JP2019074360A - Gas sensor control device - Google Patents

Abstract

To apply a gas sensor control device for a gas sensor having two cells to a gas sensor having only one cell and allow the gas sensor control device to detect whether each terminal and the cell are connected normally.SOLUTION: In a sensor control device, a control supply unit supplies control current to a gas sensor element via a second terminal portion so that potential difference occurring to the gas sensor element via a first terminal portion becomes a target value. An initial supply unit supplies initial current to the gas sensor element via the first terminal portion before the control current is supplied. A potential acquisition unit acquires potential of the first terminal portion and second terminal portion. A connection determination unit uses the control current or initial current switched as determination current, compares potential of the first terminal portion and second terminal portion when the determination current is supplied, and thereby determines whether at least one of the first terminal portion and second terminal portion is electrically connected with the gas sensor element.SELECTED DRAWING: Figure 4

Description

  The present disclosure relates to technology for controlling a gas sensor.

  Patent Document 1 below proposes a gas sensor control device that controls a gas sensor having two cells, a detection cell and an oxygen pump cell, and has a function of diagnosing a failure of the gas sensor. The oxygen pump cell is connected to the IP + terminal and the COM terminal, and the detection cell is connected to the VS + terminal and the COM terminal.

JP, 2008-070194, A

  Although the above gas sensor control device controls a gas sensor having two cells, there is a demand to use the above gas sensor control device for control of a gas sensor having only one cell. Therefore, a configuration is conceivable in which the IP + terminal and the VS + terminal are shorted and this one cell is connected to the COM terminal and the shorted terminal.

In this configuration, it is required to be able to detect whether or not the IP + terminal and the VS + terminal are normally short-circuited, that is, whether or not each terminal and the cell are normally connected.
In one aspect of the present disclosure, a gas sensor control device for a gas sensor having two cells is applied to a gas sensor having only one cell, so that it can be detected whether or not each terminal and cell are properly connected. It is desirable to do.

  In the sensor control device according to the first aspect of the present disclosure, the first terminal portion and the second terminal portion are electrically connected to each other on the gas sensor element side with respect to the first terminal portion and the second terminal portion. The second terminal portion is electrically connected to one of the pair of electrodes, and the third terminal portion is electrically connected to the other of the pair of electrodes. And a control supply unit, an initial supply unit, a potential acquisition unit, and a connection determination unit.

  The potential setting unit acquires the potentials of the first terminal unit and the second terminal unit. The pump supply unit supplies pump current to the gas sensor element via the second terminal portion such that the potential generated between the first terminal portion and the third terminal portion becomes a target value. The control supply unit supplies a control current representing a test current or a pump current for detecting the state of the gas sensor element to the gas sensor element via the second terminal portion. The initial supply unit supplies an initial current to the gas sensor element via the first terminal before the control current is supplied.

The potential acquisition unit acquires the potentials of the first terminal unit and the second terminal unit.
The connection determination unit is used by switching the control current or the initial current as the determination current, and comparing the potentials of the first terminal and the second terminal when the determination current is supplied. It is determined whether or not at least one of the first terminal portion and the second terminal portion is electrically connected to the gas sensor element.

  In this configuration, when the first terminal portion and the second terminal portion, which should be electrically connected, are not electrically connected, the potential of the first terminal portion is different from the potential of the second terminal portion. Potential is high. Therefore, the sensor control device of the present disclosure compares the potential of the first terminal portion with the potential of the second terminal portion, and at least one of the first terminal portion and the second terminal portion and the gas sensor element are electrically connected. It is determined whether or not it is connected.

According to such a sensor control device, it can be detected that at least one of the first terminal portion and the second terminal portion is not properly connected to the gas sensor element.
In the sensor control device according to the second aspect of the present disclosure, the connection determination unit sets the initial current as the determination current, and the potential of the second terminal when the determination current is supplied is lower than the potential of the first terminal In this case, it is determined that the first terminal portion and the gas sensor element are not electrically connected.

According to such a sensor control device, it can be determined whether or not the first terminal portion and the gas sensor element are electrically connected.
In the sensor control device according to the third aspect of the present disclosure, the connection determination unit monitors the potential drop of the first terminal unit and the second terminal unit while the initial current is supplied as the determination current, and the first terminal When the falling speed of the electric potential of the part is slower than the falling speed of the electric potential of the second terminal part, it is determined that the first terminal part and the gas sensor element are not electrically connected.

  According to such a sensor control device, since the falling speed of the potential is continuously monitored, the first terminal portion and the gas sensor element are electrically connected as compared with the configuration in which the potential is temporarily compared. It can be determined more reliably whether it is present or not.

  The sensor control device according to a fourth aspect of the present disclosure is a pump that prohibits the control supply portion from supplying a control current when it is determined that the first terminal portion and the gas sensor element are not electrically connected. It further has a prohibition part.

According to such a sensor control device, since the control current is prevented from flowing to the gas sensor element when there is an abnormality, the gas sensor element can be protected.
In the sensor control device according to the fifth aspect of the present disclosure, the connection determination unit sets the control current as the determination current, and the potential of the second terminal when the determination current is supplied is higher than the potential of the first terminal. In this case, it is determined that the second terminal portion and the gas sensor element are not electrically connected.

  According to such a sensor control device, it can be determined whether or not the second terminal portion and the gas sensor element are electrically connected.

It is a whole block diagram of a gas detection system provided with a sensor control device of an embodiment. It is an explanatory view showing an internal structure etc. of a sensor element. It is a flow chart showing processing contents of terminal open identification processing. It is a flow chart showing processing contents of terminal open identification processing. It is a timing chart which shows the timing of terminal open identification processing.

Hereinafter, embodiments to which the present disclosure is applied will be described using the drawings.
[1. Embodiment]
[1-1. overall structure]
FIG. 1 is an overall configuration diagram of a gas detection system 1 as an embodiment of the present disclosure.

  The gas detection system 1 is used, for example, for detecting the concentration of a specific gas (in this embodiment, oxygen) in the exhaust gas of an internal combustion engine (not shown). The gas detection system 1 includes a gas detection device 3 and a gas sensor 5. The gas detection device 3 includes a gas sensor control device 7 and an engine control device 9.

  The gas sensor control device 7 drives and controls the gas sensor 5 to measure a specific component in the gas to be measured. In particular, the gas sensor control device 7 detects the oxygen concentration in the exhaust gas as a specific component in the gas to be measured, and notifies the engine control device 9 of the detected oxygen concentration. The details of the gas sensor control device 7 will be described later.

  The engine control device 9 is a microcontroller that executes various control processes for controlling the internal combustion engine, and performs air-fuel ratio control of the internal combustion engine using the oxygen concentration detected by the gas sensor control device 7 as one of the various control processes. I do.

[1-2. Gas sensor]
Next, the gas sensor 5 will be described based on FIG.
The gas sensor 5 is an oxygen sensor that detects oxygen. The gas sensor 5 is provided in an exhaust pipe of an internal combustion engine (engine) to detect oxygen concentration in exhaust gas over a wide area, and is also called a linear sensor.

The gas sensor 5 is a so-called one-cell gas sensor provided with a gas sensor element 11 and a heater 13.
The gas sensor element 11 includes a pump cell 15. The pump cell 15 includes an oxygen ion conductive solid electrolyte body 17 formed of partially stabilized zirconia (ZrO ₂ ), and a pair of porous electrodes 19 (19a, 19b) mainly formed of platinum on the front and back surfaces thereof. ) And.

  The heater 13 is provided with a heat generating resistor which generates heat by energization from the outside. The heater 13 is provided to heat the gas sensor element 11 (in particular, the pump cell 15) to bring the gas sensor element 11 into an activated state capable of detecting the gas concentration.

  Further, as shown in FIG. 2, the gas sensor element 11 has a measurement chamber 21 in which one (first electrode 19 a) of the pair of porous electrodes 19 in the pump cell 15 is exposed and the other (second electrode) And 19b) a standard oxygen chamber 23 exposed.

  A gas to be measured (exhaust gas in the present embodiment) is introduced into the measurement chamber 21 through the diffusion rate control unit 25 that determines the diffusion of gas from the outside. The atmosphere as a reference gas is introduced into the reference oxygen chamber 23 from the outside.

  The first electrode 19a is connected to a first connector 29a which is a connection portion with the gas detection device 3 via the first lead portion 27a. The second electrode 19 b is connected to the similar second connector 29 b via the second lead portion 27 b.

The gas sensor element 11 is an oxygen sensor element that detects an oxygen concentration by a so-called limit current method. Here, the limiting current method will be briefly described.
As well known, an output characteristic showing a relationship between pump voltage Vp (ie, voltage between a pair of porous electrodes 19) and pump current Ip in pump cell 15 is a flat region parallel to the voltage axis, ie, pump It is known that there is a limit current region (limit current region) in which the current Ip is constant. The pump current Ip represents a current for causing the potential difference generated between the pair of electrodes of the gas sensor element 11 to be a target value. This flat region (limit current region) is a region in which the pump current Ip does not substantially change even when the pump voltage Vp changes, and the constant value (limit current) is maintained.

  This flat area is a limit current area that indicates the pump current Ip corresponding to the oxygen concentration (i.e., air-fuel ratio), and the change in the limit current corresponds to the change in the oxygen concentration. It is known that the pump current Ip in this limit current region increases as the oxygen concentration increases.

  For this reason, a pump voltage Vp corresponding to the limit current range is set for the pump cell 15 of the gas sensor element 11, and the pump current Ip is controlled (for example, feedback control) to achieve the pump voltage Vp. By determining the current Ip, the oxygen concentration in the exhaust gas can be detected.

  That is, as the oxygen concentration in the exhaust gas increases (the air-fuel ratio becomes lean), the limit current of the pump current Ip increases, and as the oxygen concentration in the exhaust gas decreases (the air-fuel ratio becomes rich), the limit Since the current decreases, the oxygen concentration (air-fuel ratio) can be detected based on the limit current by setting the pump voltage as an appropriate target voltage.

  In the present embodiment, a target voltage of, for example, 400 mV is set as the pump voltage Vp between the pair of porous electrodes 19 in the pump cell 15, and the pump current Ip flows between the pair of porous electrodes 19. (Eg, move oxygen between the measurement chamber 21 and the reference oxygen chamber 23). Then, as is well known, the oxygen concentration is detected based on the current value (limit current) at which the pump current Ip at the time of pumping becomes constant.

[1-3. Sensor controller]
Next, the gas sensor control device 7 will be described based on FIG.
The gas sensor control device 7 is configured to drive-control the gas sensor 5 to detect the oxygen concentration in the exhaust gas and to notify the engine control device 9 of the detected oxygen concentration.

The gas sensor control device 7 is configured of an ASIC (Application Specific IC).
In FIG. 1, the gas sensor control device 7 is shown as a functional block diagram.

  The gas sensor control device 7 includes an AD conversion unit 31 (analog-digital conversion unit 31), a PID calculation unit 33, a pump current calculation unit 34, a current DA conversion unit 35 (current digital-analog conversion unit 35), a gas detection signal calculation unit 37, A current supply unit 39, a reference potential generation unit 41, a pump voltage determination unit 43, and a control start unit 45 are provided.

Further, the gas sensor control device 7 includes an Rpvs computing unit 51, a heater control amount computing unit 53, and a heater driver 57.
Furthermore, the gas sensor control device 7 includes a pump current terminal 61 (Ip + terminal 61), a detection voltage terminal 63 (Vs + terminal 63), a reference potential terminal 65 (COM terminal 65), a terminal monitoring unit 67, an abnormality detection unit 69, and communication processing. A unit 71 is provided.

Each component will be described below.
The current supply unit 39 is configured to supply various currents to the gas sensor element 11 (specifically, the pump cell 15) through the detection voltage terminal 63.

  As various current, for example, pulse current Irpvs, minute current Icp and the like can be mentioned. The pulse current Irpvs is a current for detecting the internal resistance of the gas sensor element 11 (specifically, the pump cell 15).

  The minute current Icp is an initial current which is flowed between the detection voltage terminal 63 and the reference potential terminal 65 before feedback control of the pump current Ip, and oxygen is pumped by the gas sensor element 11 (specifically, the pump cell 15). And a minute current to generate an oxygen reference electrode.

The current supply unit 39 is configured not to always supply these currents, but to supply each current at the appropriate time.
The reference potential generation unit 41 sets the potential of the reference potential terminal 65 to a predetermined potential. Specifically, a potential obtained by adding a reference setting voltage (2.7 V in the present embodiment) with reference to the ground potential GND of the internal combustion engine is set as the potential of the reference potential terminal 65. In the present embodiment, the potential of the reference potential terminal 65 corresponds to the reference potential when controlling the gas sensor element 11 (pump cell 15).

  The AD conversion unit 31 detects the voltage across the pump cell 15 (pump voltage Vp = detection voltage Vs) based on the potential of the detection voltage terminal 63 and the potential of the reference potential terminal 65, and converts the analog value indicating the detection voltage Vs into a digital value Convert to The voltage across the pump cell 15 is referred to as a pump voltage Vp, but may be referred to as a detection voltage Vs in the description of detecting a voltage or the like.

The AD conversion unit 31 notifies each unit of the gas sensor control device 7, for example, the PID calculation unit 33, the pump voltage determination unit 43, the Rpvs calculation unit 51, etc., of the converted digital value.
The voltage across the pump cell 15 can be used as a sensor output signal Vs1 that changes according to the oxygen concentration, and can be used as a response signal Vs2 that changes according to the internal resistance of the pump cell 15 when the pulse current Irpvs is input.

  The PID operation unit 33 is configured to execute pump current control processing by digital processing. The pump current control process is a control process for controlling the pump current Ip supplied to the pump cell 15 so that the detection voltage Vs (sensor output signal Vs1) of the pump cell 15 becomes the target voltage (for example, 400 mV in this embodiment). (Ie, feedback control of the pump current Ip).

  The PID operation unit 33 that executes the pump current control process performs PID operation based on the deviation ΔVs between the target voltage (400 mV) and the detection voltage Vs (sensor output signal Vs1) of the pump cell 15 so that the deviation ΔVs approaches zero. (In other words, the energization control value (energization control current Tip) of the pump current Ip for energizing the pump cell 15 is calculated so that the detection voltage Vs approaches the target voltage.

  The pump current calculation unit 34 attenuates a frequency component higher than a predetermined first cutoff frequency (100 Hz in the present embodiment) from a digital signal representing the conduction control current Tip calculated by the PID calculation unit 33. The DAC control signal S1 (first filter signal S1) is extracted by digital operation.

  The gas detection signal calculation unit 37 attenuates frequency components higher than a predetermined second cutoff frequency (50 Hz in the present embodiment) from the digital signal representing the DAC control signal S1 extracted by the pump current calculation unit 34. The resultant gas detection signal S2 (second filter signal S2) is extracted by digital operation.

  Such a digital signal is a signal suitable for feedback control of the pump cell 15, and therefore, by supplying the pump current Ip generated based on the DAC control signal S1 to the pump cell 15, the detected voltage Vs of the pump cell 15 is According to the latest change state, pumping of oxygen (pumping and pumping) by the pump cell 15 can be appropriately performed.

The DAC control signal S1 is a digital signal including information on the current value of the conduction control value of the pump current Ip and the conduction direction (forward direction, reverse direction).
The current DA conversion unit 35 receives the DAC control signal S1 (digital value) calculated by the pump current calculation unit 34, performs DA conversion on the received DAC control signal S1, and generates a pump current as an analog value after DA conversion. A control current for controlling the gas sensor element 11 is supplied to the pump cell 15 with Ip. The control current includes at least the pump current Ip and the disconnection detection current Ipoc.

  Further, the current DA converter 35 has a first mode and a second mode. In the first mode, the current DA conversion unit 35 supplies the pump current Ip to the pump cell 15 when performing feedback control of the pump current Ip.

  In the first mode, the current D / A conversion unit 35 sets the potential difference between the detection voltage terminal 63 and the reference potential terminal 65 based on the calculation value by the pump current calculation unit 34, that is, the detection voltage Vs as the target value. Thus, the pump current Ip is supplied to the gas sensor element 11 through the pump current terminal 61.

  Further, in the second mode, the current DA conversion unit 35 supplies a minute constant current (breakdown detection current Ipoc) of 30 μA or less (for example, 22 μA) to the pump cell 15 to detect a break in the circuit.

  The gas detection signal S2 is a digital signal indicating the energization control current Tip of the pump current Ip because the number of times of the filtering process is larger than that of the DAC control signal S1, and the change in the detection voltage Vs of the pump cell 15 for a long time Is a relatively large reflected digital signal.

  Such a digital signal is a signal suitable for detection of a specific component (oxygen) contained in the gas to be measured (exhaust gas). Therefore, by using the gas detection signal S2 as a signal for detecting the concentration of oxygen contained in the exhaust gas, the concentration of oxygen contained in the exhaust gas is detected based on the long-term change in the detection voltage Vs of the pump cell 15. It becomes possible to detect. Thereby, the detection accuracy of oxygen concentration can be improved.

  The communication processing unit 71 executes communication control processing for transmitting and receiving various information to and from the engine control device 9 by communication via the SPI communication line 72. The communication processing unit 71 transmits and receives information including at least control information related to sensor control. For example, the communication processing unit 71 transmits the gas detection signal S2 to the engine control device 9.

  The engine control device 9 calculates the concentration of a specific gas (oxygen in the present embodiment) in the exhaust gas based on the gas detection signal S2. That is, the engine control device 9 measures the object to be measured based on the history data of the pump current Ip supplied to the pump cell 15 so that the oxygen concentration in the measurement chamber becomes a predetermined target concentration (for example, the oxygen concentration equivalent to the theoretical air fuel ratio). Calculate the oxygen concentration contained in the gas.

  The gas sensor control device 7 includes an EEPROM and a RAM (not shown). The EEPROM is a storage unit that stores the contents of control processing and various parameters used for the control processing. The EEPROM also stores various information (such as the maximum allowable current of the pump cell 15) which is determined according to the type and characteristics of the gas sensor 8 to be controlled. These pieces of information are stored in the EEPROM at the manufacturing stage of the gas sensor control device 7. The RAM is a storage unit that temporarily stores control data and the like used for various control processes.

The Rpvs calculator 51 calculates the internal resistance value Rpvs of the pump cell 15 based on the response signal Vs2 and the sensor output signal Vs1 notified from the AD converter 31.
The heater control amount calculation unit 53 calculates the temperature of the gas sensor 5 (specifically, the pump cell 15 of the gas sensor element 11) based on the internal resistance value Rpvs calculated by the Rpvs calculation unit 51 by digital calculation. The heater heating value necessary to bring the temperature close to or maintain the sensor target temperature is calculated.

  The heater control amount calculation unit 53 calculates the duty ratio of the power to be supplied to the heater 26 based on the calculated heater calorific value, and generates a PWM control signal according to the duty ratio.

  As the sensor target temperature, a predetermined value is stored in a storage unit (ROM, RAM, etc.). The heater control amount calculation unit 53 generates a PWM control signal using the sensor target temperature read from the storage unit.

  The heater driver 57 controls the energization of the heater 13 based on the PWM control signal from the heater control amount calculation unit 53 using the power supplied from the power supply device 59. Thereby, the calorific value of the heater 13 becomes the calorific value necessary to bring the temperature of the gas sensor 5 close to or maintain the sensor target temperature.

  The pump current terminal 61 and the detection voltage terminal 63 are connected to one (first electrode 19 a) of the pair of porous electrodes 19 in the pump cell 15 of the gas sensor element 11, and the reference potential terminal 65 is a pair of porous electrodes It is connected to the other (second electrode 19 b) of the nineteen. The pump current terminal 61 is connected to the connection path between the detection voltage terminal 63 and the second electrode 19 b on the gas sensor element 11 side inside the gas detection device 3 with respect to the detection voltage terminal 63 and the pump current terminal 61. Thus, the first electrode 19a is electrically connected.

  Specifically, the first connector 29a (and thus the first electrode 19a) is connected to the reference potential terminal 65 through the first conduction portion 73a. The second connector 29b (and thus the second electrode 19b) is connected to the detection voltage terminal 63 via the second conduction portion 73b. The pump current terminal 61 is connected to the second conduction portion 73 b.

  The terminal monitoring unit 67 detects each potential (analog value) of the pump current terminal 61, the detection voltage terminal 63, and the reference potential terminal 65, AD converts each detected potential, and converts each potential (digital value) ) To the abnormality detection unit 69.

  The abnormality detection unit 69 determines whether or not each potential of the pump current terminal 61, the detection voltage terminal 63, and the reference potential terminal 65 is included in a predetermined normal range, and a terminal whose potential deviates from the normal range It determines that it is an abnormal state.

  The abnormality detection unit 69 detects the detection voltage terminal 63 and the pump current terminal 61 when the determination current is supplied, using the control current (the disconnection detection current Ipoc in this case) or the initial current (minute current Icp) as the determination current. By comparing the potentials, it is determined whether or not at least one of the detection voltage terminal 63 and the pump current terminal 61 and the gas sensor element 11 are electrically connected.

  That is, when the detection voltage terminal 63 and the pump current terminal 61 which should be electrically connected are not electrically connected, the potential of the detection voltage terminal 63 and the potential of the pump current terminal 61 are different. It is likely to be Therefore, the gas sensor control device 7 adopts a configuration in which the abnormality is determined by comparing the potential of the detection voltage terminal 63 with the potential of the pump current terminal 61.

  The abnormality detection unit 69 detects that the detection voltage terminal 63 or the pump current terminal 61 is open, for example, by comparing the potential of the detection voltage terminal 63 with the potential of the pump current terminal 61 according to the matrix shown in FIG. can do. Note that being open means that the terminal is not electrically connected to the gas sensor element 11.

  In FIG. 3, in order to detect that the detection voltage terminal (VSP terminal) 63 is open, the minute current Icp is supplied (ON) and the disconnection detection current Ipoc is not supplied (OFF). It indicates that the potentials of the terminals should be compared. Further, in order to detect that the pump current terminal (IPP) 61 is open, the potential of each terminal is set to a state in which the minute current Icp is not supplied (OFF) and a state in which a disconnection detection current Ipoc is supplied (ON). Indicates that it is good to compare

That is, current is supplied from different terminals such as the detection voltage terminal 63 and the pump current terminal 61, and the potentials of the respective terminals at this time are sequentially compared.
Specifically, not only detecting that any one of the detection voltage terminal 63 and the pump current terminal 61 is open but also detecting by switching the terminals for supplying current sequentially in terminal open identification processing described later It is specified which of the voltage terminal 63 and the pump current terminal 61 is open.

  When the abnormality detection unit 69 determines that at least one of the terminals is in an abnormal state, the PID calculation unit 33 or the heater control amount calculation unit 53 calculates an abnormality information signal including information of the terminal determined to be an abnormal state. Send to etc. The terminal being open is an aspect of the abnormal state.

  When receiving the abnormality information signal, the PID operation unit 33 and the heater control amount operation unit 53 execute the abnormality handling process according to the abnormality information signal. For example, the PID operation unit 33 executes a process of stopping energization of the pump cell 15 as the abnormality handling process. Further, the heater control amount calculation unit 53 executes a process of reducing the power supplied to the heater 26 (in other words, the duty ratio of the voltage applied to the heater) as the abnormality handling process.

  If there is a terminal determined to be in an abnormal state, the abnormality detection unit 69 sends an abnormality information signal including information on the terminal determined to be in an abnormal state to the engine control device 9 via the communication processing unit 71. Send.

  The engine control unit 9 executes concentration detection processing so that the gas detection signal S2 output from the gas sensor control unit 7 during reception of the abnormality information signal is not a normal value but an abnormal value and is not used for oxygen concentration detection. Do. As a result, when detecting the oxygen concentration based on the gas detection signal S2 from the gas sensor control device 7, the engine control device 9 can suppress a decrease in detection accuracy.

[1-4. Terminal open identification process]
Next, the terminal open identification process executed by the gas sensor control device 7 will be described using the flowchart of FIG. 4 and the timing chart of FIG. The terminal open identification process is a process for determining the start of feedback control (FB control) of the pump current Ip when the internal combustion engine is started.

  For example, when the ignition switch of the vehicle is turned on and the engine as an internal combustion engine is started (time t1), energization to the heater 13 is started in step (hereinafter referred to as S) 110.

  In the subsequent S120, for example, the current supply unit 39 supplies the minute current Icp as the determination current to the second electrode 19b of the pump cell 15 substantially simultaneously with the energization of the heater 13, for example. The minute current Icp is, for example, a constant current of 30 μA or less (for example, 17 μA).

  In the subsequent S130, the terminal monitoring unit 67 recognizes the voltage of the detection voltage terminal 63. Since the resistance value of the solid electrolyte body 17 is large immediately after the minute current Icp is supplied, the voltage of the detection voltage terminal 63 is stuck to the upper limit value (for example, 6 V in this case) as shown in FIG. It becomes.

  However, the resistance value of the solid electrolyte body 17 eventually decreases, and the voltage of the detection voltage terminal 63 decreases accordingly. In S130 to S160, the potential drop of the detection voltage terminal 63 and the pump current terminal 61 is monitored, and the detection voltage pin 63 has a potential falling speed slower than that of the pump current terminal 61. It is determined that the gas sensor element 11 and the gas sensor element 11 are not electrically connected.

  Specifically, in the subsequent S140, the abnormality detection unit 69 determines whether the voltage of the detection voltage terminal 63 is equal to or higher than a predetermined determination value Vth. If an affirmative determination is made here, the process proceeds to S150, and if a negative determination is made, the process proceeds to S210.

  The determination value Vth is for determining that the temperature of the solid electrolyte body 17 rises after the minute current Icp is supplied, the resistance value of the solid electrolyte body 17 gradually decreases, and the voltage at the terminal decreases. It is a judgment value. If the detection voltage terminal 63 is open, as indicated by the broken line [A] in FIG.

Note that, for example, 4.2 V may be adopted as the determination value used in the present process, but this determination value can be set as appropriate based on experiments and the like.
At S150, the terminal monitoring unit 67 recognizes the voltage of the pump current terminal 61. Since pump current terminal 61 and detection voltage terminal 63 are electrically connected, when minute current Icp is supplied from detection voltage terminal 63, the voltage of pump current terminal 61 becomes the voltage of detection voltage terminal 63. It should follow. However, if the detection voltage terminal 63 is open, it may occur that the voltage of the pump current terminal 61 does not rise as shown by the broken line [B] in FIG.

  Therefore, in the subsequent S160, it is determined by the abnormality detection unit 69 whether or not the voltage of the pump current terminal 61 is less than a predetermined determination value Vth. If an affirmative determination is made here, the process proceeds to S170, and if a negative determination is made, the process returns to S120. If the situation where the negative determination is made in S160 is repeated for a certain determination time or more, the voltage of the detection voltage terminal 63 does not decrease, so the process may proceed to S180 described later.

In the subsequent S170, the supply of the minute current Icp is stopped.
In the subsequent S180, the abnormality detection unit 69 determines that the detection voltage terminal 63 is open. That is, when the potential of the pump current terminal 61 when the determination current is supplied is lower than the potential of the detection voltage terminal 63, or the falling speed of the potential of the detection voltage terminal 63 is the falling speed of the potential of the pump current terminal 61 If it is later than this, it is determined that the detection voltage terminal 63 is open.

In this case, the abnormality detection unit 69 transmits an abnormality information signal about the detection voltage terminal 63.
On the other hand, in S210, the supply of the minute current Icp is stopped.
In S220, the pump current calculation unit 34 and the current DA conversion unit 35 supply the disconnection detection current Ipoc as the determination current (at time t2 in FIG. 5).

  In the subsequent S230, the terminal monitoring unit 67 recognizes the voltage of the pump current terminal 61. Note that, since the pump current terminal 61 and the detection voltage terminal 63 are electrically connected, when the disconnection detection current Ipoc is supplied from the pump current terminal 61, the voltage of the detection voltage terminal 63 becomes equal to that of the pump current terminal 61. Should follow the voltage. However, if the pump current terminal 61 is open, it may occur that only the voltage of the pump current terminal 61 rises, as shown by the broken line [C] in FIG.

  Therefore, in the subsequent S240, it is determined by the abnormality detection unit 69 whether or not the voltage of the pump current terminal 61 is less than a predetermined determination value Vth. If an affirmative determination is made here, the process proceeds to S250, and if a negative determination is made, the process returns to S120.

In the subsequent S250, the supply of the disconnection detection current Ipoc is stopped.
In the subsequent S260, the abnormality detection unit 69 determines that the pump current terminal 61 is open. That is, when the potential of the pump current terminal 61 when the determination current is supplied is higher than the potential of the detection voltage terminal 63, it is determined that the pump current terminal 61 is open. In this case, the abnormality detection unit 69 transmits an abnormality information signal about the pump current terminal 61.

  In addition, it is good to complete this process, when the condition by which negative determination is carried out more than a certain judgment time is repeated in S240. In this case, in order to start feedback control of the pump current Ip, the control start unit 45 outputs a control signal instructing the PID operation unit to start the operation necessary for feedback control (time t3 in FIG. 5). .

  That is, since the conditions for starting feedback control of the pump current Ip are satisfied, the supply of the disconnection detection current Ipoc is stopped, feedback control of the pump current Ip is started, and detection of the oxygen concentration is started. When the pump current terminal 61 or the detection voltage terminal 63 is open, the pump current calculator 34 and the current DA converter 35 prohibit the supply of the pump current.

Further, after the process of S180 or S260, the terminal open identification process is ended.
[1-3. effect]
According to the embodiment described above, the following effects can be obtained.

  (1a) In the state where the detection voltage terminal 63 and the pump current terminal 61 are electrically connected on the gas sensor element 11 side with respect to the detection voltage terminal 63 and the pump current terminal 61, the gas sensor control device 7 described above The pump current terminal 61 is electrically connected to one of the pair of electrodes, and the reference potential terminal 65 is electrically connected to the other of the pair of electrodes. A DA conversion unit 35, a current supply unit 39, a terminal monitoring unit 67, and an abnormality detection unit 69 are provided.

  The pump current calculator 34 and the current DA converter 35 supply a control current to the gas sensor element 11 via the pump current terminal 61. The control current includes the test current and the pump current Ip. The test current represents a current for detecting an abnormality in the gas sensor element 11 such as the disconnection detection current Ipoc, the pulse current Irpvs, and the like. Further, the pump current Ip represents a current for causing a potential difference generated between a pair of electrodes of the gas sensor element 11, for example, between the reference potential terminal 65 and the detection voltage terminal 63, to be a target value.

The current supply unit 39 supplies an initial current between the detection voltage terminal 63 and the reference potential terminal 65 before the control current is supplied.
The terminal monitoring unit 67 acquires the potentials of the detection voltage terminal 63 and the pump current terminal 61.

  The abnormality detection unit 69 uses the control current or the initial current as the determination current, and compares the potentials of the detection voltage terminal 63 and the pump current terminal 61 when the determination current is supplied, thereby the detection voltage terminal 63 and the pump current It is determined whether at least one of the terminals 61 and the gas sensor element 11 are electrically connected.

  According to such a gas sensor control device 7, it can be detected that at least one of the detection voltage terminal 63 and the pump current terminal 61 is not properly connected to the gas sensor element 11.

  (1b) In the gas sensor control device 7 described above, the connection determination unit sets the initial current as the determination current, and the potential of the pump current terminal 61 when the determination current is supplied is lower than the potential of the detection voltage terminal 63 It is determined that the detection voltage terminal 63 and the gas sensor element 11 are not electrically connected.

According to such a gas sensor control device 7, it can be determined whether or not the detection voltage terminal 63 and the gas sensor element 11 are electrically connected.
(1c) In the gas sensor control device 7 described above, the connection determination unit monitors the potential drop of the detection voltage terminal 63 and the pump current terminal 61 while the initial current is supplied as the determination current, and the detection voltage terminal 63 It is determined that the detection voltage terminal 63 and the gas sensor element 11 are not electrically connected when the rate of drop of the potential is slower than the rate of drop of the potential of the pump current terminal 61.

  According to such a gas sensor control device 7, since the falling speed of the potential is continuously monitored, the detection voltage terminal 63 and the gas sensor element 11 are electrically connected as compared with the configuration in which the potential is temporarily compared. It can be determined more reliably whether or not it has been done.

  (1d) When it is determined that the detection voltage terminal 63 and the gas sensor element 11 are not electrically connected, the gas sensor control device 7 described above is controlled by the pump current calculation unit 34 and the current DA conversion unit 35 It further has a pump prohibition part which forbids being supplied.

According to such a gas sensor control device 7, since the control current is prevented from flowing to the gas sensor element 11 when there is an abnormality, the gas sensor element 11 can be protected.
(1e) In the gas sensor control device 7 described above, the connection determination unit sets the control current as the determination current, and the potential of the pump current terminal 61 when the determination current is supplied is higher than the potential of the detection voltage terminal 63 It is determined that the pump current terminal 61 and the gas sensor element 11 are not electrically connected.

According to such a gas sensor control device 7, it can be determined whether or not the pump current terminal 61 and the gas sensor element 11 are electrically connected.
[3. Other embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, It is possible in the range which does not deviate from the summary of this invention to implement in various aspects.

  (1) For example, although the said embodiment demonstrated the embodiment which uses an oxygen sensor as a sensor, it may be a gas sensor which detects gas (for example, NOx etc.) other than oxygen. Further, the sensor is not limited to the gas sensor, and may be a sensor other than the gas sensor as long as the sensor includes the element portion and the heater.

  (2) Further, for example, the current supplied to the pump cell at the start of the internal combustion engine (that is, a constant current having a minute current value) is not limited to the minute current Icp or the disconnection detection current Ipoc described above, There are various types of current that can detect a drop in pump current at startup.

  (3) As the current supply unit for supplying current to the sensor element to determine the start of feedback control, as described above, the pump current supply unit (for example, the current DA supply unit 35) and the determination current supply unit (for For example, the current supply unit 39) may be separately provided, or the pump current supply unit may function as a determination current supply unit. Furthermore, the pump current supply unit may supply the disconnection detection current Ipoc, or the determination current supply unit may supply the disconnection detection current Ipoc.

(4) Further, it may be determined whether or not any one of the first terminal portion and the second terminal portion is normally connected to the gas sensor element. That is, the connection determination unit compares the potential of the first terminal portion with the potential of the second terminal portion when the control current is supplied as the determination current, and the initial current is the determination current. Whether or not the first terminal portion and the gas sensor element are electrically connected based on the comparison result of the potential of the first terminal portion and the potential of the second terminal portion when supplied as And it may be constituted so that it may be judged whether the 2nd terminal area and the gas sensor element are electrically connected.
According to such a sensor control device, it can be detected whether or not one of the first terminal portion and the second terminal portion is normally connected to the gas sensor element. In addition, it is possible to specify which of the first terminal portion and the second terminal portion is the terminal portion that is not normally connected.
(5) Further, the function possessed by one component in the above embodiment may be shared by a plurality of components, or the function possessed by a plurality of components may be exerted by one component. In addition, part of the configuration of each of the above embodiments may be omitted. In addition, at least a part of the configuration of each of the above-described embodiments may be added to or replaced with the configuration of the other above-described embodiments. In addition, all the aspects contained in the technical thought specified from the wording as described in a claim are an embodiment of this indication.

  (6) Further, the sensor control device is not limited to the form configured by the above-described ASIC, and may be configured to include, for example, a microcomputer (hereinafter also referred to as a microcomputer). The microcomputer includes a CPU, a ROM, a RAM, and a signal input / output unit. The various functions of such a sensor control device are realized by the CPU executing a program stored in a non-transitional tangible storage medium.

  In this example, the ROM corresponds to the non-transitional tangible storage medium storing the program. By executing this program, a method corresponding to the program is executed. The signal input / output unit transmits / receives various signals to / from an external device.

  The number of CPUs, ROMs, RAMs and signal input / output units that constitute the microcomputer may be one or more. Further, part or all of the functions executed by the microcomputer may be configured as hardware by one or a plurality of ICs or the like.

  (7) The present disclosure relates to various systems such as a system having the microcomputer as a component, a program for causing a computer to function as the microcomputer, and a recording medium such as a semiconductor memory storing the program. The present disclosure can also be realized in a form.

[4. Correspondence between the configuration of the embodiment and the configuration of the present disclosure]
In the above embodiment, the detection voltage terminal 63, the pump current terminal 61, the reference potential terminal 65, the current supply unit 39, the terminal monitoring unit 67, and the reference potential generation unit 41 are sequentially referred to as a first terminal unit in the present disclosure, The second terminal unit corresponds to a third terminal unit, an initial supply unit, a potential acquisition unit, and a potential setting unit. Further, in the above embodiment, the pump current calculation unit 34 and the current DA conversion unit 35 correspond to the control supply unit in the present disclosure. Further, in the above-described embodiment, the PID operation unit 33, the pump current operation unit 34, and the current DA conversion unit 35 correspond to the pump supply unit in the present disclosure.

  Further, in the above-described embodiment, substantially the whole of the terminal open identification processing corresponds to the connection determination unit in the present disclosure, and the configuration in which S220 is not performed due to the positive determination of S140 in the terminal open identification processing is , Corresponds to the pump prohibition portion in the present disclosure.

  DESCRIPTION OF SYMBOLS 1 ... Gas detection system, 3 ... Gas detection apparatus, 5 ... Gas sensor, 7 ... Sensor control apparatus, 9 ... Engine control apparatus, 11 ... Sensor element, 13 ... Heater, 15 ... Pump cell, 17 ... Solid electrolyte body, 19 ... Porosity Quality electrode 31 analog digital conversion unit (AD conversion unit) 33 PID operation unit 34 pump current operation unit 35 current digital analog conversion unit (current DA conversion unit) 39 current supply unit 41 Reference potential generation unit 43: Pump voltage determination unit 45: Control start unit 61: Pump current terminal (Ip + terminal) 63: Detection voltage terminal (Vs + terminal) 65: Reference potential terminal (COM terminal)

Claims (5)

A gas sensor control device comprising: a first terminal portion electrically connected to a gas sensor element including a solid electrolyte body and a cell having a pair of electrodes provided on the solid electrolyte body; a second terminal portion; and a third terminal portion ,
The gas sensor control device
The first terminal portion and the second terminal portion are electrically connected in a state in which the first terminal portion and the second terminal portion are electrically connected on the gas sensor element side with respect to the first terminal portion and the second terminal portion. It is configured to be electrically connected to one of the pair of electrodes, and to electrically connect the third terminal portion to the other of the pair of electrodes,
A potential setting unit that sets the third terminal unit to a reference potential;
A pump supply unit for supplying a pump current to the gas sensor element via the second terminal portion such that a potential generated between the first terminal portion and the third terminal portion becomes a target value;
A control supply unit that supplies a test current for detecting a state of the gas sensor element or a control current representing the pump current to the gas sensor element via the second terminal portion;
An initial supply unit that supplies an initial current to the gas sensor element via the first terminal before the control current is supplied;
A potential acquisition unit that acquires the potentials of the first terminal unit and the second terminal unit;
The control current or the initial current is switched and used as a determination current, and the potentials of the first terminal portion and the second terminal portion when the determination current is supplied are compared with each other. A connection determination unit that determines whether or not at least one of the first terminal unit and the second terminal unit is electrically connected to the gas sensor element;
Sensor control device equipped with The sensor control device according to claim 1, wherein
The connection determination unit sets the initial current as the determination current, and when the potential of the second terminal when the determination current is supplied is lower than the potential of the first terminal. The sensor control apparatus comprised so that it might determine that the terminal part and the said gas sensor element are not electrically connected. The sensor control device according to claim 1, wherein
The connection determination unit monitors a drop in the potential of the first terminal portion and the second terminal portion while the initial current is supplied as the determination current, and a drop rate of the potential of the first terminal portion The sensor control device is configured to determine that the first terminal portion and the gas sensor element are not electrically connected when the velocity of the second terminal portion is slower than the potential drop speed of the second terminal portion. A sensor control apparatus according to claim 2 or 3, wherein
Sensor control further comprising a pump inhibiting unit that inhibits the control supply unit from supplying the control current when it is determined that the first terminal unit and the gas sensor element are not electrically connected. apparatus. The sensor control device according to any one of claims 1 to 4, wherein
The connection determination unit sets the control current as the determination current, and when the potential of the second terminal when the determination current is supplied is higher than the potential of the first terminal, The sensor control apparatus comprised so that it might determine that the terminal part and the said gas sensor element are not electrically connected.

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