Fuel control system for a gaseous fuel internal combustion engine with improved fuel metering and mixing means

• US 5,806,490 A
• Filed: 12/20/1996
• Issued: 09/15/1998
• Est. Priority Date: 05/07/1996
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Bruetsch, Robert I., Nogi, Toshiharu
• Primary Examiner(s): Solis, Erick R.
• Application Number:
  US08/770,261
• Time in Patent Office: 634 Days
• Field of Search: 123/527, 123/674, 123/679, 123/435, 123/704, 123/14
• US Class Current: 123/435
• CPC Class Codes: F02B 2075/025 two
• CPC Class Codes: F02B 37/16 by bypassing charging air
• CPC Class Codes: F02D 19/023 to adjust the fuel mass or volume flow
• CPC Class Codes: F02D 19/027 Determining the fuel pressure, temperature or volume flow, the fuel tank fill level or a valve position
• CPC Class Codes: F02D 2400/04 Two-stroke combustion engines with electronic control
• CPC Class Codes: F02D 35/023 by determining the cylinder pressure
• CPC Class Codes: F02D 41/0027 the fuel being gaseous non-electrical control F02D19/02
• CPC Class Codes: F02D 41/008 Controlling each cylinder individually
• CPC Class Codes: F02D 41/187 using a hot wire flow sensor
• CPC Class Codes: F02M 21/0212 comprising at least 3 C-Atoms, e.g. liquefied petroleum gas [LPG], propane or butane
• CPC Class Codes: F02M 21/0215 Mixtures of gaseous fuels; Natural gas; Biogas; Mine gas; Landfill gas
• CPC Class Codes: F02M 21/0233 Details of actuators therefor
• CPC Class Codes: F02M 21/0239 Pressure or flow regulators therefor
• CPC Class Codes: F02M 21/042 Mixer comprising a plurality of bores or flow passages
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

A fuel management system for a gaseous fuel internal combustion engine is disclosed in which a mass air flow sensor as well as a mass gas flow sensor provide input signals to an electronic control unit (ECU) which then determines the air/fuel ratio. The ECU in turn generates output signals to a fuel valve to control the mass of fuel flow to the engine and thus the air/fuel ratio. A turbocharger bypass valve, a precooler for the gaseous fuel supply, a pressure accumulator upstream from the fuel valve, as well as a system to calibrate the engine to the specific gaseous fuel is described to enhance the accuracy of the fuel management system. An improved pressure balanced valve for controlling the fuel flow to the engine is also provided as well as a cylinder pressure transducer to optionally provide an output signal to the ECU to determine the air/fuel ratio.

Claims

1. For use with an internal combustion engine having an air intake passageway, a source of fuel, a fuel supply passageway extending between said fuel source and said air intake passageway and an exhaust passageway for combustion products from the engine, a fuel management system comprising:

a first sensor, said first sensor generating an output signal representative of a first engine operating condition;

a second sensor, said second flow sensor generating an output signal representative of a second engine operating condition;

means in said fuel supply passageway for controlling fuel delivery to the engine,

a stoichiometric device positioned in the exhaust passageway, said stoichiometric device generating a distinguishable output at stoichiometric combustion of said engine;

an electronic control unit and means for coupling said output signals from said first and second sensors and said stoichiometric device as input signals to said electronic control unit, said electronic control unit having means for calculating the air/fuel ratio as a function of said input signals;

means responsive to an initial predetermined engine operating condition for actuating said fuel delivery control means so that the engine dithers about stoichiometric combustion;

means in said electronic control unit responsive to said distinguishable output from said stoichiometric device for storing said output signals from said first and second sensors each time said output signal from said stoichiometric device equals said distinguishable output;

means in said electronic control unit for averaging said stored output signals and for calculating an average stoichiometric air/fuel ratio therefrom; and

means utilizing said calculated stoichiometric air/fuel ratio and input from one of said first or second sensors for thereafter actuating said fuel delivery control means to obtain a target air/fuel ratio.

2. The invention as defined in claim 1 wherein one of said sensors comprises a mass air flow sensor positioned in said air intake passageway which generates an output signal representative of the mass air flow through said air intake passageway.

3. The invention as defined in claim 2 wherein said fuel is a gaseous fuel and wherein one of said sensors comprises a mass fuel flow sensor positioned in said fuel supply passageway which generates an output signal representative of the mass fuel flow through said fuel supply passageway.

4. The invention as defined in claim 2 wherein one of said sensors comprises a cylinder pressure sensor which generates an output signal representative of the cylinder pressure at times t₁ and t₂ and a crankshaft sensor which generates an output signal representative of the rotational position of an engine crankshaft at times t₁ and t₂.

5. The invention as defined in claim 1 wherein said target air/fuel ratio comprises an air/fuel ratio leaner than stoichiometric.

6. The invention as defined in claim 1 wherein said electronic control unit comprises a microprocessor.

7. The engine as defined in claim 1 wherein said predetermined engine operating condition comprises an engine idle condition after said engine reaches a predetermined temperature condition.

8. The invention as defined in claim 1 wherein said stoichiometric device comprises an oxygen sensor.

9. The invention as defined in claim 1 wherein said engine dithers about stoichiometric combustion for a predetermined time period.

10. The invention as defined in claim 1 wherein said engine dithers about stoichiometric combustion for a predetermined number of engine cycles.

11. The invention as described in claim 4 wherein said electronic control unit having means for calculating the mass flow of the air plus fuel mixture, G_mix, to the engine cylinder(s) as a function of said input signals in accordance with the following formula:

space="preserve" listing-type="equation">G.sub.mix =(P.sub.2 -P.sub.1)(V.sub.1 V.sub.2.sup.n)/(R.sub.1 T.sub.1)(V.sub.1 -V.sub.2.sup.n)

wherein;

P₁ and P₂ =the in-cylinder pressures at times t₁ and t₂, respectively;

V₁ and V₂ =the in-cylinder volumes at times t₁ and t₂, respectively;

R₁ =gas constant of the mixture;

T₁ =gas temperature

and the variable n is calculated as follows;

space="preserve" listing-type="equation">n=1.4(1-1/λ

)+1.3/λ

wherein

X=excess air ratio ##EQU5## wherein (A/F)_S =stoichiometric air/fuel ratio

A/F=actual air/fuel ratio;

means in said electronic control unit responsive to said distinguishable output from said stoichiometric device for storing the output signals from said cylinder pressure sensor and the other of said sensors each time said output signal from said stoichiometric device equals said distinguishable output.

12. The invention as defined in claim 11 wherein the other of said first and second sensors generates an output signal, G_a, representative of the mass air flow through said air intake passageway, and said electronic control unit has a means for calculating the mass fuel flow, G_f, in accordance with the following formula:

space="preserve" listing-type="equation">G.sub.f =G.sub.mix -G.sub.a.

13. The invention as defined in claim 11 wherein the other of said first and second sensors generates an output signal, G_f, representative of the mass fuel flow through said fuel supply passageway, and said electronic control unit has a means for calculating the mass air flow, G_a, in accordance with the following formula:

space="preserve" listing-type="equation">G.sub.a =G.sub.mix -G.sub.f.

14. The invention as defined in claim 4 wherein said cylinder pressure sensor comprises an absolute pressure sensor which generates a substantially linear signal with respect to the absolute pressure in the cylinder.

15. The invention as defined in claim 4 wherein said cylinder pressure sensor comprises a relative pressure sensor which generates a substantially linear signal with respect to the pressure change in the cylinder.