Air/fuel ratio control system for internal combustion engine

• US 6,334,425 B1
• Filed: 04/27/2000
• Issued: 01/01/2002
• Est. Priority Date: 04/28/1999
• Status: Expired due to Fees

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Sato, Masahiro, Nagatani, Shuji, Torii, Minoru
• Primary Examiner(s): Dolinar, Andrew M.
• Application Number:
  US09/559,742
• Time in Patent Office: 614 Days
• Field of Search: 123/295, 123/305
• US Class Current: 123/295
• CPC Class Codes: F02D 2200/0411 Volumetric efficiency
• CPC Class Codes: F02D 41/0065 Specific aspects of external EGR control constructional details of EGR system F02M26/00
• CPC Class Codes: F02D 41/1456 with sensor output signal being linear or quasi-linear with the concentration of oxygen
• CPC Class Codes: F02D 41/3029 further comprising a homogeneous charge spark-ignited mode
• CPC Class Codes: F02D 41/3818 for petrol engines

Abstract

An air/fuel ratio control system for a direct injection spark ignition internal combustion engine which is operated at an ultra-lean burn combustion or at a pre-mixture charged combustion. In the system, a charging efficiency correction coefficient for adjusting a charging efficiency of intake air is determined based at least on the determined desired air/fuel ratio and the form of combustion, and the desired air/fuel ratio is corrected by the coefficient. Then, the output fuel injection amount is determined based at least on the basic fuel injection amount and the corrected desired air/fuel ratio (desired air/fuel ratio correction coefficient). The charging efficiency correction coefficient is determined to be a less value when the engine is operated at the ultra-lean burn combustion than that when the engine is operated at the pre-mixture charged combustion. The coefficient is made different whether or not the operation of EGR is progress. With this, the desired air/fuel ratio is determined adequately and hence, the fuel injection amount can be determined adequately.

Claims

1. A system for controlling an air/fuel ratio for a direct injection spark ignition engine which is operated at one of two combustion forms including an ultra-lean burn combustion and a pre-mixture charged combustion;

comprising;

engine operating condition detecting means for detecting operating conditions of the engine at least including an engine speed and an engine load;

basic fuel injection amount determining means for determining a basic fuel injection amount based at least on the detected engine speed and the engine load of the engine operating conditions;

desired air/fuel ratio determining means for determining a desired air/fuel ratio of exhaust gas produced by the engine;

combustion form discriminating means for discriminating at which form of combustion the engine is operated;

charging efficiency correction coefficient determining means for determining a charging efficiency correction coefficient for adjusting a charging efficiency of intake air based at least on the determined desired air/fuel ratio and the form of combustion at which the engine is operated;

desired air/fuel ratio correcting means for correcting the desired air/fuel ratio based on the determined charging efficiency correction coefficient;

output fuel injection amount determining means for determining an output fuel injection amount by correcting the basic fuel injection amount at least by the corrected desired air/fuel ratio; and

fuel injecting means for injecting fuel into a cylinder of the engine based on the determined output fuel injection amount.

2. A system according to claim 1, further including;

EGR operation determining means for determining whether operation of EGR is present or absent; and

the charging efficiency correction coefficient determining means determines the charging efficiency correction coefficient based at least on the determined desired air/fuel ratio, the form of combustion at which the engine is operated and the presence or absence of the operation of EGR.

3. A system according to claim 1, wherein the charging efficiency correction coefficient determining means determines the charging efficiency correction coefficient to a value, when the engine is operated at the ultra-lean burn combustion, which is relatively less than that when the engine is operated at the pre-mixture charged combustion.

4. A system according to claim 2, wherein the charging efficiency correction coefficient determining means determines the charging efficiency correction coefficient to a value, when the engine is operated at the ultra-lean burn combustion, which is relatively less than that when the engine is operated at the pre-mixture charged combustion.

5. A method of controlling an air/fuel ratio for a direct injection spark ignition engine which is operated at one of two combustion forms including an ultra-lean burn combustion and a pre-mixture charged combustion;

comprising the steps of;

detecting operating conditions of the engine at least including an engine speed and an engine load;

determining a basic fuel injection amount based at least on the detected engine speed and the engine load of the engine operating conditions;

determining a desired air/fuel ratio of exhaust gas produced by the engine;

discriminating at which form of combustion the engine is operated;

determining a charging efficiency correction coefficient for adjusting a charging efficiency of intake air based at least on the determined desired air/fuel ratio and the form of combustion at which the engine is operated;

correcting the desired air/fuel ratio based on the determined charging efficiency correction coefficient;

determining an output fuel injection amount by correcting the basic fuel injection amount at least by the corrected desired air/fuel ratio; and

injecting fuel into a cylinder of the engine based on the determined output fuel injection amount.

6. A method according to claim 5, further including the step of;

determining whether operation of EGR is present or absent; and

the step of charging efficiency correction coefficient determination determines the charging efficiency correction coefficient based at least on the determined desired air/fuel ratio, the form of combustion at which the engine is operated and the presence or absence of the operation of EGR.

7. A method according to claim 5, wherein the step of charging efficiency correction coefficient determination determines the charging efficiency correction coefficient to a value, when the engine is operated at the ultra-lean burn combustion, which is relatively less than that when the engine is operated at the pre-mixture charged combustion.

8. A method according to claim 5, wherein the step of charging efficiency correction coefficient determination determines the charging efficiency correction coefficient to a value, when the engine is operated at the ultra-lean burn combustion, which is relatively less than that when the engine is operated at the pre-mixture charged combustion.