JPS5928030A - Backup device for abnormality of electronic fuel injection device - Google Patents

Abstract

PURPOSE:To secure the safety traveling of a vehicle by a method wherein in case where the abnormality of a sucked air quantity sensor is detected from the output of that sensor, the fuel injection time is corrected by a coefficient operated on the bases of signals from an idle switch, a start switch and a water temperature sensor. CONSTITUTION:An electronic fuel injection device operates such that in CPU52, the basic fuel injection time Tp is operated on the bases of the sucked air quantity QA and the rotational velocity N of the engine. Then it determines the fuel injection time Ti obtained as a result of correction of the basic fuel injection time Tp on the bases of the time Ts for correcting the variation of the response time of an injector due to a correcting rate proportional to the output signal of a water temperature sensor or an air- fuel ratio sensor and a battery voltage. In this case, when the abnormality of the sucked air quantity sensor or an interface circuit 51 is detected from the output signal from the sensor, the coefficient KF is operated on the bases of the output signals from the idle switch, the start switch and the water temperature sensor and the fuel injection time Ti is determined from the equation of Ti=K'.KF/N+Ts (wherein K' is a constant.)

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a back amplifier device when an abnormality occurs in an intake air amount sensor of an electronic fuel injection device for an automobile.

(Background Art) As a conventional electronic fuel injection device, for example, USP 383
4361, JP-A-54-141 (126), etc. An example thereof is shown in FIG. 1. This figure is a system configuration diagram of a conventional example of an engine control system using a so-called microcomputer.

The objects of control are fuel injection (EGI) control, which is performed by controlling the valve opening start timing and valve opening time of the injector 1 installed in each cylinder of the engine, and controlling the energization cutoff of the primary coil of the ignition coil 2. Ignition (I, GN) control that controls ignition timing and energization time, Exhaust recirculation (EG) (,) control that controls the lift amount of E (3R valve 3 by negative pressure control using VCM valve 4), ACC valve 5 The lift amount is controlled by negative pressure using 70M valve 4,
Throttle: Idle rotation (ISC) control performed by controlling the amount of air that bypasses the valve 6. In addition to the above, as ancillary control or information output, fuel pump 80 on/off control (
F/P) Output of fuel consumption data to fuel consumption needle 9 (F
CM) There are some things.

In order to perform the above control and output, the following control information is obtained from the engine and each part of the vehicle.

+11 The engine rotation angle and rotation speed are obtained from the crank angle sensor 10. This sensor is distributor 1
1, a slit is provided on a disc fixed to the distributor rotating shaft, and a light emitting element and a light receiving element are fixed to sandwich the slit.
By detecting the light passing through the slit, the rotation angle of the crank angle shaft (twice the rotation angle of the IJ computer) is 120.
A REF signal 12 that rises every degree and an O8 signal 13 that alternately rises and falls every 1 degree are generated. By counting the rise and fall of the PO8 signal 13 based on the EF signal 12, the rotational angular position (θ) of the crank angle shaft is determined.
can be detected. In addition, REF signal 12, PO8 signal 13
The engine rotational speed (NRPM) can be measured by measuring the frequency or period of the engine.

(2) The intake air amount (QA) of the engine is detected by an air flow meter 4. The air flow meter 14 basically consists of a flap that moves at an angle corresponding to the amount of intake air and a potentiometer that converts the angle into a voltage signal. 15 is inversely proportional.

(3) The output voltage of the 02 sensor 16 changes according to the oxygen concentration in the exhaust gas, and a signal (02)1 according to the air-fuel ratio is output.
7 is obtained.

(4) The water temperature sensor 18 is a thermistor whose resistance value changes depending on the temperature of the cooling water, and by converting it into a divided voltage with a predetermined resistance, a voltage signal 1 representing the engine temperature is generated.
9 is obtained.

(5) The onboard battery 20 supplies electricity to each part of the control system. To control unit 21, control
The main power supply 23 via the unit relay 22 and the note 2
An auxiliary power source 24 that directly enters from 0 is supplied.

The voltage signal (VB) 23 of the main power supply is also used as information for control. Note that since battery voltage is applied to the on terminal 26 of the ignition switch 250 not only in the on position but also in the start position, the main power supply 23 is supplied to the control unit 21 even during cranking.

(6) The vehicle speed sensor 27 emits a signal (V S P ) 28 having a pulse density proportional to the vehicle speed in synchronization with the rotation of a magnet fixed to the rotating shaft of the speedometer cable or by turning on and off a relay. . Vehicle speed can be measured by measuring the frequency of these pulses, and travel distance can be measured by counting the number of pulses.

(7) The ignition switch 5 is a switch that is operated by the driver to start and operate the engine, and it is possible to know whether or not cranking is in progress based on the voltage signal (START) 29 at its start terminal.

(8) The throttle valve switch 30 closes when the throttle valve 6 opens below a predetermined opening degree.]
The opening/closing of the throttle valve is detected by the opening/closing signal (IDLE) 31.

(9) Air conditioner switch 32 This is a switch that closes when the air conditioner is activated, and detects whether the air conditioner is in operation based on its terminal voltage signal (A/C) 33.

(10) Neutral switch 34c is a switch that closes when the gear position of the transmission is in neutral or parking position, and its open/close signal (
NEUT) 35 detects the gear position of the transmission.

Each of the signals described above is input to and output from the control unit 21. The control unit 21 has a microcontroller, and determines the control state of each controlled object based on the above-mentioned control information (hereinafter referred to as input signal), and sends a control signal (
It outputs an output signal (hereinafter referred to as an output signal) to optimally control the engine, and also outputs information related to this control.

Next, EGI control will be explained.

The fuel injector 1 is arranged near the intake valve of each cylinder. In the case of a 6-cylinder engine, it has 6 injectors. Fuel is pressure-fed to the injector from a fuel tank (not shown) by a fuel pump 8, and the pressure is adjusted to have a constant differential pressure with respect to the pressure inside the intake pipe by a fuel pressure regulator 36 along the way. Therefore, the amount of fuel supplied is proportional to the valve opening time. control unit 2
1 h AFM signal 15 to intake air amount per hour QA, P
The engine rotation speed NRPM is detected and calculated from the O8 signal 13. As can be seen from the calculation formula, T is a straight line that is proportional to the amount of intake air per engine revolution.

Based on this basic injection time TP, a correction factor (CO
The value obtained by multiplying the value by EF) and adding the time 'r8 to correct the difference in the response of injector 1 due to the voltage (the injection amount can be determined from the response) is calculated from ■8 signal road force. time injector drive output (EGI 0UT) 3
Turn on 7 and supply fuel.

Incidentally, in a predetermined operating state, the 0□ signal 17 is used to perform foot control by multiplying by a correction factor α for keeping the air-fuel ratio of the air-fuel mixture supplied to the engine at a constant value.

Therefore, the driving (valve opening) time Ti of the injector is basically 'PH=TPx C0BF xα+Ts. Second
The figure shows a flowchart of the calculations described above.

The above explanation relates to the function of each component in a normal case.

By the way, if a malfunction occurs in the interface circuit in the airflow meter 14 or the control unit 21, for example, when a short circuit or an open state occurs, it is simply diagnosed as a malfunction without performing a particularly active bank up, and all For example, a method is adopted in which the signal value of the airflow meter output voltage signal 15 corresponding to a preset idle is assumed in the control unit 21 under the driving conditions of 1, and the amount of fuel is injected as a result of arithmetic processing.

However, in such a conventional electronic fuel injection device, in the conventional example shown in FIG.
In the case of an abnormality, a preset constant value is given to the control unit 21 regardless of the input signal of the airflow meter 14, so in the conventional example shown in FIG. For example, since only one point is selected to match the idle state, self-blade running is possible, but unstable and dangerous.

(Objective of the Invention) The present invention was made by focusing on such conventional problems, and in order to more accurately estimate the amount of fuel injection required for driving when the intake air amount sensor is abnormal, Depending on the state of the idle switch and start switch, or
The purpose of this invention is to solve the above problems by calculating the fuel injection amount by switching the integral speed in air-fuel ratio feedback in addition to the two switch states.

(Structure and operation of the invention) The present invention will be explained below based on the drawings.

FIG. 3 is a block diagram showing one embodiment of the present invention. More specifically, the controller shown in Figure 1 removes noise from various input signals and absorbs surges to prevent the control unit 2I from malfunctioning due to noise or destruction due to surges, and also amplifies various input signals. The input interface circuit 51 is converted into a format that allows the next input interface circuit 51 to operate correctly.

The input interface circuit 51 is a signal shaping circuit (2)
Analog, -kasital (A
D) Convert it into a digital code so that it can be read as input data by the next central processing unit (CPU) 52 by converting it or counting the number of pulses during a predetermined time, and then internally storing it as input data. Store it in the register that has it. Furthermore, when the RBI'' signal 12 is input, it is detected and an interrupt request signal is issued to the CPU 52.

The CPU 52 is a central processing unit that operates in synchronization with a clock signal based on a signal transmitted from the crystal oscillator 53. The CPU 52 is connected to each section via a bus 54. The bus 54 includes an address bus that selects addresses assigned to each part, a data bus that transfers data to and from each part, and a control bus that includes a clock signal and a recent signal used as synchronization signals for data transfer timing. Bus included. The CPU 52 has a mask ROM 56 and P) in the memory 55. , 0M57, reads various input data from each register in the input interface circuit 51, performs arithmetic processing, calculates various output data, and stores the specified data in the register in the output interface circuit 59. Sends output data at the appropriate timing. Transfer of these data is performed via the bus 54 mentioned above.

The memory 55 is a data storage device, and includes a mask ROM 56,
It has a PROM 57, a RAM 59, and a storage memory 58.

The storage contents of the mask R, OM 56 are determined at the time of IC manufacture, and store the program executed by the CPU 52 and the data used when executing the program.

R, AM 57 is a readable and writable memory in which intermediate data and result data of arithmetic processing are temporarily stored and held before being sent to the output interface circuit 59. Furthermore, the memory contents of RAM57 are as follows:
Ignition switch 25 is off, main power 2
If the number 3 expires, it will not be retained.

The memory contents of masks R, 0M56 and PR, 0M57 are as follows:
It is retained permanently even if the power is turned off, but its contents cannot be changed (rewritten) without replacing it. The deployment holding memory 58 stores result data and intermediate data of arithmetic processing.
The memory is retained even when the ignition switch 5 is turned off, that is, when the vehicle is not being driven.

The output interface circuit 59 receives output data from the CPU 52 into an internal register, converts it into a pulse signal having a predetermined timing and time width, or a predetermined period and duty ratio, or converts it into a 1, 0 switching signal. The signal is sent to the drive circuit 60.

The drive circuit 60 is a power amplifier circuit that receives a signal from the output interface circuit 59 and uses a transistor or the like to generate a voltage.
Current is amplified to drive various actuators and display.

Next, the effect will be explained.

First, as a first embodiment, means for determining the fuel injection amount when the intake air amount sensor fails will be described. In the first embodiment of the present invention, instead of using one preset intake air amount, multiple (in this case, 2X2X3) preset intake air amounts are used depending on the types of conditions specified in Table 1. This enables more stable self-blade running.In other words, when idling, when idling off assuming low speed running, when starting on to ensure a reliable start, and during warm-up. In order to stabilize the water temperature, three-stage switching of water temperature increase is performed using three sensors: an idle switch, a start switch, and a water temperature sensor.

Table-1(a) Here, Table-1 will be briefly explained. ff-1 is
This is an example of the fuel injection amount that allows a certain degree of self-driving without measuring the intake air amount, and is a multiple of the above fuel injection amount when the water temperature is 80 degrees Celsius or higher and the idle is on after startup as 1.0. This is what is shown. Table 1 (a) shows a comparison of fuel injection amounts at a water temperature of 80°C, and Table 1 (b)
) is a comparison of fuel injection amount using water temperature as a parameter.

When the intake air amount sensor is abnormal, the amount of fuel shown in Table 1 will be injected.

FIG. 4 shows a flowchart of the first embodiment according to the present invention. In the first embodiment, when it is determined that the intake air amount sensor is abnormal, the fuel injection amount is determined according to the flowchart in FIG. 4, and the value is transferred to step (110) in FIG.
Replace with the TiO value.

This will be explained in detail below. In step (121), the intake air amount sensor is determined to be abnormal (intake air amount abnormality detection section), and the method is as follows. In the case of a flap type air flow meter, an abnormality occurs when the output voltage is within a predetermined upper and lower limit value (UMAXI UMIN). This makes it possible to detect failures such as short circuits, disconnections, and disconnection of the sensor. In a hot wire type air flow meter or a Kalman sensor type air flow meter, a sensor abnormality is detected by detecting a voltage, number of pulses, or pulse frequency outside a predetermined range.

When an abnormality in the intake air amount sensor is detected in step (121), the idle switch, start switch, and water temperature switch, which are the states of the vehicle, are checked in steps (122), (125), and (128). As a result, the idle volume increase K
Pidle, start increase KFsta100, water temperature increase KF
Each coefficient of TW is substituted, and in step (132) all coefficients are totaled to obtain a coefficient KF that takes discontinuous values. KF
= KFldlex KFstart x I(FTW
, the air-fuel ratio control α is α-1, and other corrections shown in Figure 2 are 'r, I KAS I
KAI, r<FC, etc. are not considered (set to zero). Next, in step (133), the final fuel injection pulse width Ti is calculated. Here, the constant ' is a constant when bank up is working, and is preset to a value such that the pulse width calculated in step (133) during idle is equal to the pulse width during normal idle. Step (133
) is used in place of Ti obtained in step (110) of FIG. That is, the fuel injection amount in step (133) becomes the back amplifier output when the intake air amount sensor is abnormal.

In addition, in order to prevent the car from running out of control when the vehicle enters the backup mode, the system shown in Figure 5 is used to notify the user that the vehicle is running in the bank up mode and that it is necessary to take the vehicle to a repair shop immediately. According to the flowchart,
Vehicle speed is limited to, for example, 501 cm/h. Figure 5 shows the vehicle speed limit during back amplifier, when the vehicle speed is 50Ian/
h (step 142), step (13,
Regardless of the value of 3), in step (143) T1-0 or a value T1≦T8 smaller than the response time T8 of the fuel injector is set, thereby substantially cutting off fuel injection.

FIG. 6 shows a flowchart of a second embodiment of the invention. This embodiment is an example of a method of estimating the intake air amount QA based on the vehicle speed. First, in step (150), a failure of the intake air amount sensor is detected. Next, it is checked in step (151) whether the idle switch is on. If the idle switch is on (when the throttle valve is fully closed), in step (152), the intake air amount QAOO corresponding to the idle time is substituted into QA, regardless of whether the engine is idle when stopped or idle when decelerating. . If the idle switch is off, the vehicle speed is read in step (153). Check the vehicle speed read in step (153), and if it is less than 5b/h in step (154), QA←QAO0,
5~30h/, h when QA4-Qxzo, 3ob/
When it is more than h, it is set as QA4-QA4o. This QAOO+
QA20 +QA40 are the intake air amounts shown in FIG. 7, respectively.

Figure 7 shows a normal driving situation, for example, when driving in a city.
It is a graph showing the relationship between vehicle speed, engine rotation speed, and intake air amount in 0 mode driving.

FIG. 8 shows a flowchart of a third embodiment of the invention. This figure shows a method for improving running performance by switching the integral constant to a larger value in the event of an abnormality in the calculation method of the correction factor α for air-fuel ratio control. The basic configuration is the second
Although it is similar to the figure, the method of determining the air-fuel ratio correction factor α is different.

In step (161,), the output voltage of the air-fuel ratio sensor ■o2
Read it and compare slice levels V8/L.

If VO2〉vs/l, then α in step (163)
. -αn-5-P”Ti(n-1) is calculated, VO2≦
Vs/l.

If so, α. = αn-1+ P + I'T+ (
Calculate n-ri.

Here, α. is the nth correction factor α of the fuel injection pulse T,
is the value of P is a proportional component, and ■ is an integral.

Ti(n-1) is the (n-1)th injection pulse width, and the unit is m sec. The value of the correction factor α changes stepwise every time the injection is performed (.In steps (165) and (166), it is determined whether the upper and lower limits of the correction factor α have been reached, and the upper and lower limits are determined. If the value is reached, α.=αm
limited to ax +α−αmin. αml. 〈α〈αm
If ax, then α. Let the own A-direction be the f-direction of α (steps 168, 169). The value of α is determined here, and from then on, the flow moves to step (109) and subsequent steps in Figure 2 (.

Here, Vs/L, P, during normal and abnormal times, 1. αm
Table 2 shows the values of ax and αm10.

When the intake air amount sensor is abnormal, the integral speed is increased several times, and is switched to, for example, I=3X]0-3 so that smooth acceleration can be immediately obtained during a transient state, such as acceleration.

Also, during bank up, the control position varies considerably, so in order to widen the correction area, αmax "1.
50, αmin = 0.6. By switching this integral constant, not only steady running but also
Responsiveness is good in transient conditions (especially at the start of acceleration), and self-blade travel is possible.

Here, the proportional portion P at the time of back amplifier may be replaced with P=0. Further, as the air-fuel ratio sensor, it is desirable to use an oxygen sensor with a heater that can indicate the correct air-fuel ratio (A/F) even in an idling state.

(Effects of the Invention) As described above, according to the present invention, when the intake air amount sensor is abnormal, the load condition is detected based on the states of the idle switch and the start switch, and in addition, the integral speed of the air-fuel ratio feedback is detected. Since the amount of fuel injection required for driving is estimated based on the switched state, the effect is that even in the event of a sensor failure, the vehicle can travel on its own to the repair shop in a safe driving state.

Furthermore, when using a back amp, the vehicle speed or medium speed (for example, 50
1 cm/h) or more, and the fuel is cut off in a way that is different from normal, so there is no danger of the vehicle driving out of control, and the driver can be promptly and reliably notified of the abnormality.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional electronic fuel injection device, FIG. 2 is a flowchart showing calculation of the fuel injection amount of the device in FIG. 1,
FIG. 3 is a block diagram showing the configuration of the present invention, FIG. 4 is a flowchart of the first embodiment of the invention, FIG. 5 is a flowchart for limiting vehicle speed during backup, and FIG. ') Flowchart of the second embodiment of the invention,
FIG. 7 is a graph showing the relationship between 10-mode driving in normal mode and the driver/output parameters, and FIG. 8 is a flowchart of a third embodiment of the present invention. 1... Injector, 2... Injection coil, 3... EGR valve, 4... VCM valve, 5
...ACC valve, 6...throttle valve,
7... Fuel pump relay, 8... Fuel pump, 9...
...Fuel consumption needle, 10...Crank angle sensor, 1
1...Distributor, 12...R, EF double signal] 3...POS signal, 14...Air flow meter, ]5...AFM signal, 16...02 sensor, 17... 02 signal, 18... water temperature sensor, 20... battery, 21... control
Unit, 5...Ignition switch, 27...Vehicle speed sensor, A...Throttle valve switch, 50...Signal shaping circuit, 51...Input interface circuit, 52...Central processing Device, 55... Memory, 5
9... Output interface circuit, 60... Drive circuit. Patent applicant Nissan Motor Co., Ltd. Patent application agent Megumi Yamamoto - Ka 4 Figure 5 Figure

Claims (4)

[Claims] (1) Basic injection time TP = -QA/NRPM (K: constant) based on the intake air amount QA obtained from the intake air amount sensor and the engine rotation speed NRPM obtained from the crank angle sensor
Based on the correction factor C0EF according to the signals output from various sensors and the time T8 for correcting the variation in the injector response time due to the battery voltage, the fuel injection time is determined by the following formula % formula %:) In the electronic fuel injection device, an abnormality detection means is provided for detecting that the intake air amount sensor or its interface circuit is in an abnormal state based on an output signal of the intake air amount sensor, and when the abnormal state is detected by the means. , a coefficient KF that takes a discontinuous value determined based on each signal of an idle switch, a start switch, and a water temperature sensor is calculated, and the fuel injection time is determined by the following formula % formula %:) backup device in the event of an emergency. (2) When the abnormality detection means detects an abnormal state, the basic injection time T,= is set based on a preset intake air amount QA that is uniquely determined based on two signals from the idle switch and the vehicle speed sensor. - Calculates QA/NRPM (K: constant), and further calculates a correction factor COE according to signals output from various other sensors, based on P and time Ts for correcting fluctuations in injector response time due to battery voltage, 2. The device according to claim 1, wherein the fuel injection time is determined by the following formula: %. (3) When the abnormality detection means detects an abnormal state, when the vehicle speed exceeds the vehicle speed detected by the vehicle speed sensor or a preset vehicle speed, the fuel injection time is a value smaller than the two-ale injector response time Ts T1≦T8 An apparatus according to any one of claims 1 to 2, characterized in that: (4) When the abnormality backup device has an air-fuel ratio sensor and the abnormality detection means detects an abnormal state, among the proportional and integral elements that determine the correction factor Claims 1 to 2 are characterized in that the correction factor α is determined based on the output voltage of the air-fuel ratio sensor and at an integration speed faster than a preset integration time in a normal state. Equipment described in Section.