As discussed in U.S. Pat. No. 6,499,442, entitled “Integral Waterpump/Electronic Engine Temperature Control Valve” as fuel is burned in an internal combustion engine, about one-third of the heat energy in the fuel is converted to power. Another third goes out the exhaust pipe unused, and the remaining third must be handled by a cooling system.
Most internal combustion engines employ a pressurized cooling system to dissipate the heat energy generated by the combustion process. The cooling system circulates water or liquid coolant through a water jacket which surrounds certain parts of the engine (e.g., block, cylinder, cylinder head, pistons, and intake manifold). The heat energy is transferred from the engine parts to the coolant in the water jacket. In hot ambient air temperature environments, or when the engine is working hard, the transferred heat energy will be so great that it will cause the liquid coolant to boil (i.e., vaporize) and destroy the cooling system. To prevent this from happening, the hot coolant is circulated through a radiator well before it reaches its boiling point. The radiator dissipates enough of the heat energy to the surrounding air to maintain the coolant in the liquid state.
In cold ambient air temperature environments, especially below zero degrees Fahrenheit, or when a cold engine is started, the coolant rarely becomes hot enough to boil. Thus, the coolant does not need to flow through the radiator. Nor is it desirable to dissipate the heat energy in the coolant in such circumstances since internal combustion engines operate most efficiently and pollute the least when they are running relatively hot. A cold running engine will have significantly greater sliding friction between the pistons and respective cylinder walls than a hot running engine because oil viscosity decreases with temperature. A cold running engine will also have less complete combustion in the engine combustion chamber and will build up sludge more rapidly than a hot running engine. In an attempt to increase the combustion when the engine is cold, a richer fuel is provided. All of these factors lower fuel economy and increase levels of hydrocarbon exhaust emissions.
To avoid running the coolant through the radiator, conventional coolant systems employ a thermostat. The thermostat operates as a one-way valve, blocking or allowing flow to the radiator. Most prior art coolant systems employ wax pellet type or bimetallic coil type thermostats. These thermostats are self-contained devices which open and close according to precalibrated temperature values.
Coolant systems must perform a plurality of functions, in addition to cooling the engine parts. In cold weather, the cooling system must deliver hot coolant to heat exchangers associated with the heating and defrosting system so that the heater and defroster can deliver warm air to the passenger compartment and windows. The coolant system must also deliver hot coolant to the intake manifold to heat incoming air destined for combustion, especially in cold ambient air temperature environments, or when a cold engine is started. Ideally, the coolant system should also reduce its volume and speed of flow when the engine parts are cold so as to allow the engine to reach an optimum hot operating temperature. Since one or both of the intake manifold and heater need hot coolant in cold ambient air temperatures and/or during engine start-up, and since these components are normally situated along the same flow circuit as the engine block, it is not practical to completely shut off the coolant flow through the engine block.
Numerous proposals have been set forth in the prior art to more carefully tailor the coolant system to the needs of the vehicle and to improve upon the relatively inflexible prior art thermostats. The inventor of the present invention has patented several such improvements. In particular, U.S. Pat. Nos. 5,503,118, 5,458,096, 5,724,931, and 6,499,442 disclose improvements to conventional cooling systems. These prior art patents are all incorporated herein in their entirety by reference.
A water pump is used in conventional engines to circulate coolant through the engine. Conventional water pumps function as the primary mechanism for forcing the fluid to flow through the cooling system. The most common form of water pump is a mechanical centrifugal pump which utilizes a circulating impeller to force water to flow into the engine. While mechanical impeller type water pumps provide a sufficient amount of pressure and are highly reliable, they cannot be actively controlled for maximizing the efficiency of the cooling system.
Recently, electric water pumps have been developed which provide for more efficient control of the flow of a fluid. Examples of some electric water pumps are described in U.S. Pat. Nos. 6,056,518 and 6,702,555, and U.S. Published Patent Application 2004/0081566, which are all assigned to Engineered Machine Products, Inc., one of the leaders in electric water pump design. These patents and patent applications are each incorporated herein by reference in their entirety.
As described above, conventional cooling systems utilize a valve for controlling circulation of coolant between the radiator and the engine. Typically, the water pump and the thermostat are mounted separate from one another. U.S. Pat. No. 6,499,442 describes a unique combination of an electric water pump and an electronic temperature control valve. In this system, the control valve is located within a housing that is directly connected to the water pump, thus permitting relatively direct fluid flow between the valve and the pump drive mechanism.
While U.S. Pat. No. 6,499,442 describes an improved combined water pump and valve arrangement, its mounting arrangement relative to the engine is not optimized. A need exists for a more efficient and optimized mounting arrangement for an electronic water pump.