DE4006298A1 - INJECTION VALVE DIAGNOSTIC SYSTEM - Google Patents

Abstract

A fault diagnosis system for a motor vehicle engine having a plurality of injectors (12) and a control unit (30) for generating a pulse signal to control the injectors (12), includes a sensor (43) which detects current supplied to the injectors (12) when the pulse signal is generated. A calculator (60a) calculates an injector load current on the basis of the current detected by the sensor (43). A diagnosis device (60b) determines whether the injectors (12) are normal by comparing the injector load current with a reference current stored in a memory (61). A device (58) judges whether a fuel cut-off condition is satisfied on the basis of signals from various sensors (10, 11, 11a, 13, 15, 19, 20 and 21) which detect driving states. An instruction device (59) operates the diagnosis device (60b) to stop the abnormality determination when the device (58) judges that the fuel cut-off condition is satisfied, whereas the determination is executed when the device (58) judges that the fuel cut-off condition is not satisfied. <IMAGE>

Description

The invention relates to an injection valve diagnostic system for diagnosing a fuel injector of a motor vehicle stuff, an electronic control unit (hereinafter referred to as ECU) is provided on the vehicle.

In a fuel-air ratio monitoring system the ECU includes a microcomputer which is to be injected Fuel quantity calculated according to the intake air quantity, to give a control signal to the injector and so on regulate the air-fuel ratio.

The control signal supplied to the injector is common Lich a pulse synchronized with the rotation of the machine signal. By controlling the fuel injection time on spray valve, i.e. the width of the pulse signal, it will Regulated fuel-air ratio.

If there is a malfunction in the function of the fuel injection valve occurs, does not affect the intake air volume adjusted amount of fuel injected. This leads to, that the air-fuel ratio is either too lean or is too fat. Therefore, the exhaust emission is deteriorated while the performance of the machine decreases and the force material consumption can be increased.

Because of this, the ECU has recently been able to equipped to diagnose whether a consumer, like actuator, depending on loaded electrical circuit  from the control signal works normally.

For example, JP-OS 63-27 769 (1988) taught by the Feed line of several electrical circuits flowing Detect current by means of a current sensor, which from a Shunt exists and is arranged in the line to detect whether the object to be controlled is in normal operation stood by the measurement signal of the current sensor with the Control signal by means of a measuring circuit at this time is verified.

However, if the machine is decelerated or overturned, the Fuel supply to the injectors to save Fuel or to protect a catalyst or the Machine switched off itself. When the fuel is shut off tet, a pulse signal of small width is generated in order the fuel injection time or injection quantity to zero represent or minimize. Accordingly, the consumption or the injector load current is made zero or minimized.

This means that the pulse signal for measuring the load current of the injection valve is generated even if the Fuel supply is switched off. It therefore finds one incorrect judgment instead of as if an abnormal current would be delivered to the injector.

The invention has for its object an injection valve diagnostic system to provide a faulty Assessment when the fuel is switched off or blocked excludes feed.

This object is solved by claim 1.

Advantageous embodiments of the invention are in the  Subclaims placed under protection.

The invention is based on the schematic drawing an exemplary embodiment with further details ten explained in more detail. It shows

Fig. 1 is a block diagram of a diagnostic system according to the invention;

Fig. 2 is a schematic representation of a machine monitoring system;

Fig. 3 is a circuit diagram for the embodiment of Fig. 1;

FIG. 4A is a view for explaining a current sensor;

4B is a diagram showing the characteristic of the current sensor.

Figure 5 is a timing diagram showing the waveforms of a STEU ersignals and an injection valve-load current. and

Fig. 6A, 6B, 6C are flowcharts ren the operation-Prozedu constitute the diagnostic system.

Referring to FIG. 2 2 1, the cylinder head of an engine having an inlet 2a and an outlet 2b, with which a respective inlet manifold 3 and a exhaust manifold 4 communicating. Furthermore, a spark plug 5 projects into a combustion chamber 1 a . An ignition coil 5 a supplies the energy to the spark plug 5 .

A throttle chamber 7 communicates with the upstream side of the intake manifold 3 via an air chamber 6 with an air cleaner 9 on the upstream side of an intake pipe 8 . An intake air amount sensor 10 (an air flow meter of the hot foil type) is arranged downstream of the air cleaner 9 .

A throttle position sensor 11 and an idle switch 11 a are arranged in the throttle chamber 7 for measuring the opening angle of the throttle valve 7 a .

An injection valve 12 is arranged in the intake manifold 3 upstream of each intake 2 a communicating with the combustion chamber 1 a of each cylinder. In a cooling channel (not shown ge) in the intake line 3 , a coolant temperature sensor 13 is arranged. Furthermore, an oxygen sensor 15 is provided in the exhaust pipe 14 , which communicates with the exhaust manifold 4 . A catalytic converter 16 is accommodated in the exhaust pipe 14 .

B at one end of a crankshaft 1, a crank rotor 17 is fixed, and a cylinder-Diskriminierrotor 18 is connected to a camshaft c. 1 The outer periphery of the crank shaft rotor 17 faces a crank angle sensor 19 , while a cam angle sensor 20 faces the cylinder discriminating rotor 18 .

An ECU 30 has as inputs the outputs of a vehicle speed sensor 21 and the sensors 10 , 11 , 13 , 15 , 19 , 20 and the idle switch 11 a . Outputs of the ECU 30 are connected to the injection valve 12 provided for each cylinder and a transistor ignition system 22 which is connected to the ignition coil 5 a provided on each cylinder. Reference numerals 23 and 24 denote an ignition switch and a battery.

Referring to FIG. 3, the ECU 30 includes a central processing unit (hereinafter CPU called) 31, a read only memory (ROM) 32, a random-access memory (RAM) 33, a backup memory (RAM) 34, a timer 35, an output Interface 36 and an input interface 37 , which are connected to one another via a bus line 38 . With the CPU 31 , an oscillator 31 a is connected to provide a system clock signal which specifies a reference timing for the CPU 31 . The system clock signal is counted by means of a free running counter (not shown) of the timer 35 . The reference time specification is detected as a value indicated by a free running counter.

Four transistors 40 are connected to the output interface 36 via resistors 39 . Each transistor 40 is also connected to an injection valve 12 of the associated cylinder via a current limiting resistor 12 a . Furthermore, a self-diagnosis lamp 41 is provided on the output interface 36 for warning when a fault occurs in the monitoring system.

A current sensor 43 is arranged in a line 42 , which leads from a battery 24 . An injection valve load current IL is fed via an electrical circuit of the line 42 via the current limiting resistor 12 a and the injection valve 12 . The current IL is detected directly by the current sensor 43 .

With the input interface 37 via an analog / Digi tal converter (A / D) 44 different measuring devices, such as the intake air quantity sensor 10 , the throttle angle sensor 11 , the coolant temperature sensor 13 and the oxygen sensor 15 are connected, driving states being measured and analog signals being generated .

Furthermore, with the input interface 37 various measuring devices, such as the crank angle sensor 19 , the cam angle sensor 20 , the vehicle speed sensor 21 and the idle switch 11 a, are connected, which generate digital signals.

The current sensor 43 is constructed as described below with reference to FIG. 4A and can be encapsulated with synthetic resin.

Around a toroidal core 43 a , which is made of ferrite, for example, wires are wound to form a converter. A part of the ring core 43 a is slotted to form an opening in which a Hall element 43 b is arranged. An amplifier 43 c is connected to the Hall element 43 b .

The current sensor 43 measures a current without direct connection to the electrical circuit, so that the current is detected without negative influences, such as change in impedance and decrease in the noise range of the electrical circuit.

When a control signal is given to the electrical circuit and a current flows therein, a magnetic field in the current sensor 43 is built up by the current. This generates a magnetic flux through the Hall element 43 b by means of the transducer formed from the core 43 a , so that the Hall element 43 b generates a voltage which is amplified by the amplifier 43 c .

The characteristic of the current sensor 43 is shown in FIG. 4B. The relationship between the current I and the output voltage V is almost linear. Due to the electrical characteristics of the Hall element 43 b , however, there is an offset voltage V ₀ even when there is no input signal.

Fixed data, such as control programs, are stored in the ROM 32 . Output data from the sensors and data calculated by the CPU 31 are stored in the RAM 33 . The support RAM 34 stores problem data regarding faults in the injection valve 12 , the ignition device 22 , the sensors 10 , 11 , 13 , 15 , 19 , 20 , 21 , the idle switch 11 a or the monitoring system, and is from the battery 24 supported to maintain stored problem data even when the ignition switch 23 is turned off.

The CPU 31 calculates various control data based on the data stored in the RAM 33 and depending on the control programs stored in the RAM 32 and temporarily stores the various control data in the RAM 33 for outputting control signals to electrical consumers, such as the injection valve 12 and the ignition device 22 , via the output interface 37 at the specified times.

For example, in the case of an injection, this procedure proceeds as follows. First, an intake air amount is calculated using an output signal of the intake air amount sensor 10 . Then the injection quantity is calculated depending on the quantity of intake air with various corrections, in order to set the time corresponding to the injection time in the timer 35 . The pulse signal of a pulse width, which corresponds to the time set in the timer 35 , is fed to the injector 2 of one of the cylinders depending on the specified time, which is synchronized with the rotation of the machine based on the output signals of the crank angle sensor 19 and the cam angle sensor 20 .

The CPU 31 carries out self-diagnosis and calculations of the various control data and actuates the self-diagnosis lamp 41 to inform the driver of an abnormality.

The functional structure of the air-fuel ratio monitor of the ECU 30 is described in detail below.

As shown in FIG. 1, the ECU 30 includes an engine speed calculation circuit 50 , an intake air quantity calculation circuit 51 , a basic injection quantity calculation circuit 52 , an increase correction coefficient setting circuit 53 , a feedback correction coefficient setting circuit 54 , an injection quantity Adjustment circuit 55 , an injection cylinder evaluation circuit 56 , an output circuit 57 , a fuel supply lock evaluation circuit 58 , a diagnosis instruction circuit 59 , an injection valve diagnosis circuit 60 with a load current calculation circuit 60 a and an abnormality evaluation circuit 60 b , a memory 61 (consisting of the ROM 32 and the support RAM 34 ) and a self-diagnostic circuit 62nd

The engine speed calculation circuit 50 calculates the engine speed N based on the output signal of the crank angle sensor 19 . The intake air amount calculation circuit 51 reads the output signal of the intake air amount sensor 10 to calculate an intake air amount Q therefrom.

The basic injection amount calculation circuit 52 calculates a basic injection amount T _p ( T _p = K × Q / N ; where K is a constant) from the engine speed N and the intake air amount Q.

The increase correction coefficient setting circuit 53 outputs an increase correction coefficient COEF including various coefficients for an increase correction when idling, an increase correction when the throttle valve is fully open, a coolant temperature correction and an acceleration correction. The feedback correction coefficient setting circuit 54 specifies a fuel air ratio feedback correction coefficient based on the output waveform of the oxygen sensor 15 .

The injection quantity setting circuit 55 corrects the basic injection quantity T _p by means of the increase correction coefficient COEF and the feedback correction coefficient to specify a fuel injection quantity according to the formula T _i ( T _i = T _p × COEF × α ).

The injection cylinder evaluation circuit 56 counts the number of cam pulses from the cam angle sensor 20 while one crank pulse is being delivered and the next crank pulse follows, and determines the cylinder following the force injection based on the number of cam pulses.

In accordance with the number of cylinders determination, a specific port of the output circuit 57 is selected, which leads to the generation of a pulse signal of a pulse width corresponding to the injection quantity T _{i in} order to actuate the injection valve 12 of the cylinder selected for the injection.

The fuel supply lock-up judging circuit 58 detects the operating state of the idle switch 11 a and compares the vehicle speed V _s transmitted from the vehicle speed sensor 21 with a predetermined value to decide whether the vehicle is in a deceleration driving state in a low speed range or in idle. Furthermore, the circuit 58 compares the engine speed N with a reference speed NFC for the fuel supply cut-off or cut-off depending on the coolant temperature T _w , which was detected by the coolant temperature sensor 13 , to decide whether the fuel cut-off condition is fulfilled.

If the fuel supply shutoff condition is satisfied, a fuel supply blocking signal from the fuel supply inhibition judgment circuit 58 to the injection quantity setting circuit 55 added to make smaller the pulse width P _i corresponding to the injection amount T _i, and is further on the diagnosis instruction circuit 59 given.

If the fuel injection quantity at the injector 12 becomes completely zero during driving without gas or with a delay, the supply of fuel to be re-injected into the inlet 2 a is delayed when the acceleration resumes. Accordingly, the pulse width is narrow because little fuel is injected during the deceleration phase.

When the engine speed N is greater than the maximum allowable engine speed N _max , the fuel supply lock condition is recognized, and there is no other way to avoid a malfunction due to the machine being overturned. The minimum engine speed that is required to block or interrupt the fuel supply is specified as a reference speed NFC and stored in the memory 32 in the form of a map, the coolant temperature T _{w being} a parameter, for example.

The diagnosis instruction circuit 59 prohibits the interruption by the timer 35 to stop the interrupt processing of the injector diagnosis circuit 60 when the fuel supply cut judgment circuit 58 in the fuel supply cut condition is satisfied, while in the case of failure, the initialization of the Interrupt processing is allowed.

The load current calculation circuit 60 a calculates a load current or a consumption current of the injection valve 12 based on an offset current corresponding to the offset voltage of the current sensor 43 and a current corresponding to the output voltage of the sensor 43 at the time when a certain time after the start of the pulse signal P _inj for fuel injection has passed.

As described above, the current sensor 43 has a small offset current (voltage V ₀ ) even in the absence of an input signal. The offset current varies with the temperature and the operating time and fluctuates with the individual properties of each sensor 43 . The load current calculation circuit 60 a reads the output signal of the sensor 43 as an offset current when the pulse signal P _{inj is} not generated, and subtracts the offset current from the current at the time when a specified time after the start of the pulse signal P _inj has elapsed to calculate the load or consumption current.

For example, according to FIG. 5, the current ILT ₁ corresponding to the output voltage V _{1 of} the current sensor 43 is detected when the specified time T _{1 has} elapsed after the pulse signal P _{inj is applied to} the injection valve 12 . The offset current ILT ₀ corresponds to the offset voltage V ₀ at the time T ₀ when the signal P _{inj is subtracted} from the current ILT ₁ by the actual load current IL ( IL = ILT ₁ - ILT ₀ ) of the injection valve 12 to calculate. This procedure is performed on every pulse.

The abnormality judging circuit 60 b compares the load current IL for the injector 12 calculated in the load current calculating circuit 60 a with a reference current IR stored in the memory 61 to decide whether the injector 12 is operating normally or Not.

The reference current IR is stored in the memory 61 (ROM 32 ) as a table with a voltage BV of the battery 24 as a parameter. When the pulse signal P _{inj is} generated, the reference current IR is read directly from the table or calculated by means of an interpolation calculation using the current battery voltage BV .

The interrupt processing of the injector diagnosis circuit 60 ( 60 a , 60 b ) is initiated to only start the diagnosis of the injector 12 upon the instruction of the diagnosis instruction circuit 59 when no fuel supply interruption is performed. Accordingly, an erroneous judgment due to the fuel supply cutoff cannot occur.

If the fuel supply is blocked, as indicated by dashed lines in FIG. 5, the pulse width P _i of the pulse signal P _{inj is} extremely narrowed. This causes the signal P _{inj to drop} before the measurement time T _{1 is reached} . The load current IL of the injection valve 12 is calculated as IL = 0 because the current ILT ₁ at the time T ₁ is substantially equal to the offset current ILT ₀ .

Accordingly, in order to avoid an erroneous decision due to fuel cut off, the timer 35 is prevented from executing the interrupt processing to stop the diagnosis of the injector 12 by the injector diagnosis circuit 60 . Then, when the fuel cut is released, the diagnosis is resumed.

If the injection valve 12, averaging circuit by the abnormality-Beurtei b 60 to be abnormal is judged self fed diagnosis circuit 62 to be stored issue data for SpeI cher 61 and further an abnormality signal to self-Dia gnoselampe 41 to turn (or flashing) by prior to warn of the abnormality of the injector 12 .

The problem data stored in the memory 61 are read out by means of an external device, for example a vehicle diagnostic tester, which is connected to the ECU 30 in order to ascertain in a simple manner the abnormality of the injection valve 2 at a vehicle dealer or a workshop.

The operating procedures of the injection valve 12 will now be explained with reference to the flow diagrams according to FIGS . 6A, 6B and 6C.

First, the fuel injection amount T _{i is} specified in step S 101 of the program shown in FIG. 6A. Then, in step S 102 is queried whether or not the fuel supply stop condition is satisfied. If it is not satisfied, the program proceeds to step S 103, as it progresses in fulfilling the lock condition to step S 104th

The interruption by means of the timer 35 is permitted in step S 103 in order to enable the interruption processing of the fault diagnosis of the injector 12 by means of the injector diagnosis circuit 60 , whereupon the program proceeds to step S 105 .

On the other hand, if the fuel supply cutoff condition is judged to be satisfied in step S 102 , the interruption by the timer 35 is prevented in step S 104 to stop the failure diagnosis of the injector 12 , whereupon the program proceeds to step S 105 .

The pulse signal P _inj for the injector 12 of the cylinder to be actuated is generated at the specified time, whereupon the program returns to step S 101 .

If the interruption of the fault diagnosis of the injection valve 12 is permitted, this interruption is carried out at the time T _{0 of} the rising edge of the pulse signal P _inj in order to process the program according to FIG . In a step S 151 , a trigger signal for performing an A / D conversion is fed to the A / D converter 44 in order to convert the output voltage signal of the current sensor 53 into a digital signal.

The program then proceeds to step S 152 to store the converted offset current ILT ₀ corresponding to the offset voltage of the current sensor 43 at the measurement time T _{0 in} FIG. 5 in a specified address of the RAM 33 .

In step S 153 , an A / D conversion fulfillment signal is output to the A / D converter 44 , and further an A / D convert renewal timing is set to the timer 35 to restart the A / D conversion if the time from T ₀ in FIG. 5 to the measurement time T _{1 has} passed, and the interrupt routine is stopped.

The measurement time T ₁ is accurately depending on the intrinsic properties of the injection valve 12 set because the load current I _inj of FIG gradually varies. 5 until _linj after the queuing of the pulse signal P _inj to a constant current.

When the measurement time T _{1 is} reached, an interrupter program starts, and an A / D conversion of the output voltage signal of the current sensor 43 is carried out in step S 201 .

The program proceeds to step S 202 in order to store the digitized output signal of the current sensor 43 , that is to say the current ILT ₁ corresponding to the output voltage V ₁ at the point in time T ₁ in FIG. 5, in a different address of the RAM 33 .

In step S 203 , the load current IL ( IL = ILT ₁ - ILT ₀ ) of the injection valve 12 is calculated using the current ILT ₁ , and the offset current ILT ₀ is in the RAM 33 in step S 152 of the interrupter program at the measurement time T ₀ saved. Then the program proceeds to step S 204 .

The reference current IR of the injection valve 12 is read from the ROM 32 in step S 204 in order to calculate the diagnostic value IDIAG ( IDIAG = IL - IR ) by means of IR and IL .

In step S 205 the polarity of IDIAG is assessed. The interruption ends as judged normal if IDIAG is greater than zero, ie if IL is greater than IR , while if IDIAG is less than zero, the program proceeds to step S 206 .

In step S 206 , an error is judged, and the self-diagnosis circuit 62 stores the problem data of the injector 12 judged to be defective in the backup memory 34, and also turns the self-diagnosis lamp 41 on (or makes it blink) to signal the occurrence of a fault.

The injector load current IL is therefore not judged to be abnormal even when IL = 0 if a fuel supply lock for the injector 12 takes place, so that the pulse width P _i of the pulse signal P _{inj is} less than the time between the two measurement times T ₀ and T _{1 of} the current sensor 43 . Accordingly, an erroneous judgment is avoided.

As described above, according to the invention instructs one Diagnostic instruction circuit when the fuel is too drove to an injector blocked or interrupted is a fuel injector diagnostic circuit to stop the error diagnosis. On the other hand, if the fuel supply If the interruption is canceled, the diagnostic instruction is given tion circuit signals to the fuel injector diagnostic circuit to carry out the diagnosis. Then a Stromsen measures sor a load or consumption current of the injection valve and compares it with a previously set Refe limit current, from which the assessment of an abnormality to derive. By doing this, a faulty one Assessment based on a fuel cut avoided. Therefore, it will always be accurate and reliable Error diagnosis carried out.

Claims (3)

1. Injector diagnosis system for a motor vehicle with a plurality of injection valves arranged on the machine and a control unit for generating a pulse signal for controlling the injection valves, characterized by
a measuring device ( 43 ) for detecting a current supplied to the injection valves upon generation of the pulse signal;
a computing device ( 60 a ) for calculating an injection valve load current based on the current detected by the measuring device ( 43 );
a device ( 31 ) for generating a reference current;
a diagnostic device ( 60 b ) for checking whether the injection valves ( 12 ) operate normally by comparing the injection valve load current and the reference current;
a judging device ( 58 ) for judging whether a fuel supply cut-off condition based on signals from various measuring devices ( 10 , 11 , 11 a , 13 , 15 , 19 , 20 , 21 ) for detecting driving states is satisfied; and
an instruction device ( 59 ) which causes the diagnosis device ( 60 b ) to terminate the diagnosis when the judgment device ( 58 ) decides that the fuel supply cut-off condition is satisfied while the diagnosis is performed when the judgment device ( 58 ) judges that the fuel supply lock condition is not satisfied. 2. Injector diagnosis system according to claim 1, characterized in that the computing device ( 60 a ) as the injector load current is the difference between an offset current which flows in the measuring device ( 43 ) when the control unit ( 30 ) does not generate a pulse signal , and the current supplied, which flows when a certain period of time has elapsed after generation of the rising edge of the signal. 3. Injector diagnostic system according to claim 1 or 2, characterized in that the Vorrich device ( 31 ) for generating the reference current determines this reference current based on the battery voltage be.