Ceramic heater

A ceramic heater for an internal combustion engine comprising:

• a cylindrical metal housing constructed and arranged to be mounted on an internal combustion engine;
• a central electrode fixed to one end of said housing and electrically insulated from said housing;
• a cylindrical ceramic insulating sleeve secured to the other end of said metal housing;
• and
• a heating element formed of a ceramic material for generating heat when supplied with electric power, said heat element having
• (i) an electrode section inserted into and secured to one end of said insulating sleeve, and having a first and a second electrode portions, and
• (ii) a heat generating section extending out of said insulating sleeve and having a first and a second heat generating portions to be directly exposed to an air-fuel mixture, both forward ends of said first and second heat generating portions being connected with each other, the cross-sectional area of said electrode section being larger than that of said heat generating section;
• means for electrically connecting said first electrode portion with said metal housing;
• and
• means for electrically connecting said second electrode portion with central electrode.