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United States Patent 
[li] Patent Number: 4,962,734  Date of Patent: Oct. 16,1990
 ELECTRICALLY DRIVEN,
CIRCUMFERENTIALLY SUPPORTED FAN
 Inventor: Iner M. Jorgensen, Renton, Wash.
 Assignee: Paccar Inc., Bellevue, Wash.
 Appl. No.: 493,510
 Filed: Mar. 14, 1990
 Int. a.5 F01P 7/10
 U.S. a 123/41.49; 123/41.12;
 Field of Search 123/41.12, 41.49;
165/51; 417/356, 423.7, 423.12, 423.14; 416/189 R, 170 R, 238, 192, 169 A; 415/104, 122.1, 124.1, 223; 310/89
 References Cited
U.S. PATENT DOCUMENTS
1,996,195 4/1935 Ferguson 230/273
2,697,986 12/1954 Meagher, Jr 103/87
3,353,028 11/1967 Braikevitch et al 290/52
3,394,682 7/1968 Bensinger 123/41.12
3,422,275 1/1969 Braikevitch et al 290/52
3,700,358 10/1972 Papst et al 417/354
4,025,831 5/1977 Webb 318/138
4,060,753 11/1977 Okuyama et al 318/175
4,065,706 12/1977 Gosling et al 318/254
4,123,666 10/1978 Miller 417/356
4,228,384 10/1980 Arnold, Jr. et al 318/138
4,242,979 1/1981 Shima 415/124.1
4,257,554 3/1981 Willingham 236/35
4,358,245 11/1982 Gray 416/189
4,360,751 11/1982 Arnold, Jr. et al 310/60
4,396,875 8/1983 Yamauchi 318/254
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4,428,719 1/1984 Hayashibara et al 417/354
4,459,087 7/1984 Barge 123/41.12
4,553,075 11/1985 Brown et al 318/254
Primary Examiner—Noah P. Kamen
Attorney, Agent, or Firm—Seed and Berry
A circumferentially supported fan assembly for drawing cooling air through a radiator of a vehicle is described. The fan includes a fan ring extending circumferentially around the periphery of the fan, the blades of the fan extending from a central region to the fan ring. The entire weight of the fan is borne by a fan support assembly which extends around the periphery of the fan ring, outside the path of air flowing through the fan. The fan is the rotor of an electrically driven motor. A rotor flange of the fan ring extends transverse to the axis of the rotation of the fan, providing a greater torque advantage for the motor. An electrical control circuit selectively controls the speed of the fan to maintain the liquid temperature of the radiator below a selected threshold value. As additional cooling is required, the electronic controller gradually and smoothly increases the power drawn from the engine to turn the fan to increase its speed towards a selected speed. The air permeability of the fan when freewheeling is significantly increased because no central shaft or support structure blocks the airflow through the fan.
20 Claims, 2 Drawing Sheets
U.S. Patent Oct. 16,1990 Sheet 1 of 2 4,962,734
U.S. Patent Oct. 16,1990 sheet 2 of 2 4,962,734
CIRCUMFERENTIALLY SUPPORTED FAN
1. Technical Field
This invention relates to cooling systems for vehicles and, more particularly, to an electrically driven fan that is circumferentially supported and driven, thus providing greater airflow for increased cooling capacity. 10
2. Background of the Invention
Internal combustion engines, such as gasoline engines in cars and diesel engines in trucks, are usually liquid cooled. A fan pulls ambient air through a radiator to cool the liquid. In most vehicles, the fan is supported at 15 its center on a shaft extending from the engine block and is coupled by a belt to the engine crankshaft.
Mechanically coupling the fan to the engine creates significant problems. The fan and the radiator are placed directly in front of the engine. Airflow out of the 20 fan is blocked by the engine, an alternator, and other components, thus decreasing the airflow through the radiator and requiring a larger fan than would be necessary without such blockage. Because the fan is mounted to the engine block and the radiator is mounted to the 25 frame, they often move relative to each other, requiring significant spacing between them. A shroud is sometimes placed around the fan to ensure that air pulled by the fan comes through the radiator, not around it. The shroud must be spaced sufficiently far from the fan 30 blades that it is not struck as the blade rotates and engine vibrates. Spacing the fan from the radiator and shroud decreases the fan efficiency.
A disadvantage of driving the fan by belts from the crankshaft is that the fan always rotates proportional to 35 engine speed. As the engine's speed increases or decreases, so does the fan's, independent of the cooling actually required. In large diesel trucks, maximum torque is developed at an engine speed well below maximum revolutions per minute (rpm), requiring greater 40 cooling. In addition, the engine slows down when loaded, such as when the vehicle climbs a hill or the truck is full, slowing the fan down also and decreasing cooling capacity when it is needed most. Going down hills and on level runs, cooling-by the fan is often not 45 required; rather, airflow through the radiator as the truck travels provides sufficient cooling.
When sufficient cooling is provided by the ambient airflow, it is desirable to turn the fan off to conserve fuel. Presently, most large trucks have a clutched coii- 50 pling between the engine and the fan. When cooling is required, the clutch engages to cause rotation of the fan. When cooling is not required, the clutch disengages, saving power. Clutch controls add complexity and weight to the system. In addition, the fan blades are 55 stressed by being suddenly pulled on at full engine speed. The fan must be mechanically strong enough to withstand the repeated maximum stress occurring by being suddenly jerked on from a standstill, requiring additional weight and resistance to fatigue. Electrically 60 driven fans for an internal combustion engine are known in the prior art per se. However, current designs of such fans still have significant drawbacks. Presently, the weight of the fan is supported by a central shaft which extends through the fan. Supporting the weight 65 of the fan on a shaft extending through the center decreases fan efficiency for many reasons. When ambient air is forced through the radiator solely by the speed of
the.truck and the fan is not being driven by the engine, the central shaft blocks airflow and decreases cooling. The shaft support structure and fan blade support structure further decrease fan permeability and airflow when the engine fan clutch is not engaged.
SUMMARY OF THE INVENTION
In summary, the present invention includes a circumferentially supported fan assembly which draws cooling air through the radiator. The fan includes a fan ring extending circumferentially around the periphery of the fan, the blades of the fan extending from a central region to the fan ring. The entire weight of the fan is borne by a fan support assembly, which extends around the periphery of the fan ring, outside the path of air flowing through the fan. The fan support assembly is coupled to the same support frame region to which the radiator is coupled. The fan is the rotor of an electrically driven, brushless DC motor. A rotor flange of the fan ring extends transverse to the axis of the rotation of the fan, providing a greater torque advantage for the motor, and minimizing the power requirement for driving the fan. Coupling the radiator and the fan support assembly to a common frame region significantly reduces relative motion between the fan, the fan shroud, and the radiator, providing an increase in fan efficiency. Airtight seals are placed around the periphery of the fan, further increasing cooling efficiency.
An electronic control circuit selectively controls the speed of the fan to maintain the liquid temperature of the radiator below a selected threshold value. As additional cooling is required, the electronic controller gradually and smoothly increases the power drawn by the fan to increase its speed slowly toward a selected speed, thus avoiding rapid start-up stress.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of the fan, fan support assembly, and radiator coupled to a common support frame.
FIG. 2 is a front elevational view of the fan. FIG. 3 is a cross-sectional view taken along lines 3—3 of FIG. 1.
FIG. 4 is a cross-sectional view of an alternative embodiment of the fan rotor and drive mechanism taken along lines 3—3 of FIG. 1.
FIG. 5 is a front elevational view of an alternative embodiment of the central region of the fan.
FIG. 6 is a block diagram of alternative radiator and fan placements relative to the engine and the vehicle.
DETAILED DESCRIPTION OF THE
FIG. 1 illustrates a fan support assembly 10, a fan shroud 12, and a radiator 14. The fan support assembly 10 and radiator 14 are coupled to a common frame support region 16. In one embodiment, the frame support 16 is a unitary metal bracket to which both the radiator 14 and fan support member 10 are attached. In an alternative embodiment, the frame support region 16 includes different members coupled to a common frame region. The fan shroud 12 is coupled to the fan support member 10 and the radiator 14, the weight of the shroud being supported by both. Brackets (not shown) extend from the fan support assembly 10 to the radiator for increased stability. In one embodiment, the fan support assembly 10 is rigidly coupled to the radiator with the