Adaptive fuel/air mixture adjustment for taking fuel characteristics into consideration

• US 5,121,732 A
• Filed: 06/03/1991
• Issued: 06/16/1992
• Est. Priority Date: 06/01/1990
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Miller, Stefan, Plapp, Guenther, Boerkel, Wolfgang, Benninger, Nikolaus
• Primary Examiner(s): Nelli, Raymond A.
• Application Number:
  US07/709,303
• Time in Patent Office: 379 Days
• Field of Search: 123/489, 123/440, 123/575, 123/1 A
• US Class Current: 123/672
• CPC Class Codes: F02B 1/04 with fuel-air mixture admission into cylinder
• CPC Class Codes: F02D 19/0628 Determining the fuel pressure, temperature or flow, the fuel tank fill level or a valve position
• CPC Class Codes: F02D 19/084 Blends of gasoline and alcohols, e.g. E85
• CPC Class Codes: F02D 19/088 by estimation, i.e. without using direct measurements of a corresponding sensor
• CPC Class Codes: F02D 2200/0612 determined by estimation
• CPC Class Codes: F02D 35/023 by determining the cylinder pressure
• CPC Class Codes: F02D 41/0025 Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
• CPC Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: F02D 41/1479 Using a comparator with variable reference
• CPC Class Codes: F02D 41/1486 with correction for particular operating conditions
• CPC Class Codes: F02D 41/1498 measuring engine roughness
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

In methods for adaptively adjusting a fuel/air mixture, the adaptation factor is rapidly adjusted to take fuel characteristics into account when it develops that after tanking, poor control results are obtained with the adaptation factor previously applicable. As soon as there is an adjustment again to good control results, the conventional relatively slow adaptation is carried out. These methods afford the advantage that they can be carried out without special expensive mixture sensors.

Claims

1. A method for adjusting a fuel/air mixture to take fuel characteristics into account, the fuel/air mixture being for an engine equipped with a control apparatus including a lambda controller for producing a lambda control factor RF and an adaptation integrator for producing an adaptative factor AF for operating on the control factor RF with a predetermined speed, the lambda control factor deviating from an amplitude 1.0 during operation of the engine, the method comprising the steps of:

monitoring the amplitude of the lambda control factor RF to determine if the amplitude deviates from said value 1.0 to exceed a first threshold value indicative of a changed composition of the fuel; and

,

if yes, then increasing the speed at which said adaptative factor AF operates on said lambda control factor RF from a first adaptation speed corresponding to the normal operation of the engine to a second adaptation speed greater than said first adaptation speed until a pregiven condition is fulfilled and thereafter reducing said speed back to said first adaptation speed.

2. The method of claim 1, wherein said pregiven condition is the elapse of a pregiven time duration starting from the increase of the adaptation speed to said second adaptation speed.

3. The method of claim 1, wherein said pregiven condition is that the deviation amplitude of the lambda control factor RF drops below a pregiven second threshold value.

4. The method of claim 3, wherein said first and second threshold values are coincident.

5. The method of claim 1, wherein full-load operation of the engine is only permitted when the condition for reducing to said first adaptation speed is fulfilled.

6. The method of claim 1, comprising the further steps of:

determining the fuel quantity of the fuel tank of the motor vehicle corresponding to said engine before and after fuel is added to the tank;

computing values for possible fuel mixtures in the tank from these fuel quantities and known fuel mixtures available at service stations;

setting the lambda value over a pregiven number of injections alternately with adaptation values as they apply to the various possible fuel mixtures in the tank;

investigating with which value the best engine running results are obtained; and

,

using the value for the best engine running obtained as the then applicable adaptation value.

7. The method of claim 6, comprising the further step of:

distributing two conceivable adaptation values amongst two cylinder groups so that cylinder assignment to an adaptation value can be varied from one cycle to the next.

8. The method of claim 6, wherein the engine running is judged with the aid of time durations during which a pregiven crankshaft angles are traversed.

9. The method of claim 1, comprising the further steps of:

after starting the engine, checking if the engine is in a condition in which control is still prohibited;

if yes, then checking if the lambda probe is operationally ready;

if yes, then checking if the probe indicates a lean mixture; and

,

if yes, adjusting the adaptation value in a direction for obtaining a rich mixture at a comparatively high speed for so long until the probe indicates a rich mixture or control is permitted.

10. The method of claim 6, comprising the further step of:

distributing two conceivable precontrol values amongst two cylinder groups so that cylinder assignment to a precontrol value can be varied from one cycle to the next.

11. A method for adjusting a fuel/air mixture to take fuel characteristics into account, the fuel/air mixture being for an engine equipped with a control apparatus including a lambda controller for producing a lambda control factor RF and an adaptation integrator for producing an adaptation factor AF for operating on the control factor RF with a predetermined speed, the lambda control factor RF deviating from the amplitude 1.0 during operation of the engine, the method comprising the steps of:

at the first switch-on of the lambda controller after switching on the ignition of the engine, increasing the speed at which said adaptative factor AF operates on the lambda control factor RF from a first adaptation speed corresponding to the normal operation of the engine to a second adaptation speed; and

,

as soon as a pregiven condition is fulfilled, reducing said adaptation speed back to said first adaptation speed.

12. The method of claim 11, wherein said pregiven condition is the elapse of a pregiven time duration starting from the increase of the adaptation speed.

13. The method of claim 11, wherein said pregiven condition is that the deviation of the amplitude of said lambda control factor RF drops below a pregiven second threshold value.

14. The method of claim 13, wherein said first and second threshold values are coincident.

15. The method of claim 11, wherein full-load operation of the engine is only permitted when the condition for resetting to the usual low adaptation speed is fulfilled.

16. The method of claim 11, comprising the further steps of:

determining the fuel quantity of the fuel tank of the motor vehicle corresponding to said engine before and after fuel is added to the tank;

computing values for possible fuel mixtures in the tank from these fuel quantities and known fuel mixtures available at service stations;

setting the lambda value over a pregiven number of injections alternately with adaptation values as they apply to the various possible fuel mixtures in the tank;

investigating with which value the best engine running results are obtained; and

,

using the value for the best engine running obtained as the then applicable adaptation value.

17. The method of claim 16, comprising the further step of:

distributing two conceivable adaptation values amongst two cylinder groups so that cylinder assignment to an adaptation value can be varied from one cycle to the next.

18. The method of claim 16, wherein the engine running is judged with the aid of time durations during which pregiven crankshaft angles are traversed.

19. The method of claim 11, comprising the further steps of:

after starting the engine, checking if the engine is in a condition in which control is still prohibited;

if yes, then checking if the lambda probe is operationally ready;

if yes, then checking if the probe indicates a lean mixture; and

,

if yes, adjusting the adaptation value in a direction for obtaining a rich mixture at a comparatively high speed for so long until the probe indicates a rich mixture or control is permitted.

20. The method of claim 16, comprising the further step of:

distributing two conceivable precontrol values amongst two cylinder groups so that cylinder assignment to a precontrol value can be varied from one cycle to the next.