Thermostat malfunction detecting system for engine cooling system

• US 20050087152A1
• Filed: 11/12/2004
• Published: 04/28/2005
• Est. Priority Date: 12/17/1996
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Wakahara, Keiji, Ichikawa, Akira
• Granted Patent: US 7,137,295 B2
• Time in Patent Office: Days
• US Class Current: 123/41.150
• CPC Class Codes: F01P 11/14 Indicating devices; Other safety devices
• 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 2023/08 Microprocessor; Microcomputer
• CPC Class Codes: F01P 2025/08 Temperature
• CPC Class Codes: F01P 2025/13 Ambient temperature
• CPC Class Codes: F01P 2025/62 Load
• CPC Class Codes: F01P 2025/64 Number of revolutions
• CPC Class Codes: F01P 2025/66 Vehicle speed
• CPC Class Codes: F01P 2031/00 Fail safe
• CPC Class Codes: F01P 2031/20 Warning devices
• CPC Class Codes: F01P 2060/14 Condenser
• CPC Class Codes: F01P 5/02 Pumping cooling-air; Arrangements of cooling-air pumps, e.g. fans or blowers
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 41/18 by measuring intake air flow
• 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: G01K 15/00 Testing or calibrating of thermometers
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A malfunction of a thermostat in a coolant circulating path is detected from an engine side coolant temperature in consideration of the following behavior of the coolant temperature. When an open-malfunction occurs, the coolant temperature becomes different considerably from that in the normal time in the temperature range in which the thermostat is to be normally closed. When a closure-malfunction occurs, the coolant temperature becomes different considerably from that during the normal time in the temperature range in which the thermostat is to be normally opened. Alternatively, the malfunction may be detected from a difference between the engine side coolant temperature and a radiator side coolant temperature.

Claims

1-36. -36. (canceled)

37. A method For detecting a malfunction of a cooling system of an internal combustion engine, comprising:

detecting a coolant temperature on a side of the engine; and

determining, when the detected temperature reaches a predetermined temperature, a malfunction of a cooling system based on a predetermined reference and a period of time elapse required for the detected coolant temperature to reach the predetermined temperature from a predetermined timing,

wherein the predetermined reference is set based on a condition of the cooling system detected at an engine start time.

38. The method as in claim 37, wherein the condition is the coolant temperature detected at the engine start time.

39. The method as in claim 37, wherein the period is calculated based on an accumulation of an intake air amount from the engine start time.

40. The method as in claim 37, wherein the period is calculated based on a number of ignitions in the engine from the engine start time.

41. The method as in claim 37, wherein the period is calculated based on a amount of heat radiation generated by the engine from the engine start time.

42. The method as in claim 37, wherein the malfunction is an open-malfunction of a thermostat in the cooling system.

43. The method as in claim 42, wherein the malfunction determination is performed only when an engine start is detected to be a cold engine start based on the detected coolant temperature.

44. The method as in claim 42, wherein the malfunction determination is performed only when the engine is in an idle operation state.

45. The method as in claim 37, wherein the period is calculated based on an amount of heat radiation generated by the engine.

46. The method as in claim 45, wherein the amount of heat radiation is calculated based on a vehicle speed.

47. The method as in claim 45, wherein the amount of heat radiation is calculated based on an intake air temperature.

48. The method as in claim 45, wherein the amount of heat radiation is calculated based on an air conditioner operation condition.

49. A method for detecting a malfunction of a cooling system of an internal combustion engine, comprising:

detecting a coolant temperature on a side of the engine; and

determining, when the detected temperature reaches a predetermined temperature, a malfunction of a cooling system based on a predetermined reference and a predetermined parameter,

wherein the predetermined reference is set based on the coolant temperature detected at an engine start time.

50. The method as in claim 49, wherein the predetermined parameter is a period of time elapse required for the detected coolant temperature to reach a predetermined temperature from an engine start time.

51. The method as in claim 50, wherein the period is calculated based on an accumulation of an intake air amount from the engine start time.

52. The method as in claim 50, wherein the period is calculated based on a number of ignitions in the engine from the engine start time.

53. The method as in claim 50, wherein the period is calculated based on an amount of heat radiation generated by the engine from the engine start time.

54. The method as in claim 49, wherein the malfunction is an open-malfunction of a thermostat in the cooling system.

55. The method as in claim 54, wherein the malfunction determination is performed only when an engine start is detected to be a cold engine start based on the detected coolant temperature.

56. The method as in claim 54, wherein the malfunction determination is performed only when the engine is in an idle operation state.

57. The method as in claim 50, wherein the period is calculated based on an amount of heat radiation generated by the engine.

58. The method as in claim 57, wherein the amount of heat radiation is calculated based on a vehicle speed.

59. The method as in claim 57, wherein the amount of heat radiation is calculated based on an intake air temperature.

60. The method as in claim 57, wherein the amount of heat radiation is calculated based on an air conditioner operation condition.

61. A method for detecting a malfunction of a cooling system of an internal combustion engine, comprising:

detecting a coolant temperature on a side of the engine; and

determining, when the detected temperature reaches a predetermined temperature, a malfunction of a cooling system based on a predetermined reference and a predetermined parameter,

wherein the malfunction determination uses the coolant temperature detected at an engine start time.

62. The method as in claim 61, wherein the predetermined parameter is a period of time elapse required for the detected coolant temperature to reach a predetermined temperature from an engine start time.

63. The method as in claim 62, wherein the period is calculated based on an accumulation of an intake air amount from the engine start time.

64. The method as in claim 62, wherein the period is calculated based on a number of ignitions in the engine from the engine start time.

65. The method as in claim 62, wherein the period is calculated based on an amount of heat radiation generated by the engine from the engine start time.

66. The method as in claim 61, wherein the malfunction is an open-malfunction of a thermostat in the cooling system.

67. The method as in claim 66, wherein the malfunction determination is performed only when an engine start is detected to be a cold engine start based on the detected coolant temperature.

68. The method as in claim 66, wherein the malfunction determination is performed only when the engine is in an idle operation state.

69. The method as in claim 62, wherein the period is calculated based on an amount of heat radiation generated by the engine.

70. The method as in claim 69, wherein the amount of heat radiation is calculated based on a vehicle speed.

71. The method as in claim 69, wherein the amount of heat radiation is calculated based on an intake air temperature.

72. The method as in claim 62, wherein the amount of heat radiation is calculated based on an air conditioner operation condition.

73. A method for detecting a malfunction of a cooling system of an internal combustion engine, comprising:

detecting a coolant temperature on a side of the engine; and

determining, when a parameter related to an intake air amount reaches a predetermined value, a malfunction of a cooling system based on the detected coolant temperature,

wherein the malfunction determination uses the coolant temperature detected at an engine start time.

74. The method as in claim 73, wherein the parameter is calculated based on an accumulation of an intake air amount from the engine start time.

75. The method as in claim 73, wherein the parameter is calculated based on an amount of heat radiation generated by the engine.

76. The method as in claim 75, wherein the amount of heat radiation is calculated based on a vehicle speed.

77. The method as in claim 75, wherein the amount of heat radiation is calculated based on an intake air temperature.

78. The method as in claim 75, wherein the amount of heat radiation is calculated based on an air conditioner operation condition.