Thermostat failure diagnosis apparatus for internal combustion engine

• US 6,532,808 B1
• Filed: 05/12/2000
• Issued: 03/18/2003
• Est. Priority Date: 05/12/1999
• Status: Expired due to Term

• Current Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Original Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Inventors: Matsumoto, Takuya, Higuchi, Yoshiaki, Kanao, Hidetsugu, Sakagami, Tomonobu, Kume, Tateo
• Primary Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US09/570,540
• Time in Patent Office: 1,040 Days
• Field of Search: 731/16, 731/172, 731/173, 731/181, 731/19.R
• US Class Current: 73/114.68
• CPC Class Codes: F01P 11/16 concerning coolant temperature F01P11/20 takes precedence
• CPC Class Codes: F01P 2023/00 Signal processing; Details thereof
• CPC Class Codes: F01P 2031/20 Warning devices
• CPC Class Codes: F01P 2031/32 Deblocking of damaged thermostat
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 41/187 using a hot wire flow sensor
• 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

In a thermostat failure diagnosis apparatus for an internal combustion engine in which a failure diagnosis of a thermostat can be effectively made, in the case where, after starting of the engine, an intake air quantity of the engine or a parameter related to the intake air quantity is equal to or higher than a predetermined value, and a cooling water temperature is equal to or higher than an intake air temperature (outside air temperature), on the basis of a time in which a rising quantity in the cooling water temperature at an upstream side of the thermostat reaches a predetermined value, or a time in which the cooling water temperature rises to a predetermined temperature, the failure of the thermostat is judged. By this, the failure diagnosis is not made in the state where an engine generating heat quantity is small so that there is a fear that an erroneous diagnosis occurs, and the failure diagnosis of the thermostat can be rationally made only in the state where the engine generating heat quantity is large to some degree so that there is no fear of erroneous diagnosis.

Claims

1. A thermostat failure diagnosis apparatus for an internal combustion engine, which diagnoses a failure of a thermostat provided in a cooling water passage of the internal combustion engine, comprising:

cooling water temperature detection means for detecting a cooling water temperature of the internal combustion engine at an upstream side of the thermostat;

parameter detection means for detecting a control parameter of the internal combustion engine;

outside air temperature detection means for detecting one of an outside air temperature and a parameter related to the outside temperature; and

diagnosis means for detecting the failure of the thermostat on the basis of at least one of a time in which an increasing amount of the cooling water temperature reaches a first predetermined value and a time in which the cooling water temperature rises to a second predetermined value, in a case where a control parameter value detected by the parameter detection means is equal to or higher than a third predetermined value after starting of the internal combustion engine, the diagnosis means stops the failure diagnosis when, at the time of engine start, the cooling water temperature detected by the cooling water temperature detection means is equal to or higher than the detected outside air temperature, and the detected water temperature does not rise to an opening/closing switching temperature of the thermostat within a predetermined time after the engine start.

2. A thermostat failure diagnosis apparatus according to claim 1, wherein the diagnosis means detects failure of the thermostat by comparing a predetermined time with one of the time in which the rising quantity in the cooling water temperature reaches the first predetermined value and the time in which the cooling water temperature rises to the second predetermined value, and the predetermined time is set based on the detected cooling water temperature.

3. A thermostat failure diagnosis apparatus according to claim 1, wherein the parameter detection means includes means for detecting one of an intake air quantity of the internal combustion engine and a parameter related to the intake air quantity.

4. A thermostat failure diagnosis apparatus for an internal combustion engine, which diagnoses a failure of a thermostat provided in a cooling water passage of the internal combustion engine comprising:

cooling water temperature detection means for detecting a cooling water temperature of the internal combustion engine at an upstream side of the thermostat;

parameter detection means for detecting a control parameter of the internal combustion engine;

diagnosis means for detecting, only when the failure of the thermostat on the basis of at least one of a time in which an increasing amount of the cooling water temperature reaches a first predetermined value and a time in which the cooling water temperature rises to a second predetermined value, in a case where a control parameter value detected by the parameter detection means is equal to or higher than a third predetermined value after starting of the internal combustion engine,

wherein the parameter detection means includes means for detecting one of a fuel injection quantity of the internal combustion engine and a parameter related to the fuel injection quantity.

5. A thermostat failure diagnosis apparatus according to claim 4, wherein the diagnosis means detects failure of the thermostat by comparing a predetermined time with at least one of the time in which the rising quantity in the cooling water temperature reaches the first predetermined value and the time in which the cooling water temperature rises to the second predetermined value, and the predetermined time is set based on the detected cooling water temperature.

6. A thermostat failure diagnosis apparatus according to claim 4, further comprising:

outside air temperature detection means for detecting one of an outside air temperature and a parameter indicative of the outside air temperature,

wherein the diagnosis diagnoses failure when, after starting of the engine, the detected cooling water temperature becomes equal to or higher than the detected outside temperature.