Internal-combustion engines – Cooling – Automatic coolant flow control
Reexamination Certificate
2002-08-14
2004-08-10
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Cooling
Automatic coolant flow control
Reexamination Certificate
active
06772714
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to controlling the rotational speed of a rotational output part of a fan used for cooling components of a motor vehicle. Typically, such fan is driven by a viscous friction clutch which is coupled to a driving rotational part by way of a shearing fluid whose effective fluid quantity determines the transferable torque. Such driving rotational part is typically driven, directly or indirectly, by the prime energy supply (e.g. internal combustion engine) of the vehicle.
Arrangements of this type are used, for example, for controlling the rotational speed of a fan for cooling motor vehicle components such as engines, engine fluids, and vehicle accessories. In such cases, the fan can be coupled to the vehicle engine by way of the fluid friction coupling. Alternatively, the fan can be driven by a separate electric motor, powered from the vehicle electrical system, through an electrical control system. Accurate cooling control is essential for efficiency gains related to engine compartment cooling.
Whether the fan is driven by a viscous friction coupling to the engine drive shaft, or by a separately powered electric motor, activation of the fan, and control of fan speed, are controlled by a control system. Improved such control systems are the subject of this invention. Thus, while the remainder of this disclosure is directed to controlling a viscous friction coupling, or clutch, which drives the cooling fan, the same inventive parameters can as well be applied to a fan which is driven by an electric motor separately powered from the vehicle electrical system and not directly connected to the mechanical power developed by the prime energy source which serves as the general power source for the vehicle.
A wide range of applied cooling capacities are required by motor vehicles, depending on the conditions in which the vehicles are operated, as well as the loads being placed on a vehicle, on the engine, on engine components, and on vehicle accessories. The degree of cooling required during engine operation varies from a low level under light load conditions in cool weather, to a high level under heavy load conditions in hot and humid weather.
The fan is used to provide cooling air flow for diverse engine-related and vehicle-related media, such as engine coolant, charge air, engine oil, transmission oil, and retarder oil. The fan is also used, as required, for cooling refrigerant of an air conditioning system.
The fan is typically positioned rearwardly, in the vehicle, of such cooling devices as a coolant radiator, an air conditioner heat exchanger/condenser, a transmission oil cooler, and the like, which are typically positioned behind the grill at the front of the vehicle. Thus, operation of the fan draws ambient cooling air under a low negative pressure through such forwardly-disposed devices, thereby assisting in transfer of heat from such devices to the ambient air.
Correspondingly, the fan is typically placed frontwardly, in the vehicle, of the vehicle engine or other main heat source, whereby the air drawn through e.g. the one or more forwardly-disposed heat exchangers, radiators, is expelled from the fan and blown under a small positive pressure toward the rear of the vehicle and over the engine block and other heat-producing components in the engine compartment, thus to dissipate heat to the so-expelled ambient air.
The operation of a single fan is thus used to provide cooling air, and corresponding heat dissipation, to a substantial number of heat sources, each of which has a different requirement for heat dissipation. All such heat sources can tolerate operating at conditions wherein an external surface of the heat source is at ambient temperature. All such heat sources have high temperature limits which cannot safely be exceeded. Some such heat sources have optimum temperatures or temperature ranges whereat efficiency is improved or optimized.
Historically, the fan was run at such cooling capacity that all cooling needs were intentionally exceeded, and whereby no further control of the fan was exercised, and no monitoring of temperatures was used in fan control. However, such intentional overcooling, in combination with the lack of use of temperatures in controlling fan speed, can result in reduced efficiencies in some heat sources, and undetected overheating of one or more such heat sources.
More recently, conventional practice is that various parameters representing existing engine and vehicle e.g. heat-related conditions are fed into a controller which processes the various inputs, determines a desired fan speed, and sends a signal corresponding to the desired fan speed, to the viscous clutch or electric motor, whichever is running the fan. Referring to the viscous clutch embodiments, the signal is received by an actuator on the viscous clutch, which actuates the clutch to adjust the effective amount of shearing which takes place in the clutch, thereby to adjust the speed of rotation of the fan. When more cooling is needed, the speed of the fan is increased. When less cooling is needed, the speed of the fan is reduced.
For this purpose, the viscous clutch has a storage chamber and a working chamber which encloses a rotational driving part in the form of a driven coupling disk and between which an inflow path and a return flow path, respectively, are provided for shearing fluid circulation. Such circulation is caused by a circulation pump which pumps the shearing fluid from the working chamber into the storage chamber. The valve, which can be actuated by e.g. a solenoid, controls the shearing fluid circulation and thus the quantity of shearing fluid which is, in each case, situated in the working chamber which is available as the effective fluid quantity for the transmission of torque.
Friction fluid couplings with timed electric driving of an adjusting unit for the variable adjusting of the effective shearing fluid quantity are disclosed in EP 0 009 415 B1.
U.S. Pat. No. 4,828,088 Mohan et al, which is herein incorporated by reference in its entirety, teaches sensing coolant temperature and adjusting fan speed according to the sensed coolant temperature.
U.S. Pat. No. 5,584,371 Kelledes et al, which is herein incorporated by reference in its entirety, teaches sensing engine speed, coolant temperature, nominal engine temperature, fan speed, and whether the air conditioner is on or off, and adjusting fan speed accordingly.
U.S. Pat. No. 5,947,247 Cummings III, which is herein incorporated by reference in its entirety, teaches a continuously variable fan output speed, and electric control circuitry which continues to alter the signal to the control valve until the sensed speed matches the desired speed. The controller is provided with a series of processing algorithms which respond to the signals from the sensors which sense the sensed conditions. The algorithms provide response signals appropriate to the sensed conditions, and thereby determine the desired fan speed. Named sensed parameters are fan drive oil temperature, engine coolant temperature, charge air temperature, hydraulic oil temperature, and engine speed.
U.S. Pat. No. 6,079,536 Hummel et al teach a temperature stage analysis in the controller feeding a rotational stage speed controller, and multiple speed demand units in parallel, wherein the signal with the highest rotational speed demand, including incorporation of correction adjusting signals, is selected for implementation of fan speed. The parameters sensed are retarder temperature, charge air temperature, engine coolant temperature, air conditioner on or off, engine speed, engine torque, momentary speed of the coupling disc of the friction clutch, actual fan speed, fan drive speed, desired fan speed, and engine brake demand. The various demand signals are fed in parallel to a maximum value selection controller, along with certain correction signals, thereby to arrive at a desired fan speed, which is then transmitted to an actuator which implements such fan speed at the fan.
The purpose of such controlling o
Fischer Douglas Robert
Laird David Rick
Miller James Anton
Pipho Michael John
Plassman Barry Edward
Deere & Company
Kamen Noah P.
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