JPH03246342A - Abnormality detecting device for fuel injection system - Google Patents

Abstract

PURPOSE:To facilitate repair or the like, by calculating the shift of an air-fuel ratio against a target air-fuel ratio from a correction value by means of each correction means at the time of fuel injection from each fuel injection valve provided plurality at one combustion chamber, and deciding that when the shift is outside a predetermined range, it is the abnormality of each injection system. CONSTITUTION:An injection control means A which makes fuel injected selectively from two fuel injecting valves 10, 11 provided at one combustion chamber, is provided. Also, a calculating means B which calculates a basic fuel injection time that is in accordance with an engine operation condition, is provided, and an air-fuel ratio is converged to a target air-fuel ratio by correcting this basic fuel injection time by means of a correcting means C on the basis of the output of an oxygen density detector 19. Also, at the time of fuel injection from each fuel injecting valve 10, 11, the shift of the air-fuel ratio against the target air-fuel ratio is calculated by means of a calculating means D from a correction value by means of each correcting means C. And whether or not the slip of the air-fuel ratio at the time of fuel injection from each fuel injecting valve 10, 11 is within a predetermined range, is decided, and the abnormality of the injection system of each fuel injecting valve 10, 11 is decided by means of a deciding means E according to its result.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an abnormality detection device for a fuel injection system.

[Conventional technology]

An internal combustion engine is known in which a plurality of fuel injection valves are provided per cylinder, and fuel is injected from one of the fuel injection valves depending on the engine load (see Japanese Patent Application Laid-open No. 36719/1983).

[Problem to be solved by the invention]

However, if multiple fuel injectors are provided per cylinder, the probability of failure of the injection system of each fuel injector increases accordingly, and furthermore, when the engine malfunctions, the injection system of any one of the fuel injectors will fail. I don't know if it is malfunctioning.

Therefore, there is a problem in that it takes a lot of effort and time to locate the malfunctioning injection system.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, as shown in the configuration diagram of the invention in FIG. 1, a pair of fuel injection valves consisting of a first fuel injection valve 10 and a second fuel injection valve 11,
injection control means A that selectively injects fuel from the first fuel injection valve 10 or the second fuel injection valve 11; injection time calculation means B that calculates the basic fuel injection time according to the operating state of the engine; a correction means C that corrects the basic fuel injection time so that the air-fuel ratio becomes the target air-fuel ratio based on the output signal of the oxygen concentration detector 19 provided in the engine exhaust passage 18; and the fuel from the first fuel injection valve 10. During injection and second fuel injection valve 1
The air-fuel ratio deviation calculation means calculates the deviation of the air-fuel ratio from the target air-fuel ratio from the correction value by the correction means C at the time of fuel injection from the first fuel injection valve 10, and the air-fuel ratio deviation is calculated in advance from the correction value by the correction means C at the time of fuel injection from the first fuel injection valve 10. If the difference in air-fuel ratio is within a predetermined range and exceeds the predetermined range when fuel is injected from the second fuel injector 11, it is determined that there is an abnormality in the injection system of the second fuel injector 11. , when the air-fuel ratio deviation is within a predetermined range during fuel injection from the second fuel injection valve 11 and the air-fuel ratio deviation exceeds the predetermined range during injection from the first fuel injection valve 10. is equipped with a determining means E for determining that there is an abnormality in the injection system of the first fuel injection valve 10.

[For production]

If the deviation in air-fuel ratio when fuel is injected from either fuel injection valve is within a predetermined range, the injection system of that fuel injection valve is normal; If the value exceeds the specified range, there is an abnormality in the injection system of that fuel injector.

Since it is determined whether there is an abnormality in the other injection system when one of the injection systems is normal, it is possible to know which injection system has the abnormality.

〔Example〕

2 to 4 show the case where the present invention is applied to a two-stroke internal combustion engine.

2 to 4, 1 is a cylinder block, 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber, 5 is a cylinder block, 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber, 5
6 is a spark plug, 6 is a pair of air supply valves, 7 is an air supply boat, 8 is a pair of exhaust valves, and 9 is an exhaust port. Inside the combustion chamber 4, there are a first fuel injection valve 10 and a second fuel injection valve. A fuel injection valve 11 is arranged. In the embodiment shown in FIG. 2, fuel is injected only from the first fuel injection valve 10 during low-load engine operation, so the first fuel injection valve 10 will hereinafter be referred to as a low-load fuel injection valve.

On the other hand, the diameter of the nozzle opening of the second fuel injection valve 11 is larger than the diameter of the nozzle opening of the low-load fuel injection valve 10, and in the embodiment shown in FIG.
Since fuel is injected from only the first fuel injection valve 11, this first fuel injection valve 11 will hereinafter be referred to as a high-load fuel injection valve. Fuel injection from these low-load fuel injection valves 10 and high-load fuel injection valves 11 is controlled based on output signals from an electronic control unit 20.

Referring to FIG. 2, the air supply boat 7 includes a surge tank 12,
Air supply duct 13, mechanical supercharger 1 driven by the engine
4 and air cleaner 1 via air flow meter 15
6, and a throttle valve 17 is installed in the air supply duct 13.
is placed. On the other hand, the exhaust port 9 is connected to an exhaust passage 18, and an oxygen concentration detector (hereinafter referred to as 02) is installed in the exhaust passage 18.
(referred to as a sensor) 19 is arranged.

The electronic control unit 20 consists of a digital combiator with ROMs connected to each other via a bidirectional bus 21.
(Read-only memory) 22, RAM (Random access memory) 23, CPU (Microprocessor) 2
4, a backup RAM 25, an input port 26, and an output port 27. Air flow meter 15 generates an output voltage proportional to intake air amount Q, and this output voltage is input to input port 26 via AD converter 28 . Also, 0. The output signal of sensor 19 is input to input port 26 via AD converter 29 . Furthermore, input port 2
6 is connected to a rotational speed sensor 30 which generates an output signal representing the engine rotational speed N. On the other hand, the output boat 27 is connected to the low-load fuel injection valve 10 and the high-load fuel injection valve 11 via corresponding drive circuits 31 and 32, respectively.

When the piston 2 descends, the exhaust valve 8 opens first.
Burnt gas in the combustion chamber 4 is discharged into the exhaust port 9.

Next, when the intake valve 6 opens, fresh air sent out from the mechanical supercharger 14 is sent into the combustion chamber 4 from the intake port 7. Next, when the piston 2 moves up past the bottom dead center, the exhaust valve 8 closes, and then the air supply valve 6 closes. Exhaust valve 8
When the fuel injection valves 10 and 11 close, fuel is injected from one of the fuel injection valves 10 and 11, and this injected fuel is ignited by the ignition plug 5. As shown in FIGS. 3 and 4, a mask wall 3 is provided on the inner wall surface of the cylinder head 3 to close the opening of the air intake valve 6 on the exhaust valve 8 side during the full opening period of the air intake valve 6.
3 is formed. Therefore, when the intake valve 6 opens, fresh air flows into the combustion chamber 4 through the opening of the intake valve 6 on the opposite side of the exhaust valve 8, and then this fresh air flows as indicated by W in FIG. Since the air flows in a loop within the combustion chamber 4, good loop scavenging is performed.

The fuel injection time TAU from each fuel injection valve 10.11 is calculated based on the following formula.

TAtl=K -TP-FAF -C-G where K is a constant predetermined for each fuel injection valve 10.11 TP is the basic fuel injection time FAF is the feedback correction coefficient C is determined by the engine cooling water temperature, etc. The correction coefficients G each indicate a learning coefficient.

The basic fuel injection time TP is determined by the engine load Q as shown in Figure 8.
/N (intake air amount Q/engine speed N) and is stored in the ROM 22 in advance as a function of the engine speed N. Regarding the constant K, it is K for the low load fuel injection valve lO.
I is given 2 for the high-load fuel injection valve 11. To these TPs.

K2 is such that the air-fuel ratio is almost the target when fuel is injected for -TP waiting time from the fuel injection valve 10 for low load and when fuel is injected for 2.TP waiting time from the fuel injection valve 11 for high load. The air-fuel ratio is determined to be the same.

Hereinafter, in order to make the invention easier to understand, the explanation will be based on the case where the target air-fuel ratio is the stoichiometric air-fuel ratio.

The 02 sensor 19 generates an output voltage of about 0.1 (V) when the air-fuel ratio is larger than the stoichiometric air-fuel ratio, that is, when it is lean, and generates an output voltage of about 0.1 (V) when the air-fuel ratio is smaller than the stoichiometric air-fuel ratio, that is, when it is rich. Generates an output voltage of about 9 V. Therefore, it is possible to determine whether the fuel is lean or rich from the output voltage of the 0□ sensor 19.

FIG. 5 shows a routine for calculating the feedback correction coefficient FAF based on the output voltage of the 02 sensor 19, and this routine is executed, for example, by interruption at regular intervals.

Referring to FIG. 5, first, in step 40, 0
Based on the output voltage of the second sensor 19, it is determined whether or not the engine is lean. If it is lean, the process proceeds to step 41, where it is determined whether it was rich in the previous processing cycle, that is, whether it changed from rich to lean between the previous processing cycle and the current processing cycle. When there is a change from rich to lean between the previous processing cycle and the current processing cycle, the process proceeds to step 42, where the skip value R is added to the feedback correction coefficient FAF.

On the other hand, if it was positive in the previous processing cycle, the process proceeds to step 43, where the integral value k (k(:R)) is added to the feedback correction coefficient FAF.

On the other hand, if it is determined in step 40 that the condition is rich, the process proceeds to step 44 to determine whether the condition was lean in the previous processing cycle, that is, the condition changed from lean to rich between the previous processing cycle and the current processing cycle. It is determined whether or not. If there is a change from lean to rich between the previous processing cycle and the current processing cycle, the process proceeds to step 45, where the skip value R is subtracted from the feedback correction coefficient FAF. On the other hand, if it was also rich in the previous processing cycle, the process proceeds to step 43 and the integral value k is subtracted from the feedback correction coefficient FAF. Therefore, the feedback correction coefficient FAF is the sixth
This will change as shown in the figure.

The air-fuel ratio is maintained at the stoichiometric air-fuel ratio by correcting -TP using the feedback correction coefficient FAF in the basic fuel injection time, which is also included in the constant. By the way, as mentioned above, if fuel is injected from each fuel injection valve 10.11 for the time K·TP, the air-fuel ratio becomes almost the stoichiometric air-fuel ratio, so the feedback correction coefficient FAF is set to 1.0 as shown in FIG. It will move up and down around the center.

However, due to changes over time, even if fuel is injected from each fuel injection valve 10□11 for a time TP, the air-fuel ratio does not reach the stoichiometric air-fuel ratio, but instead becomes rich or lean.

In this case, on the rich side, the average value of FAF becomes smaller than 1.0 in order to make the air-fuel ratio the stoichiometric air-fuel ratio, and on the lean side, the average value of FAF becomes larger than 1.0. However, when performing open loop control, FAF is set to 1.
．． It is often set to 0, and in this case, the air-fuel mixture becomes rich or lean. Therefore, the learning coefficient G mentioned above is introduced. This learning coefficient G is a value necessary to maintain the FAFO average value at 1.0. Therefore, this learning coefficient G is a value necessary to maintain the FAFO average value at 1.0. If the average value of FAF becomes smaller than 1.0, it becomes smaller. Therefore, the learning coefficient G is equal to the average value of FAF. For example, when trying to find the learning coefficient G at t in Figure 6, the average value of FAF is the peak value FAFP of the latest four FAFs.
,, FAFP2°FAFP,, It is determined from the average value ΣFAFP/4 of FAFP4.

Therefore, the learning coefficient G is calculated based on the following equation.

G-ΣFAFP/4 Therefore, if such a learning coefficient G is introduced, even if the air-fuel mixture becomes rich or lean when fuel is injected from each fuel injector 10.11 for -TP time. The average value of FAF is maintained at 1.0 even if the fuel is on the rich side, and the learning coefficient G becomes smaller when the fuel is on the rich side, and becomes larger when the fuel is on the lean side. Therefore, this learning coefficient G
indicates the deviation in air-fuel ratio due to changes over time.

Such deviations in the air-fuel ratio due to changes over time occur unavoidably, but deviations in the air-fuel ratio due to changes over time are usually within an acceptable range.For example, in the case of deviations in the air-fuel ratio due to changes over time, the learning coefficient G is set to 0. Not less than 8 and not greater than 1.2. Therefore, the learning coefficient G is 0.8fG≦1.2
When it is within the range of , it can be determined that the fuel injection system is operating normally although there is a deviation in the air-fuel ratio due to changes over time.

On the other hand, if the fuel injection valve 10.11 does not operate or if the fuel injection valve 10.11 becomes clogged, the mixture becomes extremely lean and the learning coefficient G becomes considerably large. When the injection valve 10.11 stops injecting, the mixture becomes extremely rich, so the learning coefficient G
becomes considerably smaller. In this case, if the learning coefficient G becomes smaller than 0.7 or larger than 1.3, it can be determined that there is an abnormality in the injection system of the fuel injection valve 10.11.

Therefore, it is possible to judge whether the fuel injection system is normal or abnormal based on the learning coefficient G, that is, whether Q, 8iG, 1.2, G<0.7, or G>1°3. . Regarding the learning coefficient G, G1 is given to the low-load fuel injection valve 10, and G2 is given to the high-load fuel injection valve 11. Therefore, the learning coefficient 61 is 0.8xc+<
1.2, and the learning coefficient G2 is G2<Q, 7 or G2>
If it is 1.3, it can be determined that the low-load fuel injection valve 10 is normal but there is an abnormality in the injection system of the high-load fuel injection valve 11, and the learning coefficient G2 is 0.8fG2≦1.2, If the learning coefficient GI is Gl<0.7 or Gl>1.3, it can be determined that the high-load fuel injection valve 11 is normal, but there is an abnormality in the injection system of the low-load fuel injection valve 10.

FIG. 7 shows a fuel injection control method. In FIG. 7, G, G2 are both between 0.8 and 1.2 until time t1, so it can be determined that both injection systems are operating normally. At this time, if the basic fuel injection time TP is shorter than the predetermined setting time TPO, fuel is injected from the low-load fuel injection valve 10, and if TP is longer than TPO, the fuel is injected from the high-load fuel injection valve 11. is injected. Time 1. For example, if the high-load fuel injection valve 11 becomes clogged, the learning coefficient 62 gradually increases as shown in FIG. Then, when G2 reaches 1.3, TP>
Even in TPO, fuel injection from the high-load fuel injection valve 11 is stopped, and fuel injection is performed from the low-load fuel injection valve 10 instead.

9 and 10 show a main routine for determining abnormality in the fuel injection system and controlling fuel injection.

Referring to FIG. 9, first, in step 50 during initial feeding, it is determined whether the learning coefficient 62 is 0.8iG2f1.2, that is, whether the injection system of the high-load fuel injection valve 11 is normal. . If G2<0.8 or G2>1.2, proceed to step 54. On the other hand, when the injection system of the high-load fuel injection valve 11 is normal, the process proceeds to step 51 to check whether the learning coefficient GI is 0.7<G, <1, 3, that is, the low-load fuel injection valve 10 It is determined whether or not the injection system is normal. If the injection system of the low-load fuel injection valve 10 is not abnormal, the process advances to step 52 and the low-load fuel injection valve 10
An abnormality flag F1 indicating that the injection system is abnormal is reset. The process then proceeds to step 54. On the other hand, if the injection system of the low-load fuel injection valve IO is abnormal, the routine proceeds to step 53, where the abnormality flag F1 is set. The process then proceeds to step 54. Therefore, the abnormality flag F1 is set when the injection system of the high-load fuel injection valve 11 is normal and the injection system of the low-load fuel injection valve 10 is abnormal. If the corresponding lamp is lit when the abnormality flag F1 is set, it can be seen that an abnormality has occurred in the injection system of the low-load fuel injection valve 10.

In step 54, the learning coefficient 01 is 0.8! HGIK1.
2, that is, whether or not the injection system of the low-load fuel injection valve 10 is normal. Gl<0.8 or G
When l>1.2, the process proceeds to step 58 in FIG.

On the other hand, if the injection system of the low-load fuel injection valve 10 is normal, the process proceeds to step 55 and the learning coefficient 62 is 0.7<6.
2<1.3, that is, whether the high load fuel injection valve 11
It is determined whether or not the injection system is normal. If the injection system of the high-load fuel injection valve 11 is not abnormal, step 56
Then, the abnormality flag F2 indicating that the injection system of the high-load fuel injection valve 11 is abnormal is reset. The process then proceeds to step 58. On the other hand, high load fuel injection valve 1
If the injection system No. 1 is abnormal, the process advances to step 57 and an abnormality flag F2 is set. The process then proceeds to step 58.

Therefore, the abnormality flag F2 is set when the injection system of the low-load fuel injection valve 10 is normal and the injection system of the high-load fuel injection valve 11 is abnormal. Abnormal flag F2
If the corresponding lamp is turned on when is set, it can be seen that an abnormality has occurred in the injection system of the high-load fuel injection valve 11.

In step 58, the basic fuel injection time TP is calculated based on the relationship shown in FIG. 8, and then in step 59, it is determined whether the basic fuel injection time TP is shorter than the set time TPO. When TP<TPO, the process proceeds to step 60 where i is set to 1 indicating the low-load fuel injection valve 10. The process then proceeds to step 63. - On the other hand, when TF'≧TPO, the process proceeds to step 61, where it is determined whether or not the abnormality flag F2 is set. When the abnormality flag F2 has been reset, the process proceeds to step 62, where 1 is set to 2 indicating the high-load fuel injection valve 11. Then step 63
Proceed to.

In step 63, the fuel injection time TAU is calculated based on the following equation.

TALI=Ki*TP-FAF-C-Gl Next, in step 64, a learning coefficient Gi is calculated based on the following equation.

Gi=ΣFAFP/4 This learning coefficient Gi is stored in the backup RAM 25.

Next, in step 65, it is determined whether i is 1 or not. When i=1, the process proceeds to step 66, where fuel is injected from the low-load fuel injection valve 10, and when j=2, the process proceeds to step 67, where fuel is injected from the high-load fuel injection valve 11.

On the other hand, if the abnormality flag F2 is set, the process proceeds from step 61 to step 68, where 1 is set to 1. Next, in step 69, the engine speed N is 300Or;
It is determined whether or not p and m are lower.

When N < 300Or, p, m, step 63
Proceed to. Therefore, if there is an abnormality in the injection system of the high-load fuel injection valve 11, N < 300 Or, and if pom, T
Even in P2TPO, fuel is injected from the low-load fuel injection valve 10.

On the other hand, when Nk is 3000r, p, and m, fuel injection is stopped.

〔Effect of the invention〕

Even when a plurality of fuel injection valves are used, it is possible to determine which fuel injection valve's injection system is abnormal.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the invention, Fig. 2 is an overall diagram schematically showing a two-stroke internal combustion engine, Fig. 3 is a bottom view of the cylinder head, and Fig. 4 is a side cross-section of the internal combustion engine shown in Fig. 2. Figure, 5th
The figure is a flowchart for calculating the feedback correction coefficient FAF, and Fig. 6 shows the feedback correction coefficient FAF.
7 is a time chart, FIG. 8 is a diagram showing basic fuel injection time, and FIGS. 9 and 10 are flow charts showing the main routine. 4... Combustion chamber, 10... First fuel injection valve, 11... Second fuel injection valve, 19... Oxygen concentration detector.

Claims (1)

[Claims] a pair of fuel injection valves consisting of a first fuel injection valve and a second fuel injection valve; an injection control means for selectively injecting fuel from the first fuel injection valve or the second fuel injection valve; An injection time calculation means that calculates a basic fuel injection time according to the operating condition, and an injection time calculation means that calculates the basic fuel injection time so that the air-fuel ratio becomes the target air-fuel ratio based on the output signal of an oxygen concentration detector installed in the engine exhaust passage. and an air-fuel ratio deviation that calculates the deviation of the air-fuel ratio from the target air-fuel ratio from the correction value by the correction means when fuel is injected from the first fuel injection valve and when fuel is injected from the second fuel injection valve. a calculation means; the air-fuel ratio deviation is within a predetermined range when fuel is injected from the first fuel injection valve, and the air-fuel ratio deviation exceeds the predetermined range when fuel is injected from the second fuel injection valve; If this occurs, it is determined that there is an abnormality in the injection system of the second fuel injector,
If the air-fuel ratio deviation is within a predetermined range when fuel is injected from the second fuel injection valve, and the air-fuel ratio deviation exceeds the predetermined range when fuel is injected from the first fuel injection valve, the first fuel injection valve An abnormality detection device for a fuel injection system, comprising a determining means for determining that there is an abnormality in the injection system of a fuel injection valve.