Gas detection device

Patent metadata

Field	Value
Publication number	US-10677750-B2
Application number	US-201815892851-A
Country	US
Kind code	B2
Filing date	Feb 9, 2018
Priority date	Feb 13, 2017
Publication date	Jun 9, 2020
Grant date	Jun 9, 2020

Abstract

A gas detection device includes a temperature control part configured to detect an element impedance by applying a high frequency voltage to an element part, and to control an electric power to be supplied to a heating part based on the detected element impedance. The temperature control part is configured, when the applied voltage control for SOx detection is being performed and at least a voltage decrease sweep is being performed, to perform a second element temperature control to stop detecting the element impedance to set the electric power to be supplied to the heating part to a predetermined electric power.

First claim

What is claimed is:

1. A gas detection device, comprising:
an element part, provided in an exhaust gas passage of an internal combustion engine, having an electrochemical cell including: a solid electrolyte body having oxide ion conductivity; a first electrode and a second electrode formed on respective surfaces of said solid electrolyte body; and a diffusion resistance body made of a porous material through which exhaust gas flowing through said exhaust gas passage is allowed to pass, said element part being configured so that said exhaust gas flowing through said exhaust gas passage reaches said first electrode through said diffusion resistance body;
a power supply circuit configured to apply a voltage between said first electrode and said second electrode;
an ammeter configured to detect an output current which is a current flowing between said first electrode and said second electrode;
a heater configured to generate heat having a heat amount corresponding to an electric power supplied thereto to thereby heat said element part; and
an electronic control unit including a memory including instructions, the instructions, when executed by a processor of the electronic control unit, causing the electronic control unit to:
control an applied voltage with the power supply circuit, which is said voltage applied between said first electrode and said second electrode, acquire said output current by using the ammeter, and perform, based on said acquired output current, a determination as to whether or not sulfur oxide having a concentration equal to or higher than a predetermined concentration is contained in said exhaust gas or a detection of a concentration of said sulfur oxide in said exhaust gas;
apply a high frequency voltage between said first electrode and said second electrode to thereby detect an impedance of said element part;
perform or stop said detection of said impedance of said element part by applying said high frequency voltage;
control said electric power supplied to said heater to thereby control a temperature of said element part;
perform, with the power supply circuit, applied voltage control for air-fuel ratio detection by setting said applied voltage to a voltage that brings said output current to a limiting current of oxygen, to thereby detect an air-fuel ratio of mixture supplied to said internal combustion engine based on said output current acquired during a period in which said applied voltage control for said air-fuel ratio detection is being performed;
perform, with the power supply circuit, applied voltage control for SOx detection which includes an applied voltage sweep at least for one cycle, said applied voltage sweep including a voltage increase sweep and a voltage decrease sweep, wherein
said voltage increase sweep increases said applied voltage from a first voltage to a second voltage, said first voltage is within a first voltage range higher than a lower limit voltage in a region of said limiting current and lower than a decomposition start voltage of said sulfur oxide, and said second voltage is within a second voltage range higher than said decomposition start voltage of said sulfur oxide, and
said voltage decrease sweep decreases said applied voltage from said second voltage to said first voltage,

acquire, based on said output current, a parameter correlating with a degree of a change in said output current caused by a current flowing between said first electrode and said second electrode owing to a phenomenon that sulfur adsorbed to said first electrode returns to sulfur oxide through a reoxidation reaction on said first electrode when said applied voltage becomes lower than said decomposition start voltage of said sulfur oxide while said voltage decrease sweep is being performed, said change in said output current being larger as said concentration of said sulfur oxide contained in said exhaust gas being larger;
perform, based on said acquired parameter, said determination or said detection;
perform, while said applied voltage control for said air-fuel ratio detection is being performed, a first element temperature control to control said temperature of said element part by detecting said impedance of said element part through applying said high frequency voltage and by controlling said electric power supplied to said heater based on a comparison of said detected impedance of said element part and a target impedance; and
stop applying said high frequency voltage to stop detecting said element impedance, and perform a second element temperature control to set said electric power supplied to said heater to a predetermined electric power, while said applied voltage control for said SOx detection is being performed and at least said voltage decrease sweep is being performed.

2. The gas detection device according to claim 1 , wherein the instructions, when executed by the processor of the electronic control unit, cause the electronic control unit to:
perform said first element temperature control when said voltage increase sweep is being performed while said applied voltage control for SOx detection is being performed.

3. The gas detection device according to claim 1 , wherein the instructions, when executed by the processor of the electronic control unit, cause the electronic control unit to:
change an energization control amount to thereby control said electric power supplied to said heater; and
perform said second element temperature control:
by keeping said energization control amount at an amount at a time point a predetermined time before said first element temperature control is stopped; or
by keeping said energization control amount at a preset constant amount.

4. The gas detection device according to claim 1 , wherein instructions, when executed by the processor of the electronic control unit, cause the electronic control unit to:
perform said second element temperature control so as to supply electric power having an amount which is set in advance to said heater in a period when said element impedance detection is stopped.

5. The gas detection device according to claim 1 , wherein,
a voltage decrease speed of said voltage decrease sweep is set at a speed which has a rate of said reoxidation reaction quickly increase when and immediately after said applied voltage becomes a voltage in said first voltage range and higher than said first voltage.

Assignees

• Toyota Motor Co Ltd

Inventors

• Aoki Keiichiro

Classifications

• G01N27/4071

  using sensor elements of laminated structure · CPC title

• Y02A50/248

  Cross-Sectional Technologies · mapped topic

• G01N27/4067 Primary

  Means for heating or controlling the temperature of the solid electrolyte · CPC title

• G01N27/4074

  for detection of gases other than oxygen · CPC title

• G01N33/0042

  SO2 or SO3 · CPC title