GB2229280A

GB2229280A - Abnormality detecting

Info

Publication number: GB2229280A
Application number: GB9002807A
Authority: GB
Inventors: Kazuyuki Tazawa
Original assignee: Fuji Jukogyo KK; Fuji Heavy Industries Ltd
Current assignee: Subaru Corp
Priority date: 1989-02-16
Filing date: 1990-02-08
Publication date: 1990-09-19
Also published as: JPH02216068A; DE4004413A1; GB9002807D0

Description

A 1 ABNORMALITY DETECTING SYSTEM FOR ELECTRIC CIRCUITS The present

invention relates to a system for detecting abnormality of an operating circuit, such as an electric circuit of an electronic control system for a motor vehicle.

The electronic control unit provided on a motor vehicle has a plurality of operating circuits for operating various actuators. such as fuel injectors. A recent electronic control unit has a self-diagnostic circuit for diagnosing-operations of the operating circuits.

Japanese Patent Application Laid-open No. 63-27769 discloses a selfdiagnostic system for confirming operation of the operating circuits in an electronic control system for a motor vehicle. In the self-diagnostic systemi a shunt is provided for detecting the current in a main electric line. The system has a detecting circuit comprising a window comparator and a logic product circuit for detecting the operation of each operating circuit.

There is a considerable difference between the load current at a time when all the operating circuits are operated and the load current at a time when only one operating circuit is operated. Therefore# the voltage of the battery of the vehicle 2 varies in accordance with the operating conditions of the operating circuits. Consequently, a reference current provided for determining an abnormality of a corresponding load current varies with the voltage of the battery. which causes misjudgement of the operating circuit.

In a motor vehicleg the battery has a moderate capacity on the ground of economy. The voltage at the terminals of the battery is kept constant as far as possible by an alternator and a voltage regulator but. if a large number of loads. such as headlamps, hazard lamps, rear defogger, wiper, air conditioner, and others. are turned on at the same time. the voltage at the battery reduces. If the load current in one of the operating circuits is detected in this state for determining whether the circuit is abnormal, it is misdiagnosed as being abnormal because a reduced load current dependent on the low voltage becomes lower than the reference current.

An object of the present invention is to provide an abnormality detecting system in which an abnormality of an operating circuit is reliably detected.

According to a first aspect of the present invention. a system for detecting abnormality of an operating circuit including a battery, and an actuator controlled by a control signal from a control unit 0 3 comprises first detector means for detecting the terminal voltage of the battery; first comparator means for comparing the voltage detected by the first detector means with a reference voltage and for producing a signal when the detected voltage is higher than the reference voltage; second detector means for detecting current flowing in the operating circuit as a result of the control signal; and second comparator means responsive to the signal from the first comparator means for comparing the current detected by the second detector means with a reference value to decide whether the current is abnormal.

According to a second aspect of the present invention. a method of detecting abnormality of an operating circuit including a battery as a source. an actuator controlled by a control signal from a control unit. and a current sensor for detecting current flowing in the operating circuit comprises determining the terminal voltage of the battery; comparing the terminal voltage with a reference voltage and producing an enabling signal when the detected voltage is higher than the reference voltage; detecting current flowing in the operating circuit as a result of the control signal; and deciding whether or not the current is abnormal by comparing the detected current with a reference value.

In order that the invention may be more 4 readily understood, it will now be described. by way of example only. with reference to the accompanying drawings. in which:- Figure 1 is a block diagram showing a circuit of an abnormality detecting system according to the present invention; Figure 2 is a block diagram formed in accordance with the function of the system; Figure 3a is an illustration showing a current detecting sensor of the system; 3b shows a graph showing the the sensor; shows waveforms of iniector driv Figure characteristic of Figure 4 pulse and injector Figure 5 operating circuit Figures operation of the R^ e current; is a table showing currents in an for fuel injectors; and 6a to 6c are flowcharts showing the system.

Referring to Fig. 1, an electronic control unit (ECU) 1 is provided in an automobile for controlling an engine, a transmission, an air-conditioner and others. The electronic control unit 1 comprises a central processor unit (CPU) 2p a ROM 3. a RAM 4, a backup RAM 4a. a timer 5. an output interface 6 and an input interface 7. which are connected to each other through a bus line 8. An oscillator 2a is connected to the CPU 2 for producing standard clock pulses which is divided and counted by a freerunning counter of: the timer 5. The standard clock pulses are counted for determining timings of various di agnoses. The ROM 3 stores various control programs for controlling various systems.

The engine control system will be described hereinafter.

The output interface 6 is connected to a base of each of transistors 12 and 13 and an external transistor 14 through resistors 9, 10 and 11. respectively. Collectors of the transistors 12. 13 and 14 are connected to various actuators such as a pair of coils 16a and 16b of fuel 6 injectors 16, a pair coils 18a and 18b of fuel injectors 18, and a coil 19a of an ignition coil 19, respectively.

The coils 16a and 16b, as well as the coils 18a and 18b, are connected to each other in parallel. In the four-cylinder engine, a pair of cylinders are adapted to be injected at the same time. These coils are connected to a battery 21 through a load current detecting sensor 23 and a main electric line 22. The output interface 6 is further connected to a self-diagnosis lamp 20 for indicating abnormalities of the actuators. Thus, actuator operating circuits A are formed. The load current detecting sensor 23 is provided for detecting current IL flowing in each actuator operating circuit A.

The input interface 7 is applied with voltage from the battery 21 and voltage from the load current detecting sensor 23 through an A/D converter 24. Further, output signals from various sensors 25 such as an intake-air quantity sensor, a crank angle sensor and an 0 2 sensor are applied to the input interface 7.

I The ROM 3 stores fixed data and the RAM 4 is provided for storing data of output signals from sensors 25 and data processed at the CPU 2. The backup RAM 4a is provided to store trouble data of the actuators 16, 18 and 19 and the sensors 25. The RAM 4a is backed up by the battery 21 so as to maintain the stored data even if a key switch (not shown) is in offstate.

11 7 The CPU 2 makes calculations of control value based on the data stored in the RAM 4 in accordance with the control programs stored in the ROM 3. The calculated control data is stored in the RAM 4 and applied to the actuators 16. 18 and 19 through the output interface 6 at a predetermined timing. If an abnormality is detected. the CPU 2 produces a signal to light the lamp 20 and the trouble data is stored on the RAM 4a.

Figure 3a shows the load current detecting sensor 23. The sensor 23 comprises a core 23a made of ferrite and having windings wound around the core 23a to form transformers. a Hall element 23b and an amplifier 23c. Each of the windings is connected to a corresponding line of the actuator operating circuits A. such as a line for the injector 16. The sensor 23 detects the current in the circuits A without influencing the characteristic of the current.

When power is supplied to one of the actuator operating circuits A, a magnetic field is formed in the load current detecting sensor 23. Magnetic flux flows through the Hall element 23bi so that a voltage is produced in the Hall element 23br which is amplified by the amplifier 23c. As shown in Figure 3b. the output voltage of the load.current detecting sensor 23 has a linear relationship with total current flowing in the circuits A. An offset voltage exists -

8 in the Hall element 23b and appears at the output terminal of the sensor 23 as an offset voltage VO.

Referring to Fig. 2, the electronic control unit 1 is provided with an input processing means 30 applied with output signals from the sensors 25, battery 21 and current detecting sensor 23 for performing a waveform shaping process and an analog-digital conversion process. Processed signals are applied to control value calculator means 31 and then stored in memory means 32. The calculator means 31 is provided for calculating various control values,such as fuel injection quantity, based on the input signals in accordance with the control programs.

An output processing means 33 is provided for producing control signals for controlling the actuator operating circuits A.

A circuit condition determining means is provided for determining the condition of the actuator operating circuits A. The circuit condition determining means comprises a circuit current calculating means 35a and an abnormality determining means 35b. The circuit condition determining means executes an interrupt operation for the determination of the abnormality in the CPU 2. which is started by the timer 5.

The circuit current calculating means 35a reads the offset current of the current detecting sensor 23 at a time when no control signals are applied from the output 1 Ir 1 9 processing means 33 to the operating circuits A and the output current from the sensor 23 after a predetermined time has passed since the output processing means 33 starts to produce the control signal which is applied to the operating circuit A.

The circuit current calculating means 35a calculates the load current IL flowing in one of the actuator operating circuits A in accordance with the offset current and the output from the current detecting sensor 23, and produces a load current signal which is applied to the abnormality determining means 35b.

The operation of the system is described hereinafter with reference to Figs. 1 to 4.

The offset current of the sensor 23 varies with the temperature of the sensor and with the lapse of time. Therefore, in order to detect the load current IL, the offset current is subtracted from the output of the sensor 23 as described below.

As an example, the diagnosis of the circuit of the fuel injector 16 is described hereinafter with reference to Fig. 4.

When the control signal Pi is applied to the fuel injector 16, (18), the actual load current IL at a predetermined time Tl after the beginning of the control signal Pi is obtained. The offset current ILTo at the time i 1 4 To when the control signal Pi is raised or before the generation of the control signal Pi is obtained.

Since the fuel injector 16 has an inductance load. a current Iinj of the fuel injector 16 delays with respect to the control signal Pi. Therefore, the offset current may be obtained at the time To when the control signal is generated. However, if the actuator has a. resistance load, capacitive load or lamp load, the current does not delay. Accordingly, the offset current may be obtained before the generation of the control signal.

The obtained offset current ILTo is substracted from the current ILT1 based on the output voltage of the sensor 23 at a time Tl to produce a current IL UL = ILT1 - ILTo) flowing in the corresponding actuator such as injector 16 (18).

The abnormality determining means 35b compares the current IL with a reference current IR for determining the abnormality of the operating circuit and produces a signal which is applied to a self-diagnosis means 36. The 'memory means 32 stores a plurality of reference currents IR corresponding to the operating circuits, respectively, which are arranged in a table. The reference currents IR are obtained by experiments in consideration of the decrease of the load current IL at the time when all of the actuator operating circuits A are turned on at the same time.

11 A voltage level detecting means 34 is provided for preventing the circuit condition determining means from misjudging in the determination of the abnormality of the operating circuit A. More particularly, the voltage level detecting means 34 is connected to an output terminal of the battery 21 via the input processing means for monitoring the voltage BV at the terminal of the battery 21. The voltage level detecting means 34 compares the voltage BV with a predetermined reference voltage BVo. When the voltage BV is higher than the reference voltage BVo, the voltage level detecting means 34 permits the circuit condition determining means to perform the diagnosis interrupt operation. If the voltage BV is lower than BVo, the diagnosis operation is inhibited as described hereinafter.

Referring to Fig. 5, when the other operating circuits except for the operating circuit for a pair of fuel injectors 16 or 18 are turned of f at idling of the engine, the load current IL in the fuel injector operating circuit is 0.952A. When all of the circuits for electric loads such as headlamps (high beam), hazard lamps, stoplights, rear defogger, cigar lighter, wiper, air conditioner, blower (high) and others are turned on at the same time, the load current IL is reduced to 0.769A with the decrease of the voltage BV of the battery 21.

When a - disconnection occurs only in the operating circuit of the fuel injector 16. the current IL becomes f 12 0.439A. If the reference current IR for the two fuel injectors 16 (18) is set to 0.586A. the load current IL becomes smaller than the reference current IR as shown in the table. If the diagnosis is performed under such a condition, the diagnostic system makes a mistake.

In order to prevent such a mis-judgement, when the voltage BV of the battery 21 is smaller than the reference voltage BVo, the voltage level detecting means 34 inhibits the diagnosis interrupt operation by the timer 5, thereby stopping the abnormality determining operation in the means 35. Thus, misjudging abnormality caused by the decrease of the voltage BV is prevented.

When the load reduces to an ordinary level and the voltage BV exceeds the reference voltage BVo, the abnormality determining operation in the circuit condition determining means 35 restarts.

When the circuit condition determining means 35 determines the abnormality of one of the actuator operating circuits A, an abnormality signal is applied from thh means 35b to the self-diagnosis means 36. The self-diagnosis means 36 operates to store the trouble data in the memory means 32 and to turn on the self-diagnosis lamp 20.

The trouble data stored in the memory means 32 can be read by connecting another diagnostic device which is provided in an auto shop. Thus, an abnormal position in the system can be easily known at the auto shop.

cl I 'i 13 The operation of the control unit for the fuel injectors 16 and 18 are described hereinafter with reference to the flowchart of Fig. 6a to Fig. 6c.

when a control signal for injecting fuel is applied to the fuel injectors 16 or 18, at a step S51 of Fig. 6a, the voltage level detecting means 34 detects the voltage BV of the battery 21. At a step S52, it is determined whether the voltage BV is higher than the reference voltage M or not. If the voltage BV is higher than the reference voltage BVo, the program goes to a step S53 where the interruption for detecting the abnormality is allowed and the program proceeds to a step S55.

If the voltage BV is lower than the reference voltage BVo at step S52, the program goes to a step S54 where the interruption for detecting the abnormality is inhibited and the program proceeds to the step S55.

At the step S55, a quantity for fuel injection calculated based on input signals from sensors 25 is corrected with various correction values and the control signal is applied from the output interface 6 to the fuel injectors 16 or 18.

When the interruption for detecting the abnormality is allowed and the control signal (Pi of Fig. 4) for injecting fuel is applied to the fuel injector 16, an interrupt signal is applied from the timer 5 at the timing To. Thus, an interrupt program starts. At a step S101 of Fig. 6b, a 14 trigger signal for starting analog/digital (AJD) conversion operation is applied to the A/D converter 24 at the time To. Thus, current dependent on the output voltage of the current detecting sensor 23 is converted into a digital signal.

At a step S102, the offset current ILTo at the time To converted into a digital signal at the A/D-converter 24 is stored in a predetermined address of the RAM 4. At a step S103, a terminating signal for stopping the A/D conversion operation is produced and a restarting time for the A/D conversion operation is set to the time T1, so that the conversion operation stops until the time T1. Since the fuel injector 16 has an inductance as the load, the current Iinj varies with the lapse of time until the maximum current.

At the time T1, an interrupt program for the time Tl starts. At a step S201 of Fig. 6c, the conversion of the current dependent on the output voltage of the sensor 23 into a digital signal starts. At a step S202, the operation current ILT1 at the time TI is converted into a digital signal and the digital signal is stored in another address of the RAM 4. At a step S203, the of fset current ILTo and the operating current ILT1 are read from the RAM 4 for calculating a load current IL (IL = ILT1 - ILTo). At a step S204, a reference current IR for the- circuit of the injector 16 is derived from the ROM 3 and the difference IDIAG between the reference current IR and the current IL is calculated (IDIAG =JIL - IR I).

At a step S205, it is determined whether the difference IDIAG is smaller than zero or not. If the difference IDIAG is larger than zero, the program terminates the interrupt routine. If the difference IDIAG is smaller than zero, the program goes to a step S206 where A trouble of the fuel injector 16 is determined. The self-diagnosis means 36 stores trouble data of the fuel injector 16 in the backup RAM 4a and emits the lamp 20. Though the difference IDIAG is compared with zero at the step S205, it may be possible to compare with a predetermined value in consideration of a dead load.

Further, disconnections of connectors in the actuator operating circuits and abnormalities of transistors 12, 13 and 14 can also be detected.

From the foregoing, it will be understood that the present invention provides an abnormality detecting system which detects reliably abnormality of an operating circuit without misjudging.

While the presently preferred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.

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Claims

Claims:

1. A system for detecting abnormality of an operating circuit including a battery. and an actuator controlled by a control signal from a control unitt the system comprising first detector means for detecting the terminal voltage of the battery; first comparator means for comparing the voltage detected by the first detector means with a reference voltage and for producing a signal when the detected voltage is higher than the reference voltage; second detector means for detecting current flowing in the operating circuit as a result of the control signal; and second comparator means responsive to the signal from the first comparator means for comparing the current detected by the second detector means with a reference value to decide whether the current is abnormal.

2. The system according to claim li wherein the first detector means is a voltage level detector connected to an output terminal of the battery.

1 17

3. A method of detecting abnormality of an operating circuit including a battery as a source. an actuator controlled by a control signal from a control unit. and a current sensor for detecting current flowing in the operating circuit comprising determining the terminal voltage of the battery; comparing the terminal voltage with a reference voltage and producing an enabling signal when the detected voltage is higher than the reference voltage; detecting current flowing in the operating circuit as a result of the control signal; and deciding whether or not the current is abnormal by comparing the detected current with a reference value.

4. A system for detecting abnormality of an operating circuit substantially as hereinbefore described with reference to the accompanying drawings.

5. A method of detecting abnormality of an operating circuit substantially as hereinbefore described with reference to the accompanying drawings.

Published 199DatThePatentMee, State House. 66 71.High Holborn. LondonWC1R4TP. er Copies maybe obtained from The Patent =ice.