1. An air-fuel ratio imbalance among cylinders determining apparatus, applied to a multi-cylinder internal combustion engine having a plurality of cylinders comprising:
an air-fuel ratio sensor, disposed at an exhaust-gas-aggregated-portion of an exhaust gas passage to which exhaust gases discharged from at least two or more cylinders of said plurality of cylinders aggregate or at a position downstream of said exhaust-gas-aggregated-portion in said exhaust gas passage, having an air-fuel ratio detection section including a solid electrolyte layer, an exhaust-gas-side electrode layer formed on one of surfaces of said solid electrolyte layer, a diffusion resistance layer which said exhaust gases reach and which covers said exhaust-gas-side electrode layer, an atmosphere-side electrode layer formed on the other one of surfaces of said solid electrolyte layer so as to be exposed to an air in an atmosphere chamber, said air-fuel ratio sensor outputting an output value varying depending on an air-fuel ratio of said exhaust gases passing through a position at which said air-fuel ratio sensor is disposed, based on a limiting-current flowing through said solid electrolyte layer caused by applying a predetermined electrical voltage between said exhaust-gas-side electrode layer and said atmosphere-side electrode layer;
a plurality of fuel injectors, each of said injectors provided in accordance with each of at least said two or more cylinders and injecting a fuel whose amount is in accordance with an instructed fuel injection amount, said fuel being contained in a mixture supplied to each of combustion chambers of said at least two or more cylinders;
instructed fuel injection amount control means for controlling said instructed fuel injection amount in such a manner that an air-fuel ratio of said mixture supplied to said combustion chambers of said at least two or more cylinders coincides with a target air-fuel ratio;
imbalance determining means for obtaining a parameter for imbalance determination which becomes larger as a variation of said air-fuel ratio of an exhaust gas passing through said position at which said air-fuel ratio sensor is disposed becomes larger, for determining that an air-fuel ratio imbalance state among cylinders is occurring when said obtained parameter for imbalance determination is larger than a predetermined threshold value for imbalance determination, and for determining that said air-fuel ratio imbalance state among cylinders is not occurring when said obtained parameter for imbalance determination is smaller than said predetermined threshold value for imbalance determination; wherein,
said imbalance determining means is configured in such a manner that said imbalance determining means sets said target air-fuel ratio at a non-stoichiometric air-fuel ratio which is an air-fuel ratio other than a stoichiometric air-fuel ratio and obtains said parameter for imbalance determination in a period in which a predetermined condition for obtaining a parameter for imbalance determination is satisfied, and sets said target air-fuel ratio at said stoichiometric air-fuel ratio in a period in which said predetermined condition for obtaining a parameter for imbalance determination is not satisfied.
2. The air-fuel ratio imbalance among cylinders determining apparatus according to claim 1, wherein,
said imbalance determining means is configured in such a manner that said imbalance determining means,
maintains said target air-fuel ratio at said stoichiometric air-fuel ratio and obtains said parameter for imbalance determination as a tentative parameter based on the output value of the air-fuel ratio sensor before it sets said target air-fuel ratio at said non-stoichiometric air-fuel ratio in said period in which said predetermined condition for obtaining a parameter for imbalance determination is satisfied,
determines that said air-fuel ratio imbalance state among cylinders is occurring when said obtained tentative parameter is larger than a predetermined high side threshold value,
determines that said air-fuel ratio imbalance state among cylinders is not occurring when said obtained tentative parameter is smaller than a low side threshold value which is smaller than said high side threshold value by a predetermined amount,
defers a determination as to whether or not said air-fuel ratio imbalance state among cylinders is occurring when said obtained tentative parameter is smaller than said high side threshold value and larger than said low side threshold value,
sets said target air-fuel ratio at said non-stoichiometric air-fuel ratio and obtains said parameter for imbalance determination based on said output value of said air-fuel ratio sensor as a final parameter, in a period in which said predetermined condition for obtaining a parameter for imbalance determination is satisfied in a case in which said determination as to whether or not said air-fuel ratio imbalance state among cylinders is occurring is deferred, and
determines that said air-fuel ratio imbalance state among cylinders is occurring when said obtained final parameter is larger than said threshold value for imbalance determination, and determines that said air-fuel ratio imbalance state among cylinders is not occurring when said obtained final parameter is smaller than said threshold value for imbalance determination.
3. The air-fuel ratio imbalance among cylinders determining apparatus according to claim 1, wherein,
said air-fuel ratio detection section of said air-fuel ratio sensor includes a catalytic section which facilitates an oxidation-reduction reaction and has an oxygen storage function; and
said air-fuel sensor is configured in such a manner that said exhaust gas passing through said exhaust gas passage reaches said diffusion resistance layer via said catalytic section.
4. The air-fuel ratio imbalance among cylinders determining apparatus according to claim 1, wherein,
said air-fuel sensor further comprises a protective cover, which accommodate said air-fuel ratio detecting section in its inside so as to cover said air-fuel detecting section, said cover including inflow holes for said exhaust gas passing through said exhaust gas passage to flow into said inside of said cover and outflow holes for said exhaust gas flowed into said inside of said cover to flow out to said exhaust gas passage.
5. The air-fuel ratio imbalance among cylinders determining apparatus according to claim 4, wherein,
said imbalance determining means is configured in such a manner that it obtains, as a basic indicative value, a differential value with respect to time of said output value of said air-fuel ratio sensor or a detected air-fuel ratio which is an air-fuel ratio represented by said output value of said air-fuel ratio sensor, and obtains said parameter for imbalance determination based on said obtained basic indicative value.
6. The air-fuel ratio imbalance among cylinders determining apparatus according to claim 4, wherein,
said imbalance determining means is configured in such a manner that it obtains, as a basic indicative value, a second order differential value with respect to time of said output value of said air-fuel ratio sensor or a detected air-fuel ratio which is an air-fuel ratio represented by said output value of said air-fuel ratio sensor, and obtains said parameter for imbalance determination based on said obtained basic indicative value.
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 liquid ejection head, comprising:
a nozzle plate including plural nozzles to eject droplets of liquid;
a channel plate including individual liquid chambers communicated with the nozzles;
a common-liquid-chamber member including a common liquid chamber to supply the liquid to the individual liquid chambers; and
a deformable damper area forming a wall face of the common liquid chamber,
wherein the channel plate has an end portion disposed at an end of the channel plate, in a direction perpendicular to a nozzle array direction in which the nozzles are arrayed, and
an outer surface of the end portion of the channel plate is opposed to a portion of the damper area, and
said end portion of the channel plate has a relief at a side facing said portion of the damper area to permit deformation of the damper area.
2. The liquid ejection head of claim 1, wherein the relief has at least one of a stepwise shape, a tapered shape, a round shape, and a sawtooth shape in a cross section along a liquid supply direction in which the liquid is supplied from the common liquid chamber.
3. The liquid ejection head of claim 1, further comprising a diaphragm member forming a wall face of each of the individual liquid chambers,
wherein the damper area is formed of a portion of the diaphragm member.
4. An image forming apparatus, comprising the liquid ejection head of claim 1.
5. The liquid ejection head of claim 1, wherein the damper area is a section of a wall surface member forming the wall face of the common liquid chamber.
6. The liquid ejection head of claim 5, wherein the wall surface member includes plural damper areas along the nozzle array direction.
7. The liquid ejection head of claim 6, wherein a section of the channel plate opposes the wall surface member between adjacent damper areas, and said section of the channel plate does not have a relief and is bonded with adhesive to the wall surface member.