1. A friction wheel drive comprising:
a friction wheel drive having a driving roller capable of being driven in a rotary manner, the driving roller being mounted on a bearing unit so as to be rotatable about an axis of rotation, wherein the bearing unit is displaceably guided transversely to the axis of rotation, and a circumferential surface of the driving roller can be brought into driving engagement with a friction surface;
the bearing unit being coupled to a first mechanical forced guidance system, by which the driving roller, responding to a driving force acting in a first direction, can be pressed automatically against the friction surface with a contact pressing force that increases as the driving force increases; and
wherein the bearing unit is coupled to a second mechanical forced guidance system, by which the driving roller, responding to a driving force acting in an opposite second direction, can be pressed automatically against the friction surface with a contact pressing force that increases as the driving force increases; and
the first and second mechanical forced guidance systems simultaneously and automatically producing a displacement of the bearing unit in the direction of the friction surface, independently of the direction of drive, upon displacement of the bearing unit parallel to the friction surface.
2. The friction wheel drive according to claim 1, wherein the bearing unit is pivotably mounted on a mounting arm, the mounting arm being pivotably mounted on a frame at a swivelling axis.
3. The friction wheel drive according to claim 2, wherein a pressure roller is mounted on a pressure body pivotably mounted on the frame.
4. The friction wheel drive according to claim 3, wherein pressure rollers are rotatably mounted on the bearing unit, the pressure rollers pressing against a pressure surface of the pressure body upon pivoting motion of the bearing unit relative to the mounting arm.
5. The friction wheel drive of claim 4, wherein a first axis of rotation of a first pressure roller is a first distance from a central plane, the central plane including the axis of rotation of the driving roller and a swivelling axis of the bearing unit, and a second axis of rotation of a second pressure roller is a second distance from the central plane, the first and second distances being selected such that when a driving force in either direction is applied to the driving roller, the first or second pressure roller exerts a pressure force upon the pressure body that is independent of the direction of the driving force.
6. The friction wheel drive of claim 5, wherein the first distance is less than the second distance, the first pressure roller being closer to the swivelling axis of the mounting arm than the second pressure roller.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A gas sensor comprising:
a sensor element that is configured to detect a specific gas component in a gas to be measured, the sensor element including:
a plate-shaped solid electrolyte body; and
a pair of electrodes that is stacked on the solid electrolyte body with the solid electrolyte body interposed therebetween,
wherein the pair of electrodes includes a measurement electrode portion that is exposed to the gas to be measured, and a standard electrode portion that is disposed in an inner portion of the sensor element and functions as an oxygen standard portion by inflow of oxygen via the solid electrolyte body,
wherein a lead portion, which extends in the inner portion of the sensor element along the surface of the solid electrolyte body, is connected to the standard electrode portion,
wherein the standard electrode portion is formed with a precious metal as a main ingredient and contains a ceramic,
wherein the lead portion is formed of a precious metal as a main ingredient and has a ceramic content smaller than that of the standard electrode portion, and
wherein a porous portion, which extends to the inner portion of the sensor element along the surface of the solid electrolyte body, has a gas permeability higher than that of the lead portion, is formed with a ceramic as a main ingredient, and is connected to the standard electrode portion.
2. The gas sensor according to claim 1,
wherein the porous portion has a gas permeability higher than that of the standard electrode portion.
3. The gas sensor according to claim 1,
wherein the porous portion is stacked on the lead portion along a stacking direction of the pair of electrodes.
4. The gas sensor according to claim 1,
wherein the lead portion is electrically connected to an electrode pad provided on the surface of the sensor element via a through hole conductor, and a part of the porous portion communicates with an outer portion of the sensor element via a through hole provided in the through hole conductor.
5. The gas sensor according to claim 1,
wherein the precious metal is elemental platinum or an alloy of platinum with at least one selected from the group consisting of rhodium, palladium, ruthenium and gold.