Method and system for the diagnosis of idling speed control system

• US 5,715,726 A
• Filed: 09/07/1994
• Issued: 02/10/1998
• Est. Priority Date: 09/08/1993
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Original Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Inventors: Matsumoto, Takuya, Hashimoto, Toru, Miyake, Mitsuhiro
• Primary Examiner(s): Dombroske, George M.
• Application Number:
  US08/301,908
• Time in Patent Office: 1,252 Days
• Field of Search: 73/116, 73/117.2, 73/117.3, 73/118.1, 73/118.2, 123/339.15, 364/431.03, 364/431.07
• US Class Current: 73/114.25
• CPC Class Codes: F02D 41/08 for idling F02D41/06, F02D41/16 take precedence
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A system for the diagnosis of an idling speed control system has a first timer for measuring the time elapsed since entrance to a feedback control mode, an engine speed state detection unit for detecting whether the engine speed has fallen within a predetermined speed range, a second timer for measuring the time elapsed since the engine speed has been detected to fall within the speed range, and a normality determining unit for determining that the idling speed control system is in order, when the time measured by the first timer is within a first preset time and also the engine speed is detected to have fallen within the speed range and has remained in the speed range until the time measured by said second timer reaches a second preset time. By adopting such a diagnosis method that instead of instantaneously determining an idling speed control system as being in order even after the engine speed has once fallen within a speed range to which the engine is intended to be controlled, any subsequent potential disorder of the idling speed control system is also taken into consideration. This has made it possible to obtain high-reliability information, for example, even when information for the diagnosis of a fault of the idling speed is collected on board.

Claims

1. A method for the diagnosis of an idling speed control system, said system comparing a target idling speed with an engine speed when an internal combustion engine is operated in a feedback control mode and, based on the result of the comparison, controlling the quantity of air to be fed to said engine so that the engine is feedback-controlled to make the engine speed equal to the target idling speed, which comprises:

determining that said idling speed control system is out of order when the engine speed has departed from a predetermined speed range including the target idling speed after the engine speed fell within the predetermined speed range during operation in the feedback control mode,

wherein said predetermined speed range is set so that the difference between the upper limit of the predetermined speed range and the target idling speed becomes greater than the difference between the target idling speed and the lower limit of the predetermined speed range.

2. A method for the diagnosis of an idling speed control system, said system comparing a target idling speed with an engine speed when an internal combustion engine is operated in a feedback control mode and, based on the result of the comparison, controlling the quantity of air to be fed to said engine so that the engine is feedback-controlled to make the engine speed equal to the target idling speed, which comprises:

determining that said idling speed control system is in order when the engine speed remains for a predetermined time in a predetermined speed range including the target idling speed after the engine speed has fallen within the predetermined speed range during operation in the feedback control mode,

wherein said predetermined speed range is set so that the difference between the upper limit of the predetermined speed range and the target idling speed becomes greater than the difference between the target idling speed and the lower limit of the predetermined speed range.

3. A method for the diagnosis of an idling speed control system, said system comparing a target idling speed with an engine speed when an internal combustion engine is operated in a feedback control mode and based on the result of the comparison, controlling the quantity of air to be fed to said engine so that the engine is feedback-controlled to make the engine speed equal to the target idling speed, which comprises:

determining that said idling speed control system is in order when after entrance to the feedback control mode, the engine speed fell in a first preset time within a predetermined speed range including the target idling speed and has then remained in the speed range for a second preset time.

4. A method according to claim 3, wherein said idling speed control system is determined to be out of order when the engine speed does not fall within the predetermined speed range even after the first preset time has elapsed since the entrance to the feedback control mode.

5. A method for the diagnosis of an idling speed control system, said system comparing a target idling speed with an engine speed when an internal combustion engine is operated in a feedback control mode and based on the result of the comparison, controlling the quantity of air to be fed to said engine so that the engine is feedback-controlled to make the engine speed equal to the target idling speed, which comprises:

determining that said idling speed control system is in order, when after entrance to the feedback control mode, the engine speed fell in a first preset time within a predetermined speed range including the target idling speed and has then remained in the speed range for a second preset time;

but

determining that said idling speed control system is out of order when after entrance to the feedback control mode, the engine speed falls in the first preset time within the speed range but has then departed from the speed range.

6. A method according to claim 5, wherein said idling speed control system is determined to be out of order when the engine speed does not fall within the predetermined speed range even after the first preset time has elapsed after entrance to the feedback control mode.

7. A method according to claim 5, wherein said predetermined speed range is set so that the difference between the upper limit of the predetermined speed range and the target idling speed becomes greater than the difference between the target idling speed and the lower limit of the predetermined speed range.

8. A system for the diagnosis of an idling speed control system, said idling speed control system comparing a target idling speed with an engine speed when an internal combustion engine is operated in a feedback control mode and based on the result of the comparison, controlling the quantity of air to be fed to said engine so that the engine is feedback-controlled to make the engine speed equal to the target idling speed, which comprises:

first timer means for measuring the time elapsed since the time point of entrance to the feedback control mode;

engine speed state detection means for detecting whether or not the engine speed has fallen within a predetermined speed range including the target idling speed;

second timer means for measuring the time elapsed since the engine speed has been detected by said engine speed state detection means to fall within the predetermined speed range; and

normality determining means for determining that said idling speed control system is in order, when the time measured by said first timer means is within a first preset time, the engine speed has been detected by said engine speed state detection means to have fallen within the predetermined speed range and the engine speed has remained in the predetermined speed range until the time measured by said second timer means reaches a second preset time.

9. A system according to claim 8, further comprising abnormality determining means for determining that said idling speed control system is out of order, when the time measured by said first timer means is within the first preset time and the engine speed is detected by said engine speed state detection means to have fallen within the predetermined speed range but the engine speed has then departed from the predetermined speed range.

10. A system according to claim 9, wherein said abnormality determining means determines that said idling speed control system is out of order, when the engine speed does not fall within the predetermined speed range even after the first preset time has elapsed since entrance to the feedback control mode.

11. A system according to claim 9, wherein said predetermined speed range is set so that the difference between the upper limit of the predetermined speed range and the target idling speed becomes greater than the difference between the target idling speed and the lower limit of the predetermined speed range.