Gas sensor for vehicle engine having a double-pipe cover

A gas sensor for detecting characteristics of sample gas, said gas sensor comprising:

• a housing;
• a gas sensing element held by said housing and having a gas contact portion to contact the sample gas;
• and
• an element cover connected to said housing and covering said gas contact portion, said element cover having a double pipe structure formed by laminating an inner pipe and an outer pipe, each of said inner pipe and said outer pipe being formed into a cylindrical shape with a bottom, wherein:
• said inner pipe has a side portion including a first side portion having a side hole through which the sample gas flows and a second side portion which prevents the sample gas from flowing therethrough, and a bottom portion having a bottom hole through which the sample gas flows;
• said outer pipe has a side portion having a side hole through which the sample gas flows, and a bottom portion having a bottom hole through which the sample gas flows;
• said second side portion of said inner pipe is exposed through said side hole of said outer pipe;
• and
• the sample gas introduced into said element cover through said side hole of said outer pipe is substantially prevented from being directly discharged from said bottom hole of said outer pipe without passing through said side hole of said inner pipe.

A method of guiding sample gas in a gas sensor having a gas sensing element and an element cover for covering said gas sensing element, said element cover having a double-pipe structure formed by layering an outer pipe and an inner pipe, the method comprising steps of:

• introducing the sample gas into a space formed between said outer pipe and said inner pipe through a side hole of said outer pipe;
• making the sample gas collide with a side portion of said inner pipe;
• introducing the sample gas into said inner pipe through a side hole of said inner pipe thereby to make the sample gas contact said gas sensing element;
• and
• discharging the sample gas from a bottom hole of said inner pipe and a bottom hole of said outer pipe, wherein the sample gas is restricted from being discharged from said bottom hole of said outer pipe without flowing through said side hole of said inner pipe.