JPH04191450A - Fuel characteristic detecting method for engine - Google Patents

Abstract

PURPOSE:To surely perform detection of fuel volatility without in cutting engine stall by detecting it in a low volatility when a controlling quantity with respect to a control valve which adjusts a bypass air quantity at the idling time if at a specified value or more. CONSTITUTION:A bypass air passage 15 connected to the upper and lower intake passages 8 is formed at an intake passage 8 of an engine body 1 by bypassing a throttle valve 12. A control valve 16 which adjusts a bypass air quantity is interposed at the bypass air passage 15. Opening of the control valve 16 is controlled at the idling time in a controller 20 especially, so that feedback control is performed to converge an engine speed to a target value. In this way an idling speed control means A is formed. In the above constitution, fuel volatility is detected and judged in the controller 20 according to a control signal in the idling speed feedback control. When the controlling quantity with respect to the control valve 16 is at a specified value or more, it is detected that the fuel volatility is in a low condition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine fuel property detection method for detecting a reduced state of fuel volatility.

(Prior art) In recent years, engine fuels, especially gasoline, have become commercially available with low volatility, and when fuels with different fuel properties are supplied to an engine and combusted, various control characteristics have to be adjusted using this type of fuel. It is necessary to make corrections in response to changes in fuel properties.

In other words, when a heavy fuel with low volatility is supplied, the various control characteristics that were previously set for normal fuel will not cause fuel vaporization or fog, especially during cold driving when the engine temperature is low. This results in poor running performance. On the other hand, if the fuel properties are detected and determined based on the volatility of the fuel, the fuel increase during cold operation can be corrected to increase by a predetermined amount based on the detection of the fuel properties. It is possible to improve the

Therefore, in order to detect and judge the fuel properties such as the volatility of the fuel, for example, Japanese Patent Application Laid-Open No. 62-288333,
As seen in the publication, based on the fact that heavy fuel and normal fuel have different combustion speeds, that is, pressure rises during combustion in the cylinder, the fuel properties are detected and determined based on the in-cylinder pressure detected by a pressure sensor. Techniques for this are well known.

Furthermore, since the air-fuel ratio of low-volatility fuel decreases during acceleration, it is also possible to determine the fuel properties by detecting the air-fuel ratio using an air-fuel ratio sensor.

On the other hand, a bypass air passage is provided to bypass the throttle valve of the engine and supply bypass air, and a control valve is installed in the bypass air passage to adjust the amount of bypass air at idle, and the idle rotation is controlled by the control valve. 2. Description of the Related Art Engines are known that are equipped with idle speed control means that feedback controls the number of revolutions to a target value.

(Problem to be Solved by the Invention) However, in the device that detects the volatility of fuel from the cylinder pressure as described above, it is necessary to separately install a pressure sensor for this purpose, which is disadvantageous in terms of cost. be. Also,
If the volatility of the fuel is determined from the change in the air-fuel ratio during acceleration, the detection and determination cannot be made before the vehicle is running, and a reduction in drivability is inevitable until the detection is made.

On the other hand, when trying to determine the volatility of fuel using existing sensors such as engine speed, it is preferable to detect and judge immediately after starting the engine, but in this idle state, the idle speed control means Correction control of the engine speed is performed, and if this is done, it is difficult to detect a decrease in volatility from a change in the engine speed. Then, if the rotation correction by the idle rotation speed control means is stopped and the rotation correction is detected from the rotation speed fluctuations that change due to the influence of volatility, the volatility of fuel with low volatility decreases especially during cold start. This poses a problem in that the rotational speed decreases significantly after starting, leading to the engine stopping. Furthermore, even if the fuel volatility is detected and the fuel correction is performed in response, there is a time delay before the increase correction becomes effective, and during that time the engine speed drops significantly. There is a risk that the engine will stop.

In view of the above-mentioned circumstances, the present invention has been developed to detect engine fuel properties by detecting fuel volatility while normal idle speed control is being executed, thereby making it possible to reliably detect the volatility of the fuel without causing engine stoppage. The purpose is to provide a method.

(Means for Solving the Problems) In order to achieve the above object, a method for detecting fuel properties of an engine according to the present invention provides an idle rotation speed of a control valve interposed in a bypass air passage that bypasses a throttle valve and supplies bypass air. The idling speed is feedback-controlled to a target value under control by the control means, and when the control amount for the control valve becomes larger than a predetermined value, it is detected as a state in which the volatility of the fuel is low. It is.

It is preferable to detect the volatility of the fuel when the engine is cold, immediately after starting the engine. Further, the feedback control of the control valve includes learning correction in which the basic control amount is updated by learning, and when the degree of learning update is small, it is preferable to limit the detection of fuel properties.

(Functions and Effects) In the fuel property detection method as described above, when a low-volatility fuel is supplied while the idle rotation speed is feedback-controlled to the target value by the idle rotation speed control means, the same fuel is supplied. Even if the amount of fuel actually flowing into the cylinder is reduced, the air-fuel ratio becomes lean, and in order to converge the reduced engine speed to the target value, the control valve is opened and the amount of bypass air is increased. Therefore, the feedback control amount of the idle rotation speed control means becomes larger. Then, when the control amount for this control valve becomes larger than a predetermined value, it is detected and determined as a state in which the volatility of the fuel has become low, and this detection is performed while the idle speed control is being executed. It is possible to reliably detect volatility without having to stop the engine due to volatile detection.

Furthermore, if the detection is performed immediately after the engine is started, early detection can be performed, which is good.Furthermore, when the engine is cold, the fuel does not vaporize due to the engine temperature, so the detection accuracy becomes high. On the other hand, if learning control is performed to correct individual differences in control valves in idle rotation speed feedback control, volatility is determined before the learning control has progressed to some extent after the engine has started. And by the control amount including the correction amount due to individual differences? Therefore, if the fuel property is not detected when the learning update degree is small, the detection accuracy will be increased.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is an overall configuration diagram of an engine that implements a fuel property detection method according to an embodiment.

An intake port 4 and an exhaust port 5 are communicated with a combustion chamber 3 formed above the piston 2 of the engine body 1 with a variable volume, and the openings are opened and closed at predetermined timings by an intake valve 6 and an exhaust valve 7. be done.

The intake passage 8 connected to the intake port 4 is equipped with an air flow sensor 11 that detects the amount of intake air from the upstream side, and a throttle valve 12, and the downstream portion of the surge tank 13 is branched into each cylinder. An injector 14 is disposed to inject and supply fuel to the engine.

Further, a bypass air passage 15 is formed in the intake passage 8, which bypasses the throttle valve 12 and connects to the intake passage 8 above and below the intake passage 8, and the amount of bypass air can be controlled by adjusting the opening degree of the bypass air passage 15. A control valve 16 for adjustment is interposed. Further, an ignition plug 17 is disposed facing the combustion chamber 3, and a discharge voltage is applied to the ignition plug 17 via an ignition coil 18 and a distributor 19 to adjust the ignition timing.

A control signal is output from the controller 20 to the control valve 16 of the bypass air passage 15 to control the amount of intake air during idling and other areas.

In particular, during idling, a control signal is output that performs feedback control so that the engine speed converges to a target value by controlling the opening degree of the control valve 16, that is, the amount of bypass air, and these signals perform feedback control of the idling speed. A rotation speed control means A is configured.

The ignition coil 18 also includes a controller 2.
An ignition signal is output from the injector 14.
A control signal is output from the controller 20, and fuel injection control and ignition control are performed according to the operating state.

The controller 20 includes:
A rotation signal that detects the engine rotation speed from the distributor 19, an engine water temperature signal from the water temperature sensor 22, and an idle switch 2 that operates when the throttle valve 12 is fully open.
3, an intake air amount signal from the air flow sensor 11, etc. are inputted respectively.

The controller 2o has a function of detecting and determining the volatility of fuel from a control signal in idle rotation speed feedback control, and further performs correction control of the fuel injection amount based on the detection of a state in which fuel volatility is low. It is something to do. In addition, in the feedback control of the idle rotation speed, the deviation of the basic control amount due to individual differences in the control valve 16, aging of the control system, etc. is corrected to improve the convergence of the correction control. It is also configured to perform learning control that corrects the reference value through learning updates.

Specifically, the fuel properties are determined when the feedback correction amount is a large value of 20% or more in a feedback control state of the idle rotation speed immediately after a cold start. This detection is performed on the condition that the number of learning updates is three or more times.

The reason for determining fuel properties during a cold start is that the difference in fuel volatility is noticeable in low temperature regions, and in high temperature regions, vaporization is accelerated by heating, resulting in a difference in volatility. This is because there is little variation based on this, making it difficult to detect.

The processing of the controller 20 will be explained along the flowcharts of FIGS. 2 to 4.

FIG. 2 shows the idle rotation speed feedback routine, that is, the opening degree control of the control valve 16 of the bypass air passage 15. After the control starts, it is determined in step S1 whether a feedback condition is satisfied. This feedback condition is that the throttle valve 12 is fully open and the engine is in an idling state where the engine speed is below a predetermined value (idle determination speed).

If the determination in step S2 is YES and the idle feedback condition is satisfied, basic control gGB is calculated in step S3. This basic control ff1GB is a control amount corresponding to a target rotation speed set in accordance with water temperature and the like. Next, step S4 is feedback correction 1G.
This feedback correction amount GFB is a correction amount set according to the deviation between the detected actual engine rotation speed and the target rotation speed, and when the detected engine rotation speed is lower than the target rotation speed. The value is set in the positive direction up to the upper limit of 25%, and when the rotation speed is higher than the target rotation speed, the value is set in the negative direction up to the lower limit of 25%.

Then, in step S5, it is determined whether the learning conditions are satisfied. This learning condition is a case where the rotational deviation is small and the engine rotation is stable. When the learning condition is satisfied, it is determined in step S6 whether a learning prohibition flag F, which will be described later, is in the O state. This learning prohibition flag F is set to 1 when learning is completed, and if learning is not completed, the process proceeds to step S7, where the value n of the feedback counter is incremented, and then the cumulative value ΣGFB of the feedback correction amount GFH is Calculation is performed (S8).

Step S10 is for determining whether or not the feedback counter value n has reached a predetermined value 32. When the cumulative number of times of feedback correction amount GFH reaches 32, steps Sll to S13 perform update processing of the learning value GLRN. conduct. The calculation first begins with the feedback correction amount GFB.
The cumulative amount ΣGFB of is divided by n to find the average value ΔGLRN (Sll), and 1/2 of this average value ΔGLRN is added to the previous learned value GLRN (i-1) to obtain the current learned value GLR.
N is updated (512), and the value m of the learning update counter is incremented (S13).

Further, step S14 is for determining whether or not the learning update counter value m has reached a predetermined value of 5. When the learning update is completed five times in one driving, learning is thereafter performed from the point of view of preventing erroneous learning. Since no update is performed, the above step S1
If the determination in step 4 is YES, the learning prohibition flag F is set to 1 in step S15, while if the number of times has not reached 5, the learning prohibition flag F is cleared to 0 in step 81G.

When the learning prohibition flag F is set to 1, the determination in step S6 becomes No, and in step S9 both counter values n and m are reset to 0, and in step S17, the previous learning value G L RN (i- 1) is set as the current learning value GLRN, and no learning update is performed. Note that if the step SIO is NO, the feedback correction amount GF
Step S1 until the cumulative number n of B reaches a predetermined value.
7 and uses the previous learned value G L RN (i-1).

Then, in step S19, the final control ff1G is calculated by adding the basic control amount GB, feedback correction = C, FB, and learned value GLRN, and in step S20, a signal based on the final control iG is output to the control valve 16. It is driven to a predetermined opening degree.

Further, if the idle feedback condition is not satisfied and the determination in step S2 is NO, step S1
g is used to calculate a control amount G corresponding to the opening degree of the control valve 16 according to the operating state.

In idle speed feedback control as described above,
By setting the feedback correction amount GFB, the idle rotation speed is controlled to converge the idle rotation speed to the target rotation speed, and in order to improve the convergence, the deviation of the basic control ff1GB based on individual differences in the control valve 16 is adjusted to the learning value GL.
This is corrected by calculating RN.

Next, the flowchart in FIG. 3 is a fuel volatility determination routine, in which after the control starts, various signals are read in step S21, and in step S22 it is determined whether or not the engine has just been started within a predetermined time after the engine has been started. do. If this determination is YES and the engine has just started, the volatility of the fuel is detected when the engine is cold, so it is determined in step S23 whether or not the engine water temperature is 50° C. or lower.

Then, the determinations in steps S22 and S23 are YES.
At the time of cold start in S, it is determined in step S24 whether the feedback correction amount GFB in the idle rotation speed feedback routine (FIG. 2) exceeds a predetermined value +20%. The fact that the feedback correction amount GFB is large includes a state in which the volatility of the fuel is low, and in step S25, the learning update counter value m is 3.
It is determined whether or not this is the case, and if a certain amount of learning and updating has been performed, it is determined that the volatility of the fuel is low, and the process proceeds to step 82B, where the heavy determination flag H is set to 1. On the other hand, the determination in step S24 or S25 is No.
If the fuel is normal fuel or if the learning update is insufficient, the heavy fuel determination flag H is cleared to 0 in step S27.

Next, FIG. 4 shows a fuel control routine. After the control is started, various signals are input in step S31, and based on these, basic injection ff1Tp is calculated in step S32. This basic injection ff1Tp is a fuel amount corresponding to an intake air filling amount obtained by dividing the intake air amount by the engine speed and multiplying the result by a coefficient.

Then, in step S33, it is determined whether or not the heavy fuel determination flag H is set to 1, and if it is set to 1 and the volatility of the fuel is low, the heavy weight correction amount Cg is set in step S34. While the fuel amount is increased, if it has been reset to 0, the weight correction amount Cg is set to 0 in step S35, and fuel correction based on volatility is not performed.

Step 83B is a warm-up increase correction according to the engine water temperature.
It calculates other correction amounts such as acceleration correction,
The final injection amount T is calculated in step S37 based on the basic injection amount Tp, the heavy weight correction amount Cg1, and other correction amounts, and the result is output to the injector 14 in step S38 to execute fuel injection of a predetermined amount. It is something.

Due to the above-mentioned action, when the feedback correction amount GFB becomes larger than a predetermined value while feedback control of the idle speed is being performed, a state of low fuel volatility is detected, so the engine speed is reduced. In addition to being able to detect without causing large fluctuations and without causing engine stoppage, fuel volatility can be detected after the learning has progressed to a certain extent in response to the learning correction being performed from the average value of the feedback correction amount GFB. This increases detection accuracy.

When low-volatility fuel is supplied, fuel increase correction is performed in a low-volatility region such as when the vehicle is cold to improve driving performance. At that time, even if fuel with low volatility is supplied, as the engine temperature rises, the temperature of the fuel also rises and its volatility increases, and the feedback correction amount GFB becomes a small value and the heavy fuel determination ends. However, the fuel increase correction is also reduced.

In the above embodiment, a decrease in the volatility of the fuel is detected from the magnitude of the feedback correction amount GFB, but since the control amount G also increases in accordance with the decrease in volatility, the magnitude of the control JaG itself is Detection and determination may be performed from the beginning.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an engine implementing a fuel property detection method according to an embodiment of the present invention, and FIGS. 2 to 4 are flowcharts of main parts for explaining processing of a controller. 1...Engine body, 8...Intake passage, 12...Throttle valve, 15...Bypass air passage, 16...Control valve , 20...
...Controller, A...Idle rotation speed control means. Figure 3 Figure 4

Claims (4)

[Claims] (1) A bypass air passage is provided to bypass the throttle valve and supply bypass air, and a control valve is interposed in the bypass air passage to adjust the amount of bypass air during idling,
In an engine equipped with an idle rotation speed control means that performs feedback control of the idle rotation speed to a target value by controlling the control valve, when the control amount for the control valve becomes larger than a predetermined value, it is determined that the volatility of the fuel is low. A method for detecting fuel properties of an engine, characterized in that detection is performed as a state. (2) The method for detecting fuel properties of an engine according to claim 1, characterized in that the fuel properties are detected immediately after the engine is started. (3) The method for detecting fuel properties of an engine according to claim 1 or 2, characterized in that the fuel properties are detected when the engine is cold. (4) The feedback control of the control valve includes a learning correction in which the basic control amount is updated by learning, and when the degree of learning update is small, the detection of fuel properties is limited. Property detection method.