Separate oil gallery for piston cooling with electronic oil flow control

Abstract

An engine oil distribution system for an internal combustion engine includes a main gallery and a separate oil gallery for piston cooling nozzles. The separate gallery may be controlled by a control valve that regulates the oil flow. The oil flow to the separate gallery may be controlled by an electronic control module in accordance with the piston cooling needs, for example, varied as a function of the load applied to the engine, or as a function of engine temperature. Preferably, engine temperature is sensed by coolant fluid temperature, or directly measured metal temperature, correlated to the thermal state of the piston.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to oil distribution systems in compression ignition internal combustion engines, the system having a main gallery, a separate oil gallery for piston cooling nozzles and one or multiple control valves which regulate the oil flow through the separate gallery to the piston cooling nozzles, whereby the system may match the amount of oil distributed with the piston cooling demand. [0003] 2. Background Art [0004] In general, diesel engines with pistons made of steel or aluminum require piston-cooling jets as a means of removing heat from the piston during engine operation. However, piston-cooling requirements are not uniform across the engine operating range. Maximum demand for cooling occurs at full loads, at engine speeds ranging from peak torque to rated speed, when engine thermal loading is high. If the emissions control strategy includes running the engine at retarded beginning of injection (BO...

AI Technical Summary

Benefits of technology

[0009] At part or low loads, the oil temperature is lower, viscosity slightly higher, and parasitic losses in the lubrication system higher than at full load. The control may be used to reduce, or interrupt, the oil flow through piston-cooling nozzles in accordance to piston cooling requirements, so that the total amount of oil being pumped through oil filter and oil cooler can be reduced, together with the pump power which is not needed. The reduction in the oil flow through the system is important because the flow through piston-cooling nozzles may comprise up to 35-40% of the total oil flow in the system, and important savings in parasitic losses and, ultimately, fuel consumption may be achieved.

[0010] In the preferred embodiment, engine thermal load, as suggested by fluid or metal temperature, or by engine torque or load, may be the determining factor, rather than engine speed. The invention also leads to improvements in the design and operation of oil coolers controlled by thermatic valves (also known as “oil thermostats”). Current designs that use an oil thermostat attempt to regulate the oil cooling in the oil cooler by varying the amount of oil flow being passed and cooled through the cooler as a function of oil temperature. In general, a desired oil temperature is a temperature that should be controlled to fall in between a minimum and maximum value. If the oil is overheated, its decrease in viscosity jeopardizes proper bearing lubrication and may lead to catastrophic engine failure in short time. There are also long term effects through increased oxidation rates at high temperatures, and oil properties deteriorations are mitigated through reduced oil change intervals, with negative implications on life-cycle costs and environment. Therefore, oil coolers are used to maintain the oil temperatures below the maximum limit, especially on heavy and medium duty diesel engines. If the oil temperature falls below a minimum value due to overcooling, or in winter (at low ambient temperatures), oil viscosity increases along with pumping losses and impacts negatively the fuel economy. However, with the present invention a designer may supply the piston cooling circuit, for example, the “separate gallery” only, with cooled oil at all operating conditions and ambient temperatures, and regulate the oil flow to the piston cooling jets according to prescribed algorithms, while the temperature of oil fed to the engine continues to be regulated by the temperature controlled oil cooler. A modified or a controlled oil cooler may also be employed to provide this advantage.

[0011] The invention may reduce the cost of improving piston cooling by allowing one or more control valves to regulate the flow to piston banks, for example, two valves, each controlling flow to a bank of pistons. The invention also may reduce the cylinder-to-cylinder variation in piston cooling oil flow, compared to designs where other oil consumers are fed off the main gallery or the flow is biased toward one end of the gallery. By decoupling the objective of optimized bearings lubrication oil flow control as related to engine speed, from optimized piston cooling objective via oil control responsive to engine thermal state, the present invention provides improved performance and efficiency in the design and operation of the engine.

Problems solved by technology

If the oil is overheated, its decrease in viscosity jeopardizes proper bearing lubrication and may lead to catastrophic engine failure in short time.

There are also long term effects through increased oxidation rates at high temperatures, and oil properties deteriorations are mitigated through reduced oil change intervals, with negative implications on life-cycle costs and environment.

If the oil temperature falls below a minimum value due to overcooling, or in winter (at low ambient temperatures), oil viscosity increases along with pumping losses and impacts negatively the fuel economy.

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