Method for determining the combustion chamber pressure in a cylinder of an internal-combustion engine with a pressure sensor

Claim 1

A method for measuring pressure in a cylinder chamber of an internal-combustion engine using a sensor that is in communication with the cylinder chamber, the sensor generating an electrical signal representative of sensed pressure in the cylinder chamber, the cylinder chamber defined by a cylinder containing a piston in the internal-combustion engine, during operation of the internal-combustion engine having a plurality of work cycles, each work cycle for each cylinder chamber being composed of a first cycle for intake, a second cycle for compression, a third cycle for combustion and a fourth cycle for exhaust, comprising the steps of: outputting a reference electrical signal, u0, from said sensor during each work cycle of the internal-combustion engine when the pressure in said cylinder chamber is at a known absolute reference pressure value, p0, for a reference piston position of the piston in the cylinder; outputting first and second electrical signals, u1 and u2, from said sensor during the same cycle representative of pressure in said cylinder chamber for two different first and second piston positions of said piston in said cylinder; determining a sensitivity, E, of the sensor from the absolute reference pressure value, p0, the reference electrical signal u0, the first and second electrical signals, u1 and u2, and a constant, K; defining a characteristic curve of the sensor using the reference electrical signal, u0, and the sensitivity, E; outputting a further electrical signal, ux, from the sensor representative of pressure in the cylinder chamber for an arbitrary piston position of the piston in said cylinder; deriving a further pressure value, px, from the further electrical signal, ux, using the characteristic curve; and using the further pressure value, px, as a value representing an actual pressure value in said cylinder chamber for said arbitrary piston position.

Claim 2

A method for measuring pressure in a cylinder chamber of an internal-combustion engine using a sensor that is in communication with the cylinder chamber, the sensor generating an electrical signal representative of sensed pressure in the cylinder chamber, the cylinder chamber defined by a cylinder containing a piston in the internal-combustion engine, during operation of the internal-combustion engine having a plurality of work cycles, each work cycle for each cylinder chamber being composed of a first cycle for intake, a second cycle for compression, a third cycle for combustion and a fourth cycle for exhaust, comprising the steps of: outputting a reference electrical signal, u0, from said sensor during each work cycle of the internal-combustion engine when the pressure in said cylinder chamber is at a known absolute reference pressure value, p0, for a reference piston position of the piston in the cylinder; outputting first and second electrical signals, u1 and u2, from said sensor during the same cycle representative of pressure in said cylinder chamber for two different first and second piston positions of said piston in said cylinder; determining a sensitivity, E, of the sensor from the absolute reference pressure value, p0, the reference electrical signal u0, the first and second electrical signals, u1 and u2, and a constant, K; defining a characteristic curve of the sensor using the reference electrical signal, u0, and the sensitivity, E; outputting a further electrical signal, ux, from the sensor representative of pressure in the cylinder chamber for an arbitrary piston position of the piston in said cylinder; deriving a further pressure value, px, from the further electrical signal, ux, using the characteristic curve; and using the further pressure value, px, as a value representing an actual pressure value in said cylinder chamber for said arbitrary piston position.

Claim 17

A method for measuring pressure in a cylinder chamber of an internal-combustion engine using a sensor that is in communication with the cylinder chamber, the sensor generating an electrical signal representative of sensed pressure in the cylinder chamber, the cylinder chamber defined by a cylinder containing a piston in the internal-combustion engine, during operation of the internal-combustion engine having a plurality of work cycles, each work cycle for each cylinder chamber being composed of a first cycle for intake, a second cycle for compression, a third cycle for combustion and a fourth cycle for exhaust, comprising the steps of: outputting a reference electrical signal, u0, from said sensor during each work cycle of the internal-combustion engine when the pressure in said cylinder chamber is at a known absolute reference pressure value, p0, for a reference piston position of the piston in the cylinder, the reference piston position being an upper dead center position of the piston in the cylinder; outputting first and second electrical signals, u1 and u2, from said sensor during the second cycle representative of pressure in said cylinder chamber for two different first and second piston positions of said piston in said cylinder; determining a sensitivity, E, of the sensor from the absolute reference pressure value, p0, the reference electrical signal u0, the first and second electrical signals, u1 and u2, and a constant, K; defining a characteristic curve of the sensor using the reference electrical signal, u0, and the sensitivity, E; outputting a further electrical signal, ux, from the sensor representative of pressure in the cylinder chamber for an arbitrary piston position of the piston in said cylinder during at least the third cycle; deriving a further pressure value, px, from the further electrical signal, ux, using the characteristic curve; using the further pressure value, px, as a value representing an actual pressure value in said cylinder chamber for said arbitrary piston position; wherein the sensitivity, E, of the sensor is determined according to ##EQU8## and wherein the further pressure value, px, is identified from the characteristic curve according to px=p0+E(ux-u0) and wherein the constant, K, is derived from ##EQU9## where V1 is equal to a combustion chamber volume of the cylinder at the first piston position, V2 is equal to a combustion chamber volume of the cylinder at the second piston position, and n is a polytropic constant.

Claim 18

A method for measuring pressure in a cylinder chamber of an internal-combustion engine using a sensor that is in communication with the cylinder chamber, the sensor generating an electrical signal representative of sensed pressure in the cylinder chamber, the cylinder chamber defined by a cylinder containing a piston in the internal-combustion engine, during operation of the internal-combustion engine having a plurality of work cycles, each work cycle for each cylinder chamber being composed of a first cycle for intake, a second cycle for compression, a third cycle for combustion and a fourth cycle for exhaust, comprising the steps of: outputting a reference electrical signal, u0, from said sensor during each work cycle of the internal-combustion engine when the pressure in said cylinder chamber is at a known absolute reference pressure value, p0, for a reference piston position of the piston in the cylinder, the reference piston position being an upper dead center position of the piston in the cylinder; outputting first and second electrical signals, u1 and u2, from said sensor during the second cycle representative of pressure in said cylinder chamber for two different first and second piston positions of said piston in said cylinder; determining a sensitivity, E, of the sensor from the absolute reference pressure value, p0, the reference electrical signal u0, the first and second electrical signals, u1 and u2, and a constant, K; defining a characteristic curve of the sensor using the reference electrical signal, u0, and the sensitivity, E; outputting a further electrical signal, ux, from the sensor representative of pressure in the cylinder chamber for an arbitrary piston position of the piston in said cylinder during at least the third cycle; deriving a further pressure value, px, from the further electrical signal, ux, using the characteristic curve; using the further pressure value, px, as a value representing an actual pressure value in said cylinder chamber for said arbitrary piston position; wherein the sensitivity, E, of the sensor is determined according to ##EQU8## and wherein the further pressure value, px, is identified from the characteristic curve according to px=p0+E(ux-u0) and wherein the constant, K, is derived from ##EQU9## where V1 is equal to a combustion chamber volume of the cylinder at the first piston position, V2 is equal to a combustion chamber volume of the cylinder at the second piston position, and n is a polytropic constant.