JPH04194348A - Fuel characteristic detecting method of engine - Google Patents

Abstract

PURPOSE:To improve judging accuracy of fuel volatility by detecting variation of factors in relation to a combustion result in a rapid transient condition so as to perform judgment of fuel volatility. CONSTITUTION:Engine rotational speed is detected by a crank angle from a crank angle sensor 22. It is detected whether heavy gasoline is used or not by a control unit 20 based on the condition of a drop in the speed just after starting an engine 1. In the case when the use of heavy gasoline is not confirmed, it is judged whether the heavy gasoline is used or not accurately by judging variating frequency of the rotational speed at the time of rapid acceleration. Consequently, since generation of variation in wall face adhesive quantity of fuel is utilized, judgment of the fuel volatility can be accurately performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine fuel property detection method for examining the volatility of fuel used in the engine.

(Prior art) In addition to regular fuel (regular gasoline), which has relatively good volatility, the fuel used in engines is regular fuel, which contains heavy components such as additives to increase the octane number. Fuel with worse volatility than (heavy gasoline)
There is also. Differences in the volatility of the fuels used result in differences in the amount of fuel adhering to the walls of the intake passage and the like, as well as the degree of vaporization and atomization of the fuel, which affects combustibility. For example, when the engine temperature is low, fuel with poor volatility will cause poor vaporization and the actual air-fuel ratio will become the same, and during acceleration, fuel with poor volatility will worsen acceleration response.

Conventionally, as a technique for correcting the influence of the volatility of the fuel used, for example, as shown in Japanese Patent Application Laid-Open No. 62-288335, there has been a technique equipped with a property detection means for detecting the degree of volatility of the fuel used. Based on the detection by this detection means, the correction amount for increasing the fuel injection amount according to the water temperature is adjusted according to the volatility of the fuel, and the acceleration increase of the fuel is further adjusted according to the volatility of the fuel. It has been known. As a method for detecting the properties of the fuel, for example, as shown in the above publication, the combustion rate is checked by detecting the cylinder pressure during combustion during a predetermined steady state of operation, and
There are known methods that examine volatility by comparing this burning rate with a reference value.

[Problem to be solved by the invention]

According to conventional fuel property detection methods, the accuracy of volatile detection was not sufficient. That is, in a method of checking the combustion rate based on detection of the cylinder pressure during combustion in a steady state of operation, for example, 1!
! When the phosphorus state is adjusted, there is not a sufficient difference in combustion speed between regular gasoline and heavy gasoline, and detection accuracy tends to decrease due to confusion with variations in combustion speed due to disturbances, etc. Note that it is possible to determine the volatility of the fuel from the response delay of the air-fuel ratio under accelerated driving conditions, but under moderate acceleration, even heavy gasoline with poor volatility will not increase the amount of intake air. Therefore, there is a possibility that there will not be a sufficient difference in the response delay of the air-fuel ratio between regular gasoline and heavy gasoline.

In view of these circumstances, the present invention improves the accuracy of determining the volatility of fuel, and in particular, makes it possible to accurately determine volatility by taking advantage of changes in the fuel wall adhesion layer during sudden transients. A method for detecting engine fuel properties is provided.

[Means to solve the problem]

The present invention is an engine fuel property detection method that determines the volatility of fuel based on the determination of combustion results. Fluctuations in elements related to combustion results are detected, and fuel volatility is determined based on this detection.

In this configuration, the element related to the combustion result whose fluctuation is detected when a sudden transient state occurs is, for example, the engine speed.

[Effect]

According to the method of the present invention as described above, the fuel phase on the wall surface of the intake passage changes with sudden changes in the fuel supply amount such as during sudden acceleration or sudden deceleration, and this fuel adhesion changes. During sudden transients where the amount depends on the degree of volatility of the fuel,
Based on the detection of fluctuations in elements related to the fuel results such as the engine speed, the differences in the fluctuations in the engine speed and other factors due to the amount of fuel adhering to the wall surface are investigated to ensure accurate volatilization. A determination of sex is made.

(Example) Embodiments of the present invention will be described based on the drawings.

FIG. 1 schematically shows an apparatus used in an embodiment of the method of the present invention. In this figure, an engine 1 has a combustion chamber 3 formed above the piston 2 of each cylinder, an intake port 4 and an exhaust port 5 that open into the combustion chamber 3, and each port 4.5. It is equipped with an intake valve 6 and an exhaust valve 7 that open and close, a spark plug 8 facing the combustion chamber 5, and the like.

An intake passage 10 communicating with the intake port 4 and an exhaust passage 11 communicating with the exhaust port 5 are connected to this engine 1.

The intake passage 10 is provided with an air flow meter 12 that detects the intake air amount, a throttle valve 13 that adjusts the intake air amount in response to accelerator operation, an injector 14 that injects fuel, and the like.

Further, a distributor 15 and an ignition coil 16 are electrically connected to the spark plug 8, and these constitute an ignition device.

The injector 14 and the ignition device are connected to a control unit (EC120) consisting of a microcomputer, etc.
controlled by A throttle opening sensor 2 that detects the opening of the throttle valve 13 (throttle opening) is used as an input element for controlling the fuel injection trowel and ignition timing and detecting fuel properties for the control unit 20.
1. A crank angle sensor 22 that is installed in the distributor 15 and detects the crank angle for detecting engine rotation speed, etc., and a water temperature sensor 23 that detects the temperature of engine cooling water are provided, and these sensors 21 to 23 and the above air flow A signal from the meter 12 is input to a control unit 20. Furthermore, signal 24 from the ignition switch, range determination signal 25 for vehicles equipped with an automatic transmission <AT vehicles), and clutch off signal for vehicles equipped with a manual transmission (MT vehicles). Alternatively, a neutral state detection signal 26 or the like is also input to the control unit 20. The control unit 20 outputs a 4-pulse signal to the injector 14 and an ignition signal to the ignition coil 16.

The control unit 20, based on various signals,
It controls the fuel injection amount and ignition timing according to the operating conditions, but it also detects fuel properties to determine the volatility of the fuel, and corrects the fuel injection amount based on this. There is.

Fuel property detection involves checking for sudden transient conditions in which the engine load changes rapidly, detecting fluctuations in elements related to combustion results when the sudden transient condition occurs, and based on this detection, determining the volatility of the fuel. Make a judgment. In the example shown in the flowchart described below, engine speed is examined as an element related to combustion results, and volatility is determined by first determining whether the gasoline is heavy based on the drop in engine speed immediately after starting the engine. If it is not confirmed that it is heavy gasoline, the degree of variation in rotational speed during sudden acceleration is checked to accurately determine whether it is heavy gasoline.

To roughly explain the method of this embodiment based on the time charts of FIGS. 2 and 3, first, at the time of starting, as shown in FIG. The number of revolutions settles down to idle (however, in the case of heavy gasoline, vaporization is poor, so the number of revolutions tends to drop after the number of revolutions rises. Therefore, for example,
to the third reference rotation speed N1. Set N2, Ns (No
＞Nl ＞N2 ＞N3 ) Set aside, N1~N
If the engine speed drops rapidly in the range 2 (dotted line A)
) or when the engine speed significantly drops below the third reference speed N3 (broken line 8), it is determined that the gasoline is heavy gasoline. On the other hand, if there is no such rapid or large drop in engine speed (Actual 11C), it is not determined to be heavy gasoline, but even in this case, if feedback control of idle speed is being performed, Another possibility is that although the drop in rotational speed is suppressed by lateral control, the fuel is heavy gasoline.

Therefore, with the judgment of the above starting imitation! ! If heavy gasoline is not determined, for a more accurate determination, as shown in Figure 3, check the sudden acceleration state where the rate of change in throttle opening is large, and check the rotation during AT for a certain period of time after the sudden acceleration state. Check the amount of change in number ΔN.

In this case, if it is heavy gasoline, it will be used during sudden acceleration! Since surface adhesion increases and the amount of fuel supplied to the combustion chamber decreases, the rate of increase in rotational speed becomes smaller (broken line E) compared to when regular gasoline is used (solid line D). This tendency is used to distinguish between regular gasoline and heavy gasoline.

Such determination and corresponding control will be specifically explained with reference to the flowcharts of FIGS. 4 and 5.

FIG. 4 shows a routine for determining fuel properties.

This routine starts in response to engine startup, and first, in step S1, initialization is performed, such as temporarily setting the late heavy fuel determination flag FQ to "O", and the time required to reach a stable state after startup is performed. Predetermined time 111
Set x to the timer. Next, in step S2, throttle opening TVO1 water! ! T.W.

At the same time as reading the range signal and the engine rotation speed NE etc. found by measuring the period of the crank angle, step S
In step S3, the timer is counted down, and in step S4, the value of the timer is checked to determine whether or not a predetermined time has elapsed since the start of the engine.

If it is within the predetermined time Ix, it is checked in step S5 whether the water temperature TW is less than or equal to a predetermined m degree TWa (for example, 50'C>), and if the determination is YES, the neutral state (automatic transmission If so, check whether it is in N range or D range).The reason why the water temperature is checked in step S5 above is because the difference in vaporization between regular gasoline and heavy gasoline is more likely to occur when the engine is low temperature. Yes, and the reason why the neutral state is checked in step S6 is that it is easier to check rotational fluctuations due to the quality of combustion in this state.If the determination is NO in either step 85 or Ss, step S2 Return to and repeat the following steps.

When each determination in steps 84 to S6 is YES, in step S7, the engine rotation speed after starting is set to a predetermined rotation speed N for determining completion of cranking.

It is determined whether or not the value has exceeded -1. If this judgment is NO, the process returns to step S2, but after the judgment is YES, as a heavy judgment process, in step S8, the engine speed decrease of N1 to N2 occurs within a constant and relatively short time l1y (seconds). If the determination is No, step S9
Then, it is checked whether the engine speed has decreased to below the third reference speed N3 (see FIG. 2). When the determination is YES in either step Ss or 89, the routine moves to step S10 and the heavy determination flag Fa is set to "1" before ending this routine.
If o, the process returns to step S2 and the subsequent processes are repeated.

When it is determined in step S4 that the predetermined time X has elapsed since the start of the engine, step S is performed.

After the engine start is completed, the process moves on to a process of determining whether the vehicle is heavy during sudden acceleration. On Mamio's side, first of all, as a reference condition for determining heavy weight, in engines where idle speed control is performed by feedback control of ignition timing, the tendency for combustibility to deteriorate during idling is compensated for by feedback control of ignition timing. In order to check whether this is the case, it is determined in step S11 whether or not the ignition timing feedback control value is a guard value. When this judgment is YES, - throttle opening change rate Δ〒
It is checked whether a sudden acceleration state in which VO exceeds a set value α has occurred. In this case, the set value α is set to a relatively large value so as to determine a state of rapid acceleration that causes a sufficient difference in the amount of wall surface adhesion between regular gasoline and heavy gasoline. If the determination in step St2 is YES, it is further checked in step St3 whether or not the throttle opening TVO has been at or above the predetermined opening TVOa for a predetermined period of time after the rapid acceleration described above.

If the determination is NO in any of the above steps S n to S13, the process returns to step S2, but if the heavy condition is satisfied that all of the determinations in steps S n to So are YES, the engine rotation during a certain period of time is The number fluctuation amount ΔN (see FIG. 3) is compared with a reference value for weight determination. For this comparison, in the case of driving range and non-driving range in AT cars equipped with automatic transmission, MT cars equipped with manual transmission
Since the degree of increase in rotational speed during acceleration is different between the gear-in state and the gear-off state in I, Mashio sets a reference value for heavy weight determination depending on each case. In other words, if we compare the ease with which the number of revolutions is around 1 in each of the above cases, assuming that the fuel used and the acceleration conditions are the same, we can see that due to the load applied to the engine from the transmission, it is easier to do it when the gear is off (neutral or clutch off) in a manual transmission car. The rotational speed increases most easily, followed by the non-driving range of AT cars (N range or P range), the driving range of AT cars (D range, etc.), and the gear-in range of MT cars, so please take care of these. The reference value ΔN1. ΔN2. ΔN3° and ΔN4 are set.

Then, it is determined whether the vehicle is an MT vehicle (step 514), and the M
Determination of whether gear is in or not for T vehicle (step 81+)
, based on the determination of whether or not it is in the driving range for an AT vehicle (step 516), step S17. S Yu, S Fl, 8
20, the upper engine rotational speed fluctuation position ΔN fluctuation amount is compared with one of the respective standards -N1 to N4.

If it is determined in any step 5v-820 that the engine speed fluctuation amount ΔN is less than the reference value, the process moves to step 511), sets the heavy weight determination flag Fg to "1", and then ends this routine. - On the other hand, when it is determined that the engine speed fluctuation amount ΔN is larger than the reference value, the heavy weight determination flag Fo is set to "0" in step 321, and then this routine is ended.

FIG. 5 shows a routine for fuel injection amount control. When this routine starts, various signals such as intake air amount Qa and engine speed NE are read in step S31, and the basic injection amount Tp is set to [Tp-Kx
Qa/NE] (K is a conversion coefficient). Next, in step S33, it is checked whether the heavy weight determination flag Fg is "1" or not, and if the determination is YES, in step S34, the heavy weight correction amount CQ is set to a predetermined value depending on the water temperature, etc. death,
If the determination in step S33 is No, step S35
The weight correction amount CQ is set to "O".

Next, in step S36, other correction amounts (for example, warm-up increase, etc.) C are determined, and in step S37, the basic injection amount Tp, the heavy weight correction amount Cg, other correction amounts C, and the battery voltage are determined. Based on the invalid injection time TV, the final injection amount T is calculated as T-Tpx (1+CQ+C)+Tv. Then, in step S36, the final injection amount T
After outputting an injection pulse according to the amount to the injector 14, the process returns.

According to the above-mentioned method, the drop in rotational speed is first investigated immediately after starting the engine under predetermined conditions.
It is determined that the gasoline is heavy when there is a noticeable drop in rotational speed due to deterioration in combustion conditions. In addition, if such a noticeable drop in rotational speed immediately after startup is not confirmed, it may be compensated for by ignition timing control, etc. as mentioned above, and it cannot be determined that it is not necessarily heavy gasoline. After that, a determination is made regarding sudden acceleration, which is a feature of the present invention. In other words, during sudden acceleration, when heavy gasoline is used, most of the increased fuel adheres to the wall surface, and the rate of increase in engine speed tends to be lower than when regular gasoline is used. When the conditions from Steps 811 to S are satisfied, the rotational speed fluctuation amount ΔN is compared with a reference value to determine whether the gasoline is heavy, thereby accurately determining whether it is heavy gasoline or regular gasoline. In this determination, step S%~
If the reference value is set according to the difference between an AT car and an MT car and the state of the transmission as in S20, heavy gasoline and regular gasoline can be discriminated more accurately by -1.

In addition, in the above example, volatile determination (heavy determination) is performed during sudden acceleration, but the amount of fuel adhering to the wall changes even during sudden deceleration when the throttle opening decreases rapidly, and the amount of fuel adhering to the wall changes. Since the degree of gasoline is different between heavy gasoline and regular gasoline, and this causes a difference in changes in engine speed, etc., volatility may be determined during sudden deceleration.

In addition, although it is possible to determine volatility only by determining when a sudden transition occurs, it is possible to do so by first making a determination at startup as in the above example, and then determining when a sudden transition occurs when it is uncertain. It is possible to identify heavy gasoline at an early stage within a certain range, and to make an accurate determination.

〔Effect of the invention〕

As described above, the present invention detects fluctuations in elements that cause erroneous combustion results when the engine load suddenly changes and enters a sudden transient state, for example, detects fluctuations in engine speed, and Because fuel volatility is judged based on this, during sudden transients, there is a large difference in the amount of fuel adhering to the wall between fuel with good volatility and fuel with poor volatility, resulting in fluctuations in factors related to combustion results. It is possible to accurately determine the volatility of a fuel by taking advantage of the fact that there is a significant difference between the two.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a device used in the method of one embodiment of the present invention, Fig. 2 is a time chart showing changes in engine speed during startup, and Fig. 3 is a time chart showing changes in engine speed during sudden acceleration. The charts, FIGS. 4 and 5 are flowcharts showing specific examples of volatility determination and fuel injection amount control based on the determination. DESCRIPTION OF SYMBOLS 1... Engine, 1o... Intake passage, 14... Injector, 20... Control unit, 21...
...Throttle opening sensor. Patent applicant Mazda Co., Ltd. Agent
Person Patent Attorney Etsushi Kotani Figure 2 Figure 3 Figure 5

Claims (1)

[Claims] 1. An engine fuel property detection method that determines the volatility of fuel based on the determination of combustion results, wherein the engine load is in a sudden transient state where the engine load suddenly changes by an amount of change greater than a set amount of change. 1. A method for detecting fuel properties of an engine, the method comprising: detecting fluctuations in elements related to combustion results when a sudden transient state occurs; and determining volatility of fuel based on this detection. 2. The engine fuel property detection method according to claim 1, wherein the element related to the combustion result whose fluctuation is detected when a sudden transient state occurs is the engine rotational speed.