COOLING SYSTEM FOR ENGINE

• US 20160281586A1
• Filed: 03/23/2016
• Published: 09/29/2016
• Est. Priority Date: 03/27/2015
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Hosokawa, Yohei
• Granted Patent: US 9,982,587 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F01P 11/16 concerning coolant temperature F01P11/20 takes precedence
• CPC Class Codes: F01P 2025/30 Engine incoming fluid temperature
• CPC Class Codes: F01P 2025/32 Engine outcoming fluid temperature
• CPC Class Codes: F01P 2031/32 Deblocking of damaged thermostat

Abstract

A cooling system circulates a cooling medium between an engine and a radiator. The cooling system includes a determination unit. The determination unit sets a relatively small predetermined value for a threshold when a thermostat is closed, and sets a predetermined value larger than the predetermined value for the threshold when the thermostat is open. The determination unit determines that there is a stuck-closed failure in a selector valve when a temperature difference between a coolant temperature from a first coolant temperature sensor and a coolant temperature from a second coolant temperature sensor is larger than or equal to the threshold.

Claims

1. A cooling system for an engine, comprising:

a first flow passage configured to circulate a cooling medium through the engine and a radiator in this order;

a second flow passage configured to communicate the first flow passage upstream of the engine with the first flow passage downstream of the radiator;

a third flow passage configured to communicate the first flow passage between the engine and the radiator with the second flow passage;

a first valve configured to open or close to permit or restrict flow of the cooling medium, which has flowed through the radiator in the first flow passage, to the first flow passage downstream of a connection portion of the first flow passage with the second flow passage;

a second valve configured to open or close to permit or restrict flow of the cooling medium, which has flowed through the engine in the first flow passage, to the second flow passage via the third flow passage;

a first temperature sensor installed in the first flow passage between the engine and the radiator;

a second temperature sensor installed in the second flow passage downstream of a connection portion of the second flow passage with the third flow passage; and

a determination unit configured to

(i) while the second valve is being controlled so as to open, when a temperature difference between a first temperature detected by the first temperature sensor and a second temperature detected by the second temperature sensor is larger than or equal to a threshold, determine that there is a stuck-closed failure in the second valve, and

(ii) set the threshold such that the threshold at the time when the first valve is open is larger than the threshold at the time when the first valve is closed.

2. The cooling system according to claim 1, wherein

the first valve is a thermostat, and

the determination unit is configured to estimate whether the thermostat is open or closed based on a comparison between the first temperature and a second threshold or a comparison between the second temperature and a third threshold.

3. The cooling system according to claim 2, wherein

the thermostat includes a built-in heater, and

the determination unit is configured to reduce the second threshold and the third threshold as an energization current of the heater increases.

4. The cooling system according to claim 1, wherein

the first valve is a control valve that is controlled by the determination unit to open or close, and

the determination unit is configured to set the threshold such that the threshold at the time when the control valve is being controlled so as to open is larger than the threshold at the time when the control valve is not being controlled so as to open.

5. The cooling system according to claim 1, wherein

the determination unit is configured to set the threshold such that the threshold at the time when there is a stuck-open failure in the first valve is larger than the threshold at the time when there is no stuck-open failure in the first valve and the first valve is closed.