CN101644199A - Method and device for simulating faults of zirconia-type oxygen sensor for electronic injection engine - Google Patents

Abstract

The invention relates to a fault simulation method and device for a zirconia type oxygen sensor of an EFI engine, which can generate an upper limit for an oxygen sensor (the oxygen sensor includes a front oxygen sensor, a rear oxygen sensor, or both front and rear oxygen sensors) for an EFI engine Independent fault simulation modes for voltage upper excursion, upper upper limit voltage lower excursion, lower limit voltage upper excursion, lower limit voltage lower excursion, time response delay, rising slope change of rising edge and falling slope change of falling edge and upper limit voltage excursion , lower limit voltage offset, time response delay and slope change four fault modes of arbitrary proportion mixed fault simulation mode, so that the fault simulation signal output is more consistent with the actual oxygen sensor fault signal output; so as to be used for the development and verification of OBD system and Other related research needs.

Description

Fault simulation method and device for zirconia oxygen sensor used in EFI engine

technical field

The invention belongs to a test instrument for an electric injection engine (electrically controlled gasoline injection engine), in particular to a fault simulation method and device for a zirconia type oxygen sensor used in an electronic injection engine.

Background technique

According to the requirements of the emission regulations GB18352.3-2005 "Light Vehicle Pollutant Emission Limits and Measurement Methods" issued by the State Environmental Protection Administration of China and the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on April 27, 2005, in 2008 China fully implemented the third Stage emission standards, light vehicles must be equipped with On-board diagnostic (OBD, on-board diagnostic system). According to regulations, the components monitored by the OBD system include: three-way catalytic converter, oxygen sensor, engine misfire rate, emission control components and systems, and any emissions-related circuits.

The oxygen sensor is the abbreviation of Exhaust Gas Oxygen Sensor (EGO). Its function is to obtain the air-fuel ratio signal of the mixture by monitoring the content of oxygen ions in the exhaust gas, and convert the signal into an electrical signal and input it to the ECU. According to the oxygen sensor signal, the ECU corrects the fuel injection time to realize the air-fuel ratio feedback control (closed-loop control), so that the excess air coefficient (λ) is controlled between 0.98 and 1.02 (the air-fuel ratio A/F is about 14.7), so that The engine gets the mixed gas with the best concentration, so as to achieve the purpose of reducing the emission of harmful gases and saving fuel.

In the EFI engine, the OBD system needs to monitor the oxygen sensor signal used by the engine electronic control system in real time. Once the oxygen sensor signal of the engine electronic control system is found to be abnormal, the OBD system will alarm. In the engine electronic control system, the currently used oxygen sensors can be divided into two types: 1) Zirconia oxygen sensor, which converts the change of oxygen molecule content in the exhaust gas into the change of voltage. 2) Titanium oxide type oxygen sensor, the titanium dioxide type oxygen sensor converts the change of oxygen molecular content in exhaust gas into the change of sensor resistance. The following oxygen sensors refer to zirconia type oxygen sensors.

In the following three situations, it is necessary to cause the oxygen sensor of the EFI engine to fail: 1) When developing the oxygen sensor signal monitoring function of the OBD system, the engine needs to have an oxygen sensor failure phenomenon. 2) When verifying whether the OBD system of a new car or an in-use car can effectively monitor the oxygen sensor failure, it is also necessary to make the oxygen sensor failure of the engine. 3) The test and verification of the dual oxygen sensor diagnostic algorithm for three-way catalytic converter fault diagnosis. These failures are difficult to produce in a new set of oxygen sensor of EFI engine, and it is difficult to produce quantitative oxygen sensor failure.

Chinese invention patent "A Method and Device for Oxygen Sensor Failure of Electronically Controlled Gasoline Injection Engine" (Patent No.: 200710051383.5) needs to use a separate board, mobile computer and 220v power supply, which brings inconvenience to the use of the car; there are also Shortcomings such as less fault simulation forms.

Contents of the invention

The present invention is aimed at the control system of the EFI engine, and the purpose is to provide an oxygen sensor used for the EFI engine to produce an upper limit voltage offset, an upper limit voltage lower offset, a lower limit voltage upper offset, a lower limit voltage offset, and a time response delay. , the independent fault simulation mode of the rising slope change of the rising edge and the falling slope change of the falling edge, and the arbitrary proportion mixed fault simulation mode of the four fault modes of upper limit voltage offset, lower limit voltage offset, time response delay and slope change, making the fault The analog signal output is more in line with the actual fault signal output; the fault simulation method and device for the zirconia oxygen sensor used in the EFI engine are used for the development and verification of the OBD system and other related research needs. .

In order to achieve the above object, the method adopted in the present invention is: disconnect the signal line connected between the oxygen sensor and the ECU (electronic control unit), an oxygen sensor failure simulation device is set between the oxygen sensor and the ECU, and the output of the oxygen sensor The signal is not directly input to the ECU, but is directly input to the oxygen sensor failure simulation device. The oxygen sensor failure simulation device samples the signal output by the oxygen sensor through the A/D converter. The main control unit of the oxygen sensor failure simulation device is based on this signal. Superimpose the voltage offset signal or the response delay signal or simultaneously superimpose the voltage offset signal and the response delay signal to generate an analog signal of the oxygen sensor failure, and then use the D/A converter to output the processed signal to the ECU of the EFI engine .

The above-mentioned oxygen sensor fault simulation device is composed of a main control single-chip microcomputer, a D/A output module, a liquid crystal display module, a parameter setting module and a host computer system, wherein the A/D sampling input terminal of the main control single-chip microcomputer is connected with the output signal of the oxygen sensor, D The /A output module is connected to the SPI port of the main control microcontroller and the ordinary I/O port, the liquid crystal display module is connected to the I/O port of the main control single chip computer, the parameter setting module is connected to the I/O port of the main control single chip computer, and the upper computer system It is connected with the main control microcontroller through the RS232 serial port.

The oxygen sensor fault simulation device consists of a liquid crystal display module J1, a main control microcontroller U1, a D/A conversion chip U2, a level conversion chip U3, buttons B1~B6, resistors R1-R6, and capacitors C1-C8, among which:

Disconnect the signal connection line between the oxygen sensor and the ECU, connect the output signal of the oxygen sensor directly to the fault simulation device of the oxygen sensor, and connect it to the A/D port of the main control microcontroller; the data port of the liquid crystal display module is connected to the main control microcontroller to control Ports RST, INT, BUSY, CS2, CS1, RD, WR, RS are connected to the ordinary I/O port of the main control microcontroller, T1I and resistor R10 of the level conversion chip are connected to the serial ports TXD0 and RXD0 of the main control single chip computer, and the key output B1-B6 are connected to the ordinary I/O port of the main control microcontroller; the control ports SDI, CLK, CS, DACS, REG, RSET of the D/A conversion chip are respectively connected to the MOSI and SCK of the SPI port of the main control single chip microcomputer and the common I The /O port is connected, and the output ports OUTA and OUTB of the D/A conversion chip are connected to the input interface of the ECU.

Description of drawings

Fig. 1 is a principle and connection diagram of the present invention.

Figure 2 is an electrical connection diagram of the present invention.

Fig. 3 is a fault phenomenon diagram of an upper limit voltage offset fault of an oxygen sensor signal in the present invention.

Fig. 4 is a graph showing the phenomenon of offset faults under the upper limit voltage of the oxygen sensor signal in the present invention.

Fig. 5 is a fault phenomenon diagram of the oxygen sensor signal lower limit voltage and upper offset fault phenomenon of the present invention.

Fig. 6 is a fault phenomenon diagram of the oxygen sensor signal lower limit voltage offset fault phenomenon in the present invention.

Fig. 7 is a fault phenomenon diagram of the signal time response delay of the oxygen sensor of the present invention.

Fig. 8 is a fault phenomenon diagram of the oxygen sensor signal slope change of the present invention.

Fig. 9 is a fault simulation phenomenon diagram of the oxygen sensor signal mixed mode of the present invention

In Figure 1: 1, 2-heating wires, 3, 4-signal wires.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and examples, but these examples should not be construed as limiting the present invention.

According to Figure 1 and Figure 2, the oxygen sensor fault simulation device is installed between the oxygen sensor and the electronic control unit ECU, the oxygen sensor heating lines 1 and 2 are still connected to the ECU, and the fault occurrence device does not control the heating line; the oxygen sensor signal ground 3 It is still connected with ECU, and it is processed with the power ground of the fault simulation device; the oxygen sensor signal output line 4 is disconnected from the ECU, and the output signal of the oxygen sensor is input to the A/D sampling of the main control microcontroller of the fault simulation device channel, the main control microcontroller samples the oxygen sensor signal at a period of 10ms, converts the analog signal into a digital signal, and uses the liquid crystal display module to update and display the sampling signal in real time and send the sampling signal to the upper computer system through the serial port. After scale conversion, voltage offset processing and response delay processing, the digital signal is output to the D/A conversion module and converted to analog output to the ECU of the EFI engine.

The upper computer system software of the present invention. The oxygen sensor failure simulator has two operating modes: stand-alone operation and online operation. Stand-alone operation mode: Use the oxygen sensor simulation device alone to simulate the failure of the oxygen sensor. Online operation mode: After connecting the oxygen sensor fault simulation device with the host computer system, the oxygen sensor fault simulation can be realized through the host computer software.

The corresponding parameter settings in this mode are:

Upper limit offset: used to set the upper limit upper limit or upper lower limit offset of the oxygen sensor fault signal, the range of the offset is 0~±0.3V, and the adjustment accuracy is 0.02v;

Lower limit offset: used to set the lower limit upper limit or lower limit lower limit offset of the oxygen sensor fault signal, the offset range is 0~±0.3V, and the adjustment accuracy is 0.02v;

Time delay: used to set the oxygen sensor fault signal time response delay, the delay range is 0-2S, and the adjustment accuracy is 0.01s;

Smooth processing: used to set the digital filtering and average value processing of the oxygen sensor fault signal, used to adjust the rising edge or falling edge slope of the oxygen sensor signal, the adjustment range is 0~20, and the adjustment accuracy is 1;

Normal work: normal work mode.

Fig. 3 shows a fault phenomenon diagram of an oxygen sensor signal upper limit voltage offset fault phenomenon realized by the present invention. The thick black line in the figure is the collected oxygen sensor signal, and the thin line is the output analog signal of the oxygen sensor fault after processing. When the fault shown in Figure 4 occurs, an upper offset voltage signal is superimposed on the input signal with 0.3V as the base point. When the input voltage is 0.3V, the superposition amount of the output signal calculated is 0, and the greater the difference between the voltage signal and 0.3V , the greater the amount of superimposition on the calculated output signal is, so as to realize the upper limit voltage shift, the adjustment range of the superposition amount is 0-0.3V, and the adjustment accuracy is 0.02V.

Fig. 4 shows a diagram of the offset fault phenomenon of the oxygen sensor signal under the upper limit voltage realized by the present invention. The thick black line in the figure is the collected oxygen sensor signal, and the thin line is the output analog signal of the oxygen sensor fault after processing. When the fault shown in Figure 5 occurs, a lower offset voltage signal is superimposed on the input signal with 0.3V as the base point. When the input voltage is 0.3V, the superposition amount of the output signal calculated is 0, and the difference between the signal voltage and 0.3V The larger the value is, the greater the amount of down-superimposition of the calculated output signal will be, so as to realize the down-shifting of the upper limit voltage. The adjustment range of the superposition amount is 0-0.3V, and the adjustment accuracy is 0.02V.

Fig. 5 shows the fault phenomena of the oxygen sensor signal's lower limit voltage and upper shift fault phenomenon realized by the present invention. The thick black line in the figure is the collected oxygen sensor signal, and the thin line is the output analog signal of the oxygen sensor fault after processing. When the fault shown in Figure 6 occurs, an upper offset voltage signal is superimposed on the input signal with 0.7V as the base point. The superposition amount of the output signal calculated when the input voltage is 0.7V is 0, and the difference between the signal voltage and 0.7V The larger the value is, the greater the amount of superposition of the calculated output signal will be, so as to realize the upper shift of the lower limit voltage. The adjustment range of the superposition amount is 0-0.3V, and the adjustment accuracy is 0.02V.

Fig. 6 shows a diagram of the oxygen sensor signal offset fault phenomenon under the lower limit voltage realized by the present invention. The thick black line in the figure is the collected oxygen sensor signal, and the thin line is the output analog signal of the oxygen sensor fault after processing. When the fault shown in Figure 7 occurs, with 0.7V as the base point, a voltage signal with a lower offset is superimposed on the input signal, so that the superposition amount of the output signal calculated when the input voltage is 0.7V is 0, and the signal voltage and The greater the difference of 0.7V, the greater the amount of down-superposition of the calculated output signal, thereby realizing the lower-limit voltage offset. The adjustment range of the superposition amount is 0-0.3V, and the adjustment accuracy is 0.02V.

Fig. 7 shows a fault phenomenon diagram of the signal time response delay of the oxygen sensor realized by the present invention. The thick black line in the figure is the collected oxygen sensor signal, and the thin line is the processed oxygen sensor fault analog signal. After the main control system collects the oxygen sensor signal, it saves the oxygen sensor signal collected in the previous period t0, and outputs a fixed analog signal to the ECU during this period. After the set delay time is reached, the saved signal Perform D/A output according to the principle of first-in-first-out, thereby changing the cycle of oxygen sensor signal output, and realizing the fault simulation of oxygen sensor aging. The output period of the oxygen sensor signal can be changed by changing t0, the adjustment range of time t0 is 0-2S, and the adjustment accuracy is 0.01s.

Fig. 8 shows a fault phenomenon diagram of the oxygen sensor signal slope change realized by the present invention. The thick black line in the figure is the collected oxygen sensor signal, and the thin line is the processed oxygen sensor fault analog signal. After the main control system collects the oxygen sensor signal, it calculates the average value of the oxygen sensor signal collected in the previous period t1, and changes the rising or falling slope of the oxygen sensor signal by processing the average value of the signal, and then passes the average value through D /A conversion module output to ECU. Change the slope of the oxygen sensor signal by changing t1, and the adjustment range of time t1 is 0-20.

Fig. 9 shows a fault phenomenon diagram of the oxygen sensor signal mixed fault mode realized by the present invention. The thick black line in the figure is the collected oxygen sensor signal, and the thin line is the processed oxygen sensor fault analog signal. After the main control system collects the oxygen sensor signal, it performs superimposition of the three fault simulations of upper limit voltage shift, lower limit voltage shift and time response delay on the sampled signal, and the main control system converts this signal through D/A Module output to ECU. Adjust the setting parameters of the three failure modes respectively to realize the output of failure analog signals with different mixing ratios.

The content not described in detail in this specification belongs to the prior art known to those skilled in the art.

Claims (4)

1. A method for the failure of a zirconia type oxygen sensor used in an electric injection engine, the method adopted is: disconnect the signal line connected between the oxygen sensor and the electronic control unit ECU, and set an oxygen sensor failure between the oxygen sensor and the ECU. Simulation device, the signal output by the oxygen sensor is not directly input to the ECU, but directly input to the oxygen sensor fault simulation device, the oxygen sensor fault simulation device samples the signal output by the oxygen sensor through the A/D converter, the main control of the oxygen sensor fault simulation device On the basis of this signal, the unit superimposes the voltage offset signal or the response delay signal or simultaneously superimposes the voltage offset signal and the response delay signal to generate an analog signal of the oxygen sensor failure, and then uses the D/A converter to convert the processed signal The signal is output to the EFI engine ECU. 2. The fault occurrence method of zirconia type oxygen sensor for EFI engine according to claim 1, characterized in that: said method has two operation modes, stand-alone operation and online operation, and the stand-alone operation mode refers to using oxygen alone The sensor simulation device simulates the failure of the oxygen sensor, sets the corresponding parameters through the parameter setting module, and displays the normal signal and fault simulation signal through the liquid crystal display module; the online operation mode refers to connecting the oxygen sensor failure simulation device with the host computer system The fault simulation of the oxygen sensor is realized through the host computer software, the parameters of the fault simulation are set through the host computer system software, the normal signal and the fault simulation signal are displayed through the host computer system software, and the normal signal and the fault signal are saved at the same time. 3. The fault occurrence method of zirconia type oxygen sensor for EFI engine according to claim 1, characterized in that: said oxygen sensor fault simulation device can cause the oxygen sensor to generate an upper limit voltage shift, a lower limit voltage shift, Independent fault simulation modes for lower limit voltage upper excursion, lower limit voltage excursion, time response delay, rising slope change of rising edge and falling slope change of falling edge and upper voltage excursion, lower limit voltage excursion, time response delay and slope Change the random proportion mixed fault simulation mode of the four fault modes. 4. The electronically controlled gasoline injection engine oxygen sensor failure simulation device according to claim 1 or 4, characterized in that: the oxygen sensor failure simulation device is mainly controlled by a single-chip microcomputer, a D/A output module, a liquid crystal display module, and a parameter setting module It is composed of an upper computer system, in which the A/D sampling input terminal of the main control microcontroller is connected with the output signal of the oxygen sensor, the liquid crystal display module is connected with the I/O port of the main control single chip computer, and the parameter setting module is connected with the I/O port of the main control single chip computer The upper computer system is connected to the main control microcontroller through the RS232 serial port, and the D/A output module is connected to the SPI port and the ordinary I/O port of the main control single chip. The main control system realizes the simulation of the fault signal by sampling the signal of the oxygen sensor, superimposing the signal with voltage offset or time response delay or simultaneously superimposing the voltage offset signal and time response delay signal, and the processed signal is passed through D/A The conversion module outputs to the ECU.

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