Air-fuel ratio control method reflecting brake booster inflow flow rate

Patent metadata

Field	Value
Publication number	US-10989147-B2
Application number	US-201916701289-A
Country	US
Kind code	B2
Filing date	Dec 3, 2019
Priority date	Feb 12, 2019
Publication date	Apr 27, 2021
Grant date	Apr 27, 2021

Abstract

An air-fuel ratio control method reflecting a brake booster inflow flow rate includes: determining a deviation between an actually measured pressure of an intake manifold and a model pressure of the intake manifold is equal to or greater than a predetermined value; determining that the deviation is caused by a brake operation; correcting an intake air amount by reflecting a flow rate flowing into the intake manifold from a brake booster; and performing an air-fuel ratio control based on the corrected intake air amount.

First claim

What is claimed is:

1. An air-fuel ratio control method reflecting a brake booster inflow flow rate, the method comprising:
measuring, by a manifold absolute pressure (MAP) sensor, an absolute pressure of an intake manifold of a vehicle;
comparing, by a controller, the measured absolute pressure with a model pressure of the intake manifold calculated based on an intake air amount measured by an air flow sensor;
determining, by the controller, whether a deviation between the measured absolute pressure and the model pressure of the intake manifold is equal to or greater than a predetermined value;
determining, by the controller, whether the deviation is caused by a brake operation when the deviation is equal to or greater than the predetermined value;
correcting, by the controller, the intake air amount based on a rate of a brake inflow flowing into the intake manifold from a brake booster when it is determined that the deviation is caused by the brake operation;
calculating, by the controller, a cylinder intake air amount based on the corrected intake air amount; and
performing, by the controller, an air-fuel ratio control based on the calculated cylinder intake air amount.

2. The air-fuel ratio control method of claim 1 ,
wherein in correcting the intake air amount, an inflow air amount by the brake booster is obtained by using a map in which the deviation between the measured absolute pressure and the model pressure is used as an input value, and then the inflow air amount by the brake booster is obtained, and
the intake air amount measured by the air flow sensor is corrected by using the calculated inflow air amount by the brake booster.

3. The air-fuel ratio control method of claim 2 ,
wherein when it is determined that the deviation is not caused by the brake operation, the inflow air amount by the brake booster is set to zero (0).

4. The air-fuel ratio control method of claim 1 ,
wherein correcting the intake air amount comprises:
calculating a pressure corrected amount by subtracting an effective pressure deviation in a normal state from the deviation between the measured absolute pressure and the model pressure of the intake manifold; and
correcting the model pressure of the intake manifold based on the measured intake air amount and the pressure corrected amount, and

wherein the cylinder intake air amount is calculated by using the corrected model pressure of the intake manifold.

5. The air-fuel ratio control method of claim 4 ,
wherein when it is determined that the deviation is not caused by the brake operation, the pressure corrected amount is set to zero (0).

6. The air-fuel ratio control method of claim 1 ,
wherein in correcting the intake air amount,
an inflow air amount by the brake booster is obtained by using a map in which a basic capacity of the brake booster and a number of repetitions of the brake operation are used as an input value, and then the inflow air amount by the brake booster is obtained, and
wherein the inflow air amount measured by the air flow sensor is corrected by using the calculated inflow air amount by the brake booster.

7. The air-fuel ratio control method of claim 1 ,
wherein correcting the intake air amount comprises:
calculating an inflow air amount by the brake booster by using a map in which a change amount per hour of the actually measured pressure of the intake manifold is used as an input value, and the inflow air amount by the brake booster is used as an output value, and
correcting the inflow air amount measured by the air flow sensor by using the calculated inflow air amount by the brake booster.

8. The air-fuel ratio control method of claim 1 , further comprising:
correcting a target injection fuel amount based on a flow rate flowing into the intake manifold from the brake booster when it is determined that the deviation is caused by the brake operation; and
performing the air-fuel ratio control based on the corrected target injection fuel amount.

9. The air-fuel ratio control method of claim 1 ,
wherein the vehicle comprises a lambda control unit for feedback-controlling an air-fuel ratio based on a value measured by a lambda sensor under an activation condition in which the air-fuel ratio is within a predetermined range, and
wherein the air-fuel ratio control reflecting the brake booster inflow flow rate feedback-controls the air-fuel ratio based on the measured value of the lambda sensor even in a lean condition where the air-fuel ratio is out of the predetermined range.

10. An air-fuel ratio control method reflecting a brake booster inflow flow rate, the method comprising:
determining, by a controller, whether a deviation between an actually measured pressure of an intake manifold and a model pressure of the intake manifold calculated based on an intake air amount measured by an air flow sensor is equal to or greater than a predetermined value, wherein the actually measured pressure is measured by a manifold absolute pressure (MAP) sensor;
determining, by the controller, whether the deviation is caused by a brake operation when the deviation has occurred between the actually measured pressure and the model pressure;
calculating, by the controller, a cylinder intake air amount by using the actually measured pressure of the intake manifold measured by the MAP sensor when it is determined that the deviation is caused by the brake operation; and
performing, by the controller, an air-fuel ratio control based on the calculated cylinder intake air amount.

11. The air-fuel ratio control method of claim 10 ,
wherein when it is determined that the deviation is not caused by the brake operation, the cylinder intake air amount is calculated by using the model pressure of the intake manifold using the measured intake air amount, and the air-fuel ratio control is performed based on the calculated cylinder intake air amount.

12. The air-fuel ratio control method of claim 10 , further comprising: determining whether an intake air amount correctable condition is satisfied,
wherein when the intake air amount correctable condition has been satisfied, the intake air amount is corrected.

13. The air-fuel ratio control method of claim 12 ,
wherein when a coolant temperature of an engine is within a predetermined certain range, and the MAP sensor and the air flow sensor are normally operating during a certain time after start-up, it is determined that the intake air amount correctable condition has been satisfied.

14. The air-fuel ratio control method of claim 10 ,
wherein when a vehicle is in a stop state, an engine is in an idle state, a brake is being operated, and when the deviation has occurred between the actually measured pressure and the model pressure, it is determined that the deviation is caused by the brake operation.

15. The air-fuel ratio control method of claim 10 , further comprising: confirming whether an engine is in an idle state or in a stop state,
wherein when it is determined that the engine has been in the idle state or in the stop state, the air-fuel ratio control reflecting the brake booster inflow flow rate is performed.

Assignees

• Hyundai Motor Co Ltd
• Kia Motors Corp

Inventors

• WON Min-Kyu

Classifications

• F02D2250/41

  Control to generate negative pressure in the intake manifold, e.g. for fuel vapor purging or brake booster · CPC title

• F02D2200/0406

  Intake manifold pressure · CPC title

• F02D41/18

  by measuring intake air flow · CPC title

• F02D41/1454 Primary

  the characteristics being an oxygen content or concentration or the air-fuel ratio · CPC title

• B60T13/40

  indirect, i.e. compressed air booster units {indirect systems} · CPC title