JP7128090B2 - Sensor control device and sensor control method - Google Patents

Description

The present disclosure relates to a sensor control device and a sensor control method for controlling a gas sensor that detects the concentration of a specific gas contained in exhaust gas.

Patent Document 1 discloses a device that detects the concentration of a specific gas contained in exhaust gas based on the value of current Ip both when the air-fuel ratio is on the lean side and when the air-fuel ratio is on the rich side. Have been described.

Japanese Patent Publication No. 6-16025

However, in the device that detects the concentration of the specific gas based on the value of the current Ip, there is a problem that the detection accuracy of the concentration of the specific gas contained in the exhaust gas decreases when the air-fuel ratio is on the rich side.

An object of the present disclosure is to improve the detection accuracy of the specific gas concentration when the air-fuel ratio is on the rich side.

One aspect of the present disclosure is a sensor control device that controls a gas sensor that detects the concentration of a specific gas contained in exhaust gas discharged from an internal combustion engine. The gas sensor includes a reference oxygen chamber into which air is introduced, a solid electrolyte body, an exhaust gas side electrode disposed on the solid electrolyte body and exposed to the exhaust gas, and disposed on the solid electrolyte body facing the reference oxygen chamber. and a cell having an air-side electrode.

A sensor control device according to the present disclosure includes a condition determination section and a current supply section. The condition determination unit is configured to determine whether the air-fuel ratio of the exhaust gas is equal to or less than a predetermined switching air-fuel ratio under a condition that the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio. The current supply unit is configured to supply a concentration detection current, the value of which varies according to the concentration of the specific gas, between the exhaust gas side electrode and the atmosphere side electrode.

Then, when the condition determination unit determines that the air-fuel ratio of the exhaust gas is greater than the switching air-fuel ratio, the current supply unit continuously flows the concentration detection current between the exhaust gas side electrode and the atmosphere side electrode. Further, when the condition determination unit determines that the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio, the current supply unit is in a supply state in which the concentration detection current is supplied between the exhaust gas side electrode and the atmosphere side electrode. , and a supply stop state in which no concentration detection current flows between the exhaust gas side electrode and the atmosphere side electrode are alternately repeated.

The sensor control device of the present disclosure, configured in this manner, stops the supply of oxygen when the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio, thereby preventing oxygen from flowing from the atmosphere-side electrode to the exhaust gas-side electrode. It is possible to stop the movement and suppress the decrease in the oxygen concentration in the reference oxygen chamber. Oxygen is supplied into the reference oxygen chamber by the atmosphere introduced into the reference oxygen chamber when the supply is stopped. Therefore, the sensor control device of the present disclosure can increase the oxygen in the reference oxygen chamber by setting the supply stop state as described above.

As a result, the sensor control device of the present disclosure provides the above supply state when the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio. Therefore, it is possible to suppress the occurrence of a situation in which the concentration detection current does not correspond to the concentration of the specific gas. Therefore, the sensor control device of the present disclosure can improve the detection accuracy of the specific gas concentration when the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio.

Further, in one aspect of the present disclosure, the current supply unit changes the supply stop state according to the air-fuel ratio of the exhaust gas when the condition determination unit determines that the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio. You may make it change the time which continues. As a result, the sensor control device of the present disclosure can supply the concentration detection current after an appropriate period of time corresponding to the air-fuel ratio of the exhaust gas has passed. can be suppressed.

Further, in one aspect of the present disclosure, the current supply unit continues the supply state according to the air-fuel ratio of the exhaust gas when the condition determination unit determines that the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio. You may make it change time to carry out. As a result, the sensor control device of the present disclosure can suppress the occurrence of a situation in which the detection accuracy of the specific gas concentration is lowered due to insufficient oxygen in the reference oxygen chamber while the concentration detection current is flowing.

Further, in one aspect of the present disclosure, the concentration detection current may be used at least after a preset waiting time has elapsed after switching from the supply stop state to the supply state. As a result, the sensor control device of the present disclosure calculates the concentration of the specific gas using the value of the concentration detection current when the value of the concentration detection current is not stable immediately after switching from the supply stop state to the supply state. It is possible to suppress the occurrence of a situation where the concentration of the specific gas is detected, and to further improve the detection accuracy of the concentration of the specific gas.

Further, in one aspect of the present disclosure, the switching air-fuel ratio may be an air-fuel ratio of 12.2 or less.
Another aspect of the present disclosure is a sensor control method for controlling a gas sensor that detects the concentration of a specific gas contained in exhaust gas discharged from an internal combustion engine.

A sensor control method of the present disclosure includes a condition determination procedure and a current supply procedure. The condition determination procedure determines whether or not the air-fuel ratio of the exhaust gas is equal to or less than a predetermined switching air-fuel ratio under the condition that the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio. In the current supply procedure, a concentration detection current whose value varies according to the concentration of the specific gas is passed between the exhaust gas side electrode and the atmosphere side electrode.

Then, when the condition determination procedure determines that the air-fuel ratio of the exhaust gas is greater than the switching air-fuel ratio, the current supply unit continues to flow the concentration detection current between the exhaust gas side electrode and the atmosphere side electrode. Further, when the condition determination procedure determines that the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio, the current supply procedure changes to a supply state in which the concentration detection current flows between the exhaust gas side electrode and the atmosphere side electrode. , and a supply stop state in which no concentration detection current flows between the exhaust gas side electrode and the atmosphere side electrode are alternately repeated.

The sensor control method of the present disclosure configured in this manner is a method executed by the sensor control device of the present disclosure, and by executing the method, the same effects as those of the sensor control device of the present disclosure can be obtained. can be done.

1 is a diagram showing a schematic configuration of a system including a sensor control device as a component; FIG. It is a figure which shows schematic structure of a sensor control apparatus and a gas sensor. FIG. 2 is a cross-sectional view of a sensor element; 4 is a flowchart showing switch control processing; 4 is a flowchart showing on/off control processing; 4 is a graph showing changes in pump current over time;

Embodiments of the present disclosure will be described below with reference to the drawings.
A sensor control device 1 of this embodiment is mounted on a vehicle and controls a gas sensor 3 as shown in FIG.

The sensor control device 1 is configured to be able to transmit and receive data via a communication line 8 to and from an electronic control device 9 that controls the engine 5 . The electronic control unit 9 is hereinafter referred to as an engine ECU 9 . ECU is an abbreviation for Electronic Control Unit.

The gas sensor 3 is attached to the exhaust pipe 7 of the engine 5 and detects the oxygen concentration in the exhaust gas over a wide range, and is also called a linear lambda sensor.
The gas sensor 3 includes a sensor element 11 and a heater 12, as shown in FIG.

The sensor element 11 comprises a pump cell 13 . The pump cell 13 includes an oxygen ion conductive solid electrolyte body 14 made of partially stabilized zirconia in the form of a plate, and pump electrodes 15 and 16 made mainly of platinum on the front and back surfaces thereof, respectively.

The sensor element 11 includes a measurement chamber 17 and a reference oxygen chamber 18 inside the sensor element 11, as shown in FIG. Pump electrode 15 is exposed to measurement chamber 17 and pump electrode 16 is exposed to reference oxygen chamber 18 . A gas to be measured is introduced from the outside of the sensor element 11 into the measurement chamber 17 through the porous diffusion layer 19 . Air as a reference gas is introduced into the reference oxygen chamber 18 from the outside of the sensor element 11 .

The sensor element 11 is an oxygen sensor element that detects oxygen concentration by a so-called limiting current method. The output characteristic indicating the relationship between the voltage applied between the pair of pump electrodes 15 and 16 (hereinafter referred to as sensor element voltage Vp) and the current flowing between the pair of pump electrodes 15 and 16 (hereinafter referred to as pump current Ip) is It has a proportional area and a flat area. In the proportional region, the pump current Ip changes in proportion to the increase in the sensor element voltage Vp. In the flat region, even if the sensor element voltage Vp changes, the pump current Ip does not substantially change and keeps a constant value.

This flat area is a flat area parallel to the voltage axis of the output characteristics, that is, a limit current area where the pump current Ip is constant (hereinafter referred to as a limit current area).
It is known that the pump current Ip in this limit current region has a value corresponding to the oxygen concentration, and increases as the oxygen concentration increases. That is, the higher the oxygen concentration in the exhaust gas (that is, the leaner the air-fuel ratio is), the higher the limit current of the pump current Ip, and the lower the oxygen concentration in the exhaust gas (that is, the richer the air-fuel ratio is). ), the limiting current decreases. Therefore, the oxygen concentration in the exhaust gas can be detected by applying a sensor element voltage Vp corresponding to the limit current range to the pump cell 13 of the sensor element 11 and measuring the pump current Ip obtained thereby. can be done.

As shown in FIG. 2, the heater 12 is made of a material mainly composed of alumina, and has a heating resistor inside which is made of a material mainly composed of platinum. The heater 12 is controlled by electric power supplied from the sensor control device 1 so that the temperature of the sensor element 11 becomes the activation temperature. Both ends of the heating resistor are electrically connected to the sensor control device 1 . The gas sensor 3 becomes capable of detecting gas when the sensor element 11 is activated by heating by the heater 12 .

The sensor control device 1 includes a CAN interface circuit 21 (hereinafter, CAN I/F circuit 21), a control circuit 22, a microcomputer 23 (hereinafter, microcomputer 23), connection terminals 24, 25, 26, 27, and a switch 28. and CAN is an abbreviation for Controller Area Network. Also, CAN is a registered trademark.

The CAN I/F circuit 21 transmits and receives data to and from the engine ECU 9 via the communication line 8 according to the CAN communication protocol.
Control circuit 22 is implemented in an application specific integrated circuit (ie, an ASIC). ASIC is an abbreviation for Application Specific IC.

The control circuit 22 includes a reference voltage generation unit 31, a current application unit 32, an analog-digital conversion unit 33 (hereinafter referred to as AD conversion unit 33), a PID calculation unit 34, a current digital-analog conversion unit 35 (hereinafter referred to as current DA conversion unit 35). , Rpvs calculation unit 36 , duty calculation unit 37 and heater driving unit 38 . The control circuit 22 also includes a pump current terminal 41 (hereinafter referred to as Ip+ terminal 41), a detection voltage terminal 42 (hereinafter referred to as Vs+ terminal 42), a common terminal 43 (hereinafter referred to as COM terminal 43) and a heater terminal 44 (hereinafter referred to as HTR+ terminal 44). ).

The Ip+ terminal 41 and the Vs+ terminal 42 are connected to the connection terminal 25 of the sensor control device 1 . The COM terminal 43 is connected to the connection terminal 24 of the sensor control device 1 . The pump electrodes 15 and 16 of the sensor element 11 are connected to connection terminals 24 and 25 of the sensor control device 1, respectively. Also, the HTR+ terminal 44 is connected to the connection terminal 26 of the sensor control device 1 . Both ends of the heater 12 are connected to connection terminals 26 and 27 of the sensor control device 1, respectively. Incidentally, the connection terminal 27 is grounded.

The reference voltage generator 31 generates a reference voltage applied to the COM terminal 43 . In this embodiment, the reference voltage is 2.7V.
The current application unit 32 supplies the minute current Icp and the pulse current Irpvs for detecting the internal resistance value of the pump cell 13 to the sensor element 11 via the Vs+ terminal 42 . The current application unit 32 does not always supply the minute current Icp and the pulse current Irpvs, but supplies the minute current Icp and the pulse current Irpvs at appropriate times based on commands from the microcomputer 23 .

The AD converter 33 converts the voltage value of the analog signal input from the Vs+ terminal 42 into digital data, and outputs the digital data to the PID calculator 34 and the Rpvs calculator 36 .
Based on the digital data input from the AD conversion unit 33, the PID calculation unit 34 adjusts the voltage difference between the voltage at the Vs+ terminal 42 and the voltage at the COM terminal 43 to a preset control reference voltage. A PID calculation is performed for PID-controlling the pump current Ip. In this embodiment, the control reference voltage is 450 mV. PID calculation unit 34 calculates the value of pump current Ip by PID calculation, and outputs digital data indicating this current value to current DA conversion unit 35 .

The current DA converter 35 supplies a current having a current value indicated by the digital data input from the PID calculator 34 to the sensor element 11 via the Ip+ terminal 41 .
The Rpvs calculation unit 36 performs calculation for calculating the internal resistance value Rpvs of the pump cell 13 based on the digital data input from the AD conversion unit 33 while the current application unit 32 is supplying the pulse current Irpvs. Then, digital data indicating this internal resistance value Rpvs is output to the duty calculation section 37 .

Based on the digital data input from the Rpvs calculation unit 36, the duty calculation unit 37 calculates the amount of heat generated by the heater required to maintain the temperature of the sensor element 11 at a preset sensor target temperature. Then, the duty calculation unit 37 calculates the duty ratio of the electric power supplied to the heater 12 based on the calculated amount of heat generated by the heater. Furthermore, the duty calculation unit 37 generates a PWM control signal according to the calculated duty ratio, and outputs this PWM control signal to the heater driving unit 38 . PWM is an abbreviation for Pulse Width Modulation.

The heater drive unit 38 PWM-controls the voltage Vh supplied to both ends of the heater 12 based on the PWM control signal input from the duty calculation unit 37 to cause the heater 12 to generate heat.
The microcomputer 23 has a CPU 51 , a ROM 52 and a RAM 53 . Various functions of the microcomputer are realized by the CPU 51 executing a program stored in a non-transitional substantive recording medium. In this example, the ROM 52 corresponds to the non-transitional substantive recording medium storing the program. Also, by executing this program, a method corresponding to the program is executed. Note that the number of microcomputers constituting the sensor control device 1 may be one or more. Also, part or all of the functions executed by the microcomputer 23 may be configured as hardware using one or a plurality of ICs or the like.

Based on the program stored in the ROM 52, the CPU 51 executes a process of controlling the sensor element 11 and a process of calculating the oxygen concentration based on the direction of flow of the pump current Ip and the magnitude of the pump current Ip.

The switch 28 is arranged on a conducting path that electrically connects the Ip+ terminal 41 and the connection terminal 25 . Based on the control signal from the microcomputer 23, the switch 28 electrically disconnects the Ip+ terminal 41 and the connection terminal 25 from the ON state in which the Ip+ terminal 41 and the connection terminal 25 are electrically connected. It is driven to be in either an off state or an off state.

Further, the CPU 51 of the microcomputer 23 executes switch control processing. The switch control process is started after the sensor element 11 is activated by heating by the heater 12 .
When the switch control process is executed, the CPU 51 first starts continuous ON control in S10 as shown in FIG. When continuous ON control is started, the CPU 51 first turns on the switch 28 . Then, the CPU 51 acquires digital data indicating the value of the pump current Ip (hereinafter referred to as the pump current value) from the control circuit 22 every time a preset acquisition period (eg, 1 ms in this embodiment) elapses. By starting the continuous ON control, the ON/OFF control, which will be described later, ends.

Next, in S20, it is determined whether or not the air-fuel ratio of the exhaust gas is equal to or lower than a preset switching air-fuel ratio (eg, 12.2 in this embodiment). Incidentally, the state in which the air-fuel ratio is 12.2 corresponds to the state in which the excess air ratio λ is 0.84. In addition, when the exhaust gas is discharged from the engine 5 due to the combustion of the air-fuel mixture in the engine 5, the air-fuel ratio of the air-fuel mixture that caused the generation of this exhaust gas is referred to as the "air-fuel ratio of the exhaust gas". . For example, the air-fuel ratio of the exhaust gas discharged from the combustion of the air-fuel mixture with the air-fuel ratio of 12.5 in the engine 5 is 12.5. Further, the air-fuel ratio of the exhaust gas discharged by the combustion of the air-fuel mixture whose air-fuel ratio is the stoichiometric air-fuel ratio (that is, 14.55) is the stoichiometric air-fuel ratio.

Then, in S20, the CPU 51 acquires air-fuel ratio instruction information that instructs the air-fuel ratio of the air-fuel mixture from the engine ECU 9, and if the air-fuel ratio indicated by the air-fuel ratio instruction information is equal to or lower than the switching air-fuel ratio, the air-fuel ratio of the exhaust gas is equal to or less than the switching air-fuel ratio.

Here, when the air-fuel ratio of the exhaust gas exceeds the switching air-fuel ratio, the process of S20 is repeated to wait until the air-fuel ratio of the exhaust gas becomes equal to or lower than the switching air-fuel ratio. On the other hand, when the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio, the on/off control is started in S30. As a result, the CPU 51 starts on/off control processing, which will be described later. Note that the continuous ON control ends by starting the ON/OFF control process.

Then, in S40, it is determined whether or not the air-fuel ratio of the exhaust gas exceeds the switching air-fuel ratio. Here, when the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio, the process of S40 is repeated to wait until the air-fuel ratio of the exhaust gas exceeds the switching air-fuel ratio. On the other hand, when the air-fuel ratio of the exhaust gas exceeds the switching air-fuel ratio, the process proceeds to S10.

Next, the procedure of on/off control processing executed by the CPU 51 will be described. The on/off control process is executed when the CPU 51 starts on/off control in the switch control process.

When the on/off control process is executed, the CPU 51 first turns on the switch 28 in S110, as shown in FIG. Then, in S120, it is determined whether or not a preset acquisition start time (for example, 200 ms in this embodiment) has elapsed since the switch 28 was turned on in S110. Here, if the acquisition start time has not elapsed, the process of S120 is repeated to wait until the acquisition start time has elapsed. On the other hand, if the acquisition start time has elapsed, digital data indicating the pump current value is acquired from the control circuit 22 in S130.

Then, in S140, it is determined whether or not a preset acquisition cycle (for example, 1 ms in this embodiment) has elapsed since the digital data was acquired in S130. Here, if the acquisition period has not elapsed, the process of S140 is repeated to wait until the acquisition period has elapsed. On the other hand, if the acquisition period has elapsed, it is determined in S150 whether or not a preset on end time (eg, 300 ms in this embodiment) has elapsed since the switch 28 was turned on in S110. .

Here, if the ON end time has not elapsed, the process proceeds to S130. On the other hand, if the on end time has elapsed, the switch 28 is turned off in S160. Then, in S170, it is determined whether or not a preset OFF end time (for example, 1000 ms in this embodiment) has elapsed since the switch 28 was turned on in S110.

Here, if the OFF end time has not elapsed, the process of S170 is repeated to wait until the OFF end time has elapsed. On the other hand, when the OFF end time has elapsed, the process proceeds to S110.

FIG. 6 is a graph showing temporal changes in the pump current Ip flowing through the sensor element 11 when the excess air ratio λ is 0.82, 0.83, 0.84, 0.85 and 0.89. Note that the smaller the excess air ratio λ, the richer the air-fuel ratio becomes.

As shown in FIG. 6, the pump current value when the excess air ratio λ is 0.85 and 0.89 always maintains a value corresponding to the oxygen concentration in the exhaust gas. The pump current value when the excess air ratio λ is 0.84 maintains the value according to the oxygen concentration in the exhaust gas until about 5 seconds have passed, and then fluctuates. The pump current value when the excess air ratio λ is 0.83 maintains the value according to the oxygen concentration in the exhaust gas until about 4 seconds have passed, and then fluctuates. The pump current value when the excess air ratio λ is 0.82 maintains the value according to the oxygen concentration in the exhaust gas until about 3 seconds have passed, and then fluctuates.

Thus, the smaller the excess air ratio λ, the shorter the time for maintaining the pump current value corresponding to the oxygen concentration in the exhaust gas. This is because as the excess air ratio λ becomes smaller, the amount of oxygen that moves from the reference oxygen chamber 18 side to the measurement chamber 17 side via the oxygen ion conductive solid electrolyte body 14 increases, and the oxygen in the reference oxygen chamber 18 increases. This is because the time until the shortage is short.

The sensor control device 1 configured in this way controls the gas sensor 3 that detects the concentration of oxygen contained in the exhaust gas discharged from the engine 5 . The gas sensor 3 includes a reference oxygen chamber 18 into which air is introduced, an oxygen ion conductive solid electrolyte body 14, a pump electrode 15 arranged on the oxygen ion conductive solid electrolyte body 14 and exposed to the exhaust gas, an oxygen ion a pump cell 13 having a pump electrode 16 disposed on a conductive solid electrolyte body 14 facing a reference oxygen chamber 18;

The sensor control device 1 determines whether the air-fuel ratio of the exhaust gas is equal to or less than a predetermined switching air-fuel ratio under the condition that the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio. The sensor control device 1 causes a pump current Ip whose value varies according to the concentration of oxygen to flow between the pump electrodes 15 and 16 .

Then, when determining that the air-fuel ratio of the exhaust gas is higher than the switching air-fuel ratio, the sensor control device 1 continues to flow the pump current Ip between the pump electrodes 15 and 16 . Further, when it is determined that the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio, the sensor control device 1 sets the supply state in which the pump current Ip flows between the pump electrodes 15 and 16, and the pump electrode 15 and the pump electrode 16 alternately repeat a supply stop state in which the pump current Ip does not flow.

In this way, the sensor control device 1 stops the movement of oxygen from the pump electrode 16 to the pump electrode 15 by setting the above-described supply stop state when the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio. A decrease in oxygen concentration in the oxygen chamber 18 can be suppressed. Oxygen is supplied into the reference oxygen chamber 18 by the atmosphere introduced into the reference oxygen chamber 18 in the supply stop state. Therefore, the sensor control device 1 can increase the oxygen concentration in the reference oxygen chamber 18 by setting the supply stop state as described above.

As a result, the sensor control device 1 maintains the supply state as described above when the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio. Therefore, it is possible to suppress the occurrence of a situation in which the pump current Ip does not reach a value corresponding to the oxygen concentration. Therefore, the sensor control device 1 can improve the detection accuracy of the concentration of oxygen when the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio.

Further, even when the value of the pump current Ip detected by the gas sensor 3 exposed to the atmospheric atmosphere (hereinafter referred to as the atmospheric Ip value) is increased, the sensor control device 1 does not exceed the detection limit of the air-fuel ratio on the rich side. Decrease can be suppressed. By increasing the atmospheric Ip value, it is possible to improve the detection accuracy of the oxygen concentration. In other words, when the value of the pump current Ip deviates, the deviation when converting the pump current Ip into the air-fuel ratio can be reduced.

Further, the sensor control device 1 uses the pump current Ip at least after a preset acquisition start time has elapsed after switching from the supply stop state to the supply state. In this embodiment, the sensor control device 1 acquires digital data indicating the pump current value from the control circuit 22 as the use of the pump current Ip. This prevents the sensor control device 1 from specifying the oxygen concentration using the value of the pump current Ip when the value of the pump current Ip is not stable immediately after switching from the supply stop state to the supply state. It is possible to suppress the generation and further improve the detection accuracy of the concentration of oxygen.

In the embodiment described above, the oxygen ion conductive solid electrolyte body 14 corresponds to the solid electrolyte body, the pump electrode 15 corresponds to the exhaust gas side electrode, the pump electrode 16 corresponds to the atmosphere side electrode, and the pump cell 13 corresponds to the cell. corresponds to

Further, the engine 5 corresponds to an internal combustion engine, oxygen corresponds to a specific gas, pump current Ip corresponds to a concentration detection current, and current DA conversion section 35 corresponds to a current supply section.
Further, S20 corresponds to processing as a condition determination unit and condition determination procedure, S10, S30, S110, S150, S160, and S170 correspond to processing as a current supply unit and current supply procedure, and the acquisition start time is the standby time. corresponds to

An embodiment of the present disclosure has been described above, but the present disclosure is not limited to the above embodiment, and can be implemented in various modifications.
For example, in the above-described embodiment, the switch 28 is switched from the off state to the on state after the off end time has elapsed since the switch 28 was turned on. However, when the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio, the time for which the off state continues (that is, the time corresponding to (off end time - on end time)) is changed according to the air-fuel ratio of the exhaust gas. You may make it change. As a result, the sensor control device 1 can supply the pump current Ip after an appropriate period of time corresponding to the air-fuel ratio of the exhaust gas has elapsed, thereby preventing the period in which the oxygen concentration cannot be detected from becoming unnecessarily long. can.

In the above-described embodiment, the mode in which the switch 28 is turned off after the on end time has elapsed since the switch 28 was turned on has been described. However, when the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio, the ON end time may be changed according to the air-fuel ratio of the exhaust gas. Specifically, the ON end time is shortened as the air-fuel ratio of the exhaust gas becomes smaller. As a result, the sensor control device 1 can suppress the occurrence of a situation in which the oxygen concentration in the reference oxygen chamber 18 runs short while the pump current Ip is flowing, and the detection accuracy of the oxygen concentration decreases.

In the above-described embodiment, it is determined whether or not the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio based on the air-fuel ratio instruction information acquired from the engine ECU 9 . However, based on the detection result of the gas sensor 3, it may be determined whether the air-fuel ratio of the exhaust gas is equal to or lower than the switching air-fuel ratio.

In the above embodiment, the sensor control device 1 switches from the supply stop state to the supply state. A mode is shown in which digital data indicating a pump current value (hereinafter referred to as pump current data) is acquired from the control circuit 22 after a preset acquisition start time has elapsed. However, the sensor control device 1 may switch from the supply stop state to the supply state and continuously acquire the pump current data, but may calculate the gas concentration after a preset time has elapsed. Further, the sensor control device 1 switches from the supply stop state to the supply state, continuously acquires the pump current data, and calculates the gas concentration based on the acquired pump current data. After that, gas concentration information indicating the calculated gas concentration may be transmitted to the engine ECU 9 . Also, the engine ECU 9 may receive the gas concentration information from the sensor control device 1 after a preset time has elapsed. Further, when the sensor control device 1 and the air-fuel ratio control device are installed in the engine ECU 9, the sensor control device 1 acquires pump current data, and calculates gas concentration information based on the acquired pump current data. may be transmitted to the air-fuel ratio control device. Then, the sensor control device 1 switches from the supply stop state to the supply state, continues to acquire pump current data, and continues to transmit gas concentration information to the air-fuel ratio control device. The gas concentration information from the control device 1 may be continuously received. In this case, the sensor control device 1 causes the air-fuel ratio control device to use the gas concentration information received from the sensor control device 1 for air-fuel ratio control after a preset time has elapsed. good too.

Further, in the above embodiment, an oxygen sensor is used as a gas sensor, but a gas sensor that detects gases other than oxygen (for example, NOx) may be used. Further, even when an oxygen sensor is used as a sensor, it is not limited to a sensor element that detects the oxygen concentration by a limiting current method while using one cell as in the above embodiment. For example, an oxygen pump cell having a pair of electrodes. and an oxygen concentration detection cell having a pair of electrodes.

Also, the function of one component in the above embodiment may be assigned to a plurality of components, or the function of a plurality of components may be performed by one component. Also, part of the configuration of the above embodiment may be omitted. Also, at least a part of the configuration of the above embodiment may be added, replaced, etc. with respect to the configuration of the other above embodiment.

In addition to the sensor control device 1 described above, there are various forms such as a system having the sensor control device 1 as a component, a program for causing a computer to function as the sensor control device 1, a medium recording this program, and a sensor control method. The present disclosure can also be realized in

DESCRIPTION OF SYMBOLS 1... Sensor control apparatus 3... Gas sensor 5... Engine 13... Pump cell 14... Oxygen ion conductive solid electrolyte body 15, 16... Pump electrode 18... Reference oxygen chamber

Claims (6)

A sensor control device for controlling a gas sensor that detects the concentration of a specific gas contained in exhaust gas emitted from an internal combustion engine,
The gas sensor is
a reference oxygen chamber into which atmospheric air is introduced;
A cell having a solid electrolyte body, an exhaust gas side electrode disposed on the solid electrolyte body and exposed to the exhaust gas, and an atmosphere side electrode disposed on the solid electrolyte body facing the reference oxygen chamber. and
The sensor control device
It is configured to determine whether or not the air-fuel ratio indicated by the air-fuel ratio information acquired from the internal combustion engine is equal to or less than a predetermined switching air-fuel ratio under the condition that the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio. a condition determination unit;
a current supply unit configured to supply a concentration detection current, the value of which varies depending on the concentration of the specific gas, between the exhaust gas side electrode and the air side electrode;
When the condition determination unit determines that the air-fuel ratio indicated by the air-fuel ratio information is greater than the switching air-fuel ratio, the current supply unit supplies the concentration detection current between the exhaust gas side electrode and the atmosphere side electrode. flowing continuously between
When the condition determination unit determines that the air-fuel ratio indicated by the air-fuel ratio information is equal to or less than the switching air-fuel ratio, the current supply unit causes the concentration A sensor control device that alternately repeats a supply state in which the detection current flows and a supply stop state in which the concentration detection current does not flow between the exhaust gas side electrode and the atmosphere side electrode. The sensor control device of claim 1,
The current supply unit continues the supply stop state according to the air-fuel ratio of the exhaust gas when the condition determination unit determines that the air-fuel ratio indicated by the air-fuel ratio information is equal to or less than the switching air-fuel ratio. A sensor control device that changes the time to The sensor control device according to claim 1 or claim 2,
The current supply unit continues the supply state according to the air-fuel ratio of the exhaust gas when the condition determination unit determines that the air-fuel ratio indicated by the air-fuel ratio information is equal to or less than the switching air-fuel ratio. A sensor control device that changes time. The sensor control device according to any one of claims 1 to 3,
A sensor control device that utilizes the concentration detection current at least after a preset standby time has elapsed after switching from the supply stop state to the supply state. The sensor control device according to any one of claims 1 to 4,
The sensor control device, wherein the switching air-fuel ratio is a predetermined air-fuel ratio of 12.2 or less. A sensor control method for controlling a gas sensor that detects the concentration of a specific gas contained in exhaust gas emitted from an internal combustion engine, comprising:
The gas sensor is
a reference oxygen chamber into which atmospheric air is introduced;
A cell having a solid electrolyte body, an exhaust gas side electrode disposed on the solid electrolyte body and exposed to the exhaust gas, and an atmosphere side electrode disposed on the solid electrolyte body facing the reference oxygen chamber. and
The sensor control method includes:
a condition determination procedure for determining whether or not the air-fuel ratio indicated by the air-fuel ratio information obtained from the internal combustion engine is equal to or less than a predetermined switching air-fuel ratio under the condition that the air-fuel ratio of the exhaust gas is smaller than the stoichiometric air-fuel ratio;
a current supply step of supplying a concentration detection current, the value of which varies depending on the concentration of the specific gas, between the exhaust gas side electrode and the air side electrode;
When the condition determination procedure determines that the air-fuel ratio indicated by the air-fuel ratio information is greater than the switching air-fuel ratio, the current supply procedure transfers the concentration detection current between the exhaust gas side electrode and the atmosphere side electrode. flowing continuously between
When the condition determination procedure determines that the air-fuel ratio indicated by the air-fuel ratio information is equal to or lower than the switching air-fuel ratio, the current supply procedure is to provide the concentration A sensor control method that alternately repeats a supply state in which a detection current flows and a supply stop state in which the concentration detection current does not flow between the exhaust gas side electrode and the atmosphere side electrode.

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