Oxygen sensor

An oxygen sensor comprising:

• an oxygen sensing element shaped like a shaft;
• a cylindrical casing for housing said oxygen sensing element;
• a ceramic separator being placed coaxially with said casing, supported directly or indirectly via a member in a casing support part formed at a rear end of said casing, and formed with a plurality of lead insertion holes axially penetrating said ceramic separator for inserting leads from said oxygen sensing element;
• a cover member being placed coaxially with said casing and coupled to said casing from a rear with said ceramic separator covered from an outside while allowing the leads to extend to the rear outside of said cover member;
• and
• a metal elastic member being placed at least between said cover member and said ceramic separator or between the casing support part and said ceramic separator in a compression state for producing a sandwich retaining force for said ceramic separator between said cover member and the casing support part.

An oxygen sensor comprising:

• an oxygen sensing element shaped like a shaft;
• a cylindrical casing for housing said oxygen sensing element;
• a gas introduction structure having a filter holding part making a cylindrical form coaxial with said casing on a rear of said casing, having an inside communicating with said casing, and being formed in a wall with one or more gas introduction holes and a filter being placed so as to block the gas introduction hole or holes of said filter holding part for rejecting permeation of liquid and allowing gas to pass through, said gas introduction structure for introducing outside air into said casing through the filter and the gas introduction hole or holes;
• and
• a protective cover being formed like a cylinder for covering said gas introduction structure from an outside thereof for blocking or suppressing a direct jet of liquid drops to said filter or deposition of deposits of oil, dirt, etc., on said filter.

An oxygen sensor comprising:

• an oxygen sensing element shaped like a shaft;
• a cylindrical casing for housing said oxygen sensing element;
• a gas introduction structure comprising a filter holding part making a cylindrical form almost coaxial with said casing on a rear of said casing, having an inside communicating with an inside of said casing, and being formed in a wall with one or more gas introduction holes, a filter being placed so as to block the gas introduction hole or holes on an outside of the filter holding part for rejecting permeation of liquid and allowing gas to pass through, and an auxiliary filter holding part being formed like a cylinder placed on an outside of the filter and formed in a wall with one or more auxiliary gas introduction holes for sandwiching the filter between the auxiliary filter holding part and the filter holding part, for introducing outside air into said casing through the auxiliary gas introduction hole, the filter, and the gas introduction hole;
• wherein
• the filter comes in intimate contact with an inner face of the auxiliary filter holding part at least in surroundings of the auxiliary gas introduction hole and a predetermined gap is formed between the outer face of the filter holding part and the filter at least in surroundings of the gas introduction hole.

An oxygen sensor comprising:

• an oxygen sensing element shaped like a shaft;
• a cylindrical casing for housing said oxygen sensing element;
• a filter assembly being placed almost coaxially with said casing as a cylindrical body separate from said casing and coupled to said casing from a rear while allowing leads from said oxygen sensing element to extend to the rear outside of said filter assembly;
• and
• a coupling part for coupling said filter assembly and said casing, wherein
• said filter assembly comprises:
• a filter holding part making a cylindrical form almost coaxially coupled to said casing from a rear of said casing, having an inside communicating with an inside of said casing, and being formed in a wall with one or more gas introduction holes;
• a filter being placed so as to block the gas introduction hole or holes in the filter holding part from an inner or outer face side for rejecting permeation of liquid and allowing gas to pass through;
• and
• an auxiliary filter holding part for fixing the filter to the filter holding part, outside air introducing into said casing through the filter and the gas introduction hole.

An oxygen sensor comprising:

• an oxygen sensing element shaped like a hollow shaft with a tip closed;
• a shaft-like heating element being placed in the hollow part of said oxygen sensing element for heating said oxygen sensing element;
• a cylindrical casing for housing said oxygen sensing element;
• and
• a ceramic separator being placed almost coaxially with a rear end of said oxygen sensing element and formed with a plurality of lead insertion holes axially penetrating said ceramic separator for inserting leads from said oxygen sensing element and said heating element;
• wherein
• the lead insertion holes are arranged so as to surround a center axis of said ceramic separator;
• said ceramic separator is formed with a heating element end housing hole opened at one end in the front end face of said ceramic separator with a bottom positioned in an axial intermediate part of said ceramic separator and an inner diameter set larger than an outer diameter of said heating element, the heating element end housing hole being formed by cutting away a center of said ceramic separator so as to overlap the separator lead insertion holes from the inside and the rear end part of said heating element being housed in the heating element end housing hole;
• and
• said heating element is offset so that a center axis thereof is one-sided with respect to a center axis of the hollow part of said oxygen sensing element in the proximity of a heating part of said heating element.

An oxygen sensor comprising:

• an oxygen sensing element shaped like a shaft;
• a cylindrical casing for housing said oxygen sensing element;
• a ceramic separator being placed in said casing and formed with a plurality of lead insertion holes axially penetrating said ceramic separator for inserting leads from said oxygen sensing element;
• and
• an elastic seal member being coaxially integrated with a rear opening or a rear of said casing and having an inside fitted elastically into an inside of a different cylindrical body communicating with said casing and seal lead insertion holes for inserting the leads for sealing a gap between outer faces of the leads and an inner face of said casing or the different cylindrical body;
• wherein
• an axial rear end face of said ceramic separator adheres closely to an axial front end face of said elastic seal member, that said ceramic separator is formed with a ventilation communication part axially penetrating said ceramic separator, and that an opening of the ventilation communication part on a side near to said elastic seal member in the axial direction is made at a position where the opening is not shielded by said elastic seal member.

An oxygen sensor comprising:

• an oxygen sensing element shaped like a shaft;
• a cylindrical casing for housing said oxygen sensing element;
• a gas introduction structure comprising a filter holding part making a cylindrical form almost coaxial with said casing on a rear of said casing, having an inside communicating with an inside of said casing, and being formed in a wall with one or more gas introduction holes, a filter being placed so as to block the gas introduction hole or holes on an outside of the filter holding part for rejecting permeation of liquid and allowing gas to pass through, and an auxiliary filter holding part being formed like a cylinder placed on an outside of the filter and formed in a wall with one or more auxiliary gas introduction holes for sandwiching the filter between the auxiliary filter holding part and the filter holding part, for introducing outside air into said casing through the auxiliary gas introduction hole, the filter, and the gas introduction hole;
• wherein
• the filter holding part has an axial front relative to a stepped part formed in an axial intermediate part of the filter holding part as a first portion and a rear as a second portion so that the second portion is made smaller in diameter than the first portion, the gas introduction hole being made in a wall of the second portion;
• the auxiliary filter holding part is placed so as to spread across the first and second portions of the filter holding part;
• a main coupling part for coupling the filter holding part and the auxiliary filter holding part to each other with the filter between is formed at a position corresponding to the second portion;
• and
• an auxiliary coupling part for coupling the filter holding part and the auxiliary filter holding part to each other is formed at a position corresponding to the first portion.

An oxygen sensor comprising:

• an oxygen sensing element shaped like a shaft;
• a cylindrical casing for housing said oxygen sensing element;
• a gas introduction structure having a filter holding part making a cylindrical form almost coaxial with said casing on a rear of said casing, having an inside communicating with an inside of said casing, and being formed in a wall with one or more gas introduction holes and a filter being placed so as to block the gas introduction hole or holes of the filter holding part for rejecting permeation of liquid and allowing gas to pass through, said gas introduction structure for introducing outside air into said casing through the filter and the gas introduction hole or holes;
• a ceramic separator being placed so that a rear thereof enters the inside of the filter holding part in an axial direction of said oxygen sensing element and a front enters the inside of said casing and formed with a plurality of lead insertion holes axially penetrating said ceramic separator for inserting leads from said oxygen sensing element;
• and
• an elastic seal member being fitted elastically into a rear opening of the filter holding part and having seal lead insertion holes for inserting the leads for sealing a gap between outer faces of the leads and an inner face of the filter holding part;
• wherein
• an rear end face of said ceramic separator is positioned on the rear side behind the gas introduction hole in the axial direction and a predetermined gap is formed between said elastic seal member and said ceramic separator at least at the lead insertion position.