Apparatus for controlling the air-fuel ratio of an internal combustion engine

Claim 2

Apparatus for controlling the air-fuel ratio of an internal combustion engine comprising: a lambda probe responsive to changes in said ratio and monitoring said ratio over a range of lambda values that includes a region wherein the output voltages of the probe exhibit only a weak dependence upon inputs to the probe; and, a circuit arrangement for evaluating the output of said probe and including: an operational amplifier wherein an offset voltage occurs because of drift in said circuit arrangement and temperature variations to which said probe is subjected during operation thereof; and, compensation means for compensating for said offset voltage thereby permitting a precise regulation of the air-fuel ratio in said region, said compensation means including circuit means for compensating for said offset voltage of said operational amplifier, said circuit means including switching means for switching said operational amplifier from the operation mode into and out of a compensation mode in a sequence corresponding to segments of time when it is not necessary or possible to conduct a determination of the lambda value.

Claim 3

The apparatus of claim 1, said switching means including means for setting the input voltage of said operational amplifier to zero whereby the output voltage of said amplifier is said offset voltage and for switching said operational amplifier back into said operation mode; and, said circuit means including: storage means for receiving and storing said offset voltage during said compensation mode and for subtracting said stored offset voltage from the voltage at the output of said operational amplifier after said switching means switches said amplifier back into said operation mode.

Claim 4

The apparatus of claim 2, said storage means including means for storing said processed voltage for an inlimited time; and, said circuit means including means for switching said operational amplifier into and out of said compensation mode at a preselected repetition frequency.

Claim 5

The apparatus of claim 2 said storage means including means for storing said processed voltage for an unlimited time; and, said circuit means including means for switching said operational amplifier into and out of said compensation mode in a sequence to correspond to segments of time when it is not necessary or possible to conduct a determination of the lambda value.

Claim 6

The apparatus of claim 2, said means for storing said processed voltage being analog means.

Claim 7

The apparatus of claim 2, said processing circuit means comprising: an analog-to-digital convertor for converting said output voltage into a digital quantity; a microcomputer for processing said digital quantity, said storage means being part of said microcomputer for storing said digital quantity; and, a digital-to-analog convertor for converting said digital quantity back to an analog quantity.

Claim 8

The apparatus of claim 2, said operational amplifier being a subtracting operational amplifier connected to said lambda probe for receiving the output thereof.

Claim 9

The apparatus of claim 2, said processing circuit means being configured so as to permit both lean and rich air-fuel ratios to be controlled in the region of λ˜1.2 and of λ˜0.8, respectively, with a relative accuracy lying in the range of one part per mil.

Claim 10

The apparatus of claim 8, said processing circuit means being further configured to provide a continuous control of the air-fuel ratio.

Claim 11

Apparatus for controlling the air-fuel ratio of an internal combustion engine comprising: a lambda probe responsive to changes in said ratio and monitoring said ratio over range of lambda values that includes a region wherein the output voltages of the probe exhibit only a weak dependence upon inputs to the probe; and, a circuit arrangement for evaluating the output of said probe and including an operational amplifier wherein an offset voltage occurs because of drift in said circuit arrangement and temperature variations to which said probe is subjected during operation thereof; and, compensation means for compensating for said offset voltage thereby permitting a precise regulation of the air-fuel ratio in said region, said compensation means including circuit means for compensating for the influence of said offset voltage of said operational amplifier; said circuit means including: switching means for switching said operational amplifier from the operation mode into a compensation mode by setting the input voltage of said amplifier to zero whereby the output voltage of said operational amplifier is caused exclusively by said offset voltage and for switching said operational amplifier back into said operation mode; processing circuit means for processing said output voltage and applying the processed output voltage to the input of said operational amplifier whereby the output of said amplifier is reduced to zero; and, storage means for storing said processed output voltage until the operational amplifier is again switched into the compensation mode.

Claim 12

Apparatus for controlling the air-fuel ratio of an internal combustion engine comprising: a lambda probe responsive to changes in said ratio and monitoring said ratio over range of lambda values that includes a region wherein the output voltages of the probe exhibit only a weak dependence upon inputs to the probe; and, a circuit arrangement for evaluating the output of said probe and including an operational amplifier wherein an offset voltage occurs because of drift in said circuit arrangement and temperature variations to which said probe is subjected during operation thereof; and, compensation means for compensating for said offset voltage thereby permitting a precise regulation of the air-fuel ratio in said region, said compensation means including circuit means for compensating for the influence of said offset voltage of said operational amplifier; said circuit means including: switching means for switching said operational amplifier from the operation mode into a compensation mode by setting the input voltage of said amplifier to zero whereby the output voltage of said operational amplifier is caused exclusively by said offset voltage and for switching said operational amplifier back into said operation mode; processing circuit means for processing said output voltage and applying the processed output voltage to the input of said operational amplifier whereby the output of said amplifier is reduced to zero; and, storage means for storing said processed output voltage until the operational amplifier is again switched into the compensation mode.

Claim 13

The apparatus of claim 10, said storage means including means for storing said processed voltage for an unlimited time; and, said circuit means including means for switching said operational amplifier into and out of said compensation mode at a preselected repetition frequency.

Claim 14

The apparatus of claim 10, said storage means including means for storing said processed voltage for an unlimited time; and, said circuit means including means for switching said operational amplifier into and out of said compensation mode in a sequence to correspond to segments of time when it is not necessary or possible to conduct a determination of the lambda value.

Claim 15

The apparatus of claim 10, said means for storing said processed voltage being analog means.

Claim 16

The apparatus of claim 10, said processing circuit means comprising: an analog-to-digital convertor for converting said output voltage into a digital quantity; a microcomputer for processing said digital quantity, said storage means being part of said microcomputer for storing said digital quantity; and, a digital-to-analog convertor for converting said digital quantity back to an analog quantity.

Claim 17

The apparatus of claim 10, said operational amplifier being a subtracting operational amplifier connected to said lambda probe for receiving the output thereof.

Claim 18

The apparatus of claim 10, said processing circuit means being configured so as to permit both lean and rich air-fuel ratios to be controlled in the region of λ˜1.2 and of λ˜0.8, respectively, with a relative accuracy lying in the range of one part per mil.

Claim 19

The apparatus of claim 16, said processing circuit means being further configured to provide a continuous control of the air-fuel ratio.

Claim 20

Apparatus for controlling the air-fuel ratio of heating equipment comprising: a lambda probe responsive to changes in said ratio and monitoring said ratio over a range of lambda values that includes a region wherein the output voltages of the probe exhibit only a weak dependence upon inputs to the probe; and, a circuit arrangement for evaluating the output of said probe and including an operational amplifier wherein an offset voltage occurs because of drift in said circuit arrangement and temperature variations to which said probe is subjected during operation thereof; and, compensation means for compensating for said offset voltage thereby permitting a precise regulation of the air-fuel ratio in said region, said compensation means including circuit means for compensating for said offset voltage of said operational amplifier, said circuit means including switching means for switching said operational amplifier from the operation mode into and out of a compensation mode in a sequence corresponding to segments of time when it is not necessary or possible to conduct a determination of the lambda value.

Claim 21

Apparatus for controlling the air-fuel ratio of heating equipment comprising: a lambda probe responsive to changes in said ratio and monitoring said ratio over a range of lambda values that includes a region wherein the output voltages of the probe exhibit only a weak dependence upon inputs to the probe; and, a circuit arrangement for evaluating the output of said probe and including an operational amplifier wherein an offset voltage occurs because of drift in said circuit arrangement and temperature variations to which said probe is subjected during operation thereof; and, compensation means for compensating for said offset voltage thereby permitting a precise regulation of the air-fuel ratio in said region, said compensation means including circuit means for compensating for said offset voltage of said operational amplifier, said circuit means including switching means for switching said operational amplifier from the operation mode into and out of a compensation mode in a sequence corresponding to segments of time when it is not necessary or possible to conduct a determination of the lambda value.

Claim 22

The apparatus of claim 18, said switching means including means for setting the input voltage of said operational amplifier to zero whereby the output voltage of said amplifier is said offset voltage and for switching said operational amplifier back into said operation mode; and, said circuit means including: storage means for receiving and storing said offset voltage during said compensation mode and for subtracting said stored offset voltage from the voltage at the output of said operational amplifier after said switching means switches said amplifier back into said operation mode.

Claim 23

Apparatus for controlling the air-fuel ratio of heating equipment comprising: a lambda probe responsive to changes in said ratio and monitoring said ratio over a range of lambda values that includes a region wherein the output voltages of the probe exhibit only a weak dependence upon inputs to the probe; and, a circuit arrangement for evaluating the output of said probe and including an operational amplifier wherein an offset voltage occurs because of drift in said circuit arrangement and temperature variations to which said probe is subjected during operation thereof; and, compensation means for compensating for said offset voltage thereby permitting a precise regulation of the air-fuel ratio in said region, said compensation means including circuit means for compensating for the influence of said offset voltage of said operational amplifier; said circuit means including: switching means for switching said operational amplifier from the operation mode into a compensation mode by setting the input voltage of said amplifier to zero whereby the output voltage of said operational amplifier is caused exclusively by said offset voltage and for switching said operational amplifier back into said operational mode; processing circuit means for processing said output voltage and applying the processed output voltage to the input of said operational amplifier whereby the output of said amplifier is reduced to zero; and, storage means for storing said processed output voltage until the operational amplifier is again switched into the compensation mode.

Claim 24

Apparatus for controlling the air-fuel ratio of heating equipment comprising: a lambda probe responsive to changes in said ratio and monitoring said ratio over a range of lambda values that includes a region wherein the output voltages of the probe exhibit only a weak dependence upon inputs to the probe; and, a circuit arrangement for evaluating the output of said probe and including an operational amplifier wherein an offset voltage occurs because of drift in said circuit arrangement and temperature variations to which said probe is subjected during operation thereof; and, compensation means for compensating for said offset voltage thereby permitting a precise regulation of the air-fuel ratio in said region, said compensation means including circuit means for compensating for the influence of said offset voltage of said operational amplifier; said circuit means including: switching means for switching said operational amplifier from the operation mode into a compensation mode by setting the input voltage of said amplifier to zero whereby the output voltage of said operational amplifier is caused exclusively by said offset voltage and for switching said operational amplifier back into said operational mode; processing circuit means for processing said output voltage and applying the processed output voltage to the input of said operational amplifier whereby the output of said amplifier is reduced to zero; and, storage means for storing said processed output voltage until the operational amplifier is again switched into the compensation mode.

Claim 25

The apparatus of claim 20 comprising means for controlling an extremely lean air-fuel ratio of up to lambda having a value of 1.8.

Claim 26

The apparatus of claim 19 comprising means for controlling an extremely lean air-fuel ratio of up to lambda having a value of 1.8.