JPH10252539A - Trouble diagnostic method and device for fuel injection device. - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diagnose a trouble of a fuel injection device arbitrarily at any time, including an engine stopping period. SOLUTION: An ECU(engine control unit) 1 has a CPU9, main relay circuit 8, various current generating circuits, various switching circuits, power transistors 15a to 15d, etc. Curing operation or stop of an engine, based on a command of the CPU9, a trouble decision current generating circuit 12 generates, separately from an ordinary injection current, a trouble decision current of low level without actuating a needle of an injector. This trouble decision current is detected by a current voltage converter resistor 16, based on this detection, a trouble diagnosis of a fuel injection device is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for diagnosing a failure of a fuel injection device for supplying fuel to each cylinder of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, various types of this type of technology have been proposed, for example, one described in Japanese Patent Application Laid-Open No. 2-283837, entitled "Failure Diagnosis Device for Fuel Injection Device". FIG. 7 shows a circuit diagram of this device. In this failure diagnosis device, the coils 52a to
It is to diagnose whether a normal drive current is flowing through 52f.

In the device shown in FIG. 7, fuel injection is performed as follows. An injection timing signal is output from the control circuit 50, and the injection timing signal is
0, and each driving transistor 65
a to 65c. During this predetermined time, the respective drive transistors 65a to 65c are turned on, and the drive coils 52a to 52f of the respective fuel injection valves are supplied from the battery.
, And each fuel injection valve injects fuel.

[0004] Further, the failure diagnosis device shown in FIG. 7 is provided with a failure detection circuit. This failure detection circuit includes resistors 66a to 66
c, resistors 70 and 7 for setting the set voltage Vref
1. Comparators 68a to 68c for comparing a voltage conversion value of the detected current with a set voltage Vref, and a logic circuit 80
It is composed of

[0005] The failure diagnosis in this device is performed as follows. That is, if a disconnection failure occurs in the coils 52a to 52f and its wiring system during fuel injection, the resistors 66a to 66f
6c, the resistances 66a-66
The voltage conversion value of the detection current by c also decreases and falls below the set voltage Vref. The set voltage Vr
ef is set to a voltage value at which a disconnection failure can be detected in advance. As a result, the outputs of the comparators 68a to 68c are inverted, and the information is transmitted to the control circuit 5 via the logic circuit 80.
It is input to 0 to diagnose a disconnection fault.

[0006]

In the prior art, the failure of the fuel injection device is diagnosed from the current value (voltage value) during the actual fuel injection. Therefore, when fuel injection is not performed, that is, when the engine is stopped, failure diagnosis of the fuel injection device cannot be performed. Therefore, the failure diagnosis of the fuel injection device must always be performed while the engine is running. If the failure is diagnosed by injecting fuel at the time of the failure of the fuel injection device, the failure may be propagated. There was also.

Further, the conventional failure diagnosis is performed by detecting only a normal injection current, and the normal injection current is supplied only at predetermined time intervals. For this reason, there is also an inconvenience that failure diagnosis cannot be performed at an arbitrary time.

The present invention has been made in view of the above circumstances, and has as its object to provide a fuel injection device capable of arbitrarily diagnosing a failure of the fuel injection device at any time even when the engine is stopped. To provide a failure diagnosis method and device therefor.

[0009]

According to a first aspect of the present invention, there is provided a method for diagnosing a failure in a fuel injection device of a current drive type, comprising the steps of: Generates a low current that does not work,
The gist is to diagnose a failure of the fuel injection device by detecting a current value when the low current is supplied to the fuel injection valve.

According to the above method, a failure of the fuel injection device can be diagnosed by supplying a low current to the fuel injection valve such that the fuel injection valve does not operate and detecting the current value. Therefore, the failure diagnosis of the fuel injection device can be performed at any time without operating the fuel injection valve.

According to a second aspect of the present invention, there is provided a method for diagnosing a failure of a fuel injection device according to the first aspect, wherein the failure diagnosis of the fuel injection device is performed when the engine is stopped. And

According to the above method, since the failure diagnosis of the fuel injection device is performed when the engine is stopped, even if a failure has occurred in the fuel injection device, the failure diagnosis is surely and safely confirmed. be able to.

According to a third aspect of the present invention, there is provided a failure diagnosis device for a fuel injection device of a current drive type, wherein a low current generation for generating a low current such that the fuel injection valve does not operate. And a current detecting means for detecting a current value when the low current is supplied to the fuel injection valve.

According to the above configuration, a failure of the fuel injection device is diagnosed by generating a low current so that the fuel injection valve does not operate and detecting a current value when the low current is supplied to the fuel injection valve. can do. Therefore, the failure diagnosis of the fuel injection device can be performed at any time without operating the fuel injection valve.

According to a fourth aspect of the present invention, in the failure diagnosis apparatus for a fuel injection device according to the third aspect, the low current generating means is configured to prevent the fuel injection valve from operating. The gist is that a very low current is generated when the engine is stopped.

According to the above configuration, since the failure diagnosis of the fuel injection device is performed when the engine is stopped, even if a failure has occurred in the fuel injection device, the failure diagnosis is surely and safely confirmed. be able to.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment Hereinafter, a first embodiment of a failure diagnosis device for a fuel injection device embodying the present invention will be described in detail with reference to FIGS.

As shown in FIG. 1, the ECU (engine control unit) 1 includes a CPU 9, a main relay driving circuit 8, various current generating circuits, various switching circuits, power transistors 15a to 15d, and the like.

The CPU 9 performs overall fuel injection control and failure diagnosis while taking in the signal from the engine speed sensor 6 through the input circuit 7, and mainly performs a generated current switching circuit for the control and diagnosis. 13, switching commands corresponding to various timings are issued to the switching circuits of the cylinder switching circuit 14 and the reference voltage switching circuit 17. Based on this switching command, a predetermined current is supplied to the power transistors 15a to 15d for a predetermined time. Based on such power supply control by the CPU 9, each power transistor is driven in a predetermined manner for a predetermined time, and a predetermined reference voltage is applied to the inverting input of the comparison circuit 18 for a predetermined time.

The CPU 9 controls ON / OFF of the main relay 5 through the main relay drive circuit 8 by turning on / off the ignition switch 4 to control power supply from the battery 3 to the ECU 1. In particular, when the ignition switch 4 is turned off, the CPU 9 performs “main relay control” described later in detail through the main relay drive circuit 8.

On the other hand, the generation current switching circuit 13 includes a circuit for generating a current flowing through the power transistors 15a to 15d, out of the starting current generation circuit 10, the constant current generation circuit 11, and the failure determination current generation circuit 12. , CPU 9
This is a circuit to be selected according to the instruction.

Here, the starting current generating circuit 10 is shown in FIG.
(A), a is a circuit which generates a large starting current I ₁ such as the needle of an injector (fuel injection valve) (not shown) is quickly reliably opened to the power transistors 15 a to 15 d. Also, this starting current generating circuit 1
0, as the reference voltage Vr1, the starting current I ₁ is generated slightly below the voltage of the converted voltage value when the flow through the current-voltage conversion resistor 16 is inputted to the reference voltage switching circuit 17.

As shown in FIG. 2A, the holding current generating circuit 11 holds a holding current (constant current) I ₂ that holds the needle from the fully opened state until the injection is completed. Is generated for the power transistors 15a to 15d. Switching from the activation current I ₁ to the holding current I ₂ is performed for the following reason. In other words, needle injectors, once open Shimae if also be held fully open in a small holding current I ₂ from the starting current I _1, due to being able to reduce the response delay of the needle when exiting further injection. Further, the holding current generating circuit 11 as the reference voltage Vr2, and generates a slightly below voltage converted voltage value when the holding current I ₂ flows through the current-voltage conversion resistor 16, the input to the reference voltage switching circuit 17 I do.

The fault judging current generating circuit 12 is also configured as shown in FIG.
(A), a is a circuit for generating the holding current (constant current) smaller failure determination current than I ₂ (constant current) I ₃ to the power transistor 15 a to 15 d. Incidentally, as shown in FIG. 2 (b), the needle of the injector is not influenced at all by the failure determination current I _3. In other words, does not the needle is operated to open even if the failure determination current I ₃ flows. Further, the failure determination current generating circuit 12 as the reference voltage Vr3, the failure determination current I ₃ generates slightly below the voltage conversion voltage value when the flow through the current-voltage conversion resistor 16, a reference voltage switching circuit 17 Enter

The cylinder switching circuit 14 sequentially selects one power transistor from the power transistors 15a to 15d based on a command from the CPU 9, and drives the selected power transistor for a predetermined time based on each of the current values. This is the circuit that sets the state.

The reference voltage switching circuit 17 is connected to the CPU 9
During the period in which the starting current I ₁ , the holding current I ₂ and the failure judging current I ₃ are generated, the reference voltages Vr 1, Vr 2 and Vr 3 corresponding to the starting current I ₁ , the holding current I ₂ and the failure judging current I ₃ are appropriately switched and applied to the inverting input of the comparison circuit 18. Circuit.

On the other hand, the current-voltage conversion resistor 16 converts the current value I flowing through the injector coils 2a to 2d into a voltage value Vi. Then, the converted voltage value V
i is applied to the non-inverting input of the comparison circuit 18.

The comparison circuit 18 calculates the reference voltages Vr1, Vr
r2 and Vr3 and the voltage conversion value Vi of the current flowing through the injector coils 2a to 2d are timely compared, and the result is compared with the CP.
Input to U9. That is, the voltage conversion value Vi by the current-voltage conversion resistor 16 is equal to the reference voltages Vr1, Vr2, and Vr3.
Is exceeded, that is, when the injector coil current is normally detected, the output of the comparison circuit 18 is input to the CPU 9 as a logical high level (normal information). If the injector coil current is not detected due to disconnection or the like, on the other hand, the reference voltages Vr1, Vr2, and Vr
3 exceeds the converted voltage value Vi, the output of the comparison circuit 18 is input to the CPU 9 as a logic low level (failure determination information).

In the present embodiment, a four-cylinder engine provided with four injectors (fuel injection valves) is assumed. The injectors are coils 2a to 2d
The current-driven injector is driven by a current flowing through the injector. The coils 2a to 2d are the first to fourth coils, respectively.
It shall correspond to a cylinder.

In FIG. 2, FIG. 2A shows a coil current waveform of the injector, and FIG. 2B shows an operation waveform of the needle of the injector corresponding to the current waveform. This current waveform corresponds to the waveform of the current I on the non-ground side of the current-voltage conversion resistor 16.

That is, the injector needle
Large starting current I to ensure opening ₁The injector
T on the il 2a-2d₁After flowing for a period, the needle
Fully open state at a stretch due to the electromagnetic action of the
Becomes Then start the current after the needle is fully open
Current I₁Smaller holding current I_TwoEven if you switch to
Holding current I_TwoThus, the fully opened state of the needle is maintained.
Note that the starting current I ₁And holding current I_TwoIs the injection current I
_DAnd It should be noted that current flows through each of the injector coils 2a to 2d.
Injection current I_DIs I as shown in FIG._Da, I_Db, I
_Dc, I_DdAnd 2 (a) and 2 (b).
Thus, the failure determination current I_ThreeTo the injector coils 2a to 2
The needle does not change at all even if electricity is supplied to d.

Next, a failure diagnosis method by the failure diagnosis device for a fuel injection device having the above configuration will be described with reference to timing charts shown in FIGS. In the ECU 1,
First, the CPU 9 determines the injection start timing T _{0 and the} injection time t _L from information of sensors such as the engine speed sensor 6. When the injection start timing T ₀ is reached, CP
At the same time that the starting current generating circuit 10 is started by U9,
The injector to be injected by the cylinder switching circuit 14 is determined.
The injector coils 2a to 2d of each cylinder are driven by power transistors 15a to 15d. When the CPU 9 recognizes that the starting current has reached the predetermined current value I ₁ after the elapse of the time t ₁ by the output of the comparing circuit 18, the CPU 9 switches from the starting current generating circuit 10 to the holding current generating circuit 11. The holding current I ₂ continues to flow until the injection end timing T _C , and at the same time, the current-voltage conversion resistor 16 and the comparison circuit 18 monitor whether the constant current (holding current) I ₂ is flowing accurately. The above is the normal operation.

On the other hand, the power transistor 15 of the ECU 1
a to 15d from the collector output to the injector coil 2a
When a failure such as a disconnection occurs in a route (hereinafter, referred to as a “fuel injection system”) leading to ２2d, the device of the present embodiment detects the failure by the following method.

When the fuel injection system fails, for example, as shown in FIG.
As shown in (a), when a disconnection occurs in the injector coil 2c, the ECU 1 attempts to flow the injection current I _Dc to the injector coil 2c.
Since the disconnection has occurred in c, the injection current I _Dc does not flow. Therefore, the injection current I _Dc is not detected by the current-voltage conversion resistor 16. As a result, the reference voltage Vr1 to the inverting input of the aforementioned comparison circuit 18, even Vr2 is applied, a predetermined voltage corresponding to each of these predetermined starting current I ₁ and the holding current I ₂ is non-inverting the comparison circuit 18 Since it is not input to the input, a failure determination output (low output) is output from the comparison circuit 18 to the CPU 9. This failure judgment is the normal failure determination, to do this the failure determination E _1. Incidentally, when the failure determination E ₁ is made, together with the fact is informed to the driver by a display device (not shown),
This is written in a backup memory or the like (not shown). The written contents are provided for diagnosis and repair at a dealer or the like.

[0035] When the failure determination E ₁ is made, FIG. 3
As shown in (b) and (c), the ECU ₁ outputs the failure determination current I ₃ for a predetermined time (t _f ) after a predetermined time (t _i ) from the failure determination time E ₁ . The failure determination current I ₃ is generated by the failure determination current generation circuit 12 based on a command from the CPU 9.

[0036] As described above, the failure determination current I ₃ without the injector coil 2c not operate even by flowing, yet if the failure of the fuel injection system is continuously same failure determination current I ₃ ECU
Since it does not return to 1, the failure of the fuel injection system can be determined again in the same manner as the normal failure determination. The failure determination by the failure determination current I _3, and the failure determination E _2. Even if the failure determination E ₂ is made, as in the case of failure determination E _1, with informed to the driver by a display device (not shown), the fact is written to the backup memory or the like.

The effects obtained by the above-described embodiment will be described below. - failure determination current I ₃ is therefore no influence on the movement of the needle of the injector, it is the failure diagnosis of the fuel injection system other than the normal injection time.

[0038]-normal failure determination E ₁ immediately after the failure determination E
_{Since step 2} is performed, a reliable diagnosis determination can be obtained. - because of normal failure determination E ₁ failure determination E ₂ immediately takes place, if the normal failure determination E ₁ was erroneously determined, it is possible to detect the erroneous determination immediately by the failure determination E _2.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. 4 to 6, focusing on differences from the first embodiment. In addition,
The configuration of the failure diagnosis device for a fuel injection device according to the second embodiment is the same as that of the first embodiment, and the same components as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted. .

In the first embodiment according to the present invention, the failure diagnosis of the fuel injection device is performed when the engine is operating. In the present embodiment, the failure diagnosis is performed when the engine is stopped. When the engine is stopped, the engine is stopped by turning off the ignition switch 4 (hereinafter, referred to as “ignition switch OF”).
There is a case where engine stall (engine stall) occurs for some reason (hereinafter referred to as “stall time”).

4 and 5 show timing charts for failure diagnosis when the ignition switch (IGSW) is OFF, and FIG. 6 shows timing charts for failure diagnosis when the engine stalls.

In the present embodiment, the ECU 1 employs "main relay control" in which the power supply from the battery 3 is maintained for a while even after the ignition switch is turned off, and the operation of the "main relay control" is as follows. It is like.

In FIG. 1, the ignition switch 4
Is turned on, the main relay 5 is turned on via the main relay circuit 8 in the ECU 1. As a result, power is supplied to the entire area of the ECU 1. In FIG. 4 (b), shows the ON time of the main relay 5 at T _on. Next, when the ignition switch 4 is turned off, the OFF signal enters the CPU 9 via the main relay circuit 8. This O
In response to the FF signal, the CPU 9 stops control of injection, ignition, and the like, and stops the engine.

Further, when the ignition switch 4 is
F to a certain time the power supply to the ECU1 from (t _m) O
After maintaining the N state, the power supply to the ECU 1 is stopped by turning off the main relay 5 through the main relay circuit 8 according to a command from the CPU 9. In FIG. 4B, the OFF state of the main relay 5 is indicated by T _off .
In general engine control system, IS this t _m period
Initialization of a C (idle speed control) and an EGR (exhaust gas recirculation device) motor is performed.

Next, a failure diagnosis method when the ignition switch is turned off will be described with reference to FIGS. 4 (a) to 4 (e). The failure diagnosis timing charts shown in FIGS. 4A to 4E show a case where a failure has occurred in the fuel injection system of the second cylinder.

It is assumed that a failure occurs in the fuel injection system of the second cylinder during the operation of the engine at the point A shown in FIG. Thereafter, at a point B shown in FIG. 4A, the ignition switch 4 is turned off to enter "main relay control". During this “main relay control” period t _m , the failure determination currents I _3a , I _3b , I _3c and I _3d flow from the first cylinder in order. At point C shown in FIG. 4 (e), it is detected from the failure determination current _I3b that a failure has occurred in the fuel injection system of the second cylinder.

The ECU 1 performs a normal failure determination E₁Together
Fault diagnosis timing chart when
5 (a) to 5 (d). In this case, the CPU 9
"Main relay control" period t_mWithin the normal failure judgment E ₁
The fault determination current I is applied only to the cylinders whose_ThreeShed
To make a fault diagnosis. That is, the failure diagnosis shown in FIG.
, The failure determination current I of the fuel injection system of the second cylinder_3bonly
It is also possible to diagnose the failure by flowing
Is greatly reduced.

Next, the failure detection at the time of engine stall will be described with reference to FIG.
A description will be given based on the failure diagnosis timing charts shown in FIGS. This timing chart also shows a case where a failure has occurred in the fuel injection system of the second cylinder, as in the case of the failure diagnosis shown in FIG. It is also assumed that the engine stall has occurred due to a failure in the fuel injection system of the second cylinder.

In FIG. 6C, at point D, the ECU 1 detects an engine stall based on the fact that no signal is input from the engine speed sensor 6. Thereafter, the failure determination currents I _3a , I _3b , I _3c and I _3d are passed through each cylinder, and it is detected at point E shown in FIG. 6 (e) that a failure has occurred in the fuel injection system of the second cylinder. I do. When the engine stall occurs due to a cause other than the fuel injection system, the apparatus naturally detects nothing.

The effects obtained by the above-described embodiment will be described below. In the present embodiment, since the failure diagnosis of the fuel injection device is performed when the engine is stopped, it is not necessary to restart the engine to confirm the failure of the fuel injection device. Moreover, the failure determination current I ₃ because it is set to a value smaller than the startup current I ₁ and the holding current I ₂ to open the needle of the injector, does not participate any influence on the normal fuel injection system.

The above embodiment can be embodied with the following modifications. In each of the embodiments, the failure diagnosis device for the fuel injection device in the four-cylinder engine having four injectors has been described, but the invention is not limited to this. The number of cylinders of the target engine is arbitrary.

In each of the embodiments, the current-voltage conversion resistor 16 and the comparison circuit 18 are configured common to the injector coils 2a to 2d. However, the current-voltage conversion resistance 16 and the comparison circuit 18 are provided separately for the injector coils 2a to 2d. Is also good. That is, four current-voltage conversion resistors 16 and four comparison circuits 18 may be used. Further, the current-voltage conversion resistor 16 and the comparison circuit 18 may be provided for each of the two injector coils.

In each of the embodiments, the holding current generation circuit 11 and the failure determination current generation circuit 12 have different configurations. However, since each of them is a constant current generation circuit, the failure determination current generation circuit 12 The configuration may be such that it is shared by the generation circuit 11.

In each of the embodiments, the power transistor 15 is used as a device for driving the injector coil.
Although a to 15d were used, the invention is not limited to this. A power FET or the like may be used as the driving device.

In the first embodiment, an example has been described in which the failure determination current I ₃ is supplied after the failure determination E ₁ based on the injection current _ID is confirmed to perform the failure determination E ₂ , but the present invention is not limited to this. Not something. For example, in a normal not failure determination E _1, at a predetermined time interval injection current I
It may be periodically passing a failure determination current I ₃ after _D.

According to this configuration, it is possible to detect a failure that has occurred immediately after the injection of the injection current _ID . · In the second embodiment, not an example is shown in which the failure diagnosis of the fuel injection device is not limited to this in the "main relay control" period t _m after the engine stop. For example, even when the engine is stopped, power may be supplied from the battery 3 to the failure diagnosis device of the fuel injection device, and a switch for operating the failure diagnosis device may be provided so that the failure diagnosis can be performed at any time when the engine is stopped.

Further, the technical idea grasped by the above embodiment will be described below. The failure diagnosis method for a fuel injection device according to claim 1, wherein the low current is generated immediately after a normal injection current is generated, and the fuel injection device is energized. Method.

According to this diagnosis method, the failure diagnosis is performed again immediately after the normal failure diagnosis, so that a reliable diagnosis can be obtained.

[0059]

According to the first and third aspects of the present invention, the failure diagnosis of the fuel injection device can be performed at any time without operating the fuel injection valve.

According to the second and fourth aspects of the present invention, the failure diagnosis of the fuel injection device can be performed when the engine is stopped.

[Brief description of the drawings]

FIG. 1 is a block diagram showing first and second embodiments of a failure diagnosis device for a fuel injection device according to the present invention.

FIG. 2 is a timing chart showing a relationship between an injection current _ID and opening and closing of a needle of an injector.

FIG. 3 is a timing chart showing a diagnosis mode according to the first embodiment.

FIG. 4 is a timing chart showing a diagnosis mode according to the second embodiment.

FIG. 5 is a timing chart showing a diagnosis mode according to the second embodiment.

FIG. 6 is a timing chart showing a diagnostic mode according to the second embodiment.

FIG. 7 is a block diagram showing an example of a conventional failure diagnosis device for a fuel injection device.

[Explanation of symbols]

8: Main relay drive circuit, 9: CPU, 10: Starting current generating circuit, 11: Holding current generating circuit, 12: Failure determining current generating circuit, 13: Generated current switching circuit, 14: Cylinder switching circuit, 15a to 15d Power transistors, 16 ...
Current-voltage conversion resistor, 17: reference voltage switching circuit, 18: comparison circuit.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI G01M 15/00 F02M 69/00 380F

Claims (4)

[Claims] 1. A method for diagnosing a failure in a fuel injection device of a current drive type, comprising: generating a low current such that a fuel injection valve does not operate; and detecting a current value when the low current is supplied to the fuel injection device. A failure diagnosis method for the fuel injection device, which diagnoses the failure of the fuel injection device. 2. The failure diagnosis method for a fuel injection device according to claim 1, wherein the failure diagnosis of the fuel injection device is performed when the engine is stopped. 3. A failure diagnosis device for a current drive type fuel injection device, comprising: a low current generation means for generating a low current such that a fuel injection valve does not operate; and when the low current is supplied to the fuel injection device. And a current detecting means for detecting a current value of the fuel injection device. 4. The failure diagnosis device for a fuel injection device according to claim 3, wherein the low current generation means generates a low current such that the fuel injection valve does not operate when the engine is stopped. Diagnostic device for a fuel injection device.