteristics are deteriorated, and / or the engine output. Can be prevented. Further, since the fuel evaporation characteristic is detected according to the fluctuation rate of the indicated mean effective pressure during the warm-up operation, a highly accurate evaporation characteristic can be obtained and finer correction can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention.
FIG. 2 is a flowchart (first embodiment) of a process for detecting the lead vapor pressure and performing control according to the detection result;
FIG. 3 is a flowchart (second embodiment) of processing for detecting the lead vapor pressure and performing control according to the detection result;
4 is a diagram showing a table used in the processing of FIG. 3. FIG.
[Explanation of symbols]
1 Internal combustion engine 5 Electronic control unit (shown mean effective pressure calculating means, characteristic detecting means, correcting means)
6 Fuel injection valve 11 In-cylinder pressure sensor (in-cylinder pressure detection means)
29 Spark plug

Claims (2)

In a fuel evaporation characteristic detecting device for detecting an evaporation characteristic of fuel supplied to an internal combustion engine,
In-cylinder pressure detecting means for detecting the in-cylinder pressure of the engine;
An indicated mean effective pressure calculating means for calculating an indicated mean effective pressure from the detected in-cylinder pressure;
Characteristic detecting means for detecting an evaporation characteristic of the fuel based on the indicated mean effective pressure calculated by the indicated mean effective pressure calculating means,
The characteristic detection means calculates a standard deviation and an average value for a predetermined number of data of the indicated mean effective pressure during the warm-up operation of the engine, and divides the standard deviation by the average value to obtain a variation rate. A fuel evaporation characteristic detection device that calculates and detects the fuel evaporation characteristic according to the fluctuation rate. In a control device for controlling the amount of fuel supplied to the internal combustion engine and the ignition timing,
In-cylinder pressure detecting means for detecting the in-cylinder pressure of the engine;
An indicated mean effective pressure calculating means for calculating an indicated mean effective pressure from the detected in-cylinder pressure;
Characteristic detecting means for detecting the evaporation characteristic of the fuel based on the indicated mean effective pressure calculated by the indicated mean effective pressure calculating means;
Correction means for correcting at least one of the fuel amount and the ignition timing in accordance with the fuel evaporation characteristic detected by the characteristic detection means,
The characteristic detection means calculates a standard deviation and an average value for a predetermined number of data of the indicated mean effective pressure during the warm-up operation of the engine, and divides the standard deviation by the average value to obtain a variation rate. A control apparatus for an internal combustion engine, characterized by calculating and detecting an evaporation characteristic of the fuel in accordance with the fluctuation rate.

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