We claim:
1. A method-for adjusting an oxygen concentration in a catalytic converter system with lambda control for optimizing three-way conversion properties of the catalytic converter system after the transition from lean-burn operation with a lean fuelair mix to stoichiometric operation or during permanent stoichiometric operation, the method which comprises:
providing a catalytic converter system in an exhaust train of an internal combustion engine, the catalytic converter system having:
a preliminary three-way catalytic converter;
a main three-way catalytic converter disposed downstream of the preliminary catalytic converter with respect to an exhaust flow direction;
a pre-cat oxygen sensor disposed upstream of the preliminary catalytic converter with respect to an exhaust flow direction and producing a measurement signal;
an inter-cat oxygen sensor having a constant characteristic curve, the inter-cat oxygen sensor disposed between the preliminary catalytic converter and the main catalytic converter and producing a measurement signal;
an air mass flow meter disposed in an intake section of the internal combustion engine and producing a measurement signal; and
an operation control unit receiving measurement signals from the air mass flow meter, the pre-cat oxygen sensor, and the inter-cat oxygen sensor;
switching operation to a predetermined rich fuelair mix following one of a lean-burn operation and a permanent stoichiometric operation;
determining a time at which the preliminary catalytic converter has been fully discharged through release of its stored oxygen to the exhaust gas utilizing the measurement signal from the inter-cat oxygen sensor;
calculating on an ongoing basis a quantity of oxygen released to the exhaust gas from the main catalytic converter from the determined time onward utilizing the measurement signals from the inter-cat oxygen sensor and the air mass flow meter, and comparing the oxygen quantity with a desired predetermined value corresponding to a desired oxygen concentration in the main catalytic converter;
ending operation with the rich airfuel mix as soon as the quantity of oxygen released to the exhaust gas by the main catalytic converter has reached the desired predetermined value; and
switching operation to stoichiometric mode.
2. The method according to claim 1, which further comprises, after the rich operation has ended and before stoichiometric operation commences, operating with a lean fuelair mix for a given time period until an oxygen concentration of the preliminary catalytic converter reaches a predetermined value.
3. The method according to claim 1, which further comprises determining a desired predetermined value for a quantity of oxygen to be released by the main catalytic converter based upon a characteristic diagram as a function of an air mass flow rate, a temperature, and further characteristic variables of the main catalytic converter.
4. The method according to claim 1, which further comprises:
forming characteristic values from a diagnosis of the preliminary catalytic converter and a demand for rich fuelair mix to reach a desired oxygen concentration in the preliminary catalytic converter; and
taking the characteristic values into account when determining the desired predetermined value for the quantity of oxygen to be released by the main catalytic converter.
5. The method according to claim 3, which further comprises:
forming characteristic values from a diagnosis of the preliminary catalytic converter and a demand for rich fuelair mix to reach a desired oxygen concentration in the preliminary catalytic converter; and
taking the characteristic values into account when determining the desired predetermined value for the quantity of oxygen to be released by the main catalytic converter.
6. A method for adjusting the oxygen concentration in a catalytic converter system with lambda control for optimizing the three-way conversion properties of the catalytic converter system after the transition from a rich-burn operation with a rich fuelair mix to stoichiometric operation or during permanent stoichiometric operation, which further comprises:
providing a catalytic converter system in an exhaust train of an internal combustion engine, the catalytic converter system having:
a preliminary three-way catalytic converter;
a main three-way catalytic converter disposed downstream of the preliminary catalytic converter with respect to an exhaust flow direction;
a pre-cat oxygen sensor disposed upstream of the preliminary catalytic converter with respect to an exhaust flow direction and producing a measurement signal;
an inter-cat oxygen sensor having a constant characteristic curve, the inter-cat oxygen sensor disposed between the preliminary catalytic converter and the main catalytic converter and producing a measurement signal;
an air mass flow meter disposed in an intake section of the internal combustion engine and producing a measurement signal; and
an operation control unit receiving measurement signals from the air mass flow meter, the pre-cat oxygen sensor, and the inter-cat oxygen sensor;
switching operation to a predetermined lean fuelair mix following one of a rich-burn operation and a permanent stoichiometric operation;
determining a time at which the preliminary catalytic converter is fully laden as a result of taking up oxygen from the exhaust gas using the measurement signal from the inter-cat oxygen sensor;
calculating on an ongoing basis a quantity of oxygen taken up from the exhaust gas by the main catalytic converter from the determined time onward utilizing the measurement signals from the inter-cat oxygen sensor and the air mass flow meter, and comparing the oxygen quantity with a desired predetermined value corresponding to a desired oxygen concentration in the main catalytic converter;
ending the lean-burn operation as soon as the quantity of oxygen taken up from the exhaust gas by the main catalytic converter has reached the desired predetermined value; and
switching operation to a stoichiometric fuelair mix.
7. The method according to claim 6, which further comprises, after the lean operation has ended and before stoichiometric operation commences, operating with a rich fuelair mix for a given time period until an oxygen concentration of the preliminary catalytic converter reaches a predetermined value.
8. The method according to claim 6, which further comprises determining a desired predetermined value for a quantity of oxygen to be taken up by the main catalytic converter based upon a characteristic diagram as a function of an air mass flow rate, a temperature, and further characteristic variables of the main catalytic converter.
9. The method according to claim 6, which further comprises:
forming characteristic values from a diagnosis of the preliminary catalytic converter and a demand for lean fuelair mix to reach a desired oxygen concentration in the preliminary catalytic converter; and
taking the characteristic values into account when determining the desired predetermined value for the quantity of oxygen to be taken up by the main catalytic converter.
10. The method according to claim 8, which further comprises:
forming characteristic values from a diagnosis of the preliminary catalytic converter and a demand for lean fuelair mix to reach a desired oxygen concentration in the preliminary catalytic converter; and
taking the characteristic values into account when determining the desired predetermined value for the quantity of oxygen to be taken up by the main catalytic converter.
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 height adjusting mechanism for a keyboard, wherein the keyboard comprises a casing which is adapted for being disposed on a flat surface, the height adjusting mechanism being adapted for adjusting a height of the casing from the flat surface, and comprising:
a fixing piece fixed onto the casing and comprising a container and at least a supporting part, wherein the container passes through the casing and the supporting part is disposed on the inner wall of the container;
a cylinder having at least a portion disposed inside the container, wherein the cylinder has a spiral guide configured at an sidewall thereof and the supporting part forms a sliding engagement with the cylinder;
a first gear fixed to an end face of the cylinder; and
a second gear meshed with the first gear, wherein rotating the second gear will drive and rotate the first gear and the cylinder so that the supporting part will slide along the spiral guide to change the length of the cylinder protruded from the casing, and an end of the cylinder protruded from the casing is in contact with the flat surface.
2. The height adjusting mechanism of claim 1, wherein at least a portion of gear teeth of the second gear are exposed outside of the casing.
3. The height adjusting mechanism of claim 1, wherein the first gear has a thickness greater than the second gear.
4. The height adjusting mechanism of claim 1, wherein the spiral guide has a positioning region such that a fixed distance between the cylinder and the fixing piece is maintained when the supporting part slides within the positioning region.
5. The height adjusting mechanism of claim 1, wherein the fixing piece and the casing are formed together as an integrated unit.
6. The height adjusting mechanism of claim 1, wherein the cylinder and the first gear are formed together as an integrated unit.
7. The height adjusting mechanism of claim 1, wherein the cylinder has a first engaging part at one end and the first gear has a second engaging part such that the first gear is fixed to the first engaging part of the cylinder through the second engaging part.
8. The height adjusting mechanism of claim 7, wherein the first engaging part is a protrusion and the second engaging part is a cavity.
9. The height adjusting mechanism of claim 7, wherein the first engaging part is a cavity and the second engaging part is a protrusion.
10. The height adjusting mechanism of claim 1, wherein the supporting part has a hemispherical shape.