Method and system for engine cooling system control

#The present application relates to methods and systems for inferring a fluid level in a coolant overflow container (or degas bottle), and adjusting engine operation, based on a fluid level estimated in a vertical hollow standpipe fluidically coupled to the overflow container.

#Vehicles may include cooling systems configured to reduce overheating of an engine by transferring the heat to ambient air. Therein, coolant is circulated through the engine block to remove heat from the engine, the heated coolant then circulated through a radiator to dissipate the heat. The cooling system may include various components such as a coolant reservoir coupled to the system for degassing and storing coolant. A pressurized reservoir that also serves to separate entrained air from the coolant is typically called a degas bottle. When the temperature of coolant anywhere in the system rises, thermal expansion of the coolant causes pressure to rise in the degas bottle as the trapped air volume reduces. Pressure relief can be achieved by releasing air from the degas bottle through a valve that is typically mounted in the fill cap. Then, when the temperature and pressure of coolant drops below atmospheric pressure in the degas bottle, air may be drawn back into the bottle through another valve that is often mounted in the fill cap.

#If the coolant level in bottle is too low, the air volume will be too large to build sufficient pressure to prevent boiling and cavitation at the water pump inlet. At low fluid levels, the degas bottle will also no longer be able to separate air from the coolant and air can be drawn into the cooling system, again leading to poor cooling performance. If an overflow system is employed instead of an active degas system, a similar loss in cooling system performance can be realized when fluid levels are low.

#FIG. 1 shows an engine system including an engine cooling system.

#FIG. 2 shows a block diagram of an engine cooling system.

#FIG. 3 shows part of an example cooling system, including a coolant reservoir fluidly coupled to a standpipe, the standpipe affixed to the vehicle frame.

#The following description relates to systems and methods for controlling an engine of a vehicle, the engine having a cooling system such as that of FIGS. 1-2. The cooling system may include a coolant overflow reservoir, herein also referred to as a degas bottle, fluidly connected to a narrow vertical standpipe, as discussed at FIGS. 3-8. The vertical standpipe may include a level sensor broadcasting information to an engine controller for determining an amount of coolant within the standpipe, as elaborated at FIGS. 9-12. The controller may also estimate an amount of coolant within the degas bottle (herein also referred to as a bulk coolant level), based on the amount of coolant within the standpipe (herein also referred to as a local coolant level) and various motion parameters, as described at FIGS. 13-17. Based on the estimate of coolant, the controller may indicate a coolant state, and based on the coolant state, restrictions may be placed on engine operating parameters, as discussed at FIGS. 18-19. In this way, bulk coolant levels may be inferred more accurately even during slosh events. In addition, low coolant levels may be more reliably detected and engine operating parameters may be restricted accordingly to prevent overheating of the engine.

#FIG. 1 shows an example embodiment of a vehicle system 100 including a vehicle cooling system 101 in a motor vehicle 102. Vehicle 102 has drive wheels 106, a passenger compartment 104 (herein also referred to as a passenger cabin), and an under-hood compartment 103. Under-hood compartment 103 may house various under-hood components under the hood (not shown) of motor vehicle 102. For example, under-hood compartment 103 may house internal combustion engine 10. Internal combustion engine 10 has a combustion chamber which may receive intake air via intake passage 44 and may exhaust combustion gases via exhaust passage 48. Engine 10 as illustrated and described herein may be included in a vehicle such as a road automobile, among other types of vehicles. While the example applications of engine 10 will be described with reference to a vehicle, it should be appreciated that various types of engines and vehicle propulsion systems may be used, including passenger cars, trucks, etc.

#Under-hood compartment 103 may further include cooling system 101 that circulates coolant through internal combustion engine 10 to absorb waste heat, and distributes the heated coolant to radiator 80 and/or heater core 90 via coolant lines (or loops) 82 and 84, respectively. In one example, as depicted, cooling system 101 may be coupled to engine 10 and may circulate engine coolant from engine 10 to radiator 80 via engine-driven water pump 86, and back to engine 10 via coolant line 82. Engine-driven water pump 86 may be coupled to the engine via front end accessory drive (FEAD) 36, and rotated proportionally to engine speed via a belt, chain, etc. Specifically, engine-driven pump 86 may circulate coolant through passages in the engine block, head, etc., to absorb engine heat, which is then transferred via the radiator 80 to ambient air. In one example, where pump 86 is a centrifugal pump, the pressure (and resulting flow) produced by the pump may be increased with increasing crankshaft speed, which in the example of FIG. 1, may be directly linked to the engine speed. In some examples, engine-driven pump 86 may operate to circulate the coolant through both coolant lines 82 and 84.