JP2010151804A - Device and method for gas sensor control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor control device which can reduce false detection of wrong wiring without requiring wasted time for restoration to gas concentration measuring action when the trouble of wrong wiring is solved. <P>SOLUTION: The gas sensor control device 5 is connected to a gas sensor 8 having cells 14 and 24 with a pair of electrodes on solid electrolytes 13 and 23, while having a sensor drive circuit 52. The gas sensor control device 5 includes a command means which outputs the command for setting de-energized status and energized status of the sensor drive circuit 52 to the cells 14 and 24, a setting means 55 for setting the sensor drive circuit 52 to de-energized status or energized status, and a wrong wiring detection means 58 for detecting wrong wiring of the sensor drive circuit 52 or the gas sensor 8. Further the gas sensor control device 5 includes an abnormality determining means which instructs the command means to output de-energization command and then output energization command for abnormal return identification processing when wrong wiring is detected, identifying the abnormality if the wrong wiring problem is not solved even by abnormal return identification processing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sensor control apparatus and a sensor control method for controlling the energization state of a gas sensor having at least one cell including a solid electrolyte body and a pair of electrodes provided on the solid electrolyte body.

2. Description of the Related Art An oxygen sensor that detects an oxygen concentration in exhaust gas is known as a gas sensor that improves fuel consumption and controls combustion in an internal combustion engine such as an automobile. In addition, with the tightening of exhaust gas regulations for automobiles, reduction of the amount of nitrogen oxides (NOx) in exhaust gas is required, and NOx sensors capable of directly measuring NOx concentration have been developed.
These gas sensors have a gas sensor element having one or a plurality of cells formed by forming a pair of electrodes on the surface of an oxygen ion conductive solid electrolyte such as zirconia, and are specified based on the output from the gas sensor element. The gas concentration is detected.

  As these gas sensors, two cells (an oxygen concentration detection cell and an oxygen pump cell) are arranged so as to sandwich the measurement chamber, and the gas to be measured is introduced into the measurement chamber via a diffusion resistor, and oxygen contained in the gas to be measured. A full-range air-fuel ratio sensor (hereinafter also referred to as UEGO sensor) is known. Furthermore, in addition to two cells (oxygen concentration detection cell and oxygen pump cell), a NOx gas sensor having a total of three cells in which cells for detecting NOx gas concentration are arranged is also known.

A sensor driving circuit is connected to such a gas sensor, and the cell is energized through the sensor driving circuit, and the specific gas concentration in the gas to be measured is measured based on the output of the cell, including the sensor driving circuit. It is called a gas sensor control device. In addition, the energized state of the cell includes a protective energized state for protecting the gas sensor, a pre-activated energized state in which a minute current is passed through the inactive gas sensor, and a gas concentration measurement for measuring the concentration of a specific gas. There is an energized state.
Among these, the energizing state for protection electrically cuts off the conduction between the cell and the sensor drive circuit, prevents current from flowing through the gas sensor, and protects the gas sensor. In addition, the pre-activation energization state is a mode in which oxygen serving as a reference concentration is accumulated in, for example, a reference oxygen chamber of an oxygen concentration detection cell by supplying a minute current, and prepared for gas concentration measurement.

Incidentally, wiring abnormalities such as short-circuiting or disconnection from the battery or ground may occur in the wiring (energization line) of the sensor drive circuit or gas sensor. In spite of the occurrence of the wiring abnormality, if the gas concentration measurement energization state for measuring the concentration of the specific gas continues, an excessive current may flow through the gas sensor and the gas sensor may be damaged.
For this reason, when a wiring abnormality is detected, the technology for diagnosing the content of the abnormality and the location where the abnormality has occurred is established by electrically disconnecting the connection between the sensor drive circuit side and the gas sensor and setting the current state for protection. It has been developed (see Patent Document 1). Thereby, even when a wiring abnormality occurs, an overcurrent does not continue to flow through the gas sensor, so that the gas sensor is not damaged.

In addition, if a command to switch from another energized state to an energized state for gas concentration measurement is output to the sensor drive circuit without recognizing a wiring abnormality, an excessive current flows through the gas sensor and the gas sensor may be damaged in the same manner. is there.
For this reason, a technology has been developed that detects an abnormality without damaging the gas sensor by allowing switching to the gas concentration measurement energization state only when the immediately preceding state is the pre-activation energization state. (See Patent Document 2). As a result, even if a wiring abnormality has occurred, the wiring abnormality can be detected because the applied voltage of the gas sensor deviates from the normal range in the pre-activation energization state in which a minute current is supplied to the gas sensor.

Japanese Patent No. 3833687 JP 2008-70194 A

By the way, in the case of the conventional gas sensor control device, when an abnormality is detected even once, it is immediately determined as an abnormality and the operation of the sensor is stopped, or the protective energization state is shifted. However, even though the wiring is normal, it may be erroneously detected as abnormal due to the influence of noise, etc.In addition, in such a case, the wiring abnormality may be resolved immediately, and abnormality detection If the operation of the sensor is stopped each time, it takes time to return to the gas concentration measurement operation. In particular, there is a tendency that a wiring abnormality is erroneously detected due to a short circuit.
In addition, in the case of a conventional gas sensor control device, it is necessary to set a new energization state or circuit when trying to check whether or not a wiring abnormality is a false detection, and extra circuit parts are required for the sensor drive circuit. This causes problems such as an increase in the circuit.

  Therefore, the present invention can accurately determine the presence or absence of a wiring abnormality of a sensor drive circuit or a gas sensor, and even when the wiring abnormality is resolved, a gas sensor control device that does not require wasted time for returning to the gas concentration measurement operation The purpose is to provide.

  In order to solve the above problems, a gas sensor control device of the present invention is connected to a gas sensor having at least one cell including a solid electrolyte body and a pair of electrodes provided on the solid electrolyte body, and drives the gas sensor. A gas sensor control device comprising a sensor drive circuit for energizing the cell, wherein the gas sensor control device further outputs a command for setting a non-energized state and an energized state of the sensor drive circuit to the cell. Command means; setting means for receiving the command and setting the sensor driving circuit in the non-energized state or the energized state; wiring abnormality detecting means for detecting a wiring abnormality of the sensor driving circuit or the gas sensor; and the wiring When the abnormality detection means detects the wiring abnormality, a non-energization command indicating the non-energized state is issued to the command means. And a determination means for performing a determination process for determining whether or not the wiring abnormality is resolved by the abnormality recovery confirmation process while instructing to perform an abnormality recovery confirmation process for outputting an energization command indicating the energization state. And an abnormality determining means for determining whether to determine the wiring abnormality based on the result of the determination process.

  With such a configuration, even if a wiring abnormality is detected once, it is immediately determined that it is abnormal and the operation of the gas sensor is not stopped. It is possible to prevent erroneous detection of the abnormality and to prevent the operation of the gas sensor from being wasted when the wiring abnormality is resolved immediately.

  Further, in the gas sensor control device described above, the abnormality determination unit performs the abnormality return confirmation processing by the determination unit at least once more when the determination processing determines that the wiring abnormality has not been eliminated. It is preferable to adopt a mode in which the wiring abnormality is determined when the wiring abnormality is not resolved by the determination process even if the abnormality recovery confirmation processing is performed a predetermined number of times of a total of two or more times.

  According to such a configuration, since the abnormality recovery confirmation process is performed at least twice, there is a higher possibility that an erroneous detection of a wiring abnormality and an accidental wiring abnormality will be resolved. The situation where waste is required to stop the operation and return to the gas concentration measurement operation is further suppressed.

  Furthermore, in the gas sensor control device described above, the heater is heated so that the cell is activated, and includes a heater control circuit that controls a heater provided in the gas sensor, and the heater control circuit includes: A period from when the wiring abnormality is first detected by the wiring abnormality detection means until it is determined whether or not the wiring abnormality is confirmed by the abnormality confirmation means, the heater is less than the maximum voltage, and the It is good to take the aspect which supplies with an intermediate voltage more than the voltage which can maintain the activation temperature of a cell.

  In this configuration, a heater control circuit that controls the energization of the heater for heating the cell to the activation temperature or higher is used until the wiring abnormality is detected and the wiring abnormality is confirmed. To heat up. Therefore, even if an accidental wiring abnormality is detected, and the wiring abnormality is not confirmed after that, the gas sensor can be prevented from cooling down even when the gas sensor is returned to the normal operation (gas concentration measurement operation). Can be promoted. On the other hand, once a wiring abnormality is detected, there is a case where the wiring abnormality is confirmed. If the heater is heated at the maximum voltage at that time, useless power consumption is caused. In the present invention, the heater is heated at an intermediate voltage. As a result, the burden of power consumption can be reduced.

  Furthermore, in the gas sensor control device described above, the heater control circuit may take a mode in which the heater is de-energized when the abnormality in wiring is determined by the abnormality determination means.

  In this configuration, since the heater is de-energized after the abnormality is confirmed, the cell (gas sensor) can be continuously heated using the heater even after the abnormality is confirmed, and the gas sensor can be prevented from being damaged due to excessive temperature rise. Power consumption can be reduced.

  In order to solve the above problems, a gas sensor control method of the present invention is connected to a gas sensor having at least one cell including a solid electrolyte body and a pair of electrodes provided on the solid electrolyte body, and drives the gas sensor. A control method of a gas sensor control device comprising a sensor drive circuit for energizing the cell, wherein the sensor drive circuit has a configuration in which a non-energized state or an energized state to the cell is set by an external command A wiring abnormality detection process for detecting a wiring abnormality of the sensor driving circuit or the gas sensor, and when detecting the wiring abnormality, a non-energization command indicating the non-energized state is output to the sensor driving circuit, Thereafter, an abnormal return confirmation process for outputting an energization command indicating the energization state is performed, while the abnormal wiring check is performed by the abnormal return confirmation process Having a determination process of performing determination processing for determining whether to be erased, based on the result of the determination process, and a abnormality confirmation process of determining whether to confirm the wiring anomaly.

  Further, in the gas sensor control method described above, in the abnormality determination process, when it is determined in the determination process that the wiring abnormality is not solved, the abnormality return confirmation process according to the determination process is further performed at least 1 It is preferable to adopt a mode in which the wiring abnormality is determined when the wiring abnormality is not resolved in the determination process even if the abnormality recovery confirmation processing is performed a predetermined number of times twice or more in total.

  Further, in the gas sensor control method, the gas sensor control device further includes a heater that is heated so that the cell is activated, and a heater control circuit that controls the heater provided in the gas sensor. A period of time from when the wiring abnormality is first detected in the wiring abnormality detection process until it is determined whether or not the wiring abnormality is to be determined in the abnormality determination process; And it is good to take the aspect which controls the said heater control circuit so that it supplies with the intermediate voltage of the voltage abnormality which can maintain the activation temperature of the said cell.

  Further, the gas sensor control method may be configured to control the heater control circuit so that the heater is de-energized when a previous wiring abnormality is determined in the abnormality determination process. .

  Each of these gas sensor control methods can obtain the same effects as the above gas sensor control device.

It is a schematic block diagram of an internal combustion engine control system provided with an electronic control unit. It is a circuit diagram which shows schematic structure of an electronic control unit. It is explanatory drawing showing the state of each switch with respect to each energized state (operation mode). It is a figure which shows the flowchart of the abnormality confirmation process in 1st Embodiment. It is a figure which shows the flowchart of the abnormality confirmation process in 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described.
A. First embodiment:
FIG. 1 is a schematic diagram showing a configuration of an internal combustion engine control system 1 including a gas sensor control device (electronic control unit; ECU) 5 according to an embodiment of the present invention. The internal combustion engine control system 1 executes various control processes for controlling the operating state of the internal combustion engine (engine), and detects the concentration of the specific gas (oxygen) contained in the gas to be measured (exhaust gas). Is running.
The internal combustion engine control system 1 includes an electronic control unit 5 and a gas sensor 8, and the gas sensor 8 is attached to an exhaust pipe of the engine. The electronic control unit 5 includes a sensor control circuit 2 that controls the gas sensor 8 (sensor element 10), an engine control device 9 (hereinafter also referred to as “engine CPU” 9), and a heater control circuit 60 that controls the heater 43. The control circuit 2 includes a sensor drive circuit 52. The engine control device 9 is connected to the heater control circuit 60 and controls the heater control circuit 60 so that the temperature of the sensor element 10 becomes an operating temperature (hereinafter also referred to as an activation temperature, for example, 550 to 900 ° C.). The engine control device 9 is connected to the sensor control circuit 2 via the transmission cable 71 and controls the sensor control circuit 2.

  The gas sensor 8 includes a sensor element 10 that detects an oxygen concentration in a gas to be measured (exhaust gas) over a wide area, and a heater 43 that keeps the sensor element 10 at an operating temperature, and operates as a so-called full-range air-fuel ratio sensor. . The sensor element 10 includes an oxygen pump cell 14, a porous diffusion layer 18, an oxygen concentration detection cell 24, and a reinforcing plate 30. The detailed configuration of the gas sensor 8 will be described later.

The sensor control circuit 2 includes a sensor drive circuit 52 and the like that are electrically connected to the gas sensor 8. The sensor drive circuit 52 energizes the gas sensor 8 (the oxygen pump cell 14 and the oxygen concentration detection cell 24) to perform drive control thereof, and outputs the oxygen pump cell 14 (gas detection signal) and the element impedance (actually, the oxygen concentration detection cell). The impedance signal Vrpvs) that changes according to the element impedance of 24 is detected. The sensor control circuit 2 outputs the detected gas detection signal and element resistance value signal to the engine control device 9.
The sensor control circuit 2 can be realized as an ASIC (Application Specific Integrated Circuit), for example. The gas detection signal changes according to the oxygen concentration in the gas to be measured, and is used for measuring the oxygen concentration. On the other hand, the element impedance (impedance signal) indicates the internal resistance value of the gas sensor 8 and changes with a correlation according to the temperature of the gas sensor 8, but the detection of the element impedance and the calculation of the temperature of the gas sensor 8 use known methods. The details are omitted.

  The sensor control circuit 2 (sensor drive circuit 52) includes a Vs + terminal, a COM terminal, and an Ip + terminal. These terminals are the first connection terminal 15, the second connection terminal 17, and the third connection terminal of the electronic control unit 5, respectively. 19 are electrically connected to each other. A second detection electrode 28 of the sensor element 10 to be described later is electrically connected to the Vs + terminal of the sensor control circuit 2 through the first connection terminal 15 and the wiring 61. Further, the first detection electrode 22 and the second pump electrode 16 of the sensor element 10 are electrically connected to the COM terminal of the sensor control circuit 2 through the second connection terminal 17 and the wiring 62. Similarly, the first pump electrode 12 of the sensor element 10 is electrically connected to the Ip + terminal of the sensor control circuit 2 via the third connection terminal 19 and the wiring 63. In this way, the sensor drive circuit 52 is electrically connected to the gas sensor 8 to detect a gas detection signal or an element resistance value signal.

  The control unit 55 can be configured by a logic circuit that executes various control processes in the sensor control circuit 2.

The engine control device 9 includes a CPU as a central processing unit, storage units (RAM and ROM) for storing data, programs, and the like, and an input port and an output port for inputting and outputting signals between external devices, It can comprise with a microcomputer provided with. In the engine control device 9, the CPU executes various arithmetic processes based on a program stored in the storage unit, and controls the execution of instructions such as arithmetic and data transfer. Further, the engine control device 9 reflects the signal input to the input port in the contents of the input port register, and outputs the content stored in the output port register as a signal to the output port.
The engine control device 9 calculates the oxygen concentration based on the gas detection signal Vip output from the sensor control circuit 2. The engine control device 9 controls the operating state of the internal combustion engine by executing engine combustion control (air-fuel ratio control) or the like using the oxygen concentration obtained by the calculation.

  Furthermore, the engine control device 9 also executes a command output process for outputting a command (hereinafter referred to as “switching command” as appropriate) for switching an energization state, which will be described later, to the sensor control circuit 2 and an abnormality determination process. The above-described command (switching command) corresponds to a “command” in the claims. The engine control device 9 corresponds to “command means” in the claims.

Next, the configuration of the gas sensor 8 will be described.
The oxygen pump cell 14 includes an oxygen ion conductive solid electrolyte body 13 formed in a plate shape by partially stabilized zirconia, and a first pump electrode 12 and a second pump electrode 16 formed mainly of platinum on the front and back surfaces, respectively. have. The first pump electrode 12 is electrically connected to the third connection terminal 19 of the electronic control unit 5 through the wiring 63, and the second pump electrode 16 is connected to the second pump of the electronic control unit 5 through the wiring 62. It is electrically connected to the connection terminal 17. The first pump electrode 12 is covered with a porous protective layer 29 and is protected from poisonous substances by the porous protective layer 29.
The oxygen concentration detection cell 24 includes an oxygen ion conductive solid electrolyte body 23 formed in a plate shape by partially stabilized zirconia, a first detection electrode 22 formed mainly of platinum on each of the front and back surfaces, and a second detection electrode. An electrode 28 is provided. The first detection electrode 22 is electrically connected to the second connection terminal 17 of the electronic control unit 5 via the wiring 62 and is also electrically connected to the second pump electrode 16. The second detection electrode 28 is electrically connected to the first connection terminal 15 of the electronic control unit 5 via the wiring 61.

Between the oxygen pump cell 14 and the oxygen concentration detection cell 24, an insulating layer (not shown) mainly composed of an insulating material (such as alumina) is interposed between the cells 14 and 24, A porous diffusion layer 18 is provided in a part of the insulating layer. The porous diffusion layer 18 is formed in a porous shape mainly composed of an insulating material (such as alumina) in order to control the diffusion of the gas to be measured introduced into the sensor element 10. Instead of the porous diffusion layer 18, a small hole may be provided on the side wall of the insulating layer as a diffusion regulation side portion.
A hollow measurement chamber 20 surrounded by the porous diffusion layer 18 and the insulating layer (not shown) is formed between the oxygen pump cell 14 and the oxygen concentration detection cell 24. The measurement chamber 20 is communicated with the measurement gas atmosphere via the porous diffusion layer 18 (specifically, the porous portion). Further, the second pump electrode 16 is exposed on the upper surface of the measurement chamber 20, and the first detection electrode 22 is exposed on the lower surface of the measurement chamber 20.

In addition, a reinforcing plate 30 is laminated on the surface opposite to the surface facing the measurement chamber 20 in the oxygen concentration detection cell 24 to improve the overall strength of the sensor element 10. The reinforcing plate 30 is substantially the same size as the solid electrolyte bodies 13 and 23, and is formed in a plate shape with a material mainly made of ceramic.
The second detection electrode 28 is sandwiched between the reinforcing plate 30 and the oxygen ion conductive solid electrolyte body 23 and is cut off from the outside, and a reference oxygen chamber 26 as a sealed space around the second detection electrode 28. Is formed. Accordingly, a small constant current Icp is applied in the direction from the second detection electrode 28 to the first detection electrode 22, and oxygen is pumped from the measurement chamber 20 to the second detection electrode 28 side, thereby causing the reference oxygen chamber 26 to enter. A substantially constant concentration of oxygen is accumulated. In this way, the oxygen in the reference oxygen chamber 26 becomes a reference concentration for detecting the oxygen concentration.

  On the other hand, a flat heater 43 is disposed so as to face the oxygen pump cell 14 of the sensor element 10. The heater 43 is formed of a material mainly composed of alumina, and has a heater wiring 72 formed of a material mainly composed of platinum therein. The heater 43 is controlled by a voltage (electric power) supplied from a heater control circuit 60 described later so that the temperature of the sensor element 10 is equal to or higher than an activation temperature (830 ° C. in this embodiment). Further, both ends of the heater wiring 72 are electrically connected to the heater control circuit 60. The sensor element 10 (the oxygen pump cell 14 and the oxygen concentration detection cell 24) is activated by the heating by the heater 43, and gas detection (oxygen detection) becomes possible.

Next, the operation of the gas sensor 8 (sensor element 10) will be described.
First, the gas to be measured (exhaust gas) diffuses into the measurement chamber 20 through the porous diffusion layer 18. At this time, in a state where the air-fuel mixture supplied to the engine (that is, the gas to be measured in the measurement chamber 20) is maintained at the stoichiometric air-fuel ratio, the measurement chamber 20 and the reference oxygen chamber 26 that serves as a reference for the oxygen concentration. Due to the difference in oxygen concentration, an electromotive force of 450 [mV] is generated in the oxygen concentration detection cell 24 (a potential difference of 450 [mV] is generated between the first detection electrode 22 and the second detection electrode 28).
By the way, according to the change of the air-fuel ratio of the air-fuel mixture supplied to the engine, the oxygen concentration contained in the exhaust gas changes, and the oxygen concentration in the measurement gas contained in the measurement chamber 20 also changes. Therefore, in the internal combustion engine control system 1 of the present embodiment, the sensor control circuit 2 causes the oxygen pump cell 14 to maintain the potential difference between the first detection electrode 22 and the second detection electrode 28 at 450 [mV]. The flowing Ip current is controlled. That is, oxygen pumping is performed by the oxygen pump cell 14 by controlling the Ip current so that the atmosphere in the measurement chamber 20 is in the same state as the stoichiometric air-fuel ratio.

  The oxygen pump cell 14 pumps out oxygen from the measurement chamber 20 or supplies it to the measurement chamber 20 depending on the direction of current flowing between the pair of electrodes (the first pump electrode 12 and the second pump electrode 16). The pumping of oxygen can be switched. Further, the oxygen pump cell 14 is configured to be capable of adjusting the pumping amount of oxygen in accordance with the magnitude of the current passed between the pair of electrodes. Therefore, the oxygen concentration in the gas to be measured can be calculated based on the energization state (energization direction, current value, etc.) of the Ip current.

  Next, the configuration and operation of the electronic control unit 5 will be described with reference to FIG. FIG. 2 is a circuit diagram showing a schematic configuration of the electronic control unit 5. As described above, the electronic control unit 5 includes the sensor control circuit 2, the heater control circuit 60, and the engine control device 9.

  The sensor control circuit 2 includes a sensor drive circuit 52, a terminal voltage output circuit 54, a control unit 55, a differential amplifier circuit 57, and an abnormality detection circuit 58.

The sensor drive circuit 52 includes an operational amplifier 32 for flowing an Ip current for driving the oxygen pump cell 14, a PID control circuit 56 for improving the control characteristic of the Ip current, and the periphery of the second detection electrode 28 (reference oxygen chamber 26). A constant current source 46 for supplying a constant current Icp to the oxygen concentration detection cell 24 so as to keep the oxygen concentration constant, and a constant voltage source 48 for supplying a control target voltage for the Ip current are provided.
The sensor drive circuit 52 is connected to the sensor element 10 (Vs + terminal, COM terminal, Ip + terminal) and terminals for externally determining elements that determine the characteristics of the PID control circuit 56 (P1 terminal, P2 terminal, Pout). Terminal) and switches SW1 to SW5 for changing the energization state (operation mode) of the sensor drive circuit 52 in accordance with the energization state switching command output from the engine control device 9. The operation mode of the sensor drive circuit 52 represents the energization state to the sensor element 10.

Further, the sensor driving circuit 52 includes a Vcent point connected to the COM terminal 17, and an output terminal (described later) of the PID control circuit 56, an inverting input terminal of the operational amplifier 32, and an output terminal of the operational amplifier 34 are connected to the Vcent point. Yes. The output terminal of the operational amplifier 34 is connected to the Vcent terminal via the switch SW1. Further, the inverting input terminal of the operational amplifier 34 is connected to the output terminal, and the reference voltage 3.6 V is applied to the non-inverting input terminal of the operational amplifier 34. That is, the operational amplifier 34 is a circuit that applies a reference voltage of 3.6 V to the Vcent terminal and supplies an abnormality diagnosis current for performing an abnormality diagnosis of the sensor element 10.
The second pump electrode 16 is connected to the Vcent point via the wiring 62, the second connection terminal 17, and the resistance element R1.

The voltage dividing circuit 65 and the output terminal of the operational amplifier 32 are connected to the Ip + terminal. The voltage dividing circuit 65 includes two resistance elements R7 and R8 that divide the constant power supply voltage, and the connection point of the resistance elements R7 and R8 is connected to the Ip + terminal via the switch SW4. The output terminal of the operational amplifier 32 is connected to the Ip + terminal via the switch SW3. One end of the resistance element R8 is grounded.
A PID control circuit 56 is connected to the inverting input terminal of the operational amplifier 32 via the Vcent terminal and the resistance element R2, and a reference voltage of 3.6 V is applied to the non-inverting input terminal of the operational amplifier 32. That is, the operational amplifier 32 constitutes a part of a negative feedback circuit that controls a current flowing to the sensor element 10 (specifically, the oxygen concentration detection cell 24).

The PID control circuit 56 performs a PID operation on a deviation amount ΔVs between the control target voltage 450 mV of the oxygen concentration detection cell 24 and the output voltage Vs of the oxygen concentration detection cell 24 to improve the control characteristics of the negative feedback control described above. It has a function. The PID control circuit 56 includes operational amplifiers 36 and 40, resistors R3 to R5, and capacitors C1 to C3.
The input terminal of the PID control circuit 56 (the inverting input terminal of the operational amplifier 40) is connected to the output terminal of the operational amplifier 42, and the non-inverting input terminal of the operational amplifier 42 is connected to the Vs + terminal. That is, the output voltage Vs of the oxygen concentration detection cell 24 is input to the PID control circuit 56 via the operational amplifier 42. Note that the inverting input terminal of the operational amplifier 42 is connected to the output terminal.
A constant current source 46 is connected to the Vs + terminal via the switch SW5. The constant current source 46 is a constant current Icp (for example, 17 μA) that is passed through the oxygen concentration detection cell 24 in order to keep the oxygen concentration around the second detection electrode 28 (reference oxygen chamber 26) of the oxygen concentration detection cell 24 constant. ).

The output terminal of the operational amplifier 38 is connected to the inverting input terminal of the operational amplifier 40 through a resistance element. A constant voltage source 48 is connected to the non-inverting input terminal of the operational amplifier 38, and the inverting input terminal of the operational amplifier 38 is connected to the output terminal. That is, the output of the constant voltage source 48 is input to the inverting input terminal of the operational amplifier 40 via the operational amplifier 38, and 450 mV, which is a control target for controlling the Ip current, is supplied to the PID control circuit 56 via the operational amplifier 40. Is done.
The output terminal of the operational amplifier 40 is connected to the P1 terminal, and the non-inverting input terminal of the operational amplifier 40 is connected to the Vcent terminal. Further, a resistance element is interposed between the output terminal and the inverting input terminal of the operational amplifier 40. The P1 terminal is connected in parallel to the resistor R5 side of the first series circuit of the resistor R5, the capacitor C3, and the capacitor C2, and the R4 side of the second series circuit of the resistors R4 and R3. The connection point between the capacitor C3 and the capacitor C2 of the first series circuit is connected to the P2 terminal. Similarly, the connection point between the resistors R4 and R3 of the second series circuit is also connected to the P2 terminal. Further, the capacitor C2 and the resistor R3 are connected to the capacitor C1, and the capacitor C1 is connected to the Pout terminal.

The P2 terminal is connected to the inverting input terminal of the operational amplifier 36, and the output terminal of the PID control circuit 56 (the output terminal of the operational amplifier 36) is connected to the Pout terminal via the switch SW2. On the other hand, a reference voltage of 3.6 V is applied to the non-inverting input terminal of the operational amplifier 36.
The Pout terminal is connected to the Vcent point via the resistance element R2, and the output terminal (capacitor C1) of the PID control circuit 56 is connected to the COM terminal via the resistance element R2 and the resistance element R1.
Resistors R3 to R5 and capacitors C1 to C3 are provided to determine the control characteristics of the PID control circuit 56 attached to the P1 terminal and the P2 terminal.
Further, an oscillation preventing circuit 59 composed of a series circuit of a resistor R6 and a capacitor C4 is inserted between the Vs + terminal and the Ip + terminal in order to prevent oscillation of the sensor drive circuit 52.

Next, other circuits 54, 57, and 58 included in the sensor control circuit 2 will be described.
The terminal voltage output circuit 54 outputs the terminal voltages of the Vs + terminal, the COM terminal, and the Ip + terminal to the engine control device 9 via the control unit 55. Although connection lines are omitted in the figure, the input terminals of the terminal voltage output circuit 54 are connected to the Vs + terminal, the COM terminal, and the Ip + terminal, respectively.
The differential amplifier circuit 57 outputs the voltage across the resistor element R2 (specifically, the voltage across the Vcent point and the Pout point) to the input port of the engine control device 9 as a gas detection signal. This voltage is obtained by converting the Ip current flowing through the oxygen pump cell 14 by the resistance element R2. Note that the gas detection signal may be output to the input port of the engine control device 9 via the transmission cable 71.

Next, the abnormality detection circuit 58 includes window comparators 58a, 58b and 58c and an OR circuit 58d, and the output terminals of the comparators 58a, 58b and 58c are connected in parallel to the input terminal of the OR circuit 58d. Although the connection lines are omitted in the figure, the input terminals of the comparators are connected to the Vs + terminal, the COM terminal, and the Ip + terminal, respectively.
Each of the window comparators 58a, 58b, and 58c outputs a low level signal when each terminal voltage of the Vs + terminal, the COM terminal, and the Ip + terminal is within a predetermined voltage range, and each terminal voltage is out of the predetermined voltage range. Is configured to output a high level signal.

The terminal voltage of the Vs + terminal is normally maintained at 4.05 V, which is a value obtained by adding the output voltage Vs (450 mV) of the oxygen concentration detection cell 24 to the reference voltage 3.6 V of the COM terminal. However, when the wiring 61 or the like (also referred to as a Vs + line) connected to the Vs + terminal is short-circuited to the power supply potential or the ground potential for some reason, the terminal voltage of the Vs + terminal becomes the power supply potential or the ground potential. Then, an excessive abnormal current flows through the sensor element 10 and the sensor element 10 may be damaged. Therefore, the window comparator 58a is configured to compare the terminal voltage of the Vs + terminal with a preset threshold value and output a high level signal when the terminal voltage of the Vs + terminal exceeds the threshold value.
Specifically, the upper limit of the threshold value of the window comparator 58a is set to 9V or a predetermined voltage value obtained by subtracting a predetermined value (for example, 1.5V) from the power supply voltage in consideration of the fluctuation of the power supply voltage of the sensor element control circuit 50. In addition to setting, the lower limit of the threshold is set to 1 V taking ground floating into 0 V of the ground level. When the terminal voltage at the Vs + terminal rises above the upper limit value of 9V or a predetermined voltage value, or when the terminal voltage at the Vs + terminal falls below the lower limit value of 1V, the window comparator 58a It is configured to output a signal.

  The terminal voltage of the COM terminal is normally controlled by the operational amplifier 32 so that the reference voltage is 3.6V. However, when the wiring 62 or the like (also referred to as a COM line) connected to the COM terminal is short-circuited to the power supply voltage or the ground level for some reason, the terminal voltage of the COM terminal becomes the power supply potential or the ground potential, like the Vs + terminal. Therefore, the window comparator 58b is configured to compare the terminal voltage of the COM terminal with a preset threshold value and output a high level signal when the terminal voltage of the COM terminal exceeds the threshold value. Specifically, similarly to the window comparator 58a, the upper limit of the threshold of the window comparator 58b is set to 9V or a predetermined voltage value, and the lower limit of the threshold is set to 1V. When the terminal voltage of the COM terminal rises above the upper limit value of 9V, or when the potential of the COM terminal falls below the lower limit value of 1V, the window comparator 58b outputs a high level signal. It is configured.

  Also in the Ip + terminal, when the wiring 63 or the like (also referred to as an Ip + line) connected to the Ip + terminal is short-circuited to the power supply voltage or the ground level for some reason, the terminal voltage of the Ip + terminal becomes the power supply potential or the ground potential. Therefore, the window comparator 58c is configured to compare the terminal voltage of the Ip + terminal with a preset threshold value and output a high level signal when the terminal voltage of the Ip + terminal exceeds the threshold value. Specifically, in the window comparator 58c to which the terminal voltage of the Ip + terminal is input, the upper limit of the threshold is set to 9V or a predetermined voltage value so as to sandwich the reference voltage 3.6V, similarly to the window comparator 58b. The lower limit of the threshold is set to 1V. When the terminal voltage at the Ip + terminal rises above the upper limit value of 9V or a predetermined voltage value, or when the terminal voltage at the Ip + terminal falls below the lower limit value of 1V, the window comparator 58c It is configured to output a signal.

  The OR circuit 58d calculates the logical sum of the signals from the window comparators 58a, 58b, and 58c, and sets the abnormality detection flag DIAG when a high level signal is input from any of the window comparators 58a, 58b, and 58c. DIAG = 1 and output to the engine controller 9. When the terminal voltages of the Vs + terminal, the COM terminal, and the Ip + terminal are within a predetermined voltage range, the abnormality detection circuit 58 sets the abnormality detection flag DIAG to DIAG = 0 and outputs it to the engine control device 9. As described above, the abnormality detection circuit 58 has a short circuit abnormality in any one of the Vs + line, the COM line, and the Ip + line, and the terminal voltages of the Vs + terminal, the COM terminal, and the Ip + terminal exceed the threshold values and become abnormal voltage values. In other words (in other words, when an abnormality occurs in the sensor element 10), the abnormality detection flag DIAG has a function of setting DIAG = 1.

The sensor drive circuit 52 configured as described above switches ON / OFF of each of the switches SW1 to SW5 in response to a command from the engine control device 9, and changes the energized state (operation mode) of the sensor drive circuit 52 itself to measure the gas concentration. Set to one of the energizing state for sensor, the energizing state for sensor protection, or the energizing state before activation. Each energized state will be described later.
The engine control device 9 outputs a command for switching the energization state of the sensor drive circuit 52 (specifically, a control signal for performing ON / OFF control of the switches SW1 to SW5) from the output port, and the transmission cable 71 Command to the sensor control circuit 2 (the control unit 55). Then, the control unit 55 switches (sets) the energization state of the sensor drive circuit 52.
Therefore, the control unit 55 and the switches SW1 to SW5 correspond to “setting means” in the claims. The command for setting the sensor protection energization state (non-energization state) corresponds to the “non-energization command” in the claims, and the command for setting the pre-activation energization state (energization state) is claimed. It corresponds to the “energization command” in the range of

  Further, the gas detection signal indicating the voltage across the resistance element R <b> 2 is directly input to the input port of the engine control device 9 via the differential amplifier circuit 57. Further, the abnormality detection flag DIAG from the abnormality detection circuit 58 is directly input to the input port of the engine control device 9. On the other hand, an output signal from the terminal voltage output circuit 54 is input to the control unit 55 and input to the input port of the engine control device 9 via the transmission cable 71. Although not shown in FIG. 2, an element resistance value signal reflecting the internal resistance value of the sensor element 10 that is separately detected by a known technique is also input to the control unit 55 and controlled by the engine via the transmission cable 71. Input to the input port of the device 9.

  As described above, the engine control device 9 can control the energization state of the sensor drive circuit 52, and can determine whether the sensor element 10 is abnormal based on the input signals from the abnormality detection circuit 58 and the terminal voltage output circuit 54. Can be detected. Specifically, the engine control device 9 identifies which terminal among the predetermined identification conditions the state of each input terminal voltage applies to, and the terminal where the abnormality has occurred and its abnormality content (power supply Short circuit (VB short), ground short, etc.) can be detected.

  Next, referring to FIG. 3, the energization state (operation mode) of the sensor drive circuit 52 when the switches SW1 to SW5 are switched ON / OFF will be described.

Here, the energization state for sensor protection is a state in which the electrical connection between the sensor element 10 and the sensor drive circuit 52 is cut off to protect the gas sensor 8 from current flow.
Further, in the energized state for gas concentration measurement, the value and direction of the current flowing through the oxygen pump cell 14 are controlled so that the voltage between both electrodes of the oxygen concentration detection cell 24 becomes a desired value so that the gas concentration can be measured. It is a state to make.
In the energized state before activation, a minute electric current is applied to both electrodes of at least one of the oxygen concentration detection cell 24 and the oxygen pump cell 14 so that an overvoltage is not applied to the gas sensor 8 (the two cells 14, 24). State. As a more specific pre-activation energized state, in the case of a gas sensor having a configuration in which the electrode 28 on the side not facing the measurement chamber is closed to the outside of the pair of electrodes provided in the oxygen concentration detection cell 24, In order to use 28 as an internal oxygen reference source, an energized state in which a minute current is supplied to the oxygen concentration detection cell 24 can be exemplified.
It should be noted that the energized state for sensor protection corresponds to the “non-energized state” in the claims, and the energized state for gas concentration measurement and the energized state before activation correspond to the “energized state” in the claims.

  First, in the gas concentration measurement energization state, the switches SW2, SW3, and SW5 of the sensor drive circuit 52 are turned on, and the switches SW1 and SW4 are turned off. The gas concentration measurement energization state is an operation mode in which a relatively large current can be supplied to the gas sensor 8 (specifically, the oxygen pump cell 14) for oxygen pumping or the like. At this time, the maximum current value that can be supplied to the oxygen pump cell 14 is determined by the current drive capability of the operational amplifier 32 and the operational amplifier 36, and is set to about 20 [mA] in this embodiment.

For example, when the gas to be measured becomes excessively rich (rich) in the fuel supply, the oxygen concentration in the measurement chamber 20 is deficient than the theoretical air-fuel ratio, and the output voltage Vs of the oxygen concentration detection cell 24 is the control target voltage. It becomes higher than 450 mV. Therefore, a deviation amount ΔVs between the control target voltage and the output voltage Vs is generated, and the deviation amount ΔVs is PID-calculated by the PID control circuit 56 and fed back by the operational amplifier 32. For this reason, an Ip current for pumping the insufficient oxygen into the measurement chamber 20 by the oxygen pump cell 14 flows into the oxygen pump cell 14.
On the other hand, when the gas to be measured becomes insufficient in fuel supply (lean), the oxygen concentration in the measurement chamber 20 becomes excessive than the theoretical air-fuel ratio, and the output voltage Vs of the oxygen concentration detection cell 24 is lower than the control target voltage 450 mV. Therefore, the deviation amount ΔVs is fed back by the operational amplifier 32 in the same manner as described above, and an Ip current for pumping excess oxygen from the measurement chamber 20 by the oxygen pump cell 14 flows to the oxygen pump cell 14.
In this manner, the oxygen concentration in the gas to be measured can be calculated based on the energization state (energization direction, current value, etc.) of the Ip current.

  Next, in the sensor protection energization state, all the switches SW1 to SW5 of the sensor drive circuit 52 are turned off. For this reason, the signals input to the sensor element 10 from the operational amplifiers 32, 34, and 36 and the constant current source 46 are turned OFF, and the energization from the sensor drive circuit 52 to the sensor element 10 is interrupted. Accordingly, when a wiring abnormality occurs, the sensor drive circuit 52 is set to the sensor protection energization state based on a command from the engine control device 9 to prevent the abnormal current from continuously flowing through the sensor element 10. The sensor element 10 can be protected.

In the energization state before activation, the switches SW1, SW4, and SW5 of the sensor drive circuit 52 are turned on, and the switches SW2 and SW3 are turned off. At this time, since the switch SW3 is OFF, no current is supplied from the operational amplifier 32 driving the oxygen pump cell 14, and no current is supplied from the operational amplifier 36 because the switch SW2 is OFF. Current control (feedback control) based on the output of the oxygen concentration detection cell 24 in the pump cell 14 is stopped.
Further, since the switches SW1, SW4, and SW5 are ON, the oxygen pump cell 14 and the oxygen concentration detection cell 24 are supplied with a small constant current Icp from the operational amplifier 34, the constant current source 46, and the voltage dividing circuit 65. Become. Thus, oxygen is pumped from the first detection electrode 22 to the second detection electrode 28 side, and oxygen having a substantially constant concentration is accumulated in the reference oxygen chamber 26 formed around the second detection electrode 28.

In this way, in the energized state before activation, only a very small current is supplied to the sensor element 10, and therefore an excessive current is not supplied even when a wiring abnormality occurs. Damage (blackening, etc.) is less likely to occur.
Further, as described above, the engine control device 9 detects the wiring abnormality based on the state of each input terminal voltage. However, since each terminal voltage is low in the pre-activation energization mode, the sensor element 10 is damaged. Therefore, it is possible to detect a wiring abnormality.

  For example, when the gas concentration measurement energization state is set in the wiring abnormality state in which the wiring 62 is short-circuited, an energization path from the operational amplifier 32 to the ground line via the oxygen pump cell 14 and the wiring 62 is formed. The maximum current of the current driving capability in the operational amplifier 32 is supplied from the operational amplifier 32 to the oxygen pump cell 14. In this case, an excessive current is applied to the oxygen pump cell 14, and the sensor element 10 is damaged (blackening or the like) in a short time. On the other hand, when the wiring 62 is short-circuited and the pre-activation energized state, an energization path from the voltage dividing circuit 65 to the ground line through the oxygen pump cell 14 and the wiring 62 is formed. The current supplied from the pressure circuit 65 to the oxygen pump cell 14 is very small. For this reason, an excessive current is not supplied to the oxygen pump cell 14, and the sensor element 10 can be prevented from being damaged (blackening or the like) in a short time.

Next, the contents of the abnormality confirmation process executed by the engine control device 9 (more specifically, the CPU of the engine control device 9), which is a characteristic part of the present invention, will be described.
Even if a gas sensor wiring abnormality is detected once, the present invention immediately determines that it is abnormal and does not stop the operation of the sensor. It prevents false detection of abnormalities.
In the present embodiment, the sensor energization control process, which is the main routine, is performed by the engine control device 9, and the abnormality determination process described above is called and executed as a subroutine. Therefore, the sensor energization control process that is the main routine will be described first.

First, the engine control device 9 is activated when the internal combustion engine control system 1 is turned on and executes an initialization process (such as initialization of internal variables). After the initialization process is completed, the following various controls are performed. Start processing.
Various control processes include a specific gas concentration detection process for detecting a specific gas concentration (oxygen concentration) in the exhaust gas based on a gas detection signal from the sensor control circuit 2, and switching of the energization state for the sensor control circuit 2. There are command output processing for outputting a command, air-fuel ratio control processing for performing air-fuel ratio control of the engine using a specific gas concentration detected based on a gas detection signal, and the like.

Then, the engine control device 9 starts the process when the automobile is turned on, and executes the sensor energization control process for controlling the energization state of the sensor element 10 as one of various control processes after the initialization process is completed. To do. In the sensor energization control process, an optimum energization state is determined as an energization state to the sensor element 10 based on various conditions, and a process of outputting a switching command corresponding to the energization state of the determination result to the sensor control circuit 2 is executed. To do.
As an optimal energization state determination method, for example, under conditions such as immediately after sensor activation, the pre-activation energization state is determined as the optimal energization state, and under conditions where the sensor element 10 is activated, the gas concentration The measurement energization state is determined as the optimum energization state.
On the other hand, when a wiring abnormality (such as a wiring short circuit) occurs, an abnormality confirmation process described later is performed.
The engine control device 9 receives a current state flag indicating the current energization state from the sensor control circuit 2, and can know the current energization state based on the current state flag. The engine control device 9 itself recognizes the current energization state of the sensor control circuit 2 and recognizes the energization state of the sensor element 10 without receiving the current state flag from the sensor control circuit 2. Also good.

As a more specific determination method of the optimum energized state, it is determined whether or not the gas sensor is activated based on the element resistance value signal of the gas sensor. If it is not activated, the energized state before activation is optimized. When it is determined that the current state is active and activated, the current state for gas concentration measurement is determined as the optimum current state. When the abnormality detection circuit 58 determines that the gas sensor or the energization path is abnormal, an abnormality determination process described later is performed. In addition, when the abnormality detection circuit 58 determines that the abnormality of the gas sensor or the energization path has been eliminated, the optimum energization state is determined based on the element resistance value signal of the gas sensor.
The element resistance value signal is obtained by periodically supplying a current or voltage of a predetermined magnitude to one of the oxygen pump cell 14 and the oxygen concentration detection cell 24 constituting the gas sensor 8, and then obtained via the cell. Signal. Since the element resistance value signal can be obtained by a known method (circuit configuration), description in this embodiment is omitted. However, specifically, a current of a predetermined magnitude is periodically passed to the oxygen concentration detection cell 24, and the output obtained through the oxygen concentration detection cell 24 at that time is sample-held, and this sample-held output Is output to the engine control device 9 as an element resistance value signal.

Next, the abnormality determination process will be described with reference to FIG.
When the abnormality confirmation process is started, first, the engine control device 9 detects the wiring abnormality of the gas sensor 8 or the sensor drive circuit 52 by the abnormality detection circuit 58 according to the determination result in the sensor energization control process which is the main routine. It is determined whether or not (step S10).
If a wiring abnormality is detected in step S10, the process proceeds to step S12, and the engine control device 9 outputs a command for switching the sensor drive circuit 52 to the sensor protection energization state (non-energization state) from the output port to the control unit 55. To do. Step S12 is a process for protecting the gas sensor in which the wiring abnormality is detected. The control unit 55 receives the command after completion of the initialization process similar to that of the engine control device 9, and sets each switch SW1 to SW5 of the sensor drive circuit 52 on / off based on the command.
On the other hand, if no wiring abnormality is detected in step S10, the engine control device 9 proceeds to step S26.

The process proceeds from step S12 to step S14, and the engine control device 9 determines whether or not the number of abnormal times n is n = 3. The abnormal number n is incremented in step S22, which will be described later, and cleared in step S26.
If n = 3 in step S14, the process proceeds to step S24, where the engine control device 9 determines an abnormality and ends the process. When the abnormality is determined, for example, the engine control device 9 performs processing such as lighting the sensor abnormality lamp while the sensor protection energization state is maintained.

  On the other hand, if n = 3 is not satisfied in step S14, the process proceeds to step S16, and the engine control device 9 outputs a command for switching the sensor drive circuit 52 to the pre-activation energization state (energization state) from the output port to the control unit 55. In the present invention, as the “energized state” in step S16, the gas sensor is not particularly distinguished between the energized state for gas concentration measurement and the energized state before activation, as long as the gas sensor is energized. It is preferable. This is because if the sensor protection energization state in step S12 is shifted directly to the gas concentration measurement energization state, the sensor may be damaged.

  Next, the process proceeds to step S18, and the engine control device 9 performs an abnormality determination waiting process for a predetermined time. This abnormality determination waiting process is to wait for whether or not the abnormal state of the gas sensor is changed by energizing the gas sensor 8 in step S16 without immediately determining that it is abnormal after detecting the wiring abnormality in step S10. . This prevents erroneous detection of wiring abnormality and prevents unnecessary sensor stoppage when the wiring abnormality is resolved immediately and recovered normally. The waiting time in step S18 may be counted by a timer provided in the engine control device 9 as appropriate.

  Next, the process proceeds to step S20, and the engine control device 9 determines whether or not the abnormality detection circuit 58 has detected the wiring abnormality of the gas sensor 8 or the sensor drive circuit 52 again. The process of step S20 is a process of determining whether or not the wiring abnormality is resolved by changing the state of the gas sensor according to the waiting time of step S18. If no wiring abnormality is detected in step S20, the process proceeds to step S26. In step S <b> 26, the engine control device 9 finishes the process on the assumption that there is no wiring abnormality, and clears the abnormality frequency n to n = 0. When the process of step S26 is finished, the process returns to the sensor energization control process which is the main routine.

On the other hand, if a wiring abnormality is detected in step S20, the process proceeds to step S22, and the engine control device 9 increments the number of times of abnormality n and returns to step S12.
The processing in steps S12 to S16 executed by the engine control device 9 described above corresponds to the “abnormal return confirmation processing” in the claims, and the processing in step S20 is “judgment processing in the claims”. Is equivalent to. The abnormal recovery confirmation process switches from the sensor protection energized state (non-energized state) to the pre-energized energized state (energized state) when a wiring abnormality is detected, and then performs an abnormality determination wait process for a predetermined time to recover from the abnormal condition. This is a process for confirming whether or not (wiring abnormality is eliminated).
In this way, even if a wiring abnormality of the gas sensor is detected once, it is immediately determined that it is abnormal and the operation of the sensor is not stopped. It is possible to prevent erroneous detection of an abnormality, and it is possible to prevent useless sensor stoppage when a wiring abnormality is resolved immediately.

In this embodiment, abnormality is determined when n = 3 in step S14. For this reason, the abnormality recovery confirmation process is repeated up to three times to give a lot of room for eliminating the wiring abnormality. The abnormal return confirmation processing may be performed only once (n = 1 is set as a determination criterion in step S14). However, if the abnormal recovery confirmation processing is performed twice or more, erroneous detection of wiring abnormality or accidental wiring is performed. The possibility that the abnormality is eliminated is further increased, and the situation in which the operation of the sensor is stopped each time a wiring abnormality is detected and the return to the gas concentration measurement operation is unnecessary is further suppressed.
In this embodiment, when n = 3 is incremented in step S22, the process returns to step S12 to switch from the pre-activation energized state (energized state) to the sensor protection energized state (non-energized state). Then, after entering the non-energized state, the abnormality is confirmed in step S24. If it does in this way, since an abnormality will be decided after protecting a gas sensor by non-energization, damage to a gas sensor can be prevented further.

In the present embodiment, the abnormality detection circuit 58, the engine control device 9, and the process of step S10 executed by the engine control device 9 correspond to the “wiring abnormality detection means” described in the claims. To do. Further, the process of step S10 for determining whether or not a wiring abnormality is detected by the abnormality detection circuit 58 corresponds to the “wiring abnormality detection process” described in the claims.
Further, in the present embodiment, the engine control device 9 and a series of processes of steps S12 to S22 executed by the engine control device 9 correspond to “judgment means” in the claims, and the above-described step S12. The series of processes of S22 corresponds to the “determination process” in the claims.
In the present embodiment, the engine control device 9 and the process of step S24 executed by the engine control device 9 correspond to “abnormality determination means” in the claims, and the process of step S24 described above is performed. This corresponds to the “abnormality determination process” in the claims.

B. Second embodiment:
FIG. 5 is a flowchart showing an abnormality confirmation process according to the second embodiment of the present invention, which is executed in the internal combustion engine control system provided with the gas sensor control device. The internal combustion engine control system of the second embodiment is different from the internal combustion engine control system 1 of the first embodiment only in the content of the abnormality confirmation process, and the other software configuration and hardware configuration are the same. is there. This abnormality confirmation process corresponds to FIG. 4 of the first embodiment, and corresponds to a process in which the heater control circuit 60 adds energization control to the heater 43 to the abnormality confirmation process shown in FIG.

  First, the abnormality determination process of the second embodiment is executed as a subroutine different from the sensor energization control process executed as a main routine in the engine control device 9 as in the first embodiment. Note that the engine control device 9 executes the following normal control process as the energization control of the heater 43 using the heater control circuit 60 separately from the abnormality determination process. In the normal control process, when the sensor element 10 is not activated, the heater 43 is energized and controlled at the maximum voltage (in this embodiment, 12 V which is the battery voltage), while the sensor element 10 is activated. In order to maintain the activated state, the voltage supplied to the heater 43 is set so that the sensor element 10 has the target element resistance value based on the element resistance value signal of the gas sensor separately detected. This is a process for controlling the PWM energization. Note that a method for controlling energization of the voltage supplied to the heater 43 based on the element resistance value signal is known in Japanese Patent Application Laid-Open No. 10-48180 and the like, and further description thereof is omitted.

  Now, when the abnormality confirmation process of 2nd Embodiment is started, the same step S10 and S12 as 1st Embodiment will be performed. Then, an affirmative determination is made in step S10 (step S10: YES), and when the process of step S12 ends, the process proceeds to step S13. In S13, the normal control process using the heater control circuit 60, which is separately executed by the engine control device 9, is interrupted, and the heater 43 is set to a temperature lower than the maximum voltage and the activation temperature of the sensor element 10 is set. An intermediate heat process of energizing at an intermediate voltage (8 V in the present embodiment) that is equal to or higher than a sustainable voltage is executed using the heater control circuit 60. This intermediate heat process is a process for detecting the voltage of the battery power supply and performing PWM energization control on the voltage supplied to the heater 43 so that the intermediate voltage (8 V in this embodiment) is applied to the heater 43. By performing such an intermediate heater process, the sensor element 10 is not excessively heated and is prevented from being cooled even when the wiring abnormality is subsequently eliminated. It is possible to quickly return without giving

When the process of step S13 is completed, the process of step S14 similar to that of the first embodiment is executed. If a negative determination is made in step S14 (step S14: No), steps S16 and S18 similar to those of the first embodiment are performed. , S20 is executed. If a negative determination is made in step S20 (step S20: No), the process proceeds to step S21. In this step S21, execution of normal control processing using the heater control circuit 60 described above is instructed. When receiving this instruction, if the engine control device 9 has already executed the normal control process for the heater 43, the normal control process is continuously executed. On the other hand, when receiving the above instruction, if energization control in step S13 or step S25 described later is performed on the heater 43, the energization control is interrupted and the normal control process is performed again. Become. When the process of step S21 ends, the process proceeds to step S26, and when the process of step S26 similar to the first embodiment ends, the process waits until the next abnormality diagnosis process is executed.
If an affirmative determination is made in step S20 (step S20: Yes), the process proceeds to step S22, and when the process of step S22 similar to the first embodiment is completed, the process returns to step S12 and the subsequent processes are repeated. Execute.

  On the other hand, if an affirmative determination is made in step S14 (step S14: Yes), the process proceeds to step S24, the abnormality is determined in the engine control device 9, and the process proceeds to step S25. In step S25, a process for deenergizing the heater 43 is executed. Thereby, the heating of the heater 43 that has been energized and controlled under the intermediate heat treatment is stopped, the excessive temperature rise of the sensor element 10 is prevented, and unnecessary power consumption is suppressed.

The present invention is not limited to the first and second embodiments described above, and it goes without saying that the present invention covers various modifications and equivalents included in the spirit and scope of the present invention. For example, the full-range air-fuel ratio sensor is taken up as the sensor element 10, but the present invention is not limited to this, and another cell can be added to the sensor element 10 and applied to a NOx sensor having two measurement chambers. It is.
However, in the case of the NOx sensor, since one microcomputer (controller) controls the gas sensor at a time, the command means, setting means, and wiring abnormality detection means are all realized on one controller. The controller corresponds to a gas sensor control device.

  Further, in the second embodiment, the process of deenergizing the heater 43 is executed when the abnormality is determined in step S24. However, the heater 43 is not turned on even after the abnormality is determined in step S24. Instead of energizing, the heater 43 may be continuously energized while being subjected to the intermediate heat treatment.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine control system 2 Sensor control circuit 5 Gas sensor control apparatus (electronic control unit)
8 Gas sensor 9 Engine control device 10 Sensor element 13, 23 Solid electrolyte body 14, 24 cell (oxygen pump cell, oxygen concentration detection cell)
12, 16 A pair of electrodes (first pump electrode, second pump electrode)
22, 28 A pair of electrodes (first detection electrode, second detection electrode)
43 Heater 52 Sensor Drive Circuit 55 Control Unit 58 Abnormality Detection Circuit 60 Heater Control Circuit

Claims (8)

A gas sensor control device comprising a sensor driving circuit connected to a gas sensor having at least one cell including a solid electrolyte body and a pair of electrodes provided on the solid electrolyte body, and energizing the cell to drive the gas sensor. There,
The gas sensor control device further includes command means for outputting a command for setting a non-energized state and an energized state to the cell of the sensor drive circuit,
Setting means for receiving the command and setting the sensor drive circuit in the non-energized state or the energized state;
Wiring abnormality detection means for detecting wiring abnormality of the sensor driving circuit or the gas sensor;
When the wiring abnormality detection means detects the wiring abnormality, the abnormality return confirmation processing that outputs a non-energization command indicating the non-energized state to the command means and then outputs an energization command indicating the energized state. Determination means for performing determination processing to determine whether or not the wiring abnormality is resolved by the abnormality recovery confirmation processing,
An abnormality determining means for determining whether to determine the wiring abnormality based on a result of the determination process;
A gas sensor control device comprising: The gas sensor control device according to claim 1,
The abnormality confirmation means instructs the abnormality recovery confirmation process by the determination means to be repeated at least once more when the wiring abnormality is determined not to be resolved by the determination process, and the abnormality recovery confirmation process is performed. If the wiring abnormality is not resolved by the determination process even if the predetermined number of times is two or more in total, the wiring abnormality is confirmed.
Gas sensor control device. The gas sensor control device according to claim 1 or 2,
A heater that is heated so that the cell is activated, and includes a heater control circuit that controls a heater provided in the gas sensor;
The heater control circuit sets the heater to a maximum voltage during a period from when the wiring abnormality detection unit first detects the wiring abnormality to when the abnormality determination unit determines whether to determine the wiring abnormality. Less than and energizing at an intermediate voltage higher than the voltage capable of maintaining the activation temperature of the cell,
Gas sensor control device. The gas sensor control device according to claim 3,
The heater control circuit deenergizes the heater when the wiring abnormality is confirmed by the abnormality confirmation means.
Gas sensor control device. A gas sensor control device including a sensor driving circuit connected to a gas sensor having at least one cell including a solid electrolyte body and a pair of electrodes provided on the solid electrolyte body, and energizing the cell to drive the gas sensor A control method,
The sensor drive circuit has a configuration in which the non-energized state or the energized state of the cell is set by an external command,
Wiring abnormality detection process for detecting wiring abnormality of the sensor drive circuit or the gas sensor;
When the wiring abnormality is detected, a non-energization command that indicates the non-energized state is output to the sensor drive circuit, and then an abnormality return confirmation process that outputs an energization command that indicates the energized state is performed. A determination process for performing a determination process for determining whether or not the wiring abnormality is resolved by the abnormality return confirmation process;
A gas sensor control method comprising: an abnormality determination process for determining whether to determine the wiring abnormality based on a result of the determination process. The gas sensor control device according to claim 5,
In the abnormality determination process, when it is determined in the determination process that the wiring abnormality has not been resolved, the abnormality recovery confirmation process in the determination process is repeated at least once more, and the abnormality recovery confirmation process is totaled 2 If the wiring abnormality is not resolved in the determination process even if the predetermined number of times is performed, the wiring abnormality is confirmed.
Gas sensor control method. The gas sensor control method according to claim 5 or 6, wherein:
The gas sensor control device further includes a heater that is heated so that the cell is activated, and includes a heater control circuit that controls a heater provided in the gas sensor,
A period from when the wiring abnormality is first detected in the wiring abnormality detection process until it is determined whether or not to determine the wiring abnormality in the abnormality determination process, the heater is less than the maximum voltage, and the Controlling the heater control circuit to energize at an intermediate voltage of abnormal voltage that can maintain the activation temperature of the cell;
Gas sensor control method. The gas sensor control method according to claim 7,
Controlling the heater control circuit so that the heater is de-energized when a previous wiring abnormality is determined in the abnormality determination process;
Gas sensor control method.