Air/fuel ratio controller for larger internal combustion engines
First Claim
1. Air/fuel ratio control apparatus for use with an engine having multiple cylinders with intake and exhaust manifolds, the apparatus comprising:
- an air/fuel mixer having an air inlet and a fuel inlet;
a fuel pressure regulator, for controlling the fuel pressure supplied to the fuel inlet of the mixer, in response to pressure changes in an air chamber of the regulator;
a solenoid valve coupled to the fuel pressure regulator, wherein opening the solenoid valve vents the air chamber and results in a lower fuel pressure supplied to the fuel inlet of the air/fuel mixer;
an oxygen sensor installed in the exhaust manifold, for generating a signal indicative of the oxygen level in the exhaust manifold; and
a controller having means for inputting a desired oxygen setpoint value, the controller being responsive to the signals indicative of the oxygen level, and means for generating a solenoid valve control signal, wherein the control signal is adjusted in pulse width to control the fuel pressure and flow to achieve the desired oxygen setpoint value.
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Accused Products
Abstract
Apparatus, and a corresponding method for its operation, for controlling the air/fuel ratio in a large engine having one or more banks of cylinders with separate intake and exhaust manifolds. Oxygen sensors in the manifolds are sampled periodically to provide the apparatus with an indication of the level of oxygen, and therefore an indication of the level of various pollutants, in exhaust gases discharged from the engine. The apparatus, preferably in microprocessor form, computes a fuel control correction based on the difference between the sensed oxygen level and a desired oxygen level in each exhaust manifold. The correction is applied in the form of a change to the pulse width of a binary control signal applied to a solenoid valve. In the illustrative embodiment, the solenoid valve is coupled to a fuel pressure regulator and functions to vent an air chamber in the regulator when the solenoid is actuated. Changing the pulse width of the control signal varies the average fuel pressure and thereby controls the air/fuel ratio, which in turn corrects the oxygen level in the exhaust manifold. The controller also monitors various temperatures in the engine and selectively disables control of the air/fuel ratio when selected temperatures fall outside assigned limits.
36 Citations
24 Claims
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1. Air/fuel ratio control apparatus for use with an engine having multiple cylinders with intake and exhaust manifolds, the apparatus comprising:
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an air/fuel mixer having an air inlet and a fuel inlet; a fuel pressure regulator, for controlling the fuel pressure supplied to the fuel inlet of the mixer, in response to pressure changes in an air chamber of the regulator; a solenoid valve coupled to the fuel pressure regulator, wherein opening the solenoid valve vents the air chamber and results in a lower fuel pressure supplied to the fuel inlet of the air/fuel mixer; an oxygen sensor installed in the exhaust manifold, for generating a signal indicative of the oxygen level in the exhaust manifold; and a controller having means for inputting a desired oxygen setpoint value, the controller being responsive to the signals indicative of the oxygen level, and means for generating a solenoid valve control signal, wherein the control signal is adjusted in pulse width to control the fuel pressure and flow to achieve the desired oxygen setpoint value. - View Dependent Claims (2, 3, 4, 5)
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6. Air/fuel ratio control apparatus for use with an engine having at least two banks of cylinders with separate intake and exhaust manifolds, the apparatus comprising:
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an air/fuel mixer for each bank of cylinders, the mixer having an air inlet and a fuel inlet; a fuel pressure regulator for each bank of cylinders, for controlling the fuel pressure supplied to the fuel inlet of the mixer, in response to pressure changes in an air chamber of the regulator; a solenoid valve coupled to each fuel pressure regulator, wherein opening the solenoid valve vents the air chamber and results in a lower fuel pressure supplied to the fuel inlet of the air/fuel mixer; an oxygen sensor installed in the exhaust manifold of each cylinder bank, for generating a signal indicative of the oxygen level in the exhaust manifold; and a controller having means for inputting a desired oxygen setpoint value for each cylinder bank, the controller being responsive to the signals indicative of the oxygen level, and means for generating a solenoid valve control signal for each cylinder bank, wherein the control signal is adjusted in pulse width to control the fuel pressure and flow to achieve the desired oxygen setpoint value. - View Dependent Claims (7, 8, 9, 10)
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11. A method for controlling the air/fuel ratio in an industrial natural gas engine having multiple cylinders with intake and exhaust manifolds, the method comprising:
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selecting a desired setpoint oxygen level for the exhaust manifold, the setpoint level being selected to provide a desired level of pollutants in the exhaust; sensing the oxygen level in the exhaust manifold; generating a binary fuel control signal, derived from the setpoint oxygen level and the sensed oxygen level; and applying the binary fuel control signal to a fuel control valve to regulate the flow of fuel; wherein the fuel control valve is a solenoid valve coupled to a fuel pressure regulator and the step of applying the binary fuel control signal includes opening and closing the solenoid valve to selectively vent an air chamber in the fuel pressure regulator, for indirect control of fuel pressure; and wherein the fuel control valve in an on condition serves to reduce the flow of fuel to the engine, and repeated opening and closing of the solenoid valve by the fuel control signal results in adjustment of the air/fuel ratio to conform the sensed oxygen level to the setpoint oxygen level. - View Dependent Claims (12, 13)
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14. A method for controlling the air/fuel ratio in an industrial natural gas engine having at least two banks of cylinders with separate intake and exhaust manifolds, the method comprising:
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selecting a desired setpoint oxygen level for each of the exhaust manifolds, the setpoint levels being selected to provide a desired level of pollutants in the exhaust; sensing the oxygen level in each of the exhaust manifolds; generating for each cylinder bank a binary fuel control signal, derived from the setpoint oxygen level and the sensed oxygen level; and applying the binary fuel control signal to a fuel control valve to regulate the flow of fuel; wherein the fuel control valve is a solenoid valve coupled to a fuel pressure regulator and the step of applying the binary fuel control signal includes opening and closing the solenoid valve to selectively vent an air chamber in the fuel pressure regulator, for .indirect control of fuel pressure; and wherein the fuel control valve in an on condition serves to reduce the flow of fuel to the engine, and repeated opening and closing of the valve by the fuel control signal results in adjustment of the air/fuel ratio to conform the sensed oxygen level to the setpoint oxygen level for each cylinder bank. - View Dependent Claims (15, 16)
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17. An air/fuel ratio controller for use with an industrial natural gas engine having multiple cylinders, intake and exhaust manifolds, an air/fuel mixer, and a fuel control valve, the controller comprising:
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at least one input circuit, for inputting signals indicative of sensed oxygen level in the exhaust manifold; .a control panel, including means for inputting a desired oxygen setpoint value; means for generating a binary fuel control signal having periodic pulses with a controllable pulse width; means for periodically deriving a pulse width correction from the difference between the sensed oxygen level and the oxygen setpoint value; means for periodically applying the correction to the pulse width; and an electrically operated valve coupled to a fuel pressure regulator and connected to receive the binary fuel control signal, for selectively venting the pressure regulator in accordance with the binary fuel control signal and thereby indirectly controlling fuel pressure and flow; wherein the generated binary fuel control signal effects a change in air/fuel ratio, which tends to move the sensed oxygen level closer to the oxygen setpoint value. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification