GB2228106A

GB2228106A - Abnormality detecting system for electric circuits

Info

Publication number: GB2228106A
Application number: GB8928586A
Authority: GB
Inventors: Kazuyuki Tazawa
Original assignee: Fuji Jukogyo KK; Fuji Heavy Industries Ltd
Current assignee: Subaru Corp
Priority date: 1988-12-20
Filing date: 1989-12-19
Publication date: 1990-08-15
Also published as: JPH02165069A; DE3942164A1; GB8928586D0

Description

A 1 Abnormality Detecting System for Electric Circuits The present

invention relates to a system for detecting abnormality in an electric circuit connected to an electronic control unit used in an electronic control system such as a control system for a motor vehicle.

The electronic control unit provided on the 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 63-27769 discloses a selfdiagnostic system for confirming operations of operating circuits in an electronic control system for a motor vehicle. In the self-diagnostic system, a shunt is provided in a bus for detecting current in the bus. The system has a detecting circuit comprising a window comparator and a logic product circuit for detecting the operation of each operating circuit.

When the current is in the reference voltage range of the window comparator, the comparator produces a comparator signal. The comparator signal is applied to the logic product circuit. On the other..bard.,..a control signal applied from the electronic contr61'system to a corresponding operating circuit is also applied to the logic 2 product circuit. The logic product circuit produces a confirmation signal in accordance with both the input signals.

In the diagnostic system, since the detecting circuit is provided at every operating circuit, the system becomes complicated in construction, -which causes increase of the manufacturing cost thereof, and reduction of reliability because of a large number of parts such as connector pins for connecting detecting circuits to a control unit of the electronic control system.

If a plurality of control signals are applied to corresponding operating circuits at the same time, the shunt detects the sum of currents flowing in the opening circuits. However, the operating circuits are different in magnitude of current, and hence output voltages applied to the window comparators are also different in level. Consequently, when a plurality of control signals are applied to operating circuits, it is difficult to detect any current abnormality of' an individual operating circuit.

The present invention seeks to provide an abnormality detecting system in which a single current detecting sensor is provided for detecting different currents in a plurality of operating circuits so that faults in the circuits may be reliably detected.

6.

1k, According to the present invention, there is provided an abnormality detecting system for an electrical circuit having a plurality of actuator operating circuits which are connected to a source through a bus, a current sensor provided in the bus for detecting current flowing in the actuator operating circuit, the current sensor having a plurality of sets of windings each of which corresponds to one of the operating circuits, and each set of windings having a number of turns which is determined in accordance with the expected load in the corresponding operting circuit; means for determining the current dependent on the output voltage of the current sensor; comparing means for comparing the determined current with a reference current and for producing a signal corresponding to the difference between the determined current and the reference current; and calculating means for determining whether the difference is abnormal..

Preferably the current in the sensor is determined at a predetermined time so as to detect any abnormality in a specified operating circuit, and further comprising, means for determining whether a control signal is also being applied to another operating circuit and for then restarting the determination of the current.

In a preferred form of the invention, the current sensor comprises a core having a plurality of windings and a Hall element provided in a gap formed in the core.

Some embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a block diagram showing a circuit of an abnormality detecting system according to the present invention; - 4 Fig. 2 is a block diagram formed in accordance with the function of the system; Fig. 3a is an illustration showing a current detecting sensor of the system; Fig. 3b shows a graph showing the characteristic of the sensor; Fig. 4 shows waveforms of injector drive pulse and injector current; Figs. 5a and 5b are flow charts showing the operation of the system; Fig. 6 shows waveforms in a second embodiment of the present invention; and Fig. 7a to 7c are flow charts showing the operation of the second embodiment.

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 computer unit 2 connected to a base of each of transistors 6 and 7 and an externaltransistor 8 through resistors 3, 4 and 5, respectively. Collectors of the transistors 6, 7 and 8 are connected to various actuators such as a coil 10a of fuel injector 10, a coil 11a of an idle speed control valve 11, and a coil 13a of an ignition coil 13, respectively. Further.. the computer unit 2 is applied with output signals from various sensors 14 such as an intake-air quantity z 4 sensor, a crank angle sensor and an 0 2 sensor. the computer unit 2 picks up various data from the ensors 14 in accordance with control programs stored in the unit 2 and calculates various control data.

The calculated control data are stored in a RAM of the computer unit 2 and applied to actuators 10, 11 and 13 at a predetermined timing.

A diagnostic unit 15 comprises a central processor unit (CPU) 16, a ROM 17, a RAM 18, a non-volatile RAM 18a, an output interface 19 and an input interface 20, which are connected to each other through a bus line 21. An oscillator 16a is connected to the CPU 16 for producing a train of standard clock pulses which is divided and counted by a free-running counter.' The count of the standard clock pulses is read out for determining timings for performing various diagnoses. The output interface 19 is connected to a self-diagnosis lamp 29 for indicating abnormalities of the actuators.

The input interface 20 is connected to the control unit 1 through a bus line 20a and to the sensors 14 and applied with the power from a battery 23 and voltage from a current detecting sensor 22 through an A/D converter 24. The battery 23 is connected to coils of actuators 10, 1 and 13 through the current detecting sensor 22 and bus 25. Thus, actuator operating circuits A are formed. The current detecting sensor 22 is provided for detecting current IL - 6 flowing in each actuator operating circuit A.

The ROM 17 stores diagnosis programs and fault data. The RAM 18 is provided for storing digital signals of outputs from the current detecting sensor 22 and the battery 23 converted by the A/D converter 24, data processed in the ECU 1 and data dependent on output signals of sensors 14.

The non-volatile RAM 8a is provided to store fault data of acutators 10, 11 and 13, sensors 14 and others. The RAM 18a is backed up by the battery 23 so as to maintain the stored data even if a key switch (not shown) is in offstate.

The CPU 16 diagnoses various data stored in the RAM 18 in accordance with diagnosis programs stored in the ROM 17. If an abnormality is detected, the CPU 16 produces a signal to illuminate the lamp 29 through the output interface 19, and the fault data stored in the RAM 18a.

Fig. 3a shows the current detecting sensor 22. The sensor 22 comprises a core 26 made of ferrite and having a plurality of windings wound around the core 26 to form a plurality of transformers 26a, a Hall element 27 provided in a gap of the core 26, and an amplifier 28. The transformer 26a is connected to a line of corresponding actuator operating circuit A. When the power is applied to the actuator operating circuit A, a magnetic field is formed in the current detecting sensor 22. The magnetic flux flows through the Hall element 27, so that a voltage is generated in the Hall element 27, which is amplified by the amplifier 28.

If a plurality of control signals are applied to the actuator operating circuits A at the same time, the output voltage of the Hall element 27 is the sum of the outputs of the corresponding transformers 26a.

Each transformer 26a has a proper number of turns of winding in accordance with the expected load current of the corresponding actuator operating circuit A so as to accurately detect the current. Thus, the current detecting sensor 22 can detect currents in various actuator operating circuits which are different from each other in magnitude of current.

If the number of turns of the winding of the transformer 26a is increased, the amplifier 28 may be omitted, thereby reducing the manufacturing cost of the current sensor. As shown in Fig. 3b, the current detecting sensor 22 has a linear output characteristic. An offset voltage exists in thd Hall element 27 and appears at the output terminal of the sensor 22 as an offset voltage VO.

The current detecting sensor 22 detects the current flowing in each of the circuits A to produce an output voltage representing the detected current. In accordance with the detected current, and abnormality of the actuators 8 10, 11 and 13 in the circuit is detected. if a failure of one of the sensors 14 is detected, fail-safe data stored in the ROM 17 is applied to the ECU 1. If an abnormality occurs in the ECU 1, fixed control data are produced to perform a fail-safe operation of the ECU 1.

In other words, the diagnostic unit 15 diagnoses not only failures. of actuators 10, 11 and 13, but also the ECU 1 and sensors 14. Thus, the load on the ECU 1 is reduced.

Referring to Fig. 2, the electronic control unit 1 is provided with an input processing means 30 applied with output signals from sensors 14, battery 23 and current detecting sensor 22 for performing a waveform shaping process and an analog-digital conversion process. Processed data are applied to a diagnosis means 31 and stored in a memory means 32. The diagnosis means 31 is provided for diagnosing various data based on the input signals in accordance with the diagnosis programs stored in the memory means 32. If an abnormality is detected, fault data is stored in the memory means 32 (RAY, 18a). 20 A circuit curren41-- calculator means 33 is provided for calculating the load current flowing in the actuator operating circuits A in accordance with the output from the current detecting sensor 22. A circuit condition determining means 34 is provided for determining conditions of the actuator operating circuit A.

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

The offset voltage VO of the sensor 22 varies with the factors. temperature of the sensor, with time and other / Therefore, in order to detect the load current, the offset voltage is subtracted from the output voltage of the sensor 22 as described below.

An offset voltage VO of the sensor 22 is detected when no control signals are applied to the actuator operating circuits A. The detected offset voltage is stored in the memory means 32 (RAIN1 18). The current in one of the circuits A is detected when a control signal is applied thereto, and the output voltage of the sensor 22 is stored in the P-km 18. The stored off set voltage is then substracted from the stored voltage.

As an example, the diaqnosis of the circuit of the fuel injector 10 is described hereinafter with reference to Fig. 4. The offset voltage VO at the time TO' when the control signal Pi is produced or before the generation of the control signal Pi is obtained.

Sinc.e the fuel injector 10 is an inductance load the flow-of current Iinj of the fuel injector 10 is delayed with-respect'to the control signal Pi as shown in Fig.4. Z-he offset voltage VO may be obtained at the time Tot when the aontrol signal is generated. However, if the actuator is a resistive load,. capacitive load or a lamp, the current is not.

- 10 delayed. Accordingly, the offset voltage VO must be obtained before the control signal.

If another control signal P is applied to the other circuit as shown at a time TO in Fig. 4, the voltage of the control signal P is added to the offset voltage VO. Accordingly, the offset voltage must be detected at the time when no control signals are applied to the operating circuits A.

More particularly, when the control signal Pi is applied to the fuel injector 10, it is determined whether other control signals are applied to other circuits. If no control signals are produced, a new offset voltage is detected at the generation of the control signal Pi to update the offset voltage.stored in the RAM 18 at the last time. On the other hand, if another control signal is applied to another circuit, the offset voltage stored in the RAM at the last time is used for calculating the current IL.

The obtained offset voltage VO is subtracted from the output voltage of the sensor corresponding to current flowing in the injector operating circuit to produce an operating voltage V corresponding to the load current.

The circuit condition determining means 34 compares the operating voltage V with a reference voltage VR corresponding to a reference current IR for determining abnormality and produces a signal which is applied to the diagnosis means 31. The memory means 32 stores a plurality A f 11 of reference voltages VR which are arranged in a table in accordance with the battery voltage BV as parameters. Namely, when the control signal Pi is applied to the fuel injector 10, the reference voltage YR is derived from the table.

When the difference between the operating voltage V and the reference voltage VR does not fall within a predetermined allowable range AIR, abnormality of the injector operating circuit A is determined. The diagnosis means 31 operates to store the trouble data in the memory means 32.

When the circuit condition determining means 34 determines an abnormality of one of the actuator operating circuits A, an output processing means 35 produces an abnormality signal which is applied to the self-diagnosis lamp 29 to er.it the lanIp.

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.

The operation of the control unit for the fuel injector 10 is described hereinafter with reference to the flowchart of Fig. 5 and to Fig. 4.

A control signal (Pi of Fig. 4) for injecting fuel is applied to the fuel injector 10, so that an interrupt program for the time To starts. At a step S101 of Fig. Sa, a trigger signal for starting analog/digital (A/D) 12 conversion operation is applied to the AID converter 26 at the time To. Thus, th6 output voltage signal of the current detecting sensor 22 is converted into a digital signal.

At a step S102. output conditions of control signals applied from the EM 1 to operating circuits A are read through the input interface 20. At a step S103, it determined whether other control signals are applied to the other electric circuits or not. If no control signals are applied to the other circuits, the program goes to a step S104. If at least one of the control signal is applied to one of the other circuits, the program goes to a step S105.

At step S104, the offset voltage Vo of the sensor 22 corresponding to the offset current ILTo at the time To is converted into a digital signal at the AID converter 24 and the offset voltage stored in a predetermined address of the RAM 18 at the last routine is uiDdated with the new offset voltage Vo. At the step S105, a terminating signal for stopping the AID conversion operation is produced and a restarting time for the AID conversion operation is set to the time TI, so that the conversion operation stops until T1. Since the load of the fuel injector 10 has an inductance, the current Iinj varies with time until the maximum current.

At the time T1, an interrupt program for the time Tl starts. At a step S201 of Fig. 5b, the conversion of the output voltage signal of the sensor 22 into a digital signal 1 13 starts. At a step S202, the operating voltage V of the sensor 22 corresponding to operation current ILT1 at the time Tl is converted into a digital signal and the voltage BV of the battery 23 is also converted into a digital signal. These digital signals are stored in the respective addresses of the RAM 18.

At a step S203, the offset voltage Vo and the operating voltage V are read from the RAM 18 for calculating a load current IL (II, = ILTI - ILTo). At a step S204, a reference current IR is derived from the ROM 17 in accordance with the battery voltage BV as parameter, and the difference IDIAG between the reference current IR and the current IL is calculated (IDIAG =IIL - IRI).

At a step S205, it is determined whether the difference IDIAG is smaller than a predetermined allowable value AIR or not. If the difference IDIAG is smaller than the allowable value AIR, the program terminates the interrupt routine. If the difference IDIAG is larger than the allowable value AIR, the program goes to a step S206 where a trouble of the fuel. injector 10 is determined. The diagnosis means 31 stores trouble data of the fuel injector in the non-volatile RAM 18a and emits the lamp 29.

Thus, circuit operating currents of a plurality of actuator operating circuits are precisely detected by a single current detecting sensor 22. Further, disconnections of connectors in the actuator operating circuits and C' 14 abnormalities of transistors 6, 7 and 8 can also be detected.

If at least one of the other control signals is applied to the other operating circuit after the time To. the operating current IL is compared with the sum of reference currents IRs of corresponding operating circuits.

Referring to Figs. 6 and 7 showing another embodiment of the present invention, structures and functions of the embodiment are the same as the first embodiment except for the circuit current calculator means 33.

The current of the control signal in a certain operating circuit reduces gradually in accordance with the time constant of the operating circuit after the disappearance of the control signal P. Consequently, as shown in Fig. 6, when the control signal P to the operation circuit is turned off, the current does no-11- become zero at the same time. Therefore, when the offset current ILTO is detected at a time TO1, remaining current is added to the offset current ILTO. 20 in the circuit current calculator means 33 of this embodiment, the offset current ILTO is obtained at a time before a control signal for one of the operation circuits to be diagnosed is produced and when a predetermined time DTIM2 necessary for completely reducing the current has elapsed. For example, when the control signal Pi is applied to the fuel injector 10, it is determined whether the is predetermined time DTIME has passed after the control signal to the other circuit is turned off or not. If the time DTIME has passed, the offset current ILTO is newly detected at the time when the control signal Pi is produced and the offset current ILTO stored in the RAM 8 at the last time is updated. On the other hand, if the time DTIME does not yet pass, the offset current ILTO stored in RAM at the last time is used for calculating the current IL.

Since a faulty detection of the offset current is prevented, the load current IL is accurately calculated.

The operation of the system of the second embodiment will be described with reference to flowcharts of Figs. 7a to 7c. Times Td, TO and Tl in Fig. 6 are counted by a free-running counter.

When the control signal P applied to the other circuit is turned off, an interrupt routine for time Td starts as shown in Fig. 7a. At a step S301, the time Td when the control signal P is turned off as shown in Fig. 6 is read from the free-running counter. At a step S302, the time Td is stored in the PAY. 18 and the routine is terminated.

When the control signal Pi is applied to the fuel injector 10, an interrupt routine for time.TO of Fig. 7b starts. At a step S401, the time TO when the control signal Pi is produced is read from the free-running counter. At a step S402, the time TO is stored in the RAM 18. At a step S403, the time Td and the time TO stored in the RAY, 18 are k 16 read to calculate the time AT representing the time until the control signal Pi is produced after the control signal P is turned off ( AT = TO - Td). At a step S404, it is determined whether the time A T reaches the predetermined time DTIME or not. If the time AT does not reach the time DTIME, the program proceeds to a step S407. If the time AT reaches the time DTIME, the program proceeds to a step S405.

At the step S405, a trigger signal for starting analog/digital (A/D) conversion operation is applied to the AID converter 26 at the time To. Thus, the output voltage signal of the current detecting sensor 22 is converted into a digital signal.

At a step S406, the offset voltage Vo of the sensor 22 corresponding to the offset current ILTo at the time To is converted into a digital signal by the AID converter 24 and the offset current ILTo stored in a predetermined address of the RAM 18 at the last routine is updated with the new offset current ILTo. At the step S407, a terminating signal for stopping the AID conversion operation is produced so that the conversion operation stops until T1.

Further, at the step S407, a restarting time Tl is set so that the AID converter starts the conversion operation of the output voltage of the sensor 22 at the time T1.

At the time TI, an interrupt program for the time Tl starts. The interrupt program for the time Tl shown in the ;1 k_.

17 flowchart of Fig. 7c is operated in the same manner as the flowchart of Fig. 5b of the first embodiment. Therefore, the description of the operation is omitted.

In accordance with the present,invention. the output voltage of the current sensor corresponding to current in each operating circuit can be adjusted to a proper level for diagnosing troubles in the operating circuit by adjusting the number of turns of the winding. Consequently, troubles in operating circuits where currents flowing in the circuits are different in magnitude thereof can be reliably detected.

While the presently preferred embodiments of the present invention have been shown and described, it is to b understood that these disclosures are for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention a set forth in the appended claims.

1 - (, 2 is -

Claims

1. An abnormality detecting system for an electrical circuit having a plurality of actuator operating circuits which are connected to a source through a bus, a current sensor provided in the bus for detecting current flowing in the actuator operating circuit, the current sensor having a plurality of sets of windings each of which corresponds to one of the operating circuits, and each set of windings having a number of turns which is determined in accordance with the expected load in the corresponding operating circuit; means for determining the current dependent on the output voltage of the current sensor; comparing means for comparing the determined current with a reference current and for producing a signal corresponding to the difference between the determined current and the reference current; and calculating means for determining whether the difference is abnormal.

2. A system according to claim 1, wherein: the current sensor comprises a core having a plurality of windings and a Hall element provided-in a gap formed in the core.

3.

1 l, A system according to claim 1, in which the j current in the sensor is determined at a predetermined time so as to detect any abnormality in a specified operating circuit, and further comprising, means for determining whether a control signal is also being applied to another operating circuit and for then restarting the determination of the current.

4. An abnormality detection system substantially as herein described with reference to the accompanying drawings.

Published l 990 a' The Patent Office. State House-66 71FighHolbern,Londcr. WC1R4TP Further copies maybe obtained from The Patent Office Sales Branch, St Mary Gray. Orpington Kent BR5 3RL Printed by Muliplex techniques ltd. St M ary Gray. Kent, Con. 1'87