This invention relates to engine cooling systems and more particularly to a novel and improved cooling system in a turbo charged internal combustion engine.
The development of internal combustion engines for reduced exhaust emissions has resulted in significant increases in the amount of heat dissipation into engine cooling systems. Traditionally, increases in the required amount of heat dissipation has been accomplished by improving the radiator cooling capacity through increasing the core size of the radiator. In addition, increased coolant and cooling air flow has been used to deal with the increase in required heat dissipation.
Packaging space for larger radiator cores and high energy consumption due to increased coolant and cooling air flow limit the amount of heat dissipation capacity increase that can be accomplished with these traditional approaches.
It is possible to improve cooling capacity by elevating the maximum permissible coolant temperature above traditional levels. The adoption of pressurized cooling systems which permitted operation with coolants at 100° C./212° F. was a step in this direction. The addition of expansion tanks assisted in maintaining such temperature levels. However, it has become desirable to elevate coolant temperatures to even higher levels.
Utilization of elevated coolant temperatures requires proper pressurization under all operating, stand-still and ambient conditions in order to control cooling characteristics, secure coolant flow, prevent cavitation and cavitation erosion and to prevent unwanted boiling and overflow.
Temperature and pressure increase becomes more critical as the heat dissipation from the engine approaches the cooling capacity of the cooling system. A now traditional approach for pressurizing cooling systems is to rely on closed expansion or pressure tanks which depend on temperature increases of coolant and air to create and maintain desired pressures. Such a system communicates with ambient air by opening two way pressure valves to thereby communicating the system with ambient air to entrain new air into the pressure tank when entrapped air and the coolant cool to create a vacuum in the system. Such systems are passive and vulnerable to leaks. Moreover, if such a system is depressurized for any reason, such as maintenance or top-off, pressure is reduced to ambient and operating time and cycles are needed to increase the pressure in the system.
According to the present invention, an internal combustion engine cooling system is pressurized by introducing air under pressure from an external pressurized source. More specifically, in the preferred and disclosed embodiment, air under pressure from an engine intake manifold is communicated into the cooling system thereby to pressurize the system and elevate the maximum available coolant temperature. In its simplest form, a conduit connects an engine intake manifold with a cooling system expansion tank via a flow control check valve. The flow control valve is in the form of a spring loaded non-return valve connected in the conduit for enabling unidirectional flow from the intake manifold to the expansion tank.
In an alternate embodiment, a flow control valve in the form of a spring loaded non-return valve is also used. A second spring loaded non-return valve allows decompression of the expansion tank to a threshold pressure level corresponding to the spring pressure of the second valve plus the pressure in the engine air inlet system. In order to dampen decay of pressure in the coolant system, a restrictor is interposed in series with the second non-return valve.
A further alternative includes an electric or pneumatic switch between the restrictor and the second non-return valve. A control algorithm for this switch is based on coolant pressure, temperature, engine load parameters and duty cycles for optimizing the expansion tank pressure.
In a still further alternative, a two directional two way control valve is used together with pressure sensors respectively located on opposite sides of the control valve. A control algorithm for pressure control is based on selected parameters such as coolant pressure, engine load, charge air pressure, coolant temperature, ambient temperature and pressure, cooling system capacity, cooling fan speed and duty cycles.
The alternate embodiments using electronic control units enable diagnosis of the systems actual functioning condition. The system compares actual pressure levels, time temperatures and valve positions with expected critical pressures under given conditions in the setting and design parameters for the system and components used in it. Diagnostic information is available for drivers and service information. It also can be used for actively changing the functioning of the system to enable continued use of the engine vehicle in a so-called limp home mode in case of system malfunction.
Accordingly, the objects of this invention are to provide a novel and improved engine coolant system and a method of engine cooling.
Referring to the drawings and
The engine 12 is equipped with a cooling system which includes an expansion tank 18, FIG. 2. The expansion tank 18 is a now standard tank including an outlet 20 connected to an inlet of a water or coolant pump. The tank 18 includes a fill opening equipped with a pressure cap 22. In the disclosed embodiment, the cap 22 includes a tank pressure relief and coolant overflow valve 24 and a vacuum relief valve 25 as is now conventional in coolant systems.
A conduit 26 connects the intake manifold 15 to the expansion tank 18. The conduit 26 communicates with the expansion tank 18 through an inlet 28. A floating check valve 30 functions to control unidirectional fluid flow through the inlet 28 when a level of coolant 32 in the tank 18 rises to a higher level than that depicted in FIG. 2. Thus, the check valve 28 functions to prevent coolant 32 from entering the conduit 26.
A flow control valve 34 is interposed in the conduit 26. In its simplest form, the flow control valve is a simple spring loaded non-return valve which allows pressurized flow from the manifold 15 to the tank 18, but prevents reverse flow of pressurized fluid from the tank 18 to the manifold 15.
With the embodiment of
In the embodiment of
With the embodiment of
An electronic control unit 40 controls the positioning of the directional control valve. The control algorithm for this function is based on coolant pressure, temperature, engine load parameters, and duty cycles relevant for optimizing the expansion tank pressure. Alternatively, a pneumatic switch may be substituted for the electrically control directional control valve that has been described.
The direction control valve 42 is controlled by an electronic control unit 48. A control algorithm for the control unit 48 is based on selected parameters such as coolant pressure, engine load, charge pressure, coolant temperature, ambient temperature, ambient pressure, cooling system capacity, cooling fan speed, and duty cycles. The pressure in the expansion tank is optimized by actively pressurizing to satisfy coolant system function. While the pressure is optimized, it is only to necessary pressure levels and with pressure variations and amplitudes which match the properties of materials used in the coolant system.
A passive pressure build-up in the expansion tank will take place naturally and in parallel with the active pressure control systems that have been described. How the passive pressure build-up will interact depends on which of the embodiments is employed.
The embodiments of
Diagnostic information derived when either the embodiment of
Operation
In operation from cold engine start up, operation of the turbo charger will transmit air under pressure through the conduit 26 to the expansion tank 18. Assuming the pressure relief setting of the cap pressure relief valve 24 is high enough, air under pressure will flow through the flow control valve 34 until pressure in the expansion tank 18 is approaching the relief valve opening pressure (but not higher). Should the pressure of air from the turbo charger 16 drop, the one way flow control valve 34 will prevent a pressure drop in the expansion tank 18.
With the embodiment of
With the embodiment of
With the embodiment of
The embodiment of
Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction, operation and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.
This is a Divisional application of application Ser. No. 09/788,874, filed on Feb. 20, 2001, now U.S. Pat. No. 6,532,910.
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Number | Date | Country | |
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20030150407 A1 | Aug 2003 | US |
Number | Date | Country | |
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Parent | 09788874 | Feb 2001 | US |
Child | 10360156 | US |