JPS60204946A - Fuel cut control method for gasoline engine - Google Patents

Abstract

PURPOSE:To simply suppress knocking and prevent an abnormal rise of the exhaust temperature by changing the predetermined maximum delay angle quantity to the larger maximum delay angle quantity and also cutting the fuel feed under a specific condition. CONSTITUTION:The ignition timing of a gasoline engine is controlled with the predetermined maximum delay angle quantity as the upper limit (P1) using the fuel with a predetermined octane value. When the octane value is low (P0), the predetermined maximum delay angle quantity is changed to the larger maximum delay angle quantity (P2). When the rotation speed (P3) and load (P4) of the engine become predetermined values or higher, the fuel feed to the gasoline engine is cut (P5). Accordingly, knocking can be suppressed by using the fuel with different octane values, and an ill effect due to the exhaust temperature rise can be preveted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a fuel cut control method for a gasoline engine that cuts the fuel supply to the gasoline engine when the fuel supply to the gasoline engine is inappropriate.

[Prior Art] Conventionally, in order to suppress the occurrence of knocking, methods of retarding the ignition timing and methods of using a fuel with a low octane number as a fuel for a gasoline engine are known. Although this method of retarding the ignition timing suppresses the occurrence of knocking, there is a possibility of so-called overheating due to the rise in exhaust gas temperature.

Therefore, a method is widely used in which the maximum retardation amount of ignition timing that is allowable for the octane number of the fuel used in a gasoline engine is set as an upper limit, and the ignition timing is controlled within this maximum retardation m.

However, the fuel supplied to gasoline engines does not have a specific octane rating, and various types of high and low octane are used. Moco.

Therefore, it is necessary to always refuel a vehicle with a certain type of fuel, but since there are not many high-octane fuels on the market, it is important to stop using low-octane fuel in high-octane vehicles. It is often used incorrectly or incorrectly. Even in this case, if the maximum retardation amount is set for high octane when controlling the ignition timing, the gasoline engine may be operated under conditions where knocking occurs frequently, which may cause damage to the gasoline engine. Become.

As a method to more easily solve the above problem, the inventor proposed a method in which the maximum retardation amount of the ignition timing is set to two types, one for high octane number and one for low octane number, and the maximum retardation amount is switched depending on the octane number of the fuel used. devised.

With this method, the occurrence of knocking can be controlled by simple processing without requiring a large storage wA area in the control system.

However, considering more severe conditions, there is a control method that uses this control method to further improve the operational performance of the gasoline engine and that does not cause overheating due to the rise in exhaust temperature even during long-term operation under any adverse conditions. This had become an issue.

[Purpose of the Invention] The present invention was completed as a result of the inventor's constant research in view of the above points, and it is possible to easily suppress knocking in gasoline engines that use fuels with different octane numbers, and to reduce emissions. The purpose of this project is to provide a fuel control method for gasoline engines that prevents the harmful effects of rising temperatures.

[Structure of the Invention] As shown in the first basic configuration diagram, the structure of the present invention for achieving the above object is to retard the ignition timing by a predetermined maximum amount in order to operate a gasoline engine with fuel of a predetermined octane number. The ignition timing is set to 1.1 Itllll according to the operating condition of the gasoline engine with the upper limit being (Pl), and when the octane number of the fuel used in the gasoline engine is lower than the predetermined octane number (PO), the predetermined maximum value is set. A change control 1l (P2) is performed to change the retard angle m to a larger maximum retard amount, and the change to the larger maximum retard amount is performed, and the rotation speed (P3) and load (P4) of the gasoline engine are The gist of the present invention is a fuel cut control method for a gasoline engine that cuts off the supply of fuel to the gasoline engine (P5) when the amount of fuel (P5) exceeds a predetermined value.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

First, FIG. 2 is an explanatory diagram showing a gasoline engine and its peripheral equipment to which the method of the present invention is applied.

1 is a gasoline engine body dedicated to high octane fuel, 2 is a piston, 3 is a spark plug, 4 is an exhaust manifold, 5 is an oxygen sensor provided in the exhaust manifold 4 and detects the residual oxygen concentration in exhaust gas, 6 is gasoline a fuel injection valve for injecting fuel into the intake air of the engine body 1;
1 is an intake manifold, 8 is an intake air temperature sensor that detects leakage of intake air sent to the Ganlin engine body 1, 9 is a water temperature sensor that detects the temperature of gasoline engine cooling water, 1
0 is attached to the cylinder of the gasoline engine 1 in the same way as the water temperature sensor 9, and is used to detect knocking of the gasoline engine 1!
1 is a knocking sensor that detects 1, 11 is a thrower 1 hell valve, 14 is an air flow meter that measures the amount of intake air,
Reference numeral 15 represents a surge tank that absorbs the pulsation of intake air.

16 is an igniter that outputs the high mIT required for ignition, and 17 is linked to a crankshaft (not shown) to transfer the high voltage generated by the igniter 16 to the spark plugs of each cylinder.
A distributor 18 is installed in the distributor 17 to distribute the distribution to the distributor.
91 a rotation angle sensor that outputs 24 pulse signals for every 1 rotation of the crankshaft, 19 a cylinder discrimination sensor that outputs 1 pulse signal for every 1 revolution of the distributor 17, 20 an electronic control circuit, 21 is a key switch,
22 each represent a starter morph. 26 represents a vehicle speed sensor that is linked to the axle and transmits a pulse signal according to the vehicle speed.

Next, FIG. 3 shows a block diagram of the electronic control circuit 20 and its related parts.

30 is a central processing unit (hereinafter simply referred to as CPU) that inputs and calculates data output from each sensor according to a control program and performs processing for controlling the operation of various devices; 31 is a control program and initial data; 32 is a read-only memory (hereinafter simply referred to as ROM) in which the data input to the electronic control circuit 20 and data necessary for arithmetic control n is temporarily read and used as random access memory (hereinafter simply referred to as RAM). 33 is a backup random access memory (hereinafter simply referred to as backup RAM) as a non-volatile memory backed up by a battery so as to retain data necessary for subsequent operation of the internal combustion engine even when the key switch 21 is turned off; 34 to 37 are buffers for the output signals of each sensor (t); 38 is a buffer for the output signals of each sensor (t);
30 is an A/D converter (J, 39 is an A/D converter that converts the analog signal into a digital signal, 40 is an A/D converter that selectively outputs
converts each sensor signal into CP via a buffer or via a buffer, multiplexer 38 and A/D converter 39.
Multiplexer 3 from CPU 30 as well as sending to U30
8 represents an input/output port that outputs a control signal for the A/D converter 39.

41 converts the output signal of the oxygen sensor 5 into the comparator 4.
2, and 43 represents a shaping circuit that shapes the waveforms of the output signals of each rotation sensor 18 and cylinder discrimination sensor 19. The output of the knocking sensor 10 is input to an integrating circuit 44 and a peak hold circuit 45, and the output of the peak hold circuit 45 is further transmitted to an input port 46 via a gate circuit 45Δ, and the other sensor signals are directly transmitted to Alternatively, it is sent to the CPU 30 by the input/output port 46 via the buffer 41 or the like.

Furthermore, 47.48 is connected to CP via output port 49.50.
Fuel injection valve 6 and igniter 1 are activated by the signal from U30.
6 respectively represent the drive circuits that drive 6. Also 5
1 is a path line for signals and data, 52 is a CP
It represents a clock circuit that sends a clock signal serving as a control timing to the LJ 30, ROM 31, RAM 32, etc. at predetermined intervals.

Next, the control program which is the main part of this embodiment will be explained.

4(A), FIG. 5, and FIG. 6 are flowcharts of the first embodiment of the present invention.

FIG. 4(A) shows a knocking detection routine used in the maximum retardation amount changing routine of FIG. 5, which will be described later.

A piezoelectric vibration detection sensor is widely used as the knocking sensor 10, and its detection output includes not only vibrations caused by knocking in the gasoline engine 1 but also noise components such as valve tapping sounds. Therefore, in order to accurately detect the occurrence of knocking from these detection outputs, the knocking detection routine shown in FIG. 4(A) is adopted.

The processing procedure of this routine will be explained below with reference to the timing diagram of FIG. 4(B). The figure (B) shows the case of a 6-cylinder gasoline engine as an example. The diagram shows the crank rotation angle along the horizontal axis, and the order of the cylinders in which combustion takes place, as well as the top dead center of the cylinder (hereinafter TD
Displays the crankshaft rotation angle from (referred to as C). The waveforms (a) to (d) in the figure represent brackets corresponding to the times, where (a) the waveform represents the output of knocking sensor 10, and (b) the waveform represents the output of knocking sensor 1-10 ( (a)
(waveform) as input, and the output of the integrating circuit 44 that integrates (C
) The waveform is from the input capo-1-46 to the beat hold circuit 45.
The waveform (d) represents the output of the peak hold circuit 45 which receives the output of the knocking sensor 10 (waveform <a)).

As is clear from the (d> waveform), the peak hold circuit 45 is set at the rising point of the timing signal of the waveform (C), and is reset at the falling white point.
Same timing mf! The gate circuit 45A to which the (C) waveform is input is connected so that the gate is turned on while the timing signal (C) waveform is at a high level.

Knocking is caused by a crank angle of 30"C8 to 60"O from the top dead center of the cylinder where combustion is being carried out.
The reason for this is that it usually occurs during the period leading up to A, and it is possible to capture signals only during this period.

The CPLJ30 that inputs the above waveforms is shown in Figure 4 (A
) The occurrence of knocking is detected as follows according to the flowchart.

When the CPU 30 moves to the processing of this routine, step 100 is first executed, and the output of the integration circuit 44 and the output of the peak hold circuit 45 via the gate circuit 45A are read in synchronization with the rotation angle of the crankshaft. That is, in synchronization with the top dead center of each cylinder, the output of the integrating circuit 44 is set as rAJ, and then the crankshaft rotation from the top dead center of each cylinder is 90°C.
The output from the gate circuit is taken in as rBJ in synchronization with A (see (b) and (d) in Figure 4 (13)).
.

Next, step 110 is executed, and the magnitude relationship between these captured information values rAJ and rBJ is determined. Here K
is a predetermined constant, which absorbs the effects of the amplification functions inherent in the integrating circuit 44, peak hold circuit 45, and gate circuit 45A, and also allows the output rBJ of the gate circuit 45A to be This is to determine a so-called threshold level at which it is determined that non-king occurs when an output difference of a predetermined value exists. Since the possibility of knocking occurring at the top dead center of each cylinder is extremely low, the output of the knocking sensor 10 at this time is assumed to be detecting vibrations other than knocking of the gasoline engine 10, and the output at this point is set to a predetermined value. It is determined that knocking has occurred in the gasoline engine 1 when a knocking output greater than or equal to the magnification (K) is detected within a period of 90'' OA from a crankshaft angle of 15° CA. If it is determined to be KXA, the process moves to step 120, where it is assumed that knocking has not occurred and the variable N is set to "0". Also,
If it is determined that B≧KXA, it is determined that knocking is occurring, and the process moves to the next step 130.

Step 130 uses a constant L (L>K) to determine the degree of knocking. Output B of knocking sensor 10
If B≧LXA is large, it is determined that a fairly large vibration has occurred in the gasoline engine 1, and the next step 14 is
0, the variable N is set to "2", and if B<1×8, it is determined that the knocking is small, and the process proceeds to step 150, where the variable N is set to "1".

Based on the output processing of the non-king sensor 10 performed as described above, the maximum retard angle mountain changing routine shown in FIG. 5 is executed.

This routine is interrupted by the CPU 30 for each TDC of each cylinder, for example.

When the CPU 30 shifts to processing of this routine, step 200 is executed first. Here, the contents of the flag FA are determined. As illustrated, the flag FA is set to "1" when it is determined that the Ganlin engine 1 is using low-octane fuel. Flag F
If A is "1", the next step 210 to step 2
If the processing up to 13 is other than "1", step 220
is executed.

Steps 210 to 213 are the ignition timing control method III after it is determined that low octane fuel is already being used, and it is determined whether or not knocking is currently occurring in the slap 210, like a bullet. That is, the fourth
The content of the variable N, which is obtained as a result of the execution of the knocking detection routine in Figure (A>), is searched. If N-0, it is determined that knocking has not occurred, and in step 211, the current ignition timing is By advancing the ignition timing by a predetermined amount, the gasoline engine 1 can generate higher torque and approach advance control that is more fuel efficient, and if N≧1, the ignition timing is advanced by a predetermined amount to suppress the occurrence of knocking. In step 212, the retardation process is performed on only this.

Step 213 is similar to steps 211 and 21.
In the step performed after the ignition timing tlJ]lIi control, the retardation amount of the new IC ignition timing set by the above ignition timing t, IIlj is set in advance to the maximum retardation amount θ1 for low octane. Determine whether or not the value is smaller than θH, and if it exceeds θH, reset it to the maximum retard amount θH, and even if the value exceeds θH, execute retard 1IJIII of θ)-1 or more. Perform guard processing to prevent this. Fuel with a low octane number has low anti-knock properties and tends to cause knocking, which can easily damage the gasoline engine 1. Therefore, the maximum retardation amount θH for low octane number needs to be retarded to the maximum allowable increase in exhaust gas temperature.

In any case, this maximum retardation amount θ1]
Guarding is provided in this step to prevent the retard angle from exceeding 2.

Step 220 is a determination step that is executed when it is not determined that low octane fuel II is still in use, and here the content of the flag FB is determined. Flag F″B is high octane gasoline engine 1
This indicates whether or not the ignition timing has already reached the maximum retardation amount θL for high octane.
If it has reached L, the flag FB is set to "1". If it is determined in this step that FB is not "1", high octane ignition timing control from step 221 to step 226 is executed, and if FB is rlJ, step 230 is processed.

First, the ignition timing control for high octane number from step 221 to step 226 will be explained.

This control is almost the same as normal ignition timing control. First, in step 221, it is determined whether or not the gasoline engine 1 is currently causing knocking, as shown in FIG. 4 (△). The judgment is made based on the contents of the variable N obtained by the detection routine. And N-rOJ
If so, step 222 to perform advance angle 1, II m.
If N > Ot, the process moves to step 223.

In step 222, angle control is performed in predetermined angle increments, and the processing of this routine ends.

Step 223 is to judge whether or not there is still room for retardation of the current retardation m caused by the ignition timing control compared with the maximum retardation mθL for high octane. When it is determined that θ≦θL by comparing the magnitude with the maximum retard amount θL for
A predetermined amount is added to the current retard amount θ to further increase the retard angle and the processing of this routine ends. On the other hand, if it is determined that θ>θL, step 225 is executed.

In step 225, it is determined that the retardation amount has already reached the maximum retardation amount θL for high octane number due to the ignition timing control, the aforementioned flag FB is set to "1", and the process moves to the next step 226.

In step 226, a variable OA used for time measurement as described later is set to an initial value r100J, and upon completion of this step, the entire processing of this routine ends.

Next, step 230 is executed when it is determined in step 220 that FB-1, that is, ignition timing control using the maximum retard amount θL for high octane number, has already been executed.
The following will be explained.

Step 230 decrements the variable OA set in MOOJ in step 226, and is a step to calculate how many times this routine has been executed since the time when the ignition was retarded to the maximum retardation amount θL for high octane. It is.

Then, in the next step 231, it is determined whether the decremented variable CA is CA>0.

If it is determined in step 231 that CA>0, step 232 is executed, and if CA≦○, step 234 is executed.

Step 232 is a step for determining whether the ratio of the variable N indicating the current knocking occurrence state set by the knocking determination routine shown in the flowchart in FIG. 4 (A>) is N-2.N -2, it is assumed that large knocking is occurring in the gasoline engine 1 despite the current ignition timing control using the maximum retardation amount θL for high octane numbers, and the variable CB of the large knocking count is set in step 233. Increment and also N
<If it is 2, it is assumed that knocking has not occurred, or even if knocking has occurred, it is small, and the processing of this routine ends.

Step 234, which is executed when it is determined in step 231 that OA≦O, is for resetting the flag "B". As mentioned above, the flag FB is used to ignite up to the maximum retard amount θL for high octane. When the timing is delayed, "1"
", and if this FB is set to "1" in the process of step 220, the processes from step 230 onwards will be forcibly executed in the next process of this routine. Therefore, after that, normal ignition timing control is not performed, and the variable CB is incremented every time the variable N-2 is reached in steps 232 and 233. Then, the processing of the step of counting the occurrence of knocking is completed on the condition that this routine in which CA≦0 has been continued 100 times, and the flag F is
B is reset and returns to normal ignition timing control mode.

In the next step 235, this routine performs 10 steps as described above.
While the execution has been completed 0 times, it is determined whether the content of the variable CB counted according to the occurrence of large knocking is greater than 10. Here, if CB>10, the flag FA is set to "1" in step 236, and CB≦1
If it is 0, the CB is cleared and this routine ends.

Through the processing of this routine as described above, the maximum retardation amount can be automatically set in accordance with the octane number of the fuel used in the gasoline engine 1.

In addition, this routine takes into consideration the S/N ratio of the knocking sensor 10, etc. In order to do this, if large knocking occurs in gasoline engine 1 more than 10 times while this routine is executed 100 times in a row, it is determined that gasoline engine 1 is using fuel with a low octane number. Although the method has been described, the knocking occurrence frequency for determination may be arbitrarily set based on the performance of the knocking sensor 10, the characteristics of the gasoline engine 1, etc.

Knocking that occurs in the gasoline engine 1 can be suppressed by changing the maximum retardation amount of the ignition timing controlled as described above, but the maximum retardation amount θ for high octane engines can be suppressed.
Abnormal increase in exhaust temperature that occurs when the retardation upper limit value of 1lIIItlll of the ignition timing of the gasoline engine 1, which has been set in advance, is retarded to the maximum retardation amount θH for low octane, which is a larger retardation amount. There is a possibility of occurrence.

Therefore, before the fuel supply υ'Jllll for supplying fuel to the gasoline engine 1 from the fuel injection valve 6 is executed by the CPU 30, the fuel cut control routine 11 shown in FIG. 6 is always processed.

When the CPU 30 moves to the processing of this routine, step 300 is first executed, and it is determined whether the flag FA set by the execution of FIG. 5 is set to "1". If it is FA-0, step 310 is executed, and a flag FC, which is a condition for executing fuel cut control to be described later, is reset to "0". Further, if it is determined to be FA-1, the next step 320 is executed.

In step 320, it is determined based on the output of the rotation angle sensor 18 whether or not the rotation speed NE of the gasoline engine 1 is high. Here, a rotational speed of 4000 rpIIl is used as a reference value, and if NE>400 Ortua, it is assumed that the rotation is high and the process proceeds to the next step 330; otherwise, step 310 is processed.

Step 330 is a step for determining the load condition, which is another condition for executing fuel control. That is, based on J [output of 1 meter 14 and rotation angle sensor 18], the intake air small Q/N [1/rev] per 014 rt rotation speed of gasoline engine 1 at CP IJ:30 is Compare the performance and the predetermined amount (0,6>), and if TO/N is 0°6, it is assumed that the gasoline engine 1 is operating under high load, and step 3/ l('), and if Q/N<0°6, the process moves to step 310.

In step 340, by the processing from steps 300 to 330 described above, ignition timing control is executed with the maximum retardation angle θto1 for low octane as the upper limit, and high rotation <N
E>4000ru+), high load (Q/N≧0.69
．． /rev ) (D lower T: f5 son') n: r nshin 1
is executed when the is running.

Therefore, assuming that the conditions for the exhaust gas temperature of the gasoline engine 1 to rise to - are sufficient, there is a possibility that overheating will occur if fuel is supplied to the gasoline T engine 1 any more, so the flag FC for fuel cut control is set to "1". ” and complete the processing of this routine.

As mentioned above, this routine is executed before generating the drive signal to the fuel injection valve 6, and is executed when injecting the fuel I11 determined from various operating conditions of the gasoline engine 1 by other routines. The content of this flag FC is then checked, and if it is FC-1, no drive signal is output to the fuel injection valve 6, and the purpose of fuel cut control is achieved.

If such control is performed, no fuel will be supplied to the gasoline engine 1 under adverse conditions in which the exhaust gas temperature abnormally increases, thereby eliminating the possibility of overheating.

This method suppresses the occurrence of knocking only when the octane number of the fuel used in the gasoline engine 1 is lower than a predetermined amount, and the knocking occurs by setting the maximum retardation amount to a larger value. Abnormal rises in exhaust gas temperature can also be avoided. In the normal operating state of the gasoline engine 1, the fuel cut control conditions are as shown in FIG. 6 above. High rotation (NE>400Orpm
> and when the load is high (Q/N≧0.61/rev), the VA degree is low, so even if the fuel ht is executed only under these conditions, the operation of the gasoline engine 1 will not be possible. There are very few cases where it is restricted.

Next, other embodiments will be described.

First, FIG. 7 shows a flowchart of another If and control method of the maximum retard amount changing routine explained in FIG. 5 of the first embodiment.

FIG. 7 is a flowchart for determining the 1992 octane number by adding the rotational speed NE of the gasoline engine 1 and the continuous occurrence of large knocking to the octane number determination routine shown in FIG. Since the knocking sensor 10 detects one engine shift of the gasoline engine 1, when the gasoline engine 1 reaches a high rotation speed, it detects vibrations other than knocking that occur in the gasoline engine 1 due to causes such as valve tapping noise. There is a possibility of detection t11. Therefore, the condition for determining the octane number is that the rotation speed NE of the gasoline engine 1 is low or medium rotation (NE < 4000 rpm).
). Also knocking sensor 10
From the detection results, it is clear that when large knocking occurs continuously and when it occurs intermittently, there is a higher possibility that fuel with a low octane number is being used. Therefore, in this flowchart 1r, in consideration of these cases, continuous occurrence of large knocking is weighted so that octane number can be determined more accurately.

Hereinafter, each step in FIG. 7 will be explained in detail while comparing it with the first embodiment.

Each step represented by step numbers 400 to 437 is the same as step numbers 200 to 237 in the flowchart of the first embodiment shown in FIG. It executes processing.

In this routine, step numbers with alphanumeric characters added are newly added, and these steps perform the following processing.

Step 420A is executed when the retard amount has already reached the maximum retard mo+- due to the ignition timing control in step 423. In the first embodiment, this step is not performed, and the next step 225 and step 226 are performed immediately, the flag FB is set, and the variable C△
settings have been executed. However, in this routine, in this step 420A, it is determined whether the rotation speed NE of the gasoline engine 1 is a low or medium speed rotation, and if NE < 4000 r
If it is pm, more accurate data can be obtained from the output of the knocking sensor 10, so set the flag FB, etc., and perform step 425 only when N E < 4000 rpm.
and step 426 is executed. In other cases (N
If E≧4000rpn+), this routine (1) processing ends.

Step 430A also involves determining the rotational speed NE of the gasoline engine 1 in the same manner as described above. This step is
This step is provided immediately before step 432 and step 433, where the argument is the number of large knocks that occur in the gasoline engine 1 within the time until the variable CA reaches rOJ. Execute these counting processes only when N E < 4000 rplIl, and in other cases, determine that the output of the knocking sensor 10 has a poor S/N ratio and count large knocks. Step 430C
This routine ends after processing.

The newly added steps from step 430B to step 430F are for weighting cases where large knocking occurs continuously or intermittently when counting large knockings. In the first embodiment, if large knocking had occurred in step 232, the variable CB was simply incremented and counted, but in this routine, the following process is performed by a newly added step.

First, when large knocking is detected in step 432, step 430B is executed and variable CG is incremented.

Here, the variable CC is newly provided to indicate the occurrence of large knocking. Also, check that there is no major knocking or that the rotational speed NF is 400 Or
If it is greater than or equal to +11, this variable CC is reset in step 430C.

Step 430D determines whether the variable CC incremented in step 430B is 2 or more. Continuous loud knocking 9. (CC upper 2) or whether it is occurring intermittently <CC-1). If it is CC upper 2, go to the next step 430E,
If it is CC-1, the process moves to step 433.

Step 433 is the same as in the first embodiment, and simply increments the variable CB that counts the occurrence of large knocking. However, when large knocking occurs continuously, step 430E is executed and the variable CB is incremented. It adds "2" to the contents all at once. This allows CB
The content of the signal increases rapidly when large knocking occurs continuously, and increases gradually or stagnates at other times. Step 433 or Step 4
When step 30E is executed, the processing of this routine ends.

After changing the contents of the variable CB in this way, the contents of CB are compared with a predetermined amount in the same manner as in the first embodiment, and if the value is greater than the predetermined value, it is determined that fuel with a low octane number is being used in the gasoline engine 1. That's what I do. In this routine, the predetermined value is set to "20" as shown in step 430F.

This is because, as explained in step 430E, when large knocking occurs continuously, "2" is added to the variable CB at once.

In order to determine that the fuel in the gasoline engine 1 is of low octane value through this routine that performs the processing as described above, the S/N ratio of the knocking sensor 10 must be high and this routine must be executed 100 times. This is when CB becomes greater than 20 due to large non-king occurring 10 or more times in a row, large knocking occurring 20 or more times intermittently, or a combination of these. Therefore, compared to the first embodiment, it is possible to detect a higher rfiIff by the knocking sensor 10 for determining the octane number, and since the increase in the variable CB changes depending on the occurrence of large knocking, the A phtane number It is possible to improve the accuracy of determination.

Next, the fuel cut υIt explained in FIG. 6 of the first embodiment
Another embodiment of ll will be explained based on FIG.

FIG. 8(A) performs almost the same operation as FIG. 6, and the processing timing is also the same.

(b) In the figure, step 500 and step 5
20-530 are the same as steps 300 and 320-330 in FIG.
0 is executed under the same conditions as step 340, that is, when all the conditions f1 of abnormal increase in exhaust gas temperature are satisfied, while step 510 is executed at other times.

Step 5101, step 310 and constant 111 I
, In addition to the process of setting Nifrag FC to "0",
This is a step of resetting a flag FD to be newly used this time to rOJ, which will be described later.

In addition, step 540 is performed using this newly used flag FD.
This step is to set "1" to "1".

(0) The figure shows a 4 ms interrupt routine that is processed by the CPU 30 every 41 IS, and performs the following process 5a.

Step 600 is to judge the content of the flag FD set in step 540 in the figure (a). If D-1, proceed to step 610; if FD-0, proceed to step 620.
Move to.

Step 620 is to reset the variable CD to be simulated to "0", and step 610 is to reset this variable CD to "0".
is incremented.

That is, (a) the flag F set in step 540 in the figure
The contents of D are determined in step 600 every 4 ms when this routine is executed, and the continuous time, which is FD-1, is set to 1 o'clock. If FD-0, step 620
After processing, the processing moves to other routines, and if it is FD-1, 81 o'clock processing (CD-CD+1
>, and the next step 630 is executed.

Step 630 is to determine whether the variable has reached 5000. Since this routine is interrupted every 4 ms, it takes 413x 50 to execute the step 610 5000 times in FD-1 continuously.
A time of 0.00-20 sec is required. Therefore, in this step, if Fl)-1 has passed and 20 seconds have passed, the process will proceed to the next step 640, and if the 20 SeC has not passed, this routine will be skipped and the process will proceed to another routine. Guaru.

Step 640 is a sixth step for executing fuel cut control.
This step is to set the flag FC explained in the figure to rlJ. By executing this step, all processing of this routine is completed.

As described above, in this embodiment, the flag FC is
is set to "1", but the premise is that under certain conditions, the operating state of gasoline engine 1 is set to "1" for a certain period of time (
The new condition is to continue for more than 20 seconds). In addition, the frequency of controlling the fuel flow rate of the gasoline engine 1 is kept low, so that the load following performance of the gasoline engine 1 can be kept low during long-term operation at high rotation speeds and 9 loads where overheating can occur. Therefore, it becomes possible to perform fuel cut control only in this case.

In addition, in the maximum retard angle m changing routine of FIG. Even if the maximum retardation amounts θH and θL are set as variables related to the rotational speed NE of the gasoline engine 1 and the relationship shown in FIG. do not have. In this case as well, the relationship θ1-1>θ1 holds true for all rotational speeds NEi
In contrast, there is a statement C that holds true.

[Effect of the invention] Double-1-1 real f! As explained by giving one example, the fuel cut II+ control method for gasoline engine 1 according to the present invention reduces the maximum retard amount in ignition timing control when fuel v1 lower than a predetermined octane number is used in gasoline engine engine 1. If only the maximum retardation amount, which is the value, is changed for a low octane number, and such a change is made between lj', and the engine is operated at a predetermined rotational speed and a predetermined load or less, One person has the control power to cut the fuel 1+1 to the Karin engine.

Therefore, the knocking that occurs when using fuels with different octane numbers (y+1) can be suppressed by simply changing the maximum retardation angle a! If possible, we can control the IN temperature difference caused by retard control to the minimum necessary level! (I(')
It suppresses F to R low visibility and provides 11 defenses.

[Brief explanation of drawings]

FIG. 1 is a basic flowchart of the present invention, FIG. 2 is a schematic diagram of a gasoline engine and its peripheral equipment in which an embodiment of the present invention is utilized, and FIG. 3 is a block diagram of an electronically controlled IIl device.
4(△) shows a part of the first embodiment and the second embodiment, and FIG. 4(B) shows the part 1111 of the flow.
Explanatory drawings, FIG. 5 is a flowchart 1-1 for changing the maximum retardation amount in the first embodiment, and FIG. 6 is a flowchart 1-1 for changing the maximum retardation amount in the first embodiment.
Figure 7 is a flowchart for changing the maximum retardation amount in other embodiments, Figure 8 is a flowchart for fuel cut control in other embodiments, and Figure 9 is used in Figures 5 and 7. An explanatory diagram showing an example of a change in the maximum retardation amount to the rotation speed. 1...Gasoline engine 10...Knocking sensor 18...Rotational speed sensor 20...Electronic control circuit 30...CPU 44...Integrator circuit 45...Peak hold circuit 46...Gate circuit Agent: Patent attorney Tsutomu Setatetsu and 1 other person Figure 1

Claims (1)

[Scope of Claims] In order to operate the gasoline engine using fuel with a predetermined octane number, the ignition timing is controlled according to the operating state of the gasoline engine with the ignition timing set at a predetermined maximum retard amount as the upper limit, and the ignition timing is controlled according to the operating state of the gasoline engine. When the octane number of the fuel used is lower than the predetermined octane number, the predetermined maximum retardation amount is changed to a larger maximum retardation amount, and the change to the larger maximum retardation amount is performed. A fuel cut control method for a gasoline engine, which cuts the supply of fuel to the gasoline engine when the rotation speed and load of the gasoline engine exceed a predetermined value.