JP2000356163A - Fuel evaporation characteristic detecting device and control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely detect the evaporation characteristic of the fuel under use by calculating a shown average effective pressure from a detected cylinder internal pressure, and detecting the evaporation characteristic of the fuel on the basis of the shown average effective pressure. SOLUTION: It is judged whether an engine is under warming operation or not (S11), and when the warming operation is judged, a cylinder internal pressure PCLY detected by a cylinder internal pressure sensor is read (S12), and a shown average effective pressure PMI is calculated from the cylinder internal pressure PCLY (S13). It is judged whether the calculated shown average effective pressure PMI is higher than a prescribed pressure PMIB or not (S14). When PMI is higher than PMIB or lower than PMIB, it is judged that the fuel has a high or low Reid vapor pressure RVP showing the evaporation characteristic of fuel (S15, S17), correction coefficient KRVP is set to a prescribed KRVP 1 or KRVP 2 smaller than or larger than 1, and correction term IGRP is set to a negative or a positive prescribed value IGRVP 1 or IGRVP 2 (S16, S18). According to this, the fuel feed quantity is increasingly or decreasingly corrected to correct the ignition timing in the delay or advance direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel evaporation characteristic detecting device for detecting fuel evaporation characteristics of an internal combustion engine and a control device for controlling the internal combustion engine in accordance with the detected evaporation characteristics.

[0002]

2. Description of the Related Art A reed vapor pressure measured at an air temperature of 37.8 ° C. when a ratio of a fuel amount in a gaseous state to a fuel amount in a liquid state is 4: 1 is a parameter representing a fuel evaporation characteristic of an internal combustion engine. (Reid Vaper Pressure) is known.

The air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is controlled by controlling the amount of fuel supplied in accordance with the operating state of the engine. However, even if the amount of fuel injected into the intake pipe is the same, The actual air-fuel ratio changes due to the evaporation characteristics of the air-fuel ratio. Therefore, it is desired to detect the evaporation characteristic of the fuel used during the engine operation, particularly during the warm-up operation. As a method for this, 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 is compared with a reference value. A method for determining the level of the Reid vapor pressure is known.

[0004]

However, in the above-mentioned conventional method, since the determination is made from the exhaust gas, the accuracy of the determination is low, and the method cannot be used for controlling the air-fuel ratio of the engine. The present invention has been made in view of this point, and a fuel evaporation characteristic detecting device capable of accurately detecting the evaporation characteristic of a fuel in use and a more appropriate operation of the internal combustion engine according to the detected evaporation characteristic. It is an object of the present invention to provide a control device capable of controlling the speed of the vehicle.

[0005]

According to a first aspect of the present invention, there is provided a fuel evaporation characteristic detecting apparatus for detecting an evaporation characteristic of fuel supplied to an internal combustion engine. An in-cylinder pressure detecting means for detecting, an indicated average effective pressure calculating means for calculating an indicated average effective pressure from the detected in-cylinder pressure, and a fuel pressure based on the indicated average effective pressure calculated by the indicated mean effective pressure calculating means. Characteristic detecting means for detecting the evaporation characteristic.

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. Can be detected.

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.
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; and an indicated mean effective pressure calculated by the indicated mean effective pressure calculating means Characteristic detecting means for detecting an evaporation characteristic of the fuel based on the characteristic of the fuel, and correcting means for correcting at least one of the fuel supply amount and the ignition timing in accordance with the evaporation characteristic of the fuel detected by the characteristic detecting means. It is characterized by the following.

According to this configuration, the indicated average effective pressure is calculated from the detected in-cylinder pressure, the fuel evaporation characteristic is detected based on the indicated average effective pressure, and the fuel supply amount is determined according to the detected evaporation characteristic. And / or the ignition timing is corrected, so that the fuel supply amount and / or
Alternatively, the ignition timing can be set, and waste of fuel, deterioration of exhaust gas characteristics, and / or reduction of engine output can be prevented.

[0009]

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 a control device thereof, including a fuel evaporation characteristic detection device according to a first embodiment of the present invention. A throttle valve 3 is arranged in the intake pipe 2 of the four-cylinder engine 1. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3, and outputs an electric signal corresponding to the opening of the throttle valve 3 to output an electronic control unit for engine control (hereinafter referred to as “EC”).
U ") 5.

A fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of an intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). The ECU 5 is electrically connected to the ECU 5 and controls a valve opening time of the fuel injection valve 6 based on a signal from the ECU 5.

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 mounted downstream thereof, detects the intake air temperature TA, outputs a corresponding electric signal, and supplies the electric signal to the ECU 5.

The 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 for detecting 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 outputs a signal pulse (hereinafter referred to as a “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 an intake stroke of each cylinder. ) At a crank angle position before a predetermined crank angle (for a four-cylinder engine, the crank angle is 180 °).
A TDC sensor that outputs a TDC signal pulse (for each degree) and a CRK sensor that generates one pulse (hereinafter referred to as “CRK signal pulse”) at a constant crank angle cycle (for example, a cycle of 1 to 30 degrees) shorter than the TDC signal pulse, CYL
The signal pulse, the TDC signal pulse, and the CRK signal pulse are supplied to the ECU 5. These signal pulses are used for various timing controls such as fuel injection timing, ignition timing, and the like, and detection of the engine speed NE.

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. The detection signal is sent to the ECU 5 via a charge amplifier 12 having an amplification and integration function. Supplied.
The output of the in-cylinder pressure sensor 11 is the rate of change of the in-cylinder pressure (differential value).
, And by integrating this, the in-cylinder pressure P
CYL is obtained.

A spark plug 20 provided for each cylinder of the engine 1 is connected to the ECU 5 and its operation is controlled by an EC.
Controlled by U5. The exhaust pipe 13 is provided with a three-way catalyst 16 for purifying exhaust gas.
Upstream of the proportional air-fuel ratio sensor 14 (hereinafter referred to as “LA
F sensor 14 "). This LAF
The sensor 14 outputs an electric signal substantially proportional to the oxygen concentration (air-fuel ratio) in the exhaust gas, and supplies the electric signal to the ECU 5.

The ECU 5 has an input circuit 5a having functions of shaping input signal waveforms from various sensors, correcting a voltage level to a predetermined level, converting an analog signal value to a digital signal value, and a central processing circuit ( 5b, various arithmetic programs executed by the CPU 5b, tables and maps used in the arithmetic programs,
Storage means 5c for storing calculation results and the like; an output circuit 5 for supplying drive signals to the fuel injection valve 6, the ignition plug 20 and the like
d, etc.

The CPU 5b determines various engine operating states based on the various engine parameter signals described above, and according to the determined engine operating states,
Based on the following equation (1), a fuel injection time TOUT of the fuel injection valve 6 that operates to open in synchronization with the TDC signal pulse is calculated. TOUT = TI × KRVP × KCMD × KLAF × K1 + K2 (1) Here, TI is a basic fuel injection time of the fuel injection valve 6, and is a TI map set according to the engine speed NE and the intake pipe absolute pressure PBA. Determined by searching. TI
The map is set such that the air-fuel ratio of the air-fuel mixture supplied to the engine substantially becomes 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.

KRVP is a fuel characteristic correction coefficient which is determined according to the determination result of the determination of the level of the Reid vapor pressure RVP during the warm-up operation of the engine 1. KCMD
Is a target air-fuel ratio coefficient, which is set according to engine operating parameters such as the engine speed NE, the intake pipe absolute pressure PBA, and the engine coolant temperature TW. 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 at the stoichiometric air-fuel ratio.

The detected equivalent ratio KACT calculated from the detected value of the LAF sensor 14 is equal to the target equivalent ratio KCMD.
Is an air-fuel ratio correction coefficient calculated by PID control so as to coincide with K1 and K2 are other correction coefficients and correction variables calculated according to various engine parameter signals, respectively, and are predetermined values that can optimize various characteristics such as a fuel consumption characteristic and an engine acceleration characteristic according to an engine operating state. Is determined.

The CPU 5b further calculates an ignition timing IG according to 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 in accordance with the engine speed NE and the intake pipe absolute pressure PBA, and IGRVP is the reed steam pressure RVP. This is a correction term set according to the height.

The CPU 5b supplies a drive signal for opening the fuel injection valve 6 to the fuel injection valve 6 based on the fuel injection time TOUT obtained as described above, and drives the ignition plug 20 based on the ignition timing IG. Is supplied to the ignition plug 20.

FIG. 2 shows the detection of the reed vapor pressure RVP and the fuel injection time TOU according to the detected reed vapor pressure RVP.
Correction coefficient KRVP for T and correction term IGR for ignition timing IG
9 is a flowchart of a process for calculating VP, which is executed by the CPU 5b at regular intervals or in synchronization with the generation of a TDC signal pulse.

In step S11, it is determined whether or not the engine 1 is being warmed up. If not, the correction coefficient KRVP is set to 1.0 and the correction term IGRV is set.
P is set to 0 (step S20), and the process ends. During the warm-up operation, the in-cylinder pressure PCYL detected by the in-cylinder pressure sensor 11 is read (step S1).
2) Calculate the indicated mean effective pressure PMI from the in-cylinder pressure PCYL (step S13). Specifically, the cylinder pressure PCYL
Is integrated at every predetermined crank angle (for example, 1 degree) during the compression stroke and the explosion stroke of the cylinder, and the indicated mean effective pressure PMI is calculated according to the integrated value thus obtained.

Next, it is determined whether or not the calculated indicated mean effective pressure PMI is higher than a predetermined pressure PMIB (step S1).
4), when PMI> PMIB, Reid vapor pressure R
It is determined that the fuel has a high VP (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 I.
It is set to GRVP1 (step S16). As a result, the fuel supply amount is reduced and the ignition timing IG is corrected in the retard direction.

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), and the correction coefficient KRVP is set to a predetermined coefficient value KRVP2 larger than 1 and the correction is performed. The term IGRVP is set to a predetermined positive value IGRVP2 (step S18). As a result, the fuel supply amount is increased and the ignition timing IG is corrected in the advance direction.

The predetermined pressure PMIB is set to the indicated average effective pressure PMI corresponding to the fuel having the average Reid vapor pressure. In a succeeding step S19, a learning value KRVPAVE of the correction coefficient KRVP and a learning value IGR of the correction term IGRVP are obtained.
VP is calculated by the following equations (3) and (4). KRVPAVE = A * KRVP + (1-A) * KRVPAVE (3) IGRVPAVE = A * IGRVP + (1-A) * IGRVPAVE (4)

Here, KRVPAVE and IGR on the right side
VPAVE is a previous value of the learning value, and A is a smoothing coefficient set to a value between 0 and 1. Learning value KRVP
AVE and IGRVPAVE are backup R that retains the stored contents even when the ignition switch is turned off.
It is stored in AM and is used as an initial value at the start of the next warm-up operation.

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. Therefore, it is possible to make a more accurate determination than in the past. Further, by correcting the fuel injection amount and the ignition timing according to the determination result obtained in this way, 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,
It is possible to prevent waste of fuel and deterioration of exhaust gas characteristics during the warm-up operation, and obtain a good engine output.

In the present embodiment, step S13 in FIG. 2 corresponds to the indicated mean effective pressure calculating means, and step S1 in FIG.
4, S15 and S17 correspond to the characteristic detecting means, and steps S16 and S18 correspond to the correcting means.

(Second Embodiment) In the first embodiment,
Reed vapor pressure RVP directly from indicated mean effective pressure PMI
However, in the present embodiment, the fluctuation rate RDPMI of the indicated mean effective pressure PMI is calculated by the processing in FIG.
The reed vapor pressure RVP is calculated according to the I variation rate RDPMI, and the fuel injection amount and the ignition timing are corrected according to the calculated reed vapor pressure RVP. FIG.
Are the same as those of the first embodiment except for the RVP detection correction processing shown in FIG.

Steps S21 to S23 and S31 in FIG. 3 are the same processes as steps S11 to S13 and S20 in FIG. 2, respectively. Step S24
Then, when the ignition switch is turned on, "0"
It is determined whether or not the up counter n set to is equal to or greater than 100. At first, since n <100,
Proceeding to step S25, the counter n is incremented by one, then the correction coefficient KVRP is set to 1.0, the correction term IGRVP is set to 0 (step S26), and 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.

If n ≧ 100 in step S 24, 100 detected values of the indicated mean effective pressure PMI stored in the storage means (if n is greater than 100, a new 100
PMI fluctuation rate RDP using the following equation
The MI is calculated (step S27). RDPMI = σPMI / PMIAVE

Here, σPMI is a standard deviation of 100 PMI values, and PMIAVE is an average value of 100 PMI values. In the following step S28, the RVP table shown in FIG. 4A is searched 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,
This is because the lower the Reid vapor pressure RVP, the more the actual air-fuel ratio shifts in the lean direction, so that the fluctuation rate RDPMI tends to increase.

In step S29, the Reid vapor pressure RVP
The KRVP table shown in FIG. 4B and the IGRVP table shown in FIG.
The RVP and the correction term IGRVP are calculated. The KRVP table shows that the correction coefficient K increases as the Reid vapor pressure RVP increases.
RVP is set to decrease, and the IGRVP table indicates that the correction term I increases as the reed vapor pressure RVP increases.
GRVP is set to decrease. In each table, the Reid vapor pressure RVP is an average value RVP.
When it is 0 (= 11 psi (pound / square inch)), it is set to be the uncorrected value (KRVP = 1.0, IGRVP = 0). The automotive gasoline standard in the United States defines three grades of Reid 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.

In the following step S30, the above equation (3)
The learning value KRVPAVE and IGRVPAVE of the correction coefficient KRVP and the correction term IGRVP are calculated according to (4), and this processing ends. As described above, in the present embodiment,
Since the Reid vapor pressure RVP is detected according to the PMI fluctuation rate RDPMI, it is possible to obtain a more accurate Reid vapor pressure RVP than in the first embodiment. Further, by correcting the fuel injection amount and the ignition timing using these values, more precise correction can be performed.

In this embodiment, step S23 in FIG. 3 corresponds to the indicated mean effective pressure calculating means, and step S2 in FIG.
Steps S7 and S28 correspond to the characteristic detecting means.
Corresponds to the correction means. Note that the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above-described embodiment, the detected Reid vapor pressure RVP
The fuel injection amount and ignition timing were both corrected according to
Only one of them may be corrected.

[0036]

As described above in detail, according to the first aspect of the invention, 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 characteristics can be detected with higher accuracy than in the past.

According to the second aspect of the invention, 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. At least one of the fuel supply amount and the ignition timing is corrected according to the fuel supply amount and / or the ignition timing suitable for the evaporation characteristics of the fuel. Alternatively, a decrease in engine output can be prevented.

[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 processing for detecting a Reid vapor pressure and performing control in accordance with the detection result.

FIG. 3 is a flowchart (second embodiment) of processing for detecting a Reid vapor pressure and performing control in accordance with the detection result.

FIG. 4 is a diagram showing a table used in the processing of FIG. 3;

[Explanation of symbols]

Reference Signs List 1 internal combustion engine 5 electronic control unit (illustrated average effective pressure calculating means, characteristic detecting means, correcting means) 6 fuel injection valve 11 in-cylinder pressure sensor (in-cylinder pressure detecting means) 29 spark plug

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02D 43/00 301 F02D 43/00 301J F02P 5/15 G01M 15/00 Z G01M 15/00 F02P 5/15 EB F Terms (reference) 2G087 AA26 BB13 CC11 CC28 DD13 FF07 3G022 BA01 CA02 DA02 GA00 GA01 GA02 GA05 GA07 GA09 GA12 3G084 BA15 BA17 CA02 DA01 DA04 DA10 EB09 EB15 FA11 FA14 FA20 FA21 FA26 FA29 FA33 FA38 FA39 3G301 HA01 NA01 NA01 NA01 NA01 NA01 LA NA09 NB02 NB06 NC02 ND25 NE01 NE06 PA07Z PA10Z PA11Z PB00Z PB02Z PC01Z PC02Z PD04Z PE01Z PE04Z PE05Z PE08Z

Claims (2)

[Claims] 1. A fuel evaporation characteristic detecting device for detecting an evaporation characteristic of fuel supplied to an internal combustion engine, comprising: an in-cylinder pressure detecting means for detecting an in-cylinder pressure of the engine; A fuel evaporating characteristic comprising: an indicated mean effective pressure calculating means for calculating; and a characteristic detecting means for detecting a fuel evaporation characteristic based on the indicated mean effective pressure calculated by the figure mean effective pressure calculating means. Detection device. 2. A control device for controlling an amount of fuel supplied to an internal combustion engine and an ignition timing, comprising: an in-cylinder pressure detecting means for detecting an in-cylinder pressure of the engine; and a diagram for calculating an indicated average effective pressure from the detected in-cylinder pressure. Average effective pressure calculating means, characteristic detecting means for detecting the evaporation characteristic of the fuel based on the indicated average effective pressure calculated by the figure average effective pressure calculating means, and evaporation of the fuel detected by the characteristic detecting means A control unit for correcting at least one of the fuel amount and the ignition timing according to the characteristic.