Control method and apparatus for diagnosing vehicles

• US 5,964,811 A
• Filed: 04/18/1997
• Issued: 10/12/1999
• Est. Priority Date: 08/06/1992
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kawano, Kazuya, Miura, Kiyoshi, Takaku, Yutaka, Ishii, Toshio, Mukaihira, Takashi
• Primary Examiner(s): LOUIS JACQUES, JACQUES H
• Application Number:
  US08/877,857
• Time in Patent Office: 907 Days
• Field of Search: 364/431.01, 364/431.04, 364/431.03, 364/431.055, 364/423.098, 364/424.034, 364/424.037, 364/424.038, 364/424.039, 364/424.04 , 364/424.045, 364/424.048, 364/550, 364/551.01, 364/131-138, 364/431.11, 364/431.12, 340/438, 340/439, 340/825.11, 340/825.52, 340/825.54, 73/117.3, 73/118.1, 73/116, 73/117.2, 701/35, 701/31, 701/32, 701/33, 701/114, 701/115, 701/102, 701/29, 123/479, 123/481, 123/436, 123/690, 123/480
• US Class Current: 701/29
• CPC Class Codes: B60W 2050/021 Means for detecting failure or malfunction
• CPC Class Codes: F02D 2041/227 Limping Home, i.e. taking specific engine control measures at abnormal conditions
• CPC Class Codes: F02D 41/22 Safety or indicating devices for abnormal conditions in air/fuel ratio feedback systems F02D41/1495, in electric control linkage F02D11/107, in purge control systems F02M25/0809
• CPC Class Codes: F02D 41/266 the computer being backed-up or assisted by another circuit, e.g. analogue

Abstract

A diagnostic and control system first checks the current operation status of the vehicle engine, when a malfunction or abnormal condition is detected by diagnostic sensors. A selection of optimum corrective measures is then made and carried out taking into account the safety of the vehicle, based on current operational status of the engine. For this purpose, a set of prioritized corrective measures is determined beforehand for each of the individual monitored items, according to detected changes in the engine operating status. The individual control measures are selected considering the safety of the vehicle, possible measures to correct the malfunction, assuring vehicle operability, and maintaining appropriate engine operating parameters such as exhaust gas mixture, fuel consumption and the like.

Claims

1. Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;

sensing operating parameters of each of said subsystems and providing output signals indicative thereof;

processing said output signals in a data processor to detect a malfunction at least one of said subsystems;

selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;

sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor; and

testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;

wherein said selected sequence of corrective measures includes alternative corrective measures for differing operating conditions of said subsystems, and wherein said step of sequentially implementing said corrective measures includes selection of alternative corrective measures in response to changes in operating status of said subsystems sensed in said testing step.

2. Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;

sensing operating parameters of each of said subsystems and providing output signals indicative thereof;

processing said output signals in a data processor to detect a malfunction at least one of said subsystems;

selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;

sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor; and

testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;

wherein said system is a vehicle having an internal combustion engine;

wherein said step of sensing operating parameters includes detection of an engine misfire in a combustion cylinder of said vehicle, wherein control of an accidental or improper fire has priority over control of malfunctions of other subsystems of said vehicle;

wherein said step of sensing operating parameters includes sensing engine speed and engine load of said vehicle; and

further comprising

additional steps wherein if a misfire is detected when said engine speed is in an idling range or said engine load is smaller than a predetermined value, a first check is made to detect ignition abnormalities in said vehicle and if such an abnormality is detected, to correct such abnormality by increasing magnitude and duration of an ignition current provided to said combustion cylinder;

an additional step wherein if a misfire is detected when said engine load is greater than said predetermined value, fuel supply to said combustion cylinder is interrupted for a predetermined period of time and then resumed;

an additional step wherein if said misfire continues after interruption of said fuel supply, magnitude and duration of an ignition current provided to said combustion cylinder are increased;

an additional step wherein if said misfire is not corrected, fuel supply to said combustion cylinder is stopped; and

the further step of modifying operation of other combustion cylinders firing before and after said combustion cylinder in which said misfire is detected, by one of;

decreasing fuel flow or retarding ignition timing to said other cylinders.

3. Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;

sensing operating parameters of each of said subsystems and providing output signals indicative thereof;

processing said output signals in a data processor to detect a malfunction at least one of said subsystems;

selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;

sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor; and

testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;

wherein said system is a vehicle having an internal combustion engine;

wherein said subsystems include at least one of;

cylinder ignition, exhaust catalyst, O₂ sensors, O₂ sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system; and

wherein said step of sensing operating parameters includes sensing one of engine intake air flow and engine exhaust gas temperature; and

comprising the following additional steps

an air fuel ratio of said engine of said vehicle is controlled by an air-fuel feedback signal having a periodic cycle; and

if a malfunction of said exhaust catalyst is detected when said sensed one of engine intake air flow and engine exhaust gas temperature is smaller than a predetermined value, said cycle of said air-fuel feedback signal is shortened.

4. Method according to claim 3, wherein said engine of said vehicle has a canister purge system which operates when said vehicle is operating normally, and wherein if said sensed one of engine intake air flow and engine exhaust gas temperature is greater than said predetermined value, canister purging is interrupted.

5. Method according to claim 4, comprising the further step of retarding ignition timing of the vehicle engine by a predetermined amount.

6. Method according to claim 5, wherein if said malfunction of said exhaust catalyst is not corrected after retarding said ignition timing, said air-fuel mixture is adjusted to make it leaner and interruption of said canister purging is continued.

7. Method according to claim 5, wherein said step of sequentially implementing said counter-measures further comprises returning said ignition timing to normal following adjustment of the air-fuel mixture and continued interruption of canister purging.

8. Method according to claim 5, wherein if said malfunction of said exhaust gas catalyst is eliminated after retarding said ignition timing, canister purging is restarted and the retarded ignition timing is returned to normal.

9. Method according to claim 5, wherein a check is first made to determine whether the air-fuel mixture has previously been adjusted leaner, and if so, the air-fuel mixture is further adjusted leaner or secondary air flow is increased.

10. Method according to claim 9, wherein if said malfunction of said exhaust gas catalyst is eliminated following adjustment of said air-fuel mixture or said increase of secondary air flow, further leaner adjustment of the air-fuel mixture or increase of secondary air flow is stopped.

11. Method according to claim 9, wherein if said malfunction of said exhaust gas catalyst is not eliminated following said adjustment of said air-fuel mixture or said increase of secondary air flow, then said air-fuel ratio is further adjusted leaner or said secondary air flow is further increased.

12. Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;

sensing operating parameters of each of said subsystems and providing output signals indicative thereof;

processing said output signals in a data processor to detect a malfunction at least one of said subsystems;

selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;

sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor; and

testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;

wherein said system is a vehicle having an internal combustion engine;

wherein said subsystems include at least one of;

cylinder ignition, exhaust catalyst, O₂ sensors, O₂ sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;

wherein said vehicle has an air-fuel ratio feedback control system responsive to an O₂ sensor located upstream of said exhaust catalyst; and

wherein said step of sensing operating parameters includes;

sensing a degradation index of said O₂ sensor located upstream of said exhaust catalyst;

comparing said degradation index to a first predetermined value;

if said degradation index is less than said first predetermined value, changing a gain of said air-fuel ratio feedback control system in response to magnitude of said degradation index.

13. Method according to claim 12, wherein said step of sequentially implementing said counter-measures further comprises:

if said degradation index of said upstream O₂ sensor is greater than said first predetermined value, comparing intake airflow of said vehicle with a second predetermined value; and

if said intake air flow is less than said second predetermined value, changing operation of said air-fuel ratio feedback control system to respond to a second O₂ sensor mounted downstream from said exhaust catalyst.

14. Method according to claim 13 wherein said step of sequentially implementing counter-measures further comprises:

if said intake air flow is larger than said second predetermined value, adjusting said air-fuel ratio to make it leaner.

15. Method according to claim 14, wherein said step of sequentially implementing counter-measures further comprises:

comparing said degradation index with said first predetermined value after adjustment of said air-fuel ratio; and

if said degradation index is less than said first predetermined value, changing said gain of said air-fuel ratio feedback control system in response to magnitude of said degradation index.

16. Method according to claim 15, wherein said step of sequentially implementing counter-measures further comprises:

if said degradation index remains greater than said first predetermined value, changing operation of said air-fuel ratio feedback control system to respond to said second O₂ sensor.

23. Method according to claim 12, wherein said step of sequentially implementing counter-measures comprises a further step wherein, if said air-fuel ratio control system is performing open loop control, size of said leak is estimated based on values of intake air flow, intake manifold pressure and engine speed, and said air-fuel ratio is adjusted in response thereto;

and

if said air-fuel ratio control system is performing closed loop control, processing is terminated.

24. Method according to claim 12 wherein said step of sequentially implementing counter-measures comprises further steps wherein:

if said evaporative fuel leak is determined to be caused by sticking of a canister purging valve in an open position, learning control of said air-fuel ratio control system is stopped;

if said air-fuel ratio control system is performing open loop control, size of said leak is estimated based on values of intake air flow, intake manifold pressure and engine speed, and said air-fuel ratio is adjusted in response thereto; and

if said air-fuel ratio control system is performing closed loop control, processing is terminated.

17. Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;

sensing operating parameters of each of said subsystems and providing output signals indicative thereof;

processing said output signals in a data processor to detect a malfunction at least one of said subsystems;

selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;

sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor; and

testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;

wherein said system is a vehicle having an internal combustion engine;

wherein said subsystems include at least one of;

cylinder ignition, exhaust catalyst, O₂ sensors, O₂ sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;

wherein said vehicle has an air-fuel ratio control system responsive to output signals from an O₂ sensor in an exhaust line thereof, which control system can use either of a feedback (closed loop) control process or an open loop control process, said step of sensing operating parameters includes sensing heater current of said O₂ sensor to detect an abnormal condition thereof; and

wherein said sequence of corrective measures comprises the steps of;

comparing at least one of intake air flow and exhaust gas temperature of said vehicle with a first preset value; and

if it is less than said preset value, air-fuel ratio feedback control responsive to output signals from said O₂ sensor is stopped.

18. Method according to claim 17, wherein said step of sequentially implementing counter-measures further comprises adjusting the air-fuel ratio to one of a stoichiometric mixture and a rich side mixture.

19. Method according to claim 18, wherein said step of sequentially implementing counter-measures comprises a further step wherein, if said air-fuel ratio is adjusted to a rich side mixture, initiating secondary air flow.

20. Method according to claim 17, wherein said step of sequentially implementing counter-measures comprises a further step wherein, if said at least one of intake air flow and exhaust gas temperature is greater than said first preset value and less than a second preset value, adjusting gain of said air-fuel ratio control system.

21. Method according to claim 17, wherein said step of sequentially implementing counter-measures comprises a further step wherein, if said at least one of intake air flow and exhaust gas temperature is greater than said first preset value which is larger than said second preset value, then one of the following is implemented:

normal control or correction of feedback control gain.

22. Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;

sensing operating parameters of each of said subsystems and providing output signals indicative thereof;

processing said output signals in a data processor to detect a malfunction at least one of said subsystems;

selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;

sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor; and

testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;

wherein said system is a vehicle having an internal combustion engine;

wherein said subsystems include at least one of;

cylinder ignition, exhaust catalyst, O₂ sensors, O₂ sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;

wherein said vehicle has an air-fuel ratio control system which can use either a feedback (closed loop) learning control process or an open loop control process; and

wherein said step of sensing operating parameters comprises sensing pressure of said evaporative fuel system to detect an evaporative fuel leak; and

comprising an additional step wherein if said evaporative fuel leak exceeds a predetermined value, learning control of said air-fuel ratio control system is stopped.

25. Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;

sensing operating parameters of each of said subsystems and providing output signals indicative thereof;

processing said output signals in a data processor to detect a malfunction at least one of said subsystems;

selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;

sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor; and

testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;

wherein said system is a vehicle having an internal combustion engine;

wherein said subsystems include at least one of;

cylinder ignition, exhaust catalyst, O₂ sensors, O₂ sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;

wherein said step of sensing operating parameters comprises sensing intake air pressure of said vehicle to detect exhaust gas recirculation flow of said exhaust gas recirculation valve; and

wherein said sequence of corrective measures comprises the steps of;

comparing exhaust gas recirculation flow with a first predetermined value;

if it exceeds said predetermined value, checking for new air leaks; and

if no new air leak is found, adjusting said air-fuel ratio to make it richer.

26. Method according to claim 25, wherein if said vehicle is operating in an idling mode when said adjusting of said air-fuel ratio is performed, idling speed of said vehicle is increased by a predetermined amount.

27. Method according to claim 25, comprising the further step of:

if a new air leak is detected and idling speed of said vehicle exceeds a predetermined value, stopping fuel supply to said vehicle.

28. Method according to claim 25, wherein said step of sequentially implementing counter-measures comprises the further step of:

comparing said exhaust gas recirculation flow with a second predetermined value which is lower than said first predetermined value, and if it is smaller than said second predetermined value, stopping feedback learning of an air-fuel ratio control system of said vehicle.

29. Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;

sensing operating parameters of each of said subsystems and providing output signals indicative thereof;

processing said output signals in a data processor to detect a malfunction at least one of said subsystems;

selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;

sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor; and

testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;

wherein said system is a vehicle having an internal combustion engine;

wherein said subsystems include at least one of;

cylinder ignition, exhaust catalyst, O₂ sensors, O₂ sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system;

wherein said vehicle has an air-fuel ratio control system which utilizes a feedback control process;

wherein said step of sensing operating parameters includes sensing output characteristics of an O₂ sensor downstream of a secondary air outlet of said vehicle to detect and evaluate an abnormality of an air shut off valve of said secondary air supply; and

wherein said sequence of corrective measures comprises the step of

if said air shut off valve is determined to be frozen in an open position, stopping feedback control of said air-fuel ratio control system.

30. Method according to claim 29, wherein;

if said air shut off valve is determined to be fully said vehicle exceeds a opened and engine speed of predetermined value, stopping fuel supply to said vehicle; and

if said air shut off valve is determined to be fully opened and said engine speed is predetermined value, adjusting said air fuel ration to make it leaner.

31. Method according to claim 29, wherein:

if said air shut off valve is determined to be frozen in a closed position, and said catalyst is not activated, adjusting said air-fuel ratio to make it leaner.

32. Method of controlling operation of a vehicle having an internal combustion engine and a plurality of subsystems, said method comprising the steps of:

providing a predetermined set of prioritized counter-measures for remedying predetermined malfunctions of each of said subsystems, and storing said prioritized counter-measures in a memory;

sensing operating parameters of each of said subsystems and providing output signals indicative thereof;

processing said output signals in a data processor to detect a malfunction at least one of said subsystems;

selecting a sequence of prioritized counter-measures depending on the detected malfunction and on the sensed operating parameters;

sequentially implementing said prioritized counter-measures to modify operation of said system in response to control signals from said data processor; and

testing said at least one of said subsystems by sensing said operating parameters thereof in response to control signals from said data processor after implementation of each of said counter-measures, to determine effect of said counter-measures;

wherein said system is a vehicle having an internal combustion engine;

wherein said subsystems include at least one of;

cylinder ignition, exhaust catalyst, O₂ sensors, O₂ sensor heaters, evaporative fuel system, exhaust gas recirculation valve, second air supply and fuel control system; and

wherein if a malfunction is detected in said fuel control system, said sequence of corrective measures includes the steps of

comparing throttle valve opening of said vehicle with output signals of a hot wire of an air flow sensor in said fuel control system to detect a malfunction of said air flow sensor;

if a malfunction of said air flow sensor is detected, estimating air flow based on throttle valve opening and engine speed.

33. Method according to claim 32, wherein said step of sequentially implementing counter-measures comprises additional steps of:

comparing a feedback control signal of said fuel control system with engine operating conditions to detect and evaluate a malfunction of a fuel injector of said vehicle; and

if said fuel injector is determined to be frozen in a full open condition, enrichment control of said fuel control system is stopped and feedback control of an air-fuel ratio of said vehicle is performed.

34. Method according to claim 33, wherein said step of sequentially implementing counter-measures comprises an additional step of:

if said fuel injector is determined to be frozen in a fully closed condition, then one of the following is performed;

increasing a fuel pulse duration of said injector and increasing a discharge voltage of an ignition system of said vehicle.

35. Method according to claim 32, wherein said step of sequentially implementing counter-measures comprises an additional step of:

comparing a feedback control signal of said fuel control system with engine operating conditions to detect and evaluate a malfunction of a pressure regulator of said fuel control system; and

if said malfunction can be eliminated by air-fuel ratio feedback control, then air-fuel feedback control is performed.

36. Method according to claim 35, wherein said step of sequentially implementing counter-measures comprises an additional step of:

if said malfunction cannot be eliminated by air-fuel ratio feedback control, and if said malfunction comprises an abnormally high pressure in said pressure regulator, then one of following is performed;

decreasing pump pressure and decreasing a fuel pulse duration of said injector.

37. Method according to claim 35, wherein said step of sequentially implementing counter-measures comprises an addition step of:

if said malfunction cannot be eliminated by air-fuel ratio feedback control, and if said malfunction comprises an abnormally low pressure in said pressure regulator, then one of the following is performed;

increasing pump pressure and increasing discharge voltage of an ignition system of said vehicle.