Abstract: A sensor controller for a particulate matter detection sensor includes a signal output circuit connected to the particulate matter detection sensor such that a sensor detection value is changeable in a predetermined output range by the signal output circuit, a heater configured to heat an attachment portion so as to burn and remove particulate matter attached to the attachment portion, a learning portion for calculating a sensor standard value in a state where the resistance between a pair of opposed electrodes is reduced based on an obtained sensor detection value and for storing the sensor standard value as a learning value, and a correcting portion for correcting the sensor detection value based on the sensor standard value stored by the learning portion.

Abstract: A deterioration diagnosis device, which performs a deterioration diagnosis of a catalyst, includes an exhaust-gas sensor provided downstream of the catalyst in a flow direction of exhaust gas such that an output value of the exhaust-gas sensor is used at least in the deterioration diagnosis. The deterioration diagnosis device further includes the constant current supply portion which applies a voltage to a sensor element of the exhaust-gas sensor to change an output characteristic of the exhaust-gas sensor, a response-time detection portion which detects a response time required for the output value of the exhaust-gas sensor to change from a rich threshold to a lean threshold, a response-time correction portion which controls the constant current supply portion to change the output characteristic of the exhaust-gas sensor so as to shorten the response time when the response time is longer than a predetermined reference time.

Abstract: A sensor controller is for a particulate matter detection sensor that includes a pair of opposed electrodes spaced from each other and disposed on an attachment portion. The sensor controller includes a calculation portion configured to calculate an amount of particulate matter attached to the particulate matter detection sensor based on a detection value from the particulate matter detection sensor, and a determination portion configured to determine whether water exists in the exhaust passage based on the detection value. Thus, it is possible to accurately determine whether water exists in the exhaust passage.

Abstract: An O2 sensor has a sensor element, which includes a solid electrolyte layer and a pair of electrodes. The solid electrolyte layer is held between the electrodes, which includes an atmosphere side electrode and an exhaust side electrode. A constant current circuit is installed in an electric path, which connects between the atmosphere side electrode and a ground, to induce a flow of a predetermined constant electric current between the electrodes through the solid electrolyte layer. When the sensor element generates an electromotive force, the constant current circuit conducts an electric current, which is generated while using the electromotive force of the sensor element as an electric power source, to induce the flow of the predetermined constant electric current between the electrodes in an electromotive force range, which is equal to or larger than an electromotive force of the sensor element generated at a stoichiometric air-to-fuel ratio.

Abstract: An O2 sensor has a sensor element, which includes a solid electrolyte layer and a pair of electrodes. The solid electrolyte layer is held between the electrodes, which includes an atmosphere side electrode and an exhaust side electrode. A constant current circuit is installed in an electric path, which connects between the atmosphere side electrode and a ground, to induce a flow of a predetermined constant electric current between the electrodes through the solid electrolyte layer. A voltage circuit is installed in an electric path, which connects between the exhaust side electrode and a ground, to increase an electric potential of the exhaust side electrode by a predetermined amount relative to an electric potential at an output side of the constant current circuit, from which the electric current flows out of the constant current circuit.

Abstract: An O2 sensor has a sensor element, which includes a solid electrolyte layer and a pair of electrodes. The solid electrolyte layer is held between the electrodes. The electrodes include an atmosphere side electrode, which becomes a positive side at a time of outputting an electromotive force from the sensor element, and an exhaust side electrode, which becomes a negative side at the time of outputting the electromotive force from the sensor element. A resistor is provided in an electric path that connects between the atmosphere side electrode and a ground. When the sensor element generates the electromotive force, the resistor conducts an electric current, which is generated while using the electromotive force as an electric power source, to induce a change in an output characteristic of the O2 sensor.

Abstract: A catalytic conversion characteristic of a catalyst, which indicates a relationship between an air-to-fuel ratio and a catalytic conversion efficiency of the catalyst, includes a second air-to-fuel ratio point, which is a point of starting an outflow of NOx from the catalyst and is located on a rich side of a first air-to-fuel ratio point that forms an equilibrium point for a rich component and oxygen. A constant current circuit, which induces a flow of an electric current from an exhaust side electrode to an atmosphere side electrode through a solid electrolyte layer in a sensor element, is connected to the sensor element. A microcomputer controls a current value of the electric current, which is induced by the constant current circuit, based on a difference between the first air-to-fuel ratio point and the second air-to-fuel ratio point at the catalyst.

Abstract: A constant current is made to flow between sensor electrodes by a constant current circuit provided in the outside of the oxygen sensor, whereby the output characteristics of an oxygen sensor can be changed. Further, when a specified current-switching-permission condition is met, a value of current flowing between the sensor electrodes is switched and a direct current resistance value (internal resistance value) of the oxygen sensor is computed from a difference in the output of the oxygen sensor and a difference in the value of the current between before and after switching the value of the current flowing between the sensor electrodes. Then, at the time of a constant current supply in which the constant current is made to flow between the sensor electrodes, in other words, when the output characteristics of the oxygen sensor are changed, an amount of output-voltage-variation is found from a constant current value and a direct resistance value at that time.

Abstract: In a system having an oxygen sensor arranged downstream of a NOx storage-reduction catalyst, a constant current is made to flow between sensor electrodes by a constant current circuit provided in the outside of the oxygen sensor, which makes it possible to change an output characteristic of the oxygen sensor. Further, during a lean combustion control of an engine, a sensing responsiveness to a lean component of the oxygen sensor is improved. In this way, when NOx (lean component) is emitted to the downstream of the catalyst, the NOx can be quickly sensed by the oxygen sensor. Meanwhile, during a rich combustion control of the engine, the sensing responsiveness to a rich component of the oxygen sensor is improved. In this way, when HC and CO (rich components) are emitted to the downstream of the catalyst, the HC and the CO can be quickly sensed by the oxygen sensor.

Abstract: An emission control system for an engine includes a catalyst and an exhaust-gas sensor provided downstream of the catalyst in a flow direction of exhaust gas. The exhaust-gas sensor includes a sensor element that includes a pair of electrodes and a solid electrolyte body located between the electrodes. The emission control system further includes a constant current supply portion that changes an output characteristic of the exhaust-gas sensor by applying a constant current between the electrodes, a rich direction control portion that performs a rich direction control after a fuelling-stop control, and a characteristic control portion that performs a rich responsiveness control during the rich direction control. In the rich direction control, an air-fuel ratio of the exhaust gas is made to be richer. In the rich responsiveness control, the constant current supply portion increases a detection responsiveness of the exhaust-gas sensor with respect to rich gas.

Abstract: An emission control system for an engine includes an upstream sensor provided upstream of a catalyst in a flow direction of exhaust gas, a downstream sensor provided downstream of the catalyst to detect an air-fuel ratio so that the air-fuel ratio approaches a target air-fuel ratio in a sub feedback control, a constant current supply portion which changes an output characteristic of the downstream sensor by applying a constant current on a pair of electrodes thereof. A characteristic control portion controls the constant current supply portion in the sub feedback control to advance a timing of lean detection of the downstream sensor when the air-fuel ratio is richer than the target air-fuel ratio, and to advance a timing of rich detection of the downstream sensor when the air-fuel ratio is leaner than the target air-fuel ratio.

Abstract: A particulate matter detection element includes a capacitance component disposed in parallel with a detected resistance RSEN. A direct current-power source that supplies a direct current (IDC) for particulate matter detection, and an alternating-current power source that supplies an alternating current (IAC) for disconnection detection are provided.

Abstract: An emission control system for an engine includes a catalyst and an exhaust-gas sensor provided downstream of the catalyst in a flow direction of exhaust gas. The exhaust-gas sensor includes a sensor element that includes a pair of electrodes and a solid electrolyte body located between the electrodes. The emission control system further includes a constant current supply portion that changes an output characteristic of the exhaust-gas sensor by applying a constant current between the electrodes, a catalytic-state determination portion which determines a rich/lean state of the catalyst, a rich direction control portion which performs and terminates a rich direction control depending on the rich/lean state of the catalyst, a lean direction control portion which performs a lean direction control after the rich direction control, and a characteristic control portion which performs a lean responsiveness control at least during the lean direction control.

Abstract: A gas sensor control apparatus is provided which controls an operation of a gas sensor made up of a solid electrolyte body and a pair of electrodes to output a signal indicating the concentration of a given gas component contained in gas. The gas sensor control apparatus includes a constant current circuit that is connected electrically to one of the electrodes of the gas sensor and supplies a constant current thereto and a controller. The controller supplies a constant current to the gas sensor so that it flows from one of the electrodes to the other in a selected direction, thereby changing a response time the gas sensor takes to react to a change in concentration of the gas component. This results in an increased accuracy, for example, in controlling an air-fuel ratio of a mixture to an internal combustion engine in an engine control system.

Abstract: A current detection resistance in a sensor control device is connected to a sensor element. The current flowing in the sensor element is detected through the current detection resistance. The current detection resistance is connected to an inverting amplification circuit for outputting an air/fuel output voltage to be transferred to a microcomputer. An offset setting circuit is connected to one input terminal of an operational amplifier in the inverting amplification circuit. The offset setting circuit is comprised of a switching element, a resistance connected in series to the switching element, and two dividing voltage resistances whose common node is connected to the resistance. The offset setting circuit generates and gives an offset to the A/F output voltage. The switching element is turned ON and OFF based on an offset switching signal transferred from the microcomputer.

Abstract: A particulate matter detection element includes a capacitance component disposed in parallel with a detected resistance RSEN. A direct current-power source that supplies a direct current (IDC) for particulate matter detection, and an alternating-current power source that supplies an alternating current (IAC) for disconnection detection are provided.

Abstract: A gas sensor control apparatus is provided which controls an operation of a gas sensor made up of a solid electrolyte body and a pair of electrodes to output a signal indicating the concentration of a given gas component contained in gas. The gas sensor control apparatus includes a constant current circuit that is connected electrically to one of the electrodes of the gas sensor and supplies a constant current thereto and a controller. The controller supplies a constant current to the gas sensor so that it flows from one of the electrodes to the other in a selected direction, thereby changing a response time the gas sensor takes to react to a change in concentration of the gas component. This results in an increased accuracy, for example, in controlling an air-fuel ratio of a mixture to an internal combustion engine in an engine control system.

Abstract: A sensor controller is applied to a particulate matter detection sensor that includes an attachment portion to which conductive particulate matter contained in gas is attached, and a pair of opposed electrodes spaced from each other at the attachment portion. The particulate matter detection sensor is adapted to output a detection signal corresponding to a resistance between the pair of opposed electrodes, and the sensor controller is adapted to calculate an amount of attached particulate matter based on a sensor detection value from the particulate matter detection sensor. The sensor controller includes a heater for heating the attachment portion so as to burn and remove the particulate matter attached to the attachment portion, and an abnormality diagnosis portion for obtaining the sensor detection value during a heating of the heater and for performing diagnosis of abnormality of the particulate matter detection sensor based on the obtained sensor detection value.

Abstract: A sensor controller for a particulate matter detection sensor includes a signal output circuit connected to the particulate matter detection sensor such that a sensor detection value is changeable in a predetermined output range by the signal output circuit, a heater configured to heat an attachment portion so as to burn and remove particulate matter attached to the attachment portion, a learning portion for calculating a sensor standard value in a state where the resistance between a pair of opposed electrodes is reduced based on an obtained sensor detection value and for storing the sensor standard value as a learning value, and a correcting portion for correcting the sensor detection value based on the sensor standard value stored by the learning portion.

Abstract: A sensor controller is for a particulate matter detection sensor that includes a pair of opposed electrodes spaced from each other and disposed on an attachment portion. The sensor controller includes a calculation portion configured to calculate an amount of particulate matter attached to the particulate matter detection sensor based on a detection value from the particulate matter detection sensor, and a determination portion configured to determine whether water exists in the exhaust passage based on the detection value. Thus, it is possible to accurately determine whether water exists in the exhaust passage.