JP2009079494A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect abnormal wiring of an exhaust gas sensor used for an engine control device and prevent damage and deterioration of the exhaust gas sensor. <P>SOLUTION: Each positive terminal electric potential of exhaust gas sensors 103a-103d is selected and input to an analog input terminal AN2 of a microprocessor 110 via a multiplexer 130 in an order, and offset voltage V1 is applied to each negative terminal of the exhaust gas sensor. When the positive terminal electric potential gets to the offset voltage V1 or less due to short-to-ground failure of any of the positive terminal wiring 104a-104d, apply of the offset voltage V1 is stopped by an offset voltage shut off circuit 125 and short current flowing to any of the exhaust gas sensors of short-to-positive line is stopped to prevent damage and deterioration of the exhaust gas sensor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes an abnormality diagnosing means for detecting a failure or wiring abnormality of an exhaust gas sensor externally connected to detect an air-fuel ratio, which is used in an engine control device for feedback control of the air-fuel ratio of an internal combustion engine. The present invention relates to an engine control device.

In order to feedback control the air-fuel ratio of an internal combustion engine, an exhaust gas sensor called a lambda type is widely used in practice, and this lambda type exhaust gas sensor is installed, for example, before and after a catalyst provided in an exhaust pipe, A detection voltage Vs corresponding to the oxygen concentration in the exhaust gas is generated. This detected voltage Vs is about 0.45 V at the stoichiometric air-fuel ratio as the operation target, but rapidly rises in the fuel rich state and converges to a value of 0.85 to 1.0 V, and rapidly in the fuel lean state. And has a characteristic of converging to 0.1 to 0V.
However, the detection voltage of the exhaust gas sensor in the low temperature / inactive state is small, and the internal resistance generally reaches a level of several MΩ while it is several tens of KΩ in the active temperature state. Various techniques have been proposed and put to practical use in order to detect such exhaust gas sensor failures and wiring abnormalities.

  For example, according to Patent Document 1, an offset voltage is applied to a ground line (negative line) of a lambda sensor that detects an air-fuel ratio, and a detection voltage generated between a positive signal line and a negative line of the lambda sensor. The value obtained by adding the offset voltage is digitally converted and then input to the microprocessor. If the detection voltage input to the microprocessor is less than the offset voltage, the value is positive. It is determined that the signal line is in a ground fault state in short circuit contact with the ground circuit. In addition, by connecting a pull-down resistor to the positive signal line, a signal line disconnection abnormality is detected as a ground fault abnormality.

According to Patent Document 2, an offset voltage is applied to the negative line of the air-fuel ratio sensor, and the potential of the positive signal line of the air-fuel ratio sensor is digitally converted and then input to the microprocessor. If the detected voltage input to the microprocessor is less than the offset voltage, it is determined that the positive signal line is in a short-circuit contact with the ground circuit. Yes. Also, by connecting a pull-down resistor to the positive signal line and temporarily connecting a pull-up resistor, it is possible to identify whether it is a ground fault abnormality or a disconnection abnormality. It has become.

Japanese Patent Laid-Open No. 05-107299 (paragraphs [0010] to [0011] in FIGS. 3 and 4) JP 2005-171898 A (paragraph [0023] in FIGS. 4 and 5)

According to Patent Document 1 and Patent Document 2, if the exhaust gas sensor and its wiring are normal by applying an offset voltage to the negative line of the exhaust gas sensor, the potential of the positive signal line is equal to or less than the offset voltage. The abnormality determination regarding the positive signal line is made based on the logic that it will not become. However, there is a problem that a short-circuit current based on the offset voltage flows into the exhaust gas sensor at the time of a positive ground fault, resulting in damage or deterioration of the exhaust gas sensor.
In addition, the ground fault (negative line) to which the offset voltage is applied is not detected, and the power fault is not detected. is there.
Furthermore, if the exhaust gas sensor generates a negative voltage due to flooding or contamination of the air contact surface of the exhaust gas sensor, an incorrect air-fuel ratio is detected, and various problems such as the inability to detect such a state remain. Has been.

The present invention has been made to solve the above problems, and a first object of the present invention is to detect a negative fault of the exhaust gas sensor in order to detect a ground fault abnormality in the positive terminal wiring of the exhaust gas sensor. In the case where an offset voltage is applied to the terminal, it is to prevent the exhaust gas sensor from being damaged or deteriorated by a short-circuit current flowing into the exhaust gas sensor when a ground fault abnormality occurs in the positive terminal wiring.
A second object of the present invention is to provide a short-circuit current that flows into the exhaust gas sensor when a ground fault abnormality occurs in the positive terminal wiring even if the offset voltage is further increased to detect the flooding abnormality of the exhaust gas sensor. This prevents the exhaust gas sensor from being damaged or deteriorated.
The third object of the present invention is to detect exhaust gas and to perform feedback control when a ground fault abnormality occurs in which a negative terminal wiring to which an offset voltage is applied is mixed with a ground circuit and no other abnormality occurs. It is to provide an engine control device that can continue normal operation of the engine.
A fourth object of the present invention is to provide an engine control apparatus in which a plurality of exhaust gas sensors are externally connected and an offset voltage is applied to the negative terminal wiring. It is to provide an engine control device that can be inspected and detected without overlooking various abnormal modes.

The engine control apparatus according to the present invention is configured to perform various driving operations for the internal combustion engine in response to operating states of various input sensors for monitoring the operating state of the internal combustion engine and contents of a control program stored in a program memory. The engine control apparatus includes a microprocessor for driving and controlling an electric load, wherein the various input sensors include one or a plurality of exhaust gas sensors, and the exhaust gas sensors are connected between a positive terminal and a negative terminal. An equivalent voltage source and an equivalent internal resistance, and a voltage generated by the equivalent voltage source changes between a lean-side normal voltage and a rich-side saturation voltage with a theoretical air-fuel ratio as a boundary at a predetermined activation temperature, A predetermined offset voltage generated by the offset voltage generation circuit is applied to the negative terminal of the exhaust gas sensor, and the positive terminal of the exhaust gas sensor is connected to the ground terminal. A positive terminal potential that is a voltage between circuits is digitally converted as a measurement voltage via an AD converter and stored in a RAM memory for arithmetic processing via the microprocessor, and the measurement voltage or the measurement voltage and the measurement voltage In what obtains the magnitude determination output of the air-fuel ratio by monitoring the differential voltage with the offset voltage,
The program memory includes a control program serving as at least a positive ground fault detection means, an offset voltage cutoff command means, and history information storage means,
The positive line ground fault detection means monitors the measured voltage, and the measured voltage is a value less than the offset voltage, and is equal to or lower than a first threshold voltage approaching a ground potential. It is determined that the positive terminal wiring of the gas sensor is a ground fault abnormality of the positive terminal wiring that is in contact with the ground circuit, and the offset voltage cutoff command means detects the ground fault abnormality of the positive terminal wiring. Along with the detection, it acts on the offset voltage cutoff circuit to stop the application of the offset voltage, and the history information storage means stores in the data memory whether or not the positive ground fault has occurred, and the data The contents of the memory are configured to be read by an external tool for maintenance and inspection.

  According to the engine control apparatus of the present invention, the offset voltage applied to the negative terminal of the exhaust gas sensor is cut off when the positive ground fault detection means of the exhaust gas sensor detects the ground fault of the positive terminal wiring. Thus, when a ground fault abnormality of the positive terminal wiring occurs, it is possible to prevent the short-circuit current due to the offset voltage from flowing into the exhaust gas sensor, and to prevent damage to the exhaust gas sensor. Therefore, it is possible to return to normal by releasing the ground fault of the positive terminal wiring, and there is an effect that it is not necessary to replace parts of the exhaust gas sensor itself.

  The above-described and other objects, features, and effects of the present invention will become more apparent from the detailed description and the drawings in the following embodiments.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings.
1 is a circuit block diagram showing a configuration of an engine control apparatus according to Embodiment 1 of the present invention. In FIG. 1, an in-vehicle battery 101 is connected via an output contact 102 of a power supply relay between a positive power supply terminal Vb of the engine control apparatus 100A and a negative power supply terminal connected to the ground circuit GND. The output contact 102 is closed immediately when a power switch (not shown) is closed. However, even if the power switch is opened, the output contact 102 performs a delay return operation so that power supply to the engine control device 100A is continued for a predetermined delay time. It has become.
A plurality of exhaust gas sensors 103a to 103d are installed outside the engine control device 100A housed in a sealed casing, and the positive terminals of the exhaust gas sensors are connected to the engine control device 100A by positive terminal wirings 104a to 104d, The negative terminal of each exhaust gas sensor is connected to engine control apparatus 100A by negative terminal wirings 105a to 105d.
One exhaust gas sensor is used for an exhaust collecting pipe of a four-cylinder engine, one is used for a three-cylinder branch collecting pipe of a six-cylinder engine, or the upstream and downstream positions of the catalyst in the exhaust collecting pipe are used. It is provided and used.

Various input sensors 106 input to an after-mentioned microprocessor 110 through an interface circuit (not shown) include, for example, an air flow sensor that measures the intake air amount of an engine, an accelerator position sensor that detects the degree of depression of an accelerator pedal, and a throttle valve opening. Various sensors for monitoring the operating state of the engine, such as a throttle position sensor for detecting the degree and a crank angle sensor for the engine.
Various electric loads 107 that are fed and driven from a microprocessor 110, which will be described later, via an interface circuit (not shown) include, for example, an electromagnetic coil for driving a fuel injection valve, an ignition coil for an engine, a valve opening control motor for an intake throttle, There are motors for driving exhaust circulation valves, alarms and indicators, etc.

As an internal configuration of the engine control device 100A, the microprocessor 110 includes, for example, a program memory 111A that is a nonvolatile flash memory, a RAM memory 112 for arithmetic processing, a data memory 113 that is a nonvolatile EEPROM memory, a multi-channel AD converter 114, and the like. They are bused together to cooperate.
In addition to the input / output control program as the engine control apparatus 100A, the program memory 111A stores programs serving as various abnormality diagnosis means and abnormality processing means described later with reference to FIGS.
The constant voltage power supply circuit 120 generates a control voltage Vcc = 5 V based on the power supply voltage DC10 to 16V of the in-vehicle battery 101 supplied to the positive power supply terminal Vb, and stabilizes each part including the microprocessor 110. A voltage is supplied.
The voltage dividing resistors 122 and 123 divide the control power supply voltage Vcc to generate an offset voltage V1 of 2.5 V, for example, and the negative terminal wirings 105a to 105a through the offset voltage generating circuit 121 and the current limiting resistor 127, which are operational amplifiers. The offset voltage V1 is applied to 105d, and the negative terminal potential is connected to the analog input port AN1 of the microprocessor 110 as a monitor signal.

The positive terminal wirings 104a to 104d are connected to the input terminals CH1 to CH4 of the multiplexer 130 via interface circuits 140a to 140d described in detail in FIG. In FIG. 2, only the interface circuit 140a related to the positive terminal wiring 104a is shown.
The multiplexer 130 receives selection commands SL1 and SL2 from the microprocessor 110, selects one of the analog signals input to the input terminals CH1 to CH4, and inputs the selected analog signal to the analog input port AN2 of the microprocessor 110. It has become.
A voltage-dividing resistor 123 having one end connected to the ground circuit GND is connected in parallel with a transistor serving as an offset voltage cutoff circuit 125. This transistor receives a base resistor 126 from an offset voltage control command Dr generated by the microprocessor 110. When the logic level of the offset voltage control command Dr becomes “H”, the transistor becomes conductive and the output voltage of the offset voltage generation circuit 121 becomes zero.
In order to cut off the offset voltage, a transistor connected in series with the voltage dividing resistor 122 may be provided, and the series transistor may be cut off.
The external tool 109 connected to the serial input terminal of the microprocessor 110 via the serial interface circuit 160 writes the control program and control constant in the program memory 111A, and the abnormality occurrence history information written and stored in the data memory 113. Is used for reading.

  2 is a detailed circuit diagram of the interface circuit unit in FIG. 1. In FIG. 2, the interface circuit 140a connected to the positive terminal wiring 104a of the exhaust gas sensor 103a includes an operational amplifier 141a and a non-inverting input of the operational amplifier 141a. It consists of a smoothing capacitor 142a connected between the terminal and the ground circuit, a pull-down resistor 144a, and a pull-up resistor 143a connected between the non-inverting input terminal of the operational amplifier 141a and the output terminal of the constant voltage power supply circuit 120. The output terminal and the inverting input terminal of the operational amplifier 141a are directly connected to each other to perform impedance conversion in a state where the amplification factor is 1. The interface circuits 140b to 140d are similarly configured, and the offset voltage V1 is applied to the negative terminal wirings 105a to 105d.

The measured voltage Vd, which is the output voltage of the operational amplifier 141a configured as described above, is expressed by the following equation (1). Where Vcc is the control power supply voltage, Rs is the equivalent internal resistance of the exhaust gas sensor 103a, Vs is the generated voltage of the exhaust gas sensor 103a, V1 is the offset voltage, R143 and R144 are the resistance values of the pull-up resistor 143a and pull-down resistor 144a, Assume that the relationship of R143, R144 >> Rs is established.
Vd≈Vs + V1 + ΔV1, (1)
However, ΔV1 = Vcc × (Rs / R143)

The bias voltage Vp, which is the input voltage of the operational amplifier 141a when the positive / negative terminal wiring or the sensor itself is disconnected, is expressed by the following equation (2).
Vp = Vcc x R144 / (R143 + R144) (2)

FIG. 3A shows an example of the characteristics of the generated voltage Vs of the exhaust gas sensors 103a to 103d. If the fuel is rich with the appropriate stoichiometric air-fuel ratio as a boundary, the saturation voltage Vm = 0.85 to 1.0V. If so, the normal voltage V0 = 0 to 0.1V, and when the submergence is abnormal, the abnormal drop voltage Vn = − (0.8
V to 1.0 V).
As an example, offset voltage V1 = 2.5V, control power supply voltage Vcc = 5.0V, Rs = 20KΩ,
When R143 = 510KΩ and R144 = 2700KΩ, ΔV1 = Vcc (Rs / R143) = 0.2V and Vp = Vcc × R144 / (R143 + R144) = 4.2V.
If a ground fault abnormality occurs when the negative terminal wirings 105a to 105d come into contact with the ground circuit GND, the monitor signal for the offset voltage V1 input to the analog input port AN1 decreases from the normal value 2.5V to 0V, thereby causing the microprocessor. 110 can detect a negative ground fault. Similarly, when a power fault that causes the negative terminal wirings 105a to 105d to come into contact with the power supply line occurs, the monitor signal for the offset voltage V1 increases from 2.5V to 5V, whereby the microprocessor 110 detects the negative power fault. be able to.
On the other hand, when the positive terminal wiring 104a comes into contact with the ground circuit GND, the value of the measured voltage Vd input to the analog input port AN2 is originally at least 1.5V or more is reduced to 0V. A line ground fault abnormality can be detected.
However, when a ground fault abnormality of the negative terminal wiring has already been detected, the ground fault abnormality determination of the positive terminal wiring is avoided. Similarly, when the positive terminal wiring 104a comes into contact with the power supply line, the value of the measured voltage Vd increases to 5V, which is originally 3.5V or less, so that the microprocessor 110 may detect a positive power line fault. it can.

Next, assuming that the positive terminal wiring 104a or the negative terminal wiring 105a is disconnected, the potential of the non-inverting input terminal of the operational amplifier 141a becomes the bias voltage Vp divided by the pull-up resistor 143a and the pull-down resistor 144a. If, for example, Vp = 1.0 V or 4.2 V is selected as this voltage, the microprocessor 110 can distinguish from a ground fault abnormality or a power fault abnormality of the positive terminal wiring and detect a disconnection abnormality.
However, in the circuit of FIG. 2, if the pull-up resistor 143a is not connected, it is impossible to distinguish between when the disconnection abnormality occurs and when the ground fault abnormality occurs.
Similarly, in the circuit of FIG. 2, if the pull-down resistor 144a is not connected, it is impossible to distinguish between when a disconnection abnormality occurs and when a power fault abnormality occurs.
In any case, the disconnection abnormality itself is detectable, and since the detected abnormality may be a ground fault abnormality or a power fault abnormality, it can be identified. It is desirable if not essential.

  As described above, as a result of connecting both the pull-up resistor 143a and the pull-down resistor 144a, the disconnection abnormality can be identified. However, the measured voltage Vd is divided by the pull-up resistor 143a and the internal resistor Rs in a normal state. Since the pressed minute voltage ΔV1 is added, the microprocessor 110 calculates the generated voltage Vs by subtracting the offset voltage V1 and the minute voltage ΔV1 from the measured voltage Vd as shown in the equation (1). Is something that can be done.

FIG. 3B is a list of measured voltage Vd values for combinations of the negative terminal wiring state and the positive terminal wiring state described above.
In FIG. 3B, in the case of a negative ground fault, when the measured voltage Vd is zero, it is identified whether the positive terminal wiring is normal, ground fault, or submerged. It is not possible.
Further, in the negative line power fault state, the positive terminal wiring may also be in a power fault, the positive terminal wiring may be normal, and the positive line power fault cannot be identified.
Furthermore, when a submergence abnormality of the sensor occurs, the measurement voltage Vd is in the range of 1.5 to 2.5 V. If it is within this range, it is determined that the submergence is abnormal.

Next, the operation and operation of the first embodiment of the present invention configured as shown in FIGS. 1 and 2 will be described based on the flowcharts shown in FIGS.
1 and 2, when the output contact 102 is closed, the microprocessor 110 is supplied with power from the constant voltage power supply circuit 120 and starts operating, and various input sensors 106 and exhaust gas sensors 103a to 103a are started. In response to the operation state and signal level of 103d and the contents of the input / output control program stored in the program memory 111A, drive control for various electric loads 107 is executed, and the execution process shown in FIGS. Abnormal inspection operation is performed.
In FIG. 4, a process 200 is a step in which the microprocessor 110 starts an inspection operation, and this start step is repeatedly executed after a predetermined waiting time following an operation end step shown in a process 219 described later. It has come to be.
A subsequent step 201 is a step of determining whether or not the ambient temperature of the exhaust gas sensors 103a to 103d has reached a predetermined activation temperature. In the step 201, when a predetermined time or more has elapsed after engine startup, or described later If the fuel rich determination is made in step 348c (see FIG. 8), the activation completion (YES) is determined and the process proceeds to step 203. If not completed (NO), the process proceeds to step 202. It is supposed to be.
Step 202 is a step in which the logic level of the offset voltage control command Dr is set to “H” to make the offset voltage cutoff circuit 125 conductive, and as a result, the offset voltage V1 is set to zero. To do.
The step 202 is effective in the embodiment in which the pull-up resistor 143a is not provided in FIG. 2, and the measured voltage is measured when the internal resistance Rs is excessive in the inactive state of the exhaust gas sensors 103a to 103d. The effect of lowering Vd can be suppressed.
Step 203 specifies the channel number of multiplexer 130 and sets which of the exhaust gas sensors 103a-103d is to be inspected, and subsequent process block 210 is detailed in FIGS. This is a step of executing a subroutine program serving as a second abnormality diagnosis means. In the process block 210, it is determined whether or not there is a ground fault, a power fault, or a disconnection abnormality related to the positive terminal wiring of the exhaust gas sensor specified in the step 203. It is supposed to be.
The subsequent step 204 is a step of updating and setting the channel number to be executed in the next inspection operation, and the step 203 reads the channel number updated and set in the step 204 and performs the next inspection operation. Yes.

A process block 220 constituted by a series of processes 212 to 217 following the process 204 expresses the contents of a program serving as a first abnormality diagnosis means. In the process block 220, negative values of the exhaust gas sensors 103a to 103d are expressed. The presence / absence of a ground fault and a power fault abnormality related to the terminal wiring is determined.
First, in step 212 executed following step 204, a digital conversion value D1 of the value of the offset voltage V1 input to the analog input port AN1 of the microprocessor 110 and digitally converted by the multi-channel AD converter 114 is stored in the RAM. This is a step of reading to the first address of the memory 112.
In the subsequent step 213, the magnitude relationship between the digital conversion value D1 read in step 212 and the digital conversion value DE3 corresponding to the third threshold voltage E3 is compared, and if D1 ≦ DE3, YES is determined. Then, the process proceeds to step 215a, and if D1> DE3, the determination step is NO and the process proceeds to step 216.
Note that the value of the third threshold voltage E3 is a value of 90% level, which is definitely smaller than the normal offset voltage V1 (for example, 2.5V). If it is normal, step 213 determines YES. There is nothing to do.
In step 216, the digital conversion value D1 read out in step 212 is compared with the digital conversion value DE4 of the fourth threshold voltage E4. If D1 <DE4, NO is determined and step block 230 is determined. If DE4 ≦ D1, the determination step is YES and the process proceeds to step 217.
Note that the value of the fourth threshold voltage E4 is a 110% level value that is definitely larger than the normal offset voltage V1 (for example, 2.5 V). If the value is normal, step 216 determines YES. There is nothing to do.

In step 215a, it is determined whether or not an offset voltage V1 cutoff command has been generated in step 343b (see FIG. 7) to be described later. If the offset voltage V1 is being interrupted, a determination of YES is made and the process proceeds to step block 230. If the offset voltage V1 is not shut off, the determination step is NO and the process proceeds to step 215b.
Step 215b is a step of temporarily storing a negative ground fault when a negative terminal wiring ground fault occurs.Step 217b is a step of temporarily storing a negative ground fault when a negative terminal ground fault occurs. In the temporary storage step, the temporarily stored abnormal state is reconfirmed as will be described later, and is finally stored.
The process block 230 is a subroutine program serving as an abnormality processing means that is executed when the process 215a makes a determination of YES, or when the process 216 makes a determination of NO, or following the processes 215b and 217, In the process block 230, as will be described in detail with reference to FIGS. 7 and 8, processing such as confirmation of abnormal state determination, abnormality notification, storage of abnormality history information, determination of air-fuel ratio, and the like are executed, followed by an inspection end step. The process proceeds to step 219.

As described above, in the first embodiment, the positive end abnormality and the negative end abnormality of one exhaust gas sensor are inspected by the one-round flow from the step 200 to the step 219. Abnormal inspection related to the exhaust gas sensor is performed.
The process block 220 may be executed prior to the processes 203 and 210.

Next, FIG. 5 and FIG. 6 which are flowcharts for explaining the operation relating to the second abnormality diagnosis in FIG. 4 will be described.
5 and 6, step 310 is the operation start step of the second abnormality diagnosis, which is executed subsequent to step 203 in FIG. 4 and returns to step 204 following step 319 described later. ing.
Process blocks 320a and 320b configured by a series of processes 311 to 318c subsequent to process 310 represent the contents of process block 210 in FIG.
First, in step 311 to be executed subsequent to step 310, the operation state of a flag (not shown) is monitored to determine whether or not the process block 220 in FIG. 4 has been executed. If not, the process goes to step 204 in FIG. This is a determination step for returning and causing the process block 220 to operate in advance.
If the process 311 determines that the first diagnosis by the process block 220 has been executed, the process proceeds to the process 312.
In step 312, the digital conversion value D 2 of the value of the measurement voltage Vd input to the analog input port AN 2 of the microprocessor 110 and digitally converted by the multi-channel AD converter 114 is read to the second address of the RAM memory 112.
In the subsequent step 313a, it is determined whether the negative terminal wiring is normal as a determination result by the process block 220. If normal, the determination is YES and the process proceeds to step 314a, and if abnormal, the determination is NO. This is a determination step for shifting to step 313b.

Step 313b reads out whether or not the determination by the process block 220 in FIG. 4 is a negative ground fault, and if it is a negative ground fault, the process proceeds to Step 317a, and if not, the determination step proceeds to Step 313c. It is.
In step 313c, it is determined in step 343b (see FIG. 7), which will be described later, whether or not a command to shut off the offset voltage V1 has been generated. If the offset voltage V1 is not shut off, the determination step is NO and the process proceeds to step 315.
In step 314a, the digital conversion value D2 of the measurement voltage Vd read in step 312 is compared with the band value by the digital conversion value de2 of the second threshold voltage e2, and if it is within the band, the determination of YES is made. The process proceeds to step 314b, and if it is out of the band, the determination is NO and the process proceeds to step 316a.
Note that the value of the second threshold voltage e2 is, for example, a value of 1.5 to 2.5 V, which is strictly a value less than the offset voltage V1 = 2.5 V, and is the first threshold close to the ground potential. The first threshold voltage e1 is a voltage that is not more than 1.5V, which is a value obtained by subtracting the absolute value of the abnormally reduced voltage Vn = -1V from the value of the offset voltage V1. is there.
Step 314b is a step of temporarily storing that the submergence is abnormal.

Step 315 reads whether or not the determination of the process block 220 in FIG. 4 is a negative line fault, and if it is a negative line fault, makes a determination of YES and proceeds to step 316a. This is a determination step in which NO is determined and the process proceeds to step 318a in FIG.
In step 316a, the digital conversion value D2 of the measurement voltage Vd read in step 312 is compared with the digital conversion value de1 of the first threshold voltage e1, and if Vd ≦ e1, a determination of YES is made. The process proceeds to 316b, and if Vd> e1, the determination is NO and the process proceeds to step 317a.
The first threshold voltage e1 is a value equal to or lower than 1.5V, which is a value obtained by subtracting the absolute value of the abnormally reduced voltage Vn = -1V from the value of the offset voltage V1, and is 0.5V, for example, as a value approaching the ground potential. used.
Step 316b is a step of temporarily storing the fact that the positive ground fault condition is present.
In the subsequent step 317a, if the read result in step 315 is a negative line power fault, if it is a negative line power fault, a determination of YES is made and the process proceeds to step 318a in FIG. This is a determination step in which the determination is made and the process proceeds to step 317b.

In step 317b, the digital conversion value D2 of the measurement voltage Vd read in step 312 is compared with the fourth threshold voltage e4. If e4 ≦ Vd, YES is determined and the process proceeds to step 317c. ,
If Vd <e4, this is a determination step in which NO is determined and the process proceeds to step 318a in FIG.
As the fourth threshold voltage e4, for example, 4.6 V is applied as a voltage slightly lower than the control power supply voltage Vcc.
Step 317c is a step of temporarily storing the fact that the positive line power fault is in an abnormal state.
In the subsequent step 318a, whether or not the digital conversion value D2 of the measurement voltage Vd read out in step 312 is within the band of the third threshold voltage e3 is compared. Then, the process proceeds to step 318b, and if it is out of the band, the determination is NO and the process proceeds to the return process 319.
The third threshold voltage e3 has a bandwidth of, for example, about 0.95 Vp to 1.05 Vp with the bias voltage Vp applied to the positive terminal wirings 104a to 104d as the center.
Further, the bias voltage Vp is a value of 3.5V or more of the addition value of the offset voltage V1 = 2.5V and the rich side saturation voltage Vm = 1.0V, and is lower than the control power supply voltage Vcc = 5V. The value 4.2V is used.

  The bias voltage Vp is a value equal to or less than a subtraction value of 1.5 V obtained by subtracting the absolute value of the lean side minimum voltage Vn = −1.0 V from the offset voltage V1 = 2.5 V, and is a voltage lower than that of the ground circuit. It is also possible to use, for example, 1.0 V, which is higher than the first threshold voltage e1 = 0.5 V. In short, the value is in a voltage band that does not occur in a normal state, a power fault abnormal state, or a ground fault abnormal state. Is what is used.

Step 318b determines whether the ambient temperature of the exhaust gas sensors 103a to 103d has reached a predetermined activation temperature after a predetermined time has elapsed after the start of operation, and determines NO if it is not in an activated state. This is a determination step that moves to the return step 319 and moves to step 318c if it is in the activated state.
Step 318c is a step of temporarily storing the fact that the circuit disconnection is abnormal, and then proceeds to the return step 319 and then proceeds to step 204 in FIG.

The above operations are generally described. Step 314b is a submergence abnormality detection unit, step 316b is a positive line ground fault detection unit, step 317c is a positive line fault detection unit, and step 318c is a circuit disconnection fault detection unit. Process block 320a composed of 311 to process 317c and process block 320b composed of processes 318a, 318b, and 318c are second abnormality diagnosis means, and process block 330 composed of processes 313b, 313c, and 315 is This is a positive line abnormality determination avoiding means.
By the steps 313b and 313c, the detection of the submergence abnormality in the step 314b and the detection of the positive line ground fault in the step 316b are not performed during the negative ground fault state or during the interruption of the offset voltage V1. Further, in the negative line power fault state in step 315, the flooding abnormality detection in step 314b is not performed. Similarly, in the negative line power fault state in step 317a, positive line power fault abnormality detection in step 317c is not performed.

Next, FIG. 7 and FIG. 8 which are flowcharts for explaining the operation related to the abnormality processing means 230 in FIG. 4 will be described.
7 and 8, step 340 is an operation start step of the abnormality processing means, and step 340 is executed subsequent to step block 220 in FIG. 4 and returns to step 219 following step 349 described later. It is configured.
A process block 350 constituted by a series of processes 341 to 346c following the process 340 represents the contents of the abnormality processing means in the process block 230 in FIG. 4, and is constituted by a series of subsequent processes 347a to 348d. The process block 351 expresses the contents of the air-fuel ratio determination means in the process block 230 in FIG.
In step 341 executed after step 340, a search is made as to whether or not any abnormality determination storage is performed in the process block 210 or the process block 220 of FIG. If the abnormality determination memory is stored, the process proceeds to 347a, where YES is determined and the process proceeds to step 342a.
In step 342a, the process block 220 and the process block 210 in FIG. 4 are re-executed to check whether or not the abnormality determination is a temporary malfunction determination. In the subsequent process 342b, the abnormality determination is performed again by the process 342a. If it is confirmed, the determination step is YES and the process proceeds to step 342c. If the abnormality is not reproduced, the determination is NO and the process proceeds to step 345a.

Step 342c is a step of finalizing and storing the abnormal part and abnormal mode confirmed and determined in step 342a in the RAM memory 112, and the subsequent step 343a determines whether or not the final content stored in step 342c is a positive ground fault state. If it is a positive ground fault condition, a determination of YES is made and the process proceeds to step 343b. If it is not a positive ground fault condition, the determination is NO and the process proceeds to step 344.
Step 343b is a step in which the logic level of the offset voltage control command Dr is set to “H” to make the offset voltage cutoff circuit 125 conductive, and as a result, the offset voltage V1 is set to zero. Subsequent step 344 is a step of issuing a drive command to an alarm / display unit (not shown) to notify abnormality.
In the subsequent step 345a, the offset voltage cutoff command in step 343b is temporarily canceled to determine whether it is time to enable the application of the offset voltage V1, and for example, one round of control is performed once every several hundred msec. This is a determination step in which YES is determined in the operation period and the process proceeds to Step 345b, and NO is determined in most other time zones and the process proceeds to Step 346a.
Step 345b is a step in which the offset voltage cutoff command in step 343b is temporarily canceled to enable the application of the offset voltage V1, and the presence or absence of a positive ground fault is detected.

Subsequent step 346a is a step for determining whether it is time to save the abnormality history information. For example, step 346a is after a power switch (not shown) is opened, and the output contact 102 of the power relay is continuously closed. During the predetermined period, the determination is YES and the process proceeds to step 346b. When the power switch is closed, the determination is NO and the process proceeds to step 347a.
Step 346b reads past history information already written in the non-volatile data memory 113 to obtain information on the number of occurrences of abnormality for each abnormal part and abnormality mode, and the subsequent step 346c is confirmed in Step 342c. In this step, the number of occurrences of abnormality is added by one for the stored abnormal part and abnormal mode, and the data is transferred and stored again in the data memory 113. After step 346c, the process proceeds to return step 349.

In step 347a, it is determined whether the abnormal state is reconfirmed or confirmed and stored in step 342a or step 342c. If there is an abnormality, a determination of YES is made and the process proceeds to step 347b. If there is no abnormality, a determination of NO is made. This is a determination step that moves to step 347d.
Step 347b determines whether or not the abnormality content read in step 347a is a negative ground fault, and if it is a negative ground fault, a determination of YES is made and the process proceeds to step 347d. If not abnormal, it is a determination step of determining NO and proceeding to step 347c.
In step 347c, it is determined whether or not an offset voltage cutoff command is generated in step 343b. If cutoff is in progress, a determination of YES is made and the process proceeds to step 347d. If the offset voltage V1 is effectively applied, NO is determined. This is a determination step in which the determination is made and the process proceeds to step 348e.

Step 347d is a step of calculating a differential voltage D2-D1 between the digital conversion value D2 of the measurement voltage Vd of the positive terminal potential and the digital conversion value D1 of the negative terminal potential.
In the subsequent step 348a, the differential voltage D2-D1 is within the normal range of 0 to 1.0V, which is the range of the lean side normal voltage V0 = 0 to 0.1V of the exhaust gas sensor to the rich side saturation voltage Vm = 0.85 to 1.0V. In this determination step, NO is determined if it is out of the normal range, and the process proceeds to step 348e. If it is within the normal range, YES is determined, and the process proceeds to step 348b.
In step 348b, if the comparison reference threshold value is, for example, 0.45V, the determination step is YES if the threshold value is greater than or equal to the threshold value, and the process proceeds to step 348c. It is.
Step 348c generates a fuel rich state determination output to slightly reduce the fuel injection valve opening period.Step 348d generates a fuel lean state determination output to reduce the fuel injection valve opening period. This is a step to increase slightly.
Step 348e cancels the air-fuel ratio state determination determined in steps 348c and 348d, and the microprocessor 110 detects the intake air amount detected by the airflow sensor based on the control program stored in the program memory 111A. Is divided by the stoichiometric air fuel ratio (about 15) to perform open loop control of fuel injection in the valve opening period corresponding to the required supply fuel, and the closed loop of the air fuel ratio using the exhaust gas sensor is released.

Subsequent to step 348c, step 348d, and 348e, the process proceeds to step 349, and the process proceeds from step 349 to the operation end step 219 in FIG.
In step 348b, a determination band is provided. For example, when the differential voltage calculated in step 347d is in the range of 0.3 to 0.7V, it is determined that the air-fuel ratio is controlled to be appropriate, and the fuel injection valve is opened for the current period. You may control so that it may maintain.
In the control flow described above, step 342a is a determination confirmation unit, step 343b is an offset voltage cutoff command unit, step 344 is an abnormality notification unit, step 345b is a positive line normal reconfirmation unit, and step 346c is a history information storage unit. ing.

When the ground fault abnormality and the power fault abnormality of the negative terminal wiring are not detected by the process block 220, it is not necessary to input the value of the offset voltage V1 to the multi-channel AD converter 114 as a monitor signal, and the program memory A digital value proportional to the offset voltage V1 is previously stored in 111A as a control constant, and the differential voltage in step 347d in FIG. 8 is calculated using the control constant, or the positive terminal in FIGS. It is possible to detect a ground fault, a power fault, or a circuit disconnection abnormality of the wiring.
However, in FIGS. 5 and 6, it is assumed that the negative lines are all normal, and the determination of submergence abnormality detection, positive line ground fault abnormality, positive line sky fault abnormality, and circuit disconnection abnormality is performed. If there is a sky fault, it will be detected as a positive line ground fault, and if it is a negative line ground fault, the flooding abnormality will not be detected, and it will be detected as a positive line ground fault even though the positive line is normal. .

As described above, the engine control apparatus 100A according to the first embodiment of the present invention is stored in the program memory 111A and the operating states of the various input sensors 106 that monitor the operating state of the internal combustion engine. The engine control device 100A includes a microprocessor 110 that drives and controls various electric loads 107 for driving the internal combustion engine in response to the contents of the control program, and the various input sensors 106 include one or a plurality of exhaust gases. The exhaust gas sensor includes an equivalent voltage source and an equivalent internal resistance connected between a positive terminal on the atmospheric contact surface side and a negative terminal on the exhaust gas contact surface side, and includes a predetermined activation temperature. , The generated voltage Vs of the equivalent voltage source changes between the lean-side normal voltage V0 and the rich-side saturation voltage Vm at the boundary of the theoretical air-fuel ratio, and the negative terminals of the exhaust gas sensors 103a to 103d A predetermined offset voltage V1 generated by the offset voltage generation circuit 121 is applied, and a positive terminal potential that is a voltage between the positive terminal of the exhaust gas sensor and the ground circuit GND is passed through the multi-channel AD converter 114 as the measurement voltage Vd. Is converted into digital data, stored in the RAM memory 112 for arithmetic processing via the microprocessor 110, and the measurement voltage Vd or the differential voltage between the measurement voltage Vd and the offset voltage V1 is monitored to obtain an air-fuel ratio magnitude determination output. The program memory 111A includes at least a control program serving as a positive ground fault detection means 316b, an offset voltage cutoff command means 343b, and history information storage means 346c.

  Then, the positive ground fault detection means 316b monitors the measurement voltage Vd and determines that the measurement voltage Vd is less than the offset voltage V1 and is equal to or less than the first threshold voltage e1 approaching the ground potential. The positive terminal wirings 104a to 104d of the exhaust gas sensors 103a to 103d are determined to have a ground fault abnormality in the positive terminal wiring that comes into contact with the ground circuit GND, and the offset voltage cutoff command means 343b is connected to the positive ground fault detection means 316b. When the ground fault abnormality of the positive terminal wiring is detected, the offset voltage V1 is stopped by acting on the offset voltage cutoff circuit 125, and the history information storage means 346c determines whether or not the positive ground fault has occurred. The data is stored in the nonvolatile data memory 113, and the contents of the data memory 113 are read by the external tool 109 for maintenance and inspection.

  According to the engine control apparatus of the first embodiment of the present invention configured as described above, the exhaust gas sensor detects that the positive ground fault abnormality detecting means of the exhaust gas sensor has detected the ground fault abnormality of the positive terminal wiring. Because the offset voltage applied to the negative terminal of the positive terminal wiring is released, the short-circuit current due to the offset voltage can be prevented from flowing into the exhaust gas sensor when a ground fault in the positive terminal wiring occurs, resulting in damage to the exhaust gas sensor. Deterioration can be prevented. Therefore, it is possible to return to normal by releasing the repair of the ground fault of the positive terminal wiring, and there is an effect that it is not necessary to replace parts of the exhaust gas sensor itself.

  Further, in the first embodiment, the value of the offset voltage V1 applied to the negative terminals of the exhaust gas sensors 103a to 103d is based on the absolute value of the lean side abnormal drop voltage Vn that occurs when the atmospheric contact surface of the exhaust gas sensor is flooded. The program memory 111A further includes a control program serving as a submergence abnormality detection unit 314b, and the submergence abnormality detection unit 314b has a measured voltage Vd value of the second threshold voltage e2. It is determined that the exhaust gas sensors 103a to 103d are submerged in an in-band range, and the second threshold voltage e2 is less than the offset voltage V1 and is close to the ground potential. The first threshold voltage e1 is a voltage that is equal to or lower than the value obtained by subtracting the absolute value of the abnormally reduced voltage Vn from the value of the offset voltage V1. Means 346c further stores the occurrence of flooding abnormality in the data memory 113 of the nonvolatile content of the data memory has a what is read by an external tool 109 for maintenance.

  As described above, according to the engine control apparatus of the first embodiment, the offset voltage applied to the negative terminal of the exhaust gas sensor is increased to detect the flooding abnormality of the exhaust gas sensor. It is possible to discriminate between submergence anomalies and positive line ground faults using a simple AD converter, and the repair inspection is facilitated by reading out the abnormality occurrence history information. Also, when a positive ground fault occurs, the offset voltage is cut off by the offset voltage cut-off command, so that a large short-circuit current due to a large offset voltage flows into the exhaust gas sensor, accelerating damage deterioration of the exhaust gas sensor. Absent.

  In the first embodiment, the exhaust gas sensors use a plurality of exhaust gas sensors 103a to 103d, and an offset voltage V1 is commonly applied to the negative terminals of the plurality of exhaust gas sensors. A negative terminal potential, which is a voltage between the negative terminal and the ground circuit GND, is digitally converted via the multi-channel AD converter 114, stored in the RAM memory 112 via the microprocessor 110, and the program memory 111A further includes The negative line ground fault abnormality detecting means 215b and the positive line abnormality determination avoiding means 330 are included, and the negative line ground fault abnormality detecting means 215b has a digital conversion value D1 of the negative terminal potential proportional to the offset voltage V1. Based on the value, it is determined that the negative terminal wiring is in contact with the ground line due to being too small, and the ground fault abnormality is detected. When the detecting means 215b detects a negative ground fault, or when the offset voltage cutoff circuit 125 cuts off the offset voltage V1, abnormality determination by the positive ground fault abnormality detecting means 316b and the submergence abnormality detecting means 314b is performed. If the measurement voltage Vd detects a fuel rich state without performing the detection, the detection result is validated.

Thus, in the negative line ground fault state or the offset voltage cutoff state, even if the positive terminal potential is close to the ground potential, the determination of the positive line ground fault abnormality or the flooding abnormality is avoided. In the state where no voltage is applied, there is a feature that the determination of the air-fuel ratio can be continued by monitoring the measurement voltage which is the positive terminal potential if no positive ground fault has occurred.
In addition, when a plurality of exhaust gas sensors are used and a positive ground fault has occurred in a specific exhaust gas sensor among the plurality of exhaust gas sensors, it is commonly applied to the negative terminal of each exhaust gas sensor. When the offset voltage that has been interrupted is cut off, the remaining normal exhaust gas sensor determination results can be treated as valid.

Further, the program memory 111A further includes a control program serving as the normal normal reconfirmation means 345b. The normal normal reconfirmation means 345b is in a state where the application of the offset voltage V1 is stopped by the offset voltage cutoff command means 343b. , At least at the start of the operation, immediately before the operation stop, or every predetermined period during the operation, the offset voltage V1 that has been stopped is made effective for a short time, and a new one is added to any of the plurality of exhaust gas sensors 103a to 103d. It is designed to check whether a positive ground fault has occurred.
That is, in the engine control apparatus of the first embodiment, the offset voltage that has been stopped due to the occurrence of a positive ground fault of a specific exhaust gas sensor is made effective only in a short time, and during this period The presence or absence of an abnormality in the positive line ground fault of the exhaust gas sensor is confirmed.
Therefore, the short-circuit current for the exhaust gas sensor in which a positive line ground fault has occurred is normally cut off, and the short-circuit current flows only for a short time when the normal line normal reconfirmation process is performed. There is a feature that it is possible to determine the presence or absence of a positive line ground fault or a submergence abnormality of a plurality of exhaust gas sensors while suppressing deterioration.

Further, in the engine control apparatus of the first embodiment, the positive terminals of the plurality of exhaust gas sensors 103a to 103d are connected to the high resistance pull-down resistor 144a (to 144d) and the pull-up resistor 143a (connected to the ground circuit GND). To 143d), the program memory 111A further includes a first abnormality diagnosing means 220 including at least a negative ground fault detecting means 215b, and a positive ground fault abnormality. It includes a control program that becomes the second abnormality diagnosis means 320a, 320b including the detection means 316b and the abnormality processing means 350 including the history information storage means 346c.
Further, the first abnormality diagnosis means 220 further includes a power fault abnormality in which the negative terminal wiring is in contact with the power supply line because the digital conversion value D1 of the negative terminal potential is excessive on the basis of the value proportional to the offset voltage V1. The negative line fault detection means 217 for determining that the error is detected, and the second fault diagnosis means 320a, 320b include a control program that becomes the positive line fault detection means 317c and the circuit disconnection fault detection means 318c. ing.

  Further, the positive line power fault abnormality detecting means 317c is excessive with respect to the value obtained by converting the digital conversion value D2 of the positive terminal potential in proportion to the added value V1 + Vm of the offset voltage V1 and the rich-side saturation voltage Vm. When the voltage becomes equal to or higher than the fourth threshold voltage e4 approaching the voltage Vcc, it is determined that the positive terminal wiring is in a power fault abnormality in contact with the power supply line, and the circuit disconnection abnormality detecting means 318c detects the digital conversion value of the positive terminal potential. When D2 falls within the band of the third threshold voltage e3 having a band value centered on the bias voltage Vp applied to each of the positive terminal wirings 104a to 104d, the positive terminal wiring or the sensor internal or negative terminal wiring It is determined that any one of the circuit disconnections is abnormal, and the bias voltage Vp is a value equal to or higher than the added value V1 + Vm of the offset voltage V1 and the rich saturation voltage Vm and lower than the control power supply voltage Vcc, or Offset The subtracted value V1− | Vn |, which is the subtraction value obtained by subtracting the absolute value of the lean side abnormal drop voltage Vn from the voltage V1, is higher than the ground circuit GND, and is in a normal state, a power fault abnormal state, or a ground fault A value within the voltage band that does not occur in the abnormal state is used, and the abnormality processing means 350 responds to the diagnosis result by the first and second abnormality diagnosis means to store the abnormality occurrence history information in the data memory 113 by the history information storage means 346c. And an alarm / display output is generated by the abnormality notifying means 344.

  As described above, according to the engine control apparatus of the first embodiment, the presence or absence of a fault, ground fault or disconnection abnormality on the positive terminal side of the exhaust gas sensor, and the presence or absence of a fault or ground fault on the negative terminal side are individually determined. Then, the abnormality is notified. Therefore, even if a ground fault in the negative terminal wiring occurs, it can be confirmed that no other abnormality has occurred, and normal operation in a state requiring attention can be continued. Therefore, it is possible to prevent the occurrence of failures by encouraging maintenance inspection.

Embodiment 2. FIG.
FIG. 9 is a circuit block diagram showing the configuration of the engine control apparatus according to the second embodiment of the present invention. Hereinafter, the difference from FIG. 1 will be mainly described. In each figure, the same numerals indicate the same or corresponding parts.
The difference between FIG. 9 and FIG. 1 is that the configuration of the negative terminal wiring of the exhaust gas sensors 103a to 103d is different, and the main difference is that FIG.
9, the engine control apparatus 100B is connected to an in-vehicle battery 101, a power relay output contact 102, various input sensors 106, and various electric loads 107, as in FIG.
Further, the positive terminals of the plurality of exhaust gas sensors 103a to 103d are connected to the engine control device 100B by positive terminal wirings 104a to 104d.
The negative terminal of the exhaust gas sensor 103a is connected to the engine control device 100B by the first negative terminal wiring 108a, and the negative terminals of the exhaust gas sensors 103a to 103d are sequentially connected by the transition wirings 108b to 108d. Is connected to the engine control device 100B by a second negative terminal wiring 108e.

As shown in FIG. 1, the microprocessor 110 includes, for example, a program memory 111B that is a nonvolatile flash memory, a RAM memory 112 for arithmetic processing, such as a data memory 113 that is a nonvolatile EEPROM memory, They are connected to each other by a bus so as to cooperate with the channel AD converter 114.
In addition to the input / output control program as the engine control apparatus 100B, the program memory 111B stores programs serving as various abnormality diagnosis means and abnormality processing means described later with reference to FIGS.
The constant voltage power supply circuit 120 and the voltage dividing resistors 122 and 123, the offset voltage generation circuit 121, and the offset voltage cut-off circuit 125 are configured in the same manner as in FIG. 1, but are output voltages of the offset voltage generation circuit 121. The offset voltage V1 is applied to the negative terminals of the exhaust gas sensors 103a to 103d by the current limiting resistor 127, the first negative terminal wiring 108a, and the transition wirings 108b to 108d, and is also transmitted via the second negative terminal line 108e. The offset voltage V1 is connected to the analog input port AN1 of the microprocessor 110 as a monitor signal. The first and second negative terminal wires 108a and 108e are always short-circuited by the inspection opening / closing element 124 inside the engine control apparatus 100B.

Therefore, when the negative terminal wiring is disconnected somewhere or there is a contact failure of the connector, the offset voltage V1 is generated from the first negative terminal wiring 108a side or the second negative terminal wiring 108e. It is supplied from the side and is in a state where normal operation can be continued.
However, when such a negative disconnection abnormality occurs, the abnormality can be determined in the manner described later by temporarily opening the inspection opening / closing element 124 by the inspection instruction CNT of the microprocessor 110. It has become.
On the other hand, the positive terminal wirings 104a to 104d are connected to the input terminals CH1 to CH4 of the multiplexer 130 via the interface circuits 140a to 140d detailed in FIG.
The multiplexer 130 receives selection commands SL1 and SL2 from the microprocessor 110, selects one of the analog signals input to the input terminals CH1 to CH4, and inputs the selected analog signal to the analog input port AN2 of the microprocessor 110. It has become.

  A smoothing capacitor 142e is connected to the analog input port AN1 that monitors the value of the offset voltage V1, and a voltage divider formed by the second pull-up resistor 143e and the second pull-down resistor 144e, which are high resistances. The voltage is applied as the second bias voltage Vpp. The second bias voltage Vpp is a voltage that is clearly different from the offset voltage V1 (= 2.5V), for example, Vpp = 1.25V level.

Next, the operation and operation of the engine control apparatus of the second embodiment configured as shown in FIG. 9 will be described based on the flowcharts shown in FIGS.
First, in the configuration as shown in FIG. 9, when the output contact 102 is closed, the microprocessor 110 is supplied with power from the constant voltage power supply circuit 120 and starts operating, and the operations of the various input sensors 106 and exhaust gas sensors 103a to 103d are started. Drive control for various electric loads 107 is executed in response to the state and signal level and the contents of the input / output control program stored in the program memory 111B. During the execution process, the abnormality check operation shown in FIGS. Is to be done.
In FIG. 10, which is a flowchart for explaining the inspection operation in FIG. 9, step 400 is a step in which the microprocessor 110 starts the inspection operation, and this start step is subsequent to the operation end step shown in step 419 described later. Thus, it is repeatedly executed again after a predetermined waiting time.
The subsequent step 401 is to specify the channel number of the multiplexer 130 and set which of the exhaust gas sensors 103a to 103d is to be inspected. The subsequent process block 410 is the same as that described above with reference to FIGS. This is a step of executing a subroutine program as a second abnormality diagnosis means. In process block 410, it is determined whether or not there is a ground fault, a power fault, or a disconnection abnormality related to the positive terminal wiring of the exhaust gas sensor designated in process 401. It has become.
Subsequent step 409 is a step of updating and setting the channel number to be executed in the next inspection operation, and step 401 reads the channel number updated and set in step 409 and performs the next inspection operation. Yes.

A series of process blocks 420 following the process 409 serve as a first abnormality diagnosis means to be described later with reference to FIG. 11. In the process block 420, a ground fault, a power fault, and a disconnection related to the negative terminal wiring of the exhaust gas sensors 103a to 103d. It is determined whether or not there is an abnormality.
Subsequent process block 430 is a subroutine program serving as a determination processing means. As described in detail in FIGS. 7 and 8, processing such as determination of abnormal state determination, abnormality notification, storage of abnormal history information, determination of air-fuel ratio, and the like are performed. Then, the process proceeds to step 419 which is an inspection end step. Accordingly, also in the second embodiment, the positive end abnormality and negative end abnormality of one exhaust gas sensor are inspected by one round flow from step 400 to step 419, and another exhaust gas is sequentially executed by repeating the circulation of one round flow. Abnormal inspection related to the gas sensor is performed. The process block 420 may be executed prior to the processes 401 to 409.

In FIG. 11 which is a flowchart for explaining the operation showing the detailed contents of the process block 420, the process 450 is an operation start step for detecting a negative wire breakage, and the process 450 is executed following the process 409 of FIG. It is configured to return to the process block 430 following the process 459 described later.
A process block constituted by a series of processes 451a to 457 following the process 450 expresses the contents of the process block 420 in FIG.
First, in step 451a executed subsequent to step 450, the microprocessor 110 opens the inspection opening / closing element 124 by the inspection command output CNT.
In the subsequent step 452a, the digital conversion value D1 of the offset voltage V1 input to the analog input port AN1 of the microprocessor 110 and digitally converted by the multi-channel AD converter 114 is read to the first address of the RAM memory 112. It is.
In the subsequent step 453, it is determined whether or not the digital conversion value D1 read in step 452a is within the band of the digital conversion value of the second threshold voltage E2, and if it is within the band, YES is determined. The process shifts to step 455c, and if it is out of the band, it is determined that NO is determined and the process shifts to step 451b.

The second threshold voltage E2 is 90% to 110% level of the digital conversion value with respect to the second bias voltage Vpp (for example, 1.25 V) determined by the second pull-up resistor 143e and the second pull-down resistor 144e. As the band value, 1.1 to 1.4V is used.
In step 455c, the occurrence of the negative wire disconnection abnormality is temporarily stored, and the process proceeds to step 451b.
Step 451b is a step in which the microprocessor 110 stops the inspection command output CNT and closes the inspection opening / closing element 124.
In the subsequent step 452b, a digital conversion value D1 of the value of the offset voltage V1 input to the analog input port AN1 of the microprocessor 110 and digitally converted by the multi-channel AD converter 114 is read to the first address of the RAM memory 112. It is.
In the following step 454, the magnitude relationship between the digital conversion value D1 read in step 452b and the digital conversion value DE1 of the first threshold voltage E1 is compared. If D1> DE1, NO is determined. The process proceeds to 456, and if D1 ≦ DE1, the determination is YES, and the process proceeds to step 455a.

Note that the value of the first threshold voltage E1 is lower than the second bias voltage Vpp and higher than the ground potential, for example, 1.1 V.
In step 455a, it is determined whether or not the offset voltage V1 cutoff command has been generated in step 343b of FIG. 7. If the offset voltage V1 is in the cutoff state, a determination of YES is made and the process proceeds to return step 459, where the offset voltage If V1 is not shut off, the determination step is NO and the process proceeds to step 455b.
Step 455b is a step in which it is determined that the negative terminal wiring is grounded when the determination in step 454 is the first threshold voltage E1 or less, and this state is temporarily stored in the RAM memory 112.
In step 456, the digital conversion value D1 read out in step 452b is compared with the digital conversion value DE4 of the fourth threshold voltage E4. If D1 <DE4, NO is determined and the return step is performed. The process shifts to 459, and if DE4 ≦ D1, the determination is YES and the process proceeds to step 457.

As the value of the fourth threshold voltage E4, a value of 110% level, which is surely larger than the normal offset voltage V1, is used, and if it is normal, the process 456 does not make a YES determination. It has become.
Step 457 is a step of determining that the negative terminal wiring is in a fault due to the determination in step 456 being the fourth threshold voltage E4 or higher, and temporarily storing this state in the RAM memory 112. Subsequent to 457, the process proceeds to the return step 459.
The process 455b is a step of temporarily storing a negative line ground fault abnormality, the process 455c is a step of temporarily storing a negative line break fault, and the process 457 is a step of temporarily storing a negative line fault fault. The abnormal state is confirmed and memorized after being reconfirmed in the process block 430 described above.

As described above, the engine control device 100B according to the second embodiment of the present invention includes the operating states of the various input sensors 106 that monitor the operating state of the internal combustion engine, and the control stored in the program memory 111B. The engine control apparatus 100B includes a microprocessor 110 that drives and controls various electric loads 107 for driving the internal combustion engine in response to the contents of the program, and the various input sensors 106 are one or a plurality of exhaust gas sensors. 103a-103d, this exhaust gas sensor has an equivalent voltage source and an equivalent internal resistance connected between a positive terminal on the air contact surface side and a negative terminal on the exhaust gas contact surface side, and at a predetermined activation temperature. The generated voltage Vs of the equivalent voltage source changes between the lean-side normal voltage V0 and the rich-side saturation voltage Vm with the theoretical air-fuel ratio as a boundary, and the negative terminals of the exhaust gas sensors 103a to 103d are A predetermined offset voltage V1 generated by the offset voltage generation circuit 121 is applied, and a positive terminal potential which is a voltage between the positive terminal of the exhaust gas sensor and the ground circuit GND is passed through the multi-channel AD converter 114 as the measurement voltage Vd. Is converted into digital data, stored in the RAM memory 112 for arithmetic processing via the microprocessor 110, and the measurement voltage Vd or the differential voltage between the measurement voltage Vd and the offset voltage V1 is monitored to obtain an air-fuel ratio magnitude determination output. The program memory 111B includes at least a control program serving as a positive ground fault abnormality detecting unit 316b, an offset voltage cutoff command unit 343b, and a history information storing unit 346c.

  As the exhaust gas sensor, a plurality of exhaust gas sensors 103a to 103d are used, and an offset voltage V1 is commonly applied to the negative terminals of the plurality of exhaust gas sensors, and the negative terminals of the exhaust gas sensors 103a to 103d are connected to the ground. The negative terminal potential, which is a voltage between the circuit GNDs, is digitally converted via the multi-channel AD converter 114 and stored in the RAM memory 112 via the microprocessor 110, and the program memory 111B further includes a negative line ground. It includes a control program that serves as an abnormality detection unit 455b and a positive line abnormality determination avoiding unit 330.

  Further, the positive terminals of the plurality of exhaust gas sensors 103a to 103d are individually connected to the engine control device 100B by individual positive terminal wirings 104a to 104d. Among the plurality of exhaust gas sensors, the negative terminal of the first exhaust gas sensor 103a is The negative terminals of the other exhaust gas sensors 103b to 103d are sequentially connected to each other via the transition wires 108b to 108d, and the negative terminal of the final exhaust gas sensor 103d is connected to the engine control device 100B by the first negative terminal wiring 108a. The first negative terminal wiring 108e is connected to the engine control device 100B, and the first and second negative terminal wirings 108a and 108e are connected in the engine control device 100B to form a circular circuit, and a common offset voltage The generator circuit 121 is connected.

  According to the engine control apparatus of the second embodiment of the present invention configured as described above, the negative terminal wiring of the exhaust gas sensor has a ring circuit formed by the first negative terminal wiring, the transition wiring, and the second negative terminal wiring. Because it is configured, normal operation can be maintained even if part of the negative terminal wiring is disconnected, and when three or more exhaust gas sensors are used, compared to individual connection of the negative terminal wiring Therefore, the number of connector terminals can be reduced.

The first and second negative terminal wires 108a and 108e are connected to each other through the inspection opening / closing element 124 in the engine control apparatus 100B, and the output voltage of the offset voltage generation circuit 121 is the inspection opening / closing element 124. Is connected to the analog input terminal AN1 of the multi-channel AD converter 114 as a monitor signal voltage via the second pull-down resistor 144e connected to the ground circuit GND, or a constant voltage power source. At least one resistance (or both resistances) of the second pull-up resistor 143e connected to the output terminal of the circuit 120 is connected, and the program memory 111B further controls the negative wire breakage abnormality detecting means 455c. Including the program, the negative wire breakage abnormality detecting means 455c determines whether the value of the monitor signal voltage and the offset voltage V1 match when the inspection switching element 124 is temporarily opened. The presence or absence of disconnection abnormality in the wiring from the offset voltage generation circuit 121 to the multi-channel AD converter 114 via the first negative terminal wiring 108a, the transition wirings 108b to 108d, and the second negative terminal wiring 108e Is supposed to be detected.
Thus, according to the engine control apparatus of the second embodiment, the first negative terminal wiring and the second negative terminal wiring of the exhaust gas sensor are annularly connected via the inspection opening / closing element and connected to the offset voltage. The offset voltage is connected to the multi-channel AD converter via a pull-up resistor or a pull-down resistor. Therefore, there is a feature that it is possible to detect a disconnection of a negative wire and to prompt a maintenance inspection without causing a failure.

Embodiment 3 FIG.
FIG. 12 is a circuit block diagram showing the configuration of the engine control apparatus according to the third embodiment of the present invention. Hereinafter, the difference from FIG. 1 will be mainly described.
In the third embodiment of FIG. 12, the difference from FIG. 1 is that the contents of the interface circuit for the exhaust gas sensors 103a to 103d are different, and sensor resistance measuring means for detecting a short circuit abnormality is added. Is the main difference. The same reference numerals as those in FIG. 1 indicate the same or corresponding parts.
In FIG. 12, the engine control apparatus 100C includes an in-vehicle battery 101, an output contact 102 of a power relay, a plurality of exhaust gas sensors 103a to 103d, various input sensors 106, various electric loads 107, as in FIG. Is connected.
As shown in FIG. 1, the microprocessor 110 includes a program memory 111C that is a nonvolatile flash memory, a RAM memory 112 for arithmetic processing, for example, a data memory 113 that is a nonvolatile EEPROM memory, They are connected to each other by a bus so as to cooperate with the channel AD converter 114.
In the program memory 111C, in addition to the input / output control program as the engine control apparatus 100C, programs serving as various abnormality diagnosis means and abnormality processing means, which will be described later with reference to FIGS. 14 and 15, are stored.
The constant voltage power supply circuit 120, the voltage dividing resistors 122 and 123, the offset voltage generation circuit 121, and the offset voltage cut-off circuit 125 are configured in the same manner as in FIG. 1, but instead of the interface circuits 140a to 140d, FIG. Interface circuits 150a to 150d described later in FIG. 13 are used, and the microprocessor 110 generates inspection commands CK1 to CK4 to control the interface circuits 150a to 150d.

In FIG. 13 which is a detailed circuit diagram of the interface circuit unit of FIG. 12, the exhaust gas sensor 103a
The interface circuit 150a connected to the positive terminal wiring 104a includes an operational amplifier 151a, a smoothing capacitor 152a connected to the non-inverting input terminal of the operational amplifier 151a, a bias resistor 153a, and a voltage dividing resistor 155a. The output terminal of the amplifier 151a is negatively connected to the inverting input terminal and is selectively connected to the analog input port AN2 of the microprocessor 110 via the multiplexer 130.
The voltage dividing resistor 155a is connected to the ground circuit by a series switching element 156a which is an NPN transistor, and the series switching element 156a is opened and closed by a driving resistor 157a connected to the inspection command output CK1 of the microprocessor 110. It is like that.
The low-voltage dividing resistors 158 and 159 divide the output voltage of the constant voltage power supply circuit 120 to generate the bias voltage Vp, and the bias voltage Vp by the voltage dividing resistors 158 and 159 is applied to one end of the bias resistor 153a. Has been.
The interface circuits 150b to 150d are similarly configured, and the offset voltage V1 is applied to the negative terminal wirings 105a to 105d.

  The measurement voltage Vd, which is the output voltage of the operational amplifier 151a configured as described above, is expressed by the following equations (3) and (4). Where Vcc is the control power supply voltage, Rs is the equivalent internal resistance of the exhaust gas sensor 103a, Vs is the generated voltage of the exhaust gas sensor 103a, V1 is the offset voltage, R153 is the resistance value of the bias resistor 153a, and R155 is the resistance value of the voltage dividing resistor 155a. It is assumed that the relationship of R153 >> R155≈Rs is established.

First, when the measurement voltage Vd when the series switching element 156a is open is Voff, the following equation (3) is established.
Voff ≒ Vs + (V1 + ΔV2) (3)
However, ΔV2 = Vp × Rs / R153
Next, when the measured voltage Vd when the series switching element 156a is closed is Von, the following equation (4) is established. However, when the series switching element 156a is closed, the offset voltage cutoff circuit 126 is also closed so that the offset voltage V1 is not applied.
Von≈ [Vs + ΔV2] × R155 / (Rs + R155) (4)
When the formulas (3) and (4) are put together, the following formula (5) is obtained.
Von≈ (Voff−V1) × R155 / (Rs + R155) (5)

When the equation (5) is modified, the internal resistance Rs is calculated by the following equation (6).
Rs = [(Voff−V1) / Von−1] × R155 (6)
As an example, when V1 = 2.5V, Vs = 0-1.0V, Vcc = 5.0V, Rs = 20KΩ, R153 = 1000KΩ, R155 = 20KΩ, Vp = 4.2V, ΔV2 = Vp (Rs / R153) = 0.08V.

Next, the operation and operation of the third embodiment of the present invention configured as shown in FIGS. 12 and 13 will be described based on the flowcharts shown in FIGS.
First, in the one configured as shown in FIGS. 12 and 13, when the output contact 102 is closed, the microprocessor 110 is powered by the constant voltage power supply circuit 120 and starts operating, and various input sensors 106 and exhaust gas sensors 103a are started. Drive control for the various electric loads 107 is executed in response to the operation states and signal levels of .about.103d and the contents of the input / output control program stored in the program memory 111C. In the execution process, the abnormality check operation shown in FIGS. 14 and 15 is performed.

Next, in FIG. 14, a process 500 is a step in which the microprocessor 110 starts an inspection operation, and this start step is followed by an operation end step shown in a process 519 described later, after a predetermined waiting time. And it is repeatedly executed again.
A process block 520 constituted by a series of processes 512 to 517 following the process 500 expresses the contents of a program serving as a first abnormality diagnosis means. In the process block 520, the negative terminal wiring of the exhaust gas sensors 103a to 103d is expressed. Whether or not there is a ground fault or a power fault abnormality is determined.
First, in step 512 executed following step 500, the digital conversion value D1 of the value of the offset voltage V1 input to the analog input port AN1 of the microprocessor 110 and digitally converted by the multi-channel AD converter 114 is stored in the RAM. This is a step of reading to the first address of the memory 112.
In subsequent step 513, the digital conversion value D1 read out in step 512 is compared with the digital conversion value DE3 corresponding to the third threshold voltage E3, and if D1 ≦ DE3, YES is determined. Then, the process proceeds to step 515a, and if D1> DE3, the determination is NO and the process proceeds to step 516.
Note that the value of the third threshold voltage E3 is a value of 90% level that is definitely smaller than the normal offset voltage V1 (for example, 2.5 V). If the value is normal, step 513 determines YES. There is nothing to do.

Step 516 compares the digital conversion value D1 read out in step 512 with the digital conversion value DE4 of the fourth threshold voltage E4. If D1 <DE4, NO is determined and step 501 is performed. If DE4 ≦ D1, the determination step is YES and the process proceeds to step 517.
As the value of the fourth threshold voltage E4, a value of 110% level that is definitely larger than the normal offset voltage V1 (for example, 2.5V) is used. If it is normal, step 516 determines YES. There is nothing to do.
In step 515a, it is determined whether or not the offset voltage V1 cutoff command has been generated in step 343b of FIG. 7. If the offset voltage V1 is being shut off, a determination of YES is made and the flow proceeds to step 501 to enter the offset voltage V1. If NO is not shut off, the determination step is NO and the process proceeds to step 515b.
Step 515b is a step of temporarily storing the negative ground fault when a negative terminal wiring ground fault occurs and moving to Step 501, and step 517 is when a negative terminal wiring power fault occurs. This is a step of temporarily storing the negative power sky abnormality and proceeding to step 501, but the temporarily stored abnormal state is confirmed and stored again after reconfirmation as described later.

Step 501 designates the channel number of the multiplexer 130 and sets which of the exhaust gas sensors 103a to 103d is to be inspected, and the subsequent process block 510 is described above with reference to FIGS. This is a step of executing a subroutine program serving as a second abnormality diagnosis means. In this process block 510, it is determined whether or not there is a ground fault, a power fault, or a disconnection abnormality related to the positive terminal wiring of the exhaust gas sensor designated in step 501. It is supposed to be. A subsequent process block 508 is a subroutine program serving as a sensor diagnosis means described in detail with reference to FIG. 15. By this process block 508, the presence or absence of an internal short circuit abnormality or an internal disconnection abnormality of the exhaust gas sensor is determined.
In subsequent step 509, it is determined whether all the inspection operations of the plurality of exhaust gas sensors 103a to 103d are completed. If not completed, the process returns to step 501, and the inspection operation of the remaining exhaust gas sensors is continued and completed. If so, it is a determination step that moves to process block 530.

The process block 530 is a subroutine program serving as a determination processing means. As described above with reference to FIGS. 7 and 8, the process block 530 includes determination of abnormal state determination, abnormality notification, storage of abnormal history information, and determination of air-fuel ratio. Then, the process proceeds to step 519 which is an inspection end step.
Therefore, in the third embodiment, after checking the negative end abnormality by the process block 520, the positive end abnormality and the sensor abnormality of all exhaust gas sensors are inspected by a single flow from the step 501 to the step 509. Subsequently, the determination process by the process block 530 is executed, the control flow of one round is completed, and the operation start process 500 is subsequently activated.

In FIG. 15, which is a flowchart for explaining the operation related to the sensor diagnosis means 508 in FIG. 14, step 550 is an operation start step of the sensor diagnosis means, and this step 550 is executed following the process block 510 in FIG. It is configured to return to Step 509 following Step 559 described later.
A process block constituted by a series of processes 551 to 558 following the process 550 expresses the contents of the process block 508 in FIG.
First, in step 551 executed subsequent to step 550, the microprocessor 110 closes the series switching element 156a by the inspection command output CK1, and generates the offset voltage control command Dr to operate the offset voltage cutoff circuit 125. It has become.
In the subsequent step 552, the digital conversion value D2 of the value of the measurement voltage Vd input to the analog input port AN2 of the microprocessor 110 and digitally converted by the multi-channel AD converter 114 is used as the value of the closed circuit voltage Von in the RAM memory 112. This is a step of reading to the third address.
When the process block 510 is executed, the digital conversion value D2 of the value of the measured voltage Vd is read and stored in the second address of the RAM memory 112 as the value of the open circuit voltage Voff by the process 312 of FIG.
In the subsequent step 553, the equivalent internal resistance Rs of the exhaust gas sensor is calculated by the equation (6) based on the value of the closed circuit voltage Von read and stored in step 552 and the value of the open circuit voltage Voff read and stored in the process block 510. This is a calculating step.

In subsequent step 554, it is determined whether or not the internal resistance Rs calculated in step 553 is close to a predetermined normal value. When the internal resistance Rs is substantially equal to the normal value, a determination of YES is made and the process proceeds to step 558. When the value deviates from the normal value, the determination step shifts to step 555a.
Step 555a is a determination step in which the process proceeds to process 556a if the internal resistance Rs calculated in process 553 is too small with respect to the normal value, and the process proceeds to process 555b if it is excessive.
Step 555b is, for example, determining whether or not the warm-up operation for several minutes has been completed. If the warm-up is completed, the process proceeds to step 556b, and if not warm-up is completed, the process proceeds to step 558. Yes.
Step 556a is a step of making a sensor or wiring short-circuit abnormality determination and temporarily storing it in the RAM memory 112, and step 556b is a sensor or wiring disconnection abnormality determination and temporarily storing it in the RAM memory 112. Although it is a step, the disconnection of the sensor and the disconnection of the wiring cannot be identified, and are detected as a circuit disconnection in step 318c of FIG.
When step 554 is YES, or when step 555b is NO, or in step 558 executed subsequent to steps 556a and 556b, the series opening / closing element 156a closed in step 551 The offset voltage cutoff circuit 125 is opened, and then the process proceeds to step 509 in FIG.

In the control flow described above, step 553 serves as sensor resistance measuring means, and step 556a serves as sensor short circuit abnormality determining means.
The normal value of the internal resistance Rs of the exhaust gas sensor is stored and stored in the program memory 111C in advance, but the value of the internal resistance Rs calculated in step 553 is averaged sequentially to determine the internal resistance of the actual product used. It can also be used as a normal value.
Further, with respect to the internal resistance Rs learned and stored in this way, the initial value of engine operation is stored as an initial value, and when the internal resistance Rs at the current time has changed significantly from this initial value, It can also be determined that the exhaust gas sensor is abnormally deteriorated.

Main Points and Features of Embodiment 3 As described above, the engine control device 100C according to Embodiment 3 of the present invention includes the operating states of the various input sensors 106 that monitor the operating state of the internal combustion engine, and the control stored in the program memory 111C. The engine control apparatus 100C includes a microprocessor 110 that drives and controls various electric loads 107 for driving the internal combustion engine in response to the contents of the program, and the various input sensors 106 include one or a plurality of exhaust gas sensors. 103a-103d, this exhaust gas sensor has an equivalent voltage source and an equivalent internal resistance connected between a positive terminal on the air contact surface side and a negative terminal on the exhaust gas contact surface side, and at a predetermined activation temperature. The generated voltage Vs of the equivalent voltage source changes between the lean-side normal voltage V0 and the rich-side saturation voltage Vm with the theoretical air-fuel ratio as a boundary, and the negative terminals of the exhaust gas sensors 103a to 103d are A predetermined offset voltage V1 generated by the offset voltage generation circuit 121 is applied, and a positive terminal potential which is a voltage between the positive terminal of the exhaust gas sensor and the ground circuit GND is passed through the multi-channel AD converter 114 as the measurement voltage Vd. Is converted into digital data, stored in the RAM memory 112 for arithmetic processing via the microprocessor 110, and the measurement voltage Vd or the differential voltage between the measurement voltage Vd and the offset voltage V1 is monitored to obtain an air-fuel ratio magnitude determination output. The program memory 111C includes a control program including at least a positive ground fault abnormality detecting unit 316b, an offset voltage cutoff command unit 343b, and a history information storing unit 346c.

  As the exhaust gas sensor, a plurality of exhaust gas sensors 103a to 103d are used, and an offset voltage V1 is commonly applied to the negative terminals of the plurality of exhaust gas sensors, and the negative terminals of the exhaust gas sensors 103a to 103d are connected to the ground. The negative terminal potential, which is a voltage between the circuit GNDs, is digitally converted via the multi-channel AD converter 114 and stored in the RAM memory 112 via the microprocessor 110, and the program memory 111C further includes a negative line ground. Including a control program serving as a fault detection means 515b and a positive line abnormality judgment avoidance means 330, the negative ground fault detection means 515b is based on a value in which the digital conversion value D1 of the negative terminal potential is proportional to the offset voltage V1. Thus, it is determined that the negative terminal wiring is ground fault abnormality in contact with the ground line due to being too small, and the positive line abnormality determination avoiding means 330 is the negative line ground fault abnormality detecting means 515b. When a negative ground fault is detected or when the offset voltage cutoff circuit 125 cuts off the offset voltage V1, the fault judgment by the positive ground fault detection means 316b and the submergence fault detection means 314b is not performed. If the voltage Vd detects a fuel rich state, the detection result is validated.

  A predetermined bias voltage Vp is applied to each positive terminal of the plurality of exhaust gas sensors 103a to 103d via a high-resistance bias resistor 153a (to 153d), and the program memory 111C further includes at least a negative line. The first abnormality diagnosis means 520 including the ground fault abnormality detection means 515b, the second abnormality diagnosis means 320a and 320b including the positive line ground fault abnormality detection means 316b, and the abnormality processing including the history information storage means 346c. The first abnormality diagnosis means 520 further includes a control program to be means 350, and the negative terminal wiring is further reduced when the digital conversion value D1 of the negative terminal potential is excessive on the basis of the value proportional to the offset voltage V1. Including a negative wire fault detection means 517 that determines that the power supply line is in contact with the power fault, the second fault diagnosis means 320a, 320b further includes a positive power fault detection means 317c and a circuit disconnection fault detection. Control program to be means 318c In response to the diagnosis result by the first and second abnormality diagnosis means, the abnormality processing means 350 stores the abnormality occurrence history information in the data memory 113 by the history information storage means 346c, and notifies the abnormality. Means 344 generates an alarm / display output.

As described above, according to the engine control apparatus of the third embodiment, the presence or absence of a fault, ground fault or disconnection abnormality on the positive terminal side of the exhaust gas sensor, and the presence or absence of a fault or ground fault on the negative terminal side are individually determined. Because it is judged and anomaly notification is made, even if a ground fault in the negative terminal wiring occurs, check that no other anomalies have occurred, and perform normal operation in a state of caution. There is a feature that it is possible to prevent the occurrence of a failure by informing the abnormality of this state and prompting maintenance inspection.
In particular, a voltage dividing resistor for obtaining a bias voltage is commonly used for each exhaust gas sensor, and it is not necessary to provide a pull-up resistor and a pull-down resistor separately. Therefore, the bias applied to each exhaust gas sensor is inexpensive. There is a feature that fluctuations in voltage are eliminated.

Further, the potentials of the positive terminals of the plurality of exhaust gas sensors 103a to 103d are selectively connected to one analog input terminal AN2 of the multi-channel AD converter 114 via the multiplexer 130, and the negative terminals of the plurality of exhaust gas sensors 103a to 103d are connected. The output voltage of the offset voltage generation circuit 121 commonly connected to the terminal is connected to the other input terminal AN1 of the multi-channel AD converter 114, and the multiplexer 130 is analogized by the selection commands SL1 and SL2 from the microprocessor 110. An input signal is selected and connected.
As described above, in the engine control apparatus of Embodiment 3, the potential of the positive terminal of the exhaust gas sensor is selectively connected to one analog input terminal of the multi-channel AD converter via the multiplexer, and the potential of the negative terminal is Since it is connected to other input terminals, it is possible to monitor the negative terminal side potential without increasing the number of analog inputs of the multi-channel AD converter, and to a specific exhaust gas sensor among a plurality of exhaust gas sensors. When attention is paid, there is a feature that the generated voltage can be quickly calculated by calculating the difference.

The positive terminals of the exhaust gas sensors 103a to 103d are connected to a series circuit of a voltage dividing resistor 155a (to 155d) connected to the ground circuit GND and a series switching element 156a (to 156d), and a program memory. 111C further includes a control program serving as a sensor resistance measuring unit 553 and a sensor short circuit abnormality determining unit 556a. The sensor resistance measuring unit 553 is a positive terminal when the series switching element 156a (˜156d) is temporarily closed. The internal resistance Rs of the exhaust gas sensors 103a to 103d is calculated by comparing the potential Von with the positive terminal potential Voff immediately before closing the series opening / closing element 156a (to 156d) or immediately after restarting, and sensor short circuit abnormality determining means 556a indicates that the internal resistance Rs of the exhaust gas sensors 103a to 103d measured by the sensor resistance measuring means 553 is equal to or less than a predetermined threshold value, thereby indicating that there is an internal short circuit abnormality of the exhaust gas sensors 103a to 103d. It is adapted to constant.
In this way, by measuring the internal resistance of the sensor, the presence or absence of an internal short circuit of the sensor is determined, so in addition to the abnormality of the positive terminal wiring and negative terminal wiring, the abnormality of the exhaust gas sensor itself is detected. In addition, the air-fuel ratio control can be prevented from becoming abnormal, and the efficiency of maintenance inspection can be improved.

Further, in the engine control apparatus of the third embodiment, the series opening / closing element 156a (to 156d) operates in connection with the multiplexer 130 selecting and specifying one of the plurality of exhaust gas sensors 103a (to 103d). If the series opening / closing element 156a (-156d) is closed at the time of selection designation, the synchronous control is performed to open the circuit at the time of this selection designation.
Therefore, the internal resistance can be measured without increasing the number of stages selected by the multiplexer and the number of analog input points of the multi-channel AD converter.

It is a circuit block diagram which shows the structure of the engine control apparatus by Embodiment 1 of this invention. It is a detailed circuit diagram of the interface circuit part in Embodiment 1 of this invention. FIG. 3 is a characteristic diagram (FIG. 3A) of the generated voltage of the exhaust gas sensor according to Embodiment 1 of the present invention and a list (FIG. 3B) showing the relationship between the state of the positive and negative terminal wirings and the value of the measured voltage Vd. It is a flowchart for operation | movement explanation which made the main the 1st abnormality diagnosis in Embodiment 1 of this invention. It is a flowchart for the first half operation | movement description regarding the 2nd abnormality diagnosis in Embodiment 1 of this invention. It is a flowchart for the latter half operation | movement description regarding the 2nd abnormality diagnosis in Embodiment 1 of this invention. It is a flowchart for operation | movement description regarding the abnormality process means in Embodiment 1 of this invention. It is a flowchart for operation | movement description regarding the air fuel ratio determination means in Embodiment 1 of this invention. It is a circuit block diagram which shows the structure of the engine control apparatus by Embodiment 2 of this invention. It is a flowchart for general inspection operation | movement description in Embodiment 2 of this invention. It is a flowchart for operation | movement description regarding the 1st abnormality diagnosis in Embodiment 2 of this invention. It is a circuit block diagram which shows the structure of the engine control apparatus by Embodiment 3 of this invention. It is a detailed circuit diagram of the interface circuit part in Embodiment 3 of this invention. It is a flowchart for operation | movement explanation which made the main the 1st abnormality diagnosis in Embodiment 3 of this invention. It is a flowchart for operation | movement description regarding the sensor abnormality detection means in Embodiment 3 of this invention.

Explanation of symbols

100A; 100B; 100C engine control device 210; 410; 510 second abnormality diagnosis means
103a to 103d exhaust gas sensor 215b; 455b; 515b Negative wire ground fault detection means
104a-104d positive terminal wiring 217; 457; 517 Negative wire power fault detection means
105a to 105d Negative terminal wiring 455c Negative wire breakage detection means
106 Various input sensors 220; 420; 520
107 Various electric loads 230; 430; 530 judgment processing means
108a first negative terminal wiring
108b-108d Crossover wiring 314b Flooding abnormality detection means
108e Second negative terminal wiring 316b Positive ground fault detection means
109 External tool 317c Positive line power fault detection means
110 microprocessor 318c circuit disconnection abnormality detection means
111A; 111B; 111C Program memory 320a / 320b
112 RAM memory 330 Positive line abnormality judgment avoidance means
113 data memory
114 multi-channel AD converter 342a judgment confirmation means
120 Constant voltage power supply circuit 343b Offset voltage cutoff command means
121 Offset voltage generator 344 Abnormality notification means
124 Inspection open / close element 345b Positive line normal reconfirmation means
125 offset voltage cutoff circuit 346c history information storage means
130 multiplexer 350 abnormality processing means, 351 air-fuel ratio determination means

140a; 140a; 150a interface circuit 553 sensor resistance measuring means
141a; 141a; 151a operational amplifier 556a sensor short circuit abnormality judging means
143a pull-up resistor
153a bias resistor
143e second pull-up resistor
144a pull-down resistor
144e second pull-down resistor
152a / 152e smoothing capacitors
153a bias resistor
155a voltage divider resistor
156a Series switching element
158/159 partial resistance

Vcc control power supply voltage V1 offset voltage
SL1 / SL2 selection command
GND ground circuit Dr offset voltage control command Rs internal resistance Vs generated voltage Vm rich side saturation voltage V0 lean side normal voltage Vn lean side abnormal drop voltage Vp bias voltage Vd measurement voltage

ΔV1 Micro voltage D1 Digital conversion value of negative terminal potential D2 Digital conversion value of positive terminal potential
CNT inspection command output
CK1 to CK4 inspection command output Vb power supply terminal Vpp second bias voltage

E1 to E4 First threshold voltage to fourth threshold voltage e1 to e4 First threshold voltage to fourth threshold voltage

Claims (10)

A microprocessor for driving and controlling various electric loads for driving and driving the internal combustion engine in response to the operating state of various input sensors for monitoring the operating state of the internal combustion engine and the contents of the control program stored in the program memory. The various input sensors include one or a plurality of exhaust gas sensors, and the exhaust gas sensors have an equivalent voltage source and an equivalent internal resistance connected between a positive terminal and a negative terminal. The generated voltage of the equivalent voltage source changes between the lean-side normal voltage and the rich-side saturation voltage at a predetermined activation temperature as a boundary at the stoichiometric air-fuel ratio, and the negative terminal of the exhaust gas sensor has an offset voltage A predetermined offset voltage generated by the generation circuit is applied, and the positive terminal potential, which is the voltage between the positive terminal of the exhaust gas sensor and the ground circuit, is As a measurement voltage, it is digitally converted via an AD converter, stored in a RAM memory for arithmetic processing via the microprocessor, and by monitoring the measurement voltage or a differential voltage between the measurement voltage and the offset voltage In what obtains the air-fuel ratio magnitude judgment output,
The program memory includes a control program serving as at least a positive ground fault detection means, an offset voltage cutoff command means, and history information storage means,
The positive line ground fault detection means monitors the measured voltage, and the measured voltage is less than the offset voltage and is equal to or lower than a first threshold voltage approaching a ground potential. It is determined that the positive terminal wiring is in a ground fault abnormality of the positive terminal wiring in contact with the ground circuit, and the offset voltage cutoff command means detects the ground fault abnormality in the positive terminal wiring. Accordingly, the application of the offset voltage is stopped by acting on the offset voltage cut-off circuit, and the history information storing means stores in the data memory whether or not the positive ground fault has occurred, and the data memory The engine control device is characterized in that the content of is read by an external tool for maintenance and inspection.   The value of the offset voltage applied to the negative terminal of the exhaust gas sensor is an expanded offset voltage that is larger than the absolute value of the lean-side abnormal drop voltage that occurs when the atmospheric contact surface of the exhaust gas sensor is submerged. The program memory further includes a control program serving as a submergence abnormality detection unit, and the submergence abnormality detection unit includes a submergence abnormality of the exhaust gas sensor when the value of the measured voltage is within a band of a second threshold voltage. The second threshold voltage value is a value less than the offset voltage and a band value exceeding the first threshold voltage approaching the ground potential, and the first threshold voltage Is a voltage that is equal to or less than the value obtained by subtracting the absolute value of the abnormal drop voltage from the value of the offset voltage, and the history information storage means further generates the occurrence of the submergence abnormality. The presence or absence of stored in the data memory, the contents of the data memory, the engine control apparatus according to claim 1, characterized in that the external tools for maintenance and inspection are those read. As the exhaust gas sensor, a plurality of exhaust gas sensors are used, and the offset voltage is commonly applied to each negative terminal of the plurality of exhaust gas sensors, and a negative voltage that is a voltage between the negative terminal of each exhaust gas sensor and the ground circuit. The terminal potential is digitally converted via a multi-channel AD converter and stored in the RAM memory via the microprocessor. The program memory further includes a negative ground fault detection means, a positive line fault Includes a control program that is a judgment avoidance means,
The negative ground fault detection means detects a ground fault in which the negative terminal wiring is in contact with the ground circuit when the digital conversion value of the negative terminal potential is too small with reference to a value proportional to the offset voltage. It is determined that there is a positive line abnormality determination avoiding means when the negative line ground fault abnormality detecting means detects a negative ground fault, or when the offset voltage cutoff circuit cuts off the offset voltage, 3. The abnormality detection by the positive ground fault abnormality detecting means and the submergence abnormality detecting means is not performed, and the detection result is validated if the measured voltage detects a fuel rich state. The engine control device described in 1.   The program memory further includes a control program serving as a positive line normal reconfirmation unit, and the positive line normal reconfirmation unit is at least in a state where application of the offset voltage is stopped by the offset voltage cutoff command unit. At the start of operation, immediately before operation stop or every predetermined period during operation, the offset voltage that has been stopped is enabled for a short time, and a new positive ground fault occurs in one of the multiple exhaust gas sensors The engine control apparatus according to claim 3, wherein it is confirmed whether or not it is not.   A predetermined bias voltage is applied to each positive terminal of the plurality of exhaust gas sensors via a high-resistance pull-down resistor and a pull-up resistor connected to a ground circuit, or a high-resistance bias resistor, and the program The memory further includes at least a first abnormality diagnosis means including the negative ground fault detection means, a second abnormality diagnosis means including the positive ground fault detection means, and the history information storage means. A control program serving as an abnormality processing means, wherein the first abnormality diagnosing means is further configured to supply power to the negative terminal wiring when the negative terminal potential is excessive with reference to a value proportional to the offset voltage. Including a negative line power fault abnormality detecting means for determining a power fault abnormality in contact with the line, and the second abnormality diagnosis means further includes a positive power line fault detection means and a circuit disconnection abnormality detection means. The positive line power fault abnormality detecting means includes a control program in which the positive terminal potential is excessive on the basis of a value proportional to an addition value of the offset voltage and the rich saturation voltage, It is determined that the positive terminal wiring is in contact with the power supply line due to a voltage exceeding the fourth threshold voltage approaching the power supply voltage, and the circuit disconnection abnormality detecting means detects that the positive terminal potential is equal to each positive voltage. Judged as a circuit disconnection abnormality in either the positive terminal wiring or the sensor or the negative terminal wiring by being within the third threshold voltage band having a band value centered on the bias voltage applied to the terminal wiring. The bias voltage is a value equal to or higher than the sum of the offset voltage and the rich saturation voltage and lower than the control power supply voltage Vcc, or the lean side abnormal reduction voltage from the offset voltage. A value within a voltage band that is a value equal to or lower than the subtraction value obtained by subtracting the absolute value of the pressure and higher than the ground circuit and does not occur in a normal state, a power fault abnormality state, or a ground fault abnormality state is used. The abnormality processing means stores the abnormality occurrence history information in the data memory by the history information storage means in response to the diagnosis result by the first and second abnormality diagnosis means, and outputs an alarm / display output by the abnormality notification means. The engine control device according to claim 3, wherein the engine control device is generated.   Positive terminals of the plurality of exhaust gas sensors are individually connected to the engine control device by individual positive terminal wirings, and a negative terminal of the first exhaust gas sensor among the plurality of exhaust gas sensors is a first negative terminal wiring. Connected to the engine control device, the negative terminals of the other exhaust gas sensors are sequentially connected to each other by a jumper wiring, and the negative terminal of the final exhaust gas sensor is connected to the engine control device by a second negative terminal wiring. The first and second negative terminal wires are connected in the engine control device to form a ring circuit and connected to a common offset voltage generating circuit. The engine control device described.   The first negative terminal wiring and the second negative terminal wiring are connected via an inspection switching element in the engine control device, and an output voltage of the offset voltage generation circuit is connected to the inspection switching element. Connected to an analog input terminal of the multi-channel AD converter as a monitor signal voltage, and an input circuit for the analog input terminal includes a second pull-down resistor connected to a ground circuit, or an output terminal of a constant voltage power supply circuit At least one of the resistances of the second pull-up resistor connected to the terminal is connected, and the program memory further includes a control program serving as negative wire breakage abnormality detection means, , Comparing whether the value of the monitor signal voltage and the offset voltage match when the inspection switch is temporarily opened And detecting whether or not there is a disconnection abnormality in the wiring from the offset voltage generation circuit to the multi-channel AD converter via the first negative terminal wiring, the transition wiring, and the second negative terminal wiring. The engine control device according to claim 6.   The potentials of the positive terminals of the plurality of exhaust gas sensors are selectively connected to one analog input terminal of the multi-channel AD converter via a multiplexer and commonly connected to the negative terminals of the plurality of exhaust gas sensors. The output voltage of the offset voltage generation circuit is connected to another input terminal of the multi-channel AD converter, and the multiplexer performs selection connection of an analog input signal according to a selection command from the microprocessor. The engine control device according to claim 3, wherein   A series circuit of a voltage dividing resistor connected to a ground circuit and a series switching element is connected to the positive terminal of the exhaust gas sensor, and the program memory further includes a sensor resistance measuring unit and a sensor short circuit abnormality determining unit. The sensor resistance measuring means includes a positive terminal potential when the series switching element is temporarily closed, and a positive terminal immediately before closing the series switching element or immediately after restarting the series switching element. The internal resistance of the exhaust gas sensor is calculated by comparing the potential with the electric potential, and the sensor short-circuit abnormality determining means is configured such that the internal resistance of the exhaust gas sensor measured by the sensor resistance measuring means is equal to or less than a predetermined threshold value. The engine control apparatus according to claim 8, wherein it is determined that an internal short circuit abnormality of the exhaust gas sensor is detected.   The series switching element operates in association with the multiplexer selecting and specifying one of the plurality of exhaust gas sensors. If the series switching element is closed at the time of the previous selection designation, the series switching element is opened at the time of the current selection designation. The engine control device according to claim 9, wherein the engine control device is synchronously controlled.

Images