JP2657713B2 - Fuel leak diagnosis system for electronically controlled fuel injection type internal combustion engine - Google Patents

Description

The present invention relates to an internal combustion engine having an electronic control fuel injection device and performing learning control of an air-fuel ratio feedback control system, and diagnosing a fuel leak. Related to the device.

<Prior Art> A fuel injection valve used in an electronically controlled fuel injection device is opened by a drive pulse signal given in synchronization with rotation of an engine, and injects fuel at a predetermined pressure during the opening period. Has become. Therefore, the fuel injection amount is controlled by the pulse width of the drive pulse signal. If this pulse width is used as a control signal corresponding to the fuel injection amount as Ti, in order to obtain the stoichiometric air-fuel ratio which is the target air-fuel ratio, Ti is given by the following equation. Determined by

Ti = Tp · COEF · α + Ts Here, Tp is a basic pulse width corresponding to the basic fuel injection amount, and is referred to as a basic fuel injection amount for convenience. Tp = K · Q / N, where K is a constant, Q is the engine intake air flow rate, and N is the engine speed. CO
EF is various correction coefficients such as water temperature correction. α is a feedback correction coefficient for air-fuel ratio feedback control (λ control) described later. Ts is a voltage correction amount for correcting a change in the injection flow rate of the fuel injection valve due to a change in the battery voltage.

For λ control, an O ₂ sensor is provided in the exhaust system to detect the actual air-fuel ratio, and whether the air-fuel ratio is higher or lower than the stoichiometric air-fuel ratio is controlled by the slice level,
Therefore, the feedback correction coefficient α is determined, and the stoichiometric air-fuel ratio is maintained by changing this α.

By the way, if the base air-fuel ratio under the λ control condition, that is, the air-fuel ratio when α = 1 can be set to the stoichiometric air-fuel ratio (λ = 1), the feedback control is unnecessary, but actually, the components ( For example, an air flow meter,
The base air-fuel ratio from λ = 1 due to factors such as variations in fuel injectors, pressure regulators, and control units), changes over time, non-linearities in the pulse width-flow rate characteristics of fuel injectors, changes in operating conditions and environment, etc. Since a shift occurs, feedback control is performed.

If the base air-fuel ratio deviates from λ = 1, the air-fuel ratio control is performed in a range that is considerably different from the stoichiometric air-fuel ratio. In addition to the cost increase due to an increase in the amount of noble metal, the catalyst must be replaced due to further deterioration of the conversion efficiency accompanying the deterioration of the catalyst.

Therefore, by setting the base air-fuel ratio to λ = 1 by learning, λ = 1 resulting from a step of the base air-fuel ratio during transition is obtained.
The applicant has filed an application for a learning control device for learning the air-fuel ratio which eliminates the deviation from the control and improves the controllability (JP-A-59-20).
No. 3828). This is because a map of the learning correction coefficient Kl corresponding to the engine operating conditions such as the engine speed and the load is provided on the RAM, and when calculating the fuel injection amount Ti, the learning correction of the basic fuel injection amount Tp is performed as shown in the following equation. The correction is performed by the coefficient Kl.

Ti = Tp · COEF · Kl · α + Ts And learning of Kl proceeds in the following procedure.

(1) detecting a region of engine operating condition at that time in the steady state, and detects the deviation [Delta] [alpha] (alpha-alpha ₁₎ from the reference value alpha ₁ therebetween alpha as an average value.

(2) Search for Kl that has been learned up to now corresponding to the engine operating state area.

(3) The value of Kl + M · Δα is determined from Kl and Δα, and the result (learning value) is updated as a new Kl _NEW in the memory.
M is a constant and 0 <M <1.

Further, the applicant has found that in such an electronically controlled fuel injection type internal combustion engine, there is a possibility that the fuel injection valve may steadily leak due to failure or deterioration over time. Learning correction coefficient in the setting area of
An application has been filed for a fuel leak diagnosis device for an electronically controlled fuel injection type internal combustion engine that is capable of self-diagnosis of a steady fuel leak from a fuel injection valve based on the correlation of the amount of change from the steady value of K1 ( JP-A-63-65155).

<Problems to be Solved by the Invention> Incidentally, in this type of fuel leak diagnosis apparatus for an electronically controlled fuel injection type internal combustion engine, there is a concern that an erroneous determination will be made as described below.

That is, due to poor starting, so-called oil dilution may occur, in which gasoline that is not vaporized mixes with the lubricating oil on the cylinder wall and the entire oil is diluted. Then, as the oil temperature rises after the start, the gasoline mixed in the oil is vaporized, and the gasoline is sucked again via the blow-by passage.

Here, since the clearance between the piston and the cylinder wall is larger at low temperatures, the amount of gasoline related to the oil dilution is large, and further, in the idle operation region immediately after the start, the fuel injection amount Ti _IDLE itself is reduced. Because there are few,
The ratio of the gasoline amount to the fuel injection amount Ti _IDLE becomes large, so that the learning correction coefficient Kl _IDLE of the air-fuel ratio feedback control in the idling operation region greatly changes. Therefore, as one of the plurality of setting areas,
For example, when the idle operation region is adopted, the amount of change from the steady value in the idle operation region becomes large, and there is a possibility that the fuel is erroneously determined to be a fuel leak in the internal combustion engine even though the fuel is not leaking.

The present invention has been made in view of such a conventional situation, and is directed to a diagnostic device for self-diagnosing a steady fuel leak from a fuel injection valve. It is an object of the present invention to provide a fuel leak diagnosis device for an electronically controlled fuel injection type internal combustion engine that can prevent such erroneous determination of fuel leak and improve diagnosis accuracy.

<Means for Solving the Problems> The present invention is constituted by the following means (A) to (E) as shown in FIG. 1 in order to achieve the above object.

(A) Engine operating state detecting means for detecting an engine operating state including an engine speed, an engine intake air flow rate, and a cooling water temperature of the engine. (B) Basic fuel based on the engine operating state detected by the engine operating state detecting means. Basic fuel injection amount setting means for setting the injection amount (C) Storage means for storing a learning correction coefficient for correcting the basic fuel injection amount for each region of the engine operation state (D) Idle operation region and other predetermined Fuel leak diagnostic means for diagnosing whether fuel is leaking from the fuel injection valve based on whether the difference between the learning correction coefficient and the operating region is equal to or greater than a determination value; The determination value changing means for greatly changing the determination value in the fuel leak diagnosis means for a predetermined period set based on the above. The means E may be constituted by E1, E2 and E3 as described below.

(E1) Cumulative time measuring means for measuring the cumulative time when the start switch is on (E2) Elapsed time measuring means for measuring the elapsed time since the start switch was turned on (E3) If the time is less than a predetermined time set based on time, the determination value is set based on the cooling water temperature detected by the engine operating state detecting means and the cumulative time measured by the cumulative time measuring time. Modification means for changing to a predetermined value <Operation> A learning correction coefficient for correcting the basic fuel injection amount set based on the engine operating state is stored for each area of the engine operating state. When the difference between the learning correction coefficient and the predetermined operation range is equal to or greater than the determination value, the fuel leak diagnosis means determines that fuel is leaking from the fuel injection valve.

Here, as an operation according to the present invention, the determination value in the fuel leak diagnosis unit is largely changed during a predetermined period determined by the determination value changing unit based on the degree of starting performance.

The accumulated time during which the start switch is on is measured as a representative of the degree of starting performance.

Further, when the elapsed time from when the start switch is turned on is shorter than a predetermined time set based on the accumulated time, the determination value according to the determination value changing means is changed.

<Example> An example of the present invention will be described below with reference to the drawings.

In FIG. 2, air is sucked into the engine 1 through an air cleaner 2, an intake duct 3, a throttle chamber 4, and an intake manifold 5.

The intake duct 3 is provided with an air flow meter 6 for detecting the intake air flow rate Q, and outputs a voltage signal corresponding to the intake air flow rate Q signal. Throttle chamber 4
Is provided with a throttle valve 7 interlocked with an accelerator pedal (not shown) to control the intake air flow rate Q. Further, an auxiliary air passage 9 that bypasses the throttle valve 7 is provided.
10 are interposed. A fuel injection valve 11 is provided in the intake manifold 5 or an intake port of the engine 1. The fuel injection valve 11 is an electromagnetic fuel injection valve that is energized by a solenoid to open, is de-energized, and is closed, and is energized by a drive pulse signal to open and is pressure-fed from a fuel pump (not shown). Fuel controlled to a predetermined pressure by the pressure regulator is injected and supplied to the engine 1.

Exhaust gas is discharged from the engine 1 through an exhaust manifold 12, an exhaust duct 13, a three-way catalyst 14, and a muffler 15. The three-way catalyst 14 is a catalyst device that efficiently oxidizes or reduces CO, HC, and NO _X in the exhaust components near the stoichiometric air-fuel ratio of the air-fuel mixture to convert them to other harmless substances.

In addition, a crank angle sensor 17 is provided. The crank angle sensor 17 has a signal disk plate 19 provided on a crank pulley 18 and outputs, for example, a reference signal every 120 ° and a position signal every 1 ° by teeth provided on the outer periphery of the plate 19. Here, the engine speed N can be calculated by measuring the period of the reference signal.

Output signals from the air flow meter 6 and the crank angle sensor 17 are both input to the control unit 30. Furthermore, the voltage of the battery 20 is applied to the control unit 30 via the engine key switch 21 and directly for detecting the power supply voltage. Furthermore, if necessary, the control unit 30
Signals from a water temperature sensor 22 for detecting the temperature of the engine cooling water, a throttle sensor 23 including an idle switch for detecting a throttle valve opening of the throttle valve 7, and the like are input.
The control unit 30 performs arithmetic processing based on various input signals, outputs a drive pulse signal having an optimum pulse width to the fuel injection valve 11, and obtains a fuel injection amount for obtaining an optimum air-fuel ratio. That is, the air flow meter 6, the crank angle sensor 17, the water temperature sensor 22, the throttle sensor 23 and the like constitute an engine operating state detecting means.

Here, the microcomputer in the control unit 30 performs input / output operations and arithmetic processing in accordance with a program based on the flowcharts (fuel injection amount calculation routine, determination value change routine and fuel leak diagnosis routine) shown in FIGS. Then, the fuel injection amount is controlled and the fuel leak from the fuel injection valve is diagnosed.

In addition, basic fuel injection amount setting means, fuel leak diagnosis means,
The judgment value changing means, the accumulated time measuring means, the elapsed time measuring means and the changing means are achieved by the routine.

Next, the operation will be described with reference to the flowcharts shown in FIGS.

In the fuel injection amount calculation routine shown in FIG. 3, in step 1 (referred to as S1 in the figure, the same applies hereinafter), the intake air flow rate Q obtained from the signal from the air flow meter 6 and the engine rotation obtained from the signal from the crank angle sensor 17 are used. Number N
From this, the basic fuel injection amount Tp (= K · Q / N) is calculated. This part corresponds to basic fuel injection amount setting means.

In step 2, various correction coefficients COEF are set as needed.

In step 3, a learning correction coefficient Kl corresponding to the engine speed N representing the engine operating state and the basic fuel injection amount (load) Tp is calculated.
Search for.

Here, the learning correction coefficient Kl is obtained by dividing the map on a map of about 8 × 8 with the engine speed N as the horizontal axis and the basic fuel injection amount Tp as the vertical axis, dividing the area, and storing each area on the RAM. The learning correction coefficient Kl is stored every time. That is, the RAM functions as a storage unit. At the time when the learning is not started, all the learning correction coefficients Kl are set to the initial value 1.

In step 4, the voltage correction Ts is set based on the voltage value of the battery 20.

In step 5, it is determined whether or not the condition is a λ control condition.

Here, when the λ control condition is not satisfied, for example, in a high rotation, high load region, or the like, step 5 is performed with the feedback correction coefficient α clamped at the previous value (or the reference value 1).
Then, the process proceeds to Step 10 described later.

In the case of the λ control condition, the output voltage V _O2 of the O ₂ sensor 16 is compared with the slice level voltage V _REF corresponding to the stoichiometric air-fuel ratio in Steps 6 to 8 to determine the rich / lean air-fuel ratio, and perform integral control or proportional control. A feedback correction coefficient α is set by integral control. Specifically, in the case of the integral control, when it is determined that the air-fuel ratio = rich ( _VO2 > _VREF ) by the comparison in step 6, the feedback correction coefficient α is determined in step 7
Is reduced by a predetermined integral (I) with respect to the previous value. Conversely, when it is determined that the air-fuel ratio = lean ( _VO2 < _VREF ), the feedback correction coefficient α is set to the predetermined value (step S8). I) Increase by minutes. In the case of the proportional integral control, in addition to this, when the rich / lean is inverted, the larger proportional proportional (P) is increased or decreased in the same direction as the integral (I).

In the next step 9, a learning routine of the learning correction coefficient Kl performed in another routine is executed.

Then, in step 10, the fuel injection amount Ti is calculated according to the following equation.

Ti = Tp · COEF · Kl · α + Ts Here, as Kl, the one searched in step 3 or the one corrected in the learning routine is used.

When the fuel injection amount Ti is calculated, a drive pulse signal having a pulse width of the Ti is output at a predetermined timing in synchronization with the engine rotation, and fuel injection is performed.

Next, the determination value changing routine will be described with reference to the flowchart shown in FIG.

In step 31, the intake air flow rate Q detected by the air flow meter 6, the engine speed detected by the crank angle sensor 17 N, the engine coolant temperature Tw detected by the water temperature sensor 22, on the engine key switch 21S _EN An off signal and an on / off signal of a start switch (not shown) _{SST which} is also used by the engine key switch 21 are input.

In step 32, it is determined whether or not the engine key switch 21S _EN is ON.

If turned on the process proceeds to step 33 and executes the elapsed time measurement t _EN from the measurement and the start switch S _ST of cumulative time t _ST had turned on the start switch S _ST is turned on.

That is, step 33 functions as a cumulative time measuring means and an elapsed time measuring means.

In step 34, it is determined whether the fuel leak diagnosis condition is satisfied, that is, whether the engine load Tp and the engine speed N
A determination is made as to whether or not both have stayed in the large predetermined diagnosis target area for a predetermined time.

If the fuel leak diagnosis condition is satisfied, the routine proceeds to step 35, where a determination time CAT2 used in step 36 described later is searched from a three-dimensional map of the accumulated time t _ST and the engine coolant temperature Tw.

The process proceeds to step 36, the elapsed time t _EN determines whether less than the determination time CAT2 searched at step 35.

Here, as the determination time CAT2, as the cumulative performance time t _ST is shorter, and the starting performance degree indicating the difficulty of the startability of the engine is better, the probability of occurrence of oil dilution is lower, so that erroneous determination is less likely to occur. , Shortened.

The shorter the cooling water temperature Tw, the shorter. It is considered that the higher the cooling water temperature Tw, the higher the temperature of the entire engine 1, and the gasoline mixed into the oil by the oil dilution evaporates earlier, so that the erroneous determination related to the oil dilution does not occur. Because.

Then, in step 36, the elapsed time t _EN is equal to the determination time CAT.
If it is determined to be less than 2, the routine proceeds to step 37, where a three-dimensional map of the accumulated time t _ST and the engine coolant temperature Tw is used to determine a leak determination value DM used in a fuel leak diagnosis routine described later.
Search for RNG.

Here, the leak determination value DMRNG is set to be small, as the probability of occurrence of oil dilution becomes lower as the cumulative time t _ST becomes shorter and the starting performance becomes better, so that erroneous determination hardly occurs.

In addition, the cooling water temperature Tw is made larger as it becomes higher.
This is because the higher the cooling water temperature Tw, the higher the temperature of the entire engine 1, and the gasoline that has been mixed into the oil by the oil dilution evaporates earlier, and the erroneous determination related to the oil dilution is more likely to occur. Because it is possible.

On the other hand, in step 36, the elapsed time t _EN is equal to the determination time CAT2.
If it is determined that the above is the case, the process proceeds to step 38 to perform a normal leak diagnosis, and the leak determination value DMRNG is set to the reference determination value N.
Fixed to GFIX (for example, 20%).

That is, steps 36 to 38 serve the function of the changing means.

As described above, in the present embodiment, the accumulated time t
_The starting performance is determined based on _ST , and the elapsed time t
Determination time CAT in which _EN is set based on the accumulated time t _ST
If the value is less than 2, the leak determination value DMRNG is greatly changed.

Therefore, erroneous determination of fuel leak related to oil dilution due to deterioration of startability is prevented, and diagnostic accuracy can be improved.

Next, an outline of a fuel leak diagnosis performed using the leak determination value DMRNG will be described.

In the fuel leak diagnosis routine shown in FIG.
In 41, the learning correction coefficient Kl _IDLE for the air-fuel ratio feedback control in the idling operation region, the engine load Tp and the engine speed are selected from among the learning correction coefficients Kl stored and corrected for each region by the fuel injection amount calculation routine. The learning correction coefficient Kl ₁ of the predetermined diagnosis target area where both N are large is read.

In step 42, a difference ΔKl = Kl _IDLE −Kl ₁ between the learning correction coefficient Kl _IDLE and the learning correction coefficient Kl ₁ of the diagnosis target area is calculated.

In step 43, it is determined whether or not the ΔKl is equal to or greater than a leak determination value DMRNG obtained by the above-described determination value change routine. (Not shown).

That is, a fuel leak diagnosis unit is performed by the fuel leak diagnosis routine.

<Effects of the Invention> As described above, according to the present invention, for example, when the elapsed time since the start switch is turned on is shorter than a predetermined time set based on the accumulated time, that is, when the engine is started. During the predetermined period determined based on the degree of starting performance indicating the difficulty of sex, the determination value for comparing the difference in the learning correction coefficient between the idling operation region and another predetermined operation region is greatly changed.

Therefore, in a diagnostic device for self-diagnosis of a steady fuel leak from a fuel injection valve, erroneous determination of fuel leak related to oil dilution caused by deterioration of startability is prevented, and diagnostic accuracy is improved. There is an effect that improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention, FIG. 2 is a configuration diagram showing one embodiment of the present invention, and FIGS. 3 to 5 are flowcharts showing control contents according to the embodiment. . 1 ... engine, 6 ... air flow meter, 11 ... fuel injection valve, 17 ... crank angle sensor, 21 ... engine key switch, 22 ... water temperature sensor, 30 ... control unit

Claims (2)

(57) [Claims] An engine operating state detecting means for detecting an engine operating state including an engine speed, an engine intake air flow rate and a cooling water temperature of the engine, and an engine operating state detected based on the engine operating state detected by the engine operating state detecting means. Basic fuel injection amount setting means for setting the fuel injection amount, storage means for storing a learning correction coefficient for correcting the basic fuel injection amount for each region of the engine operating state, an idling operation region and other predetermined operations A fuel leak diagnostic means for diagnosing whether or not fuel is leaking from the fuel injection valve based on whether or not a difference between the learning correction coefficient with the region is equal to or greater than a determination value; and a starting performance degree indicating difficulty in starting the engine. A determination value changing means for largely changing a determination value in the fuel leak diagnosis means for a predetermined period set by the fuel leak diagnosis means. Cross-sectional devices. 2. The method according to claim 1, wherein the determination value changing means includes a cumulative time measuring means for measuring a cumulative time during which the start switch is on, and an elapsed time measuring means for measuring an elapsed time after the start switch is turned on. When the elapsed time is less than a predetermined time set based on the cumulative time, the determination value is calculated based on the coolant temperature detected by the engine operating state detecting means and the cumulative value measured by the cumulative time measuring means. 2. A changing means for changing to a predetermined value set on the basis of time.
A fuel leak diagnosis device for an electronically controlled fuel injection type internal combustion engine according to claim 1.