Fan drive actuator

A fan drive for the cooling fan of an internal combustion motor vehicle in which the temperature of the engine coolant is constantly sensed and, in response to a sensed predetermined coolant temperature, heated air is directed by a blower through a conduit from a heat sink adjacent the exhaust manifold to the temperature sensing element of the fan drive. The heated air impacting on the temperature sensing element causes the element to react in a sense to engage the fan drive and cool the coolant.

BACKGROUND OF THE INVENTION 
This invention relates to fan drives for motor vehicles and, more 
particularly, to an improved actuator for a motor vehicular fan drive. 
Fan drives for driving the cooling fan of an internal combustion engine are 
well-known. See, for example, U.S. Pat. No. 3,809,197. Typically, such 
drives include input and output members which have interdigitated portions 
or lands and grooves which are spaced closely adjacent each other with a 
fluid shear medium positioned in the space therebetween. The fluid shear 
medium functions to transmit the drive from the input member to the output 
member on which the fan is mounted. The extent to which the fan drive is 
engaged is dependent on the amount of viscous fluid present in the space 
between the input and output members and the amount of fluid is controlled 
by a temperature control valve device. The temperature control valve 
device includes a temperature sensing element, such for example as a coil 
spring bimetallic element, disposed at the front of the fan drive in a 
position to be influenced by the air passing through the radiator of the 
vehicle. Briefly, when the temperature of the air passing through the 
radiator is relatively cool, the fan drive is disengaged. When the air 
temperature passing through the radiator increases to a predetermined 
value, the temperature sensing element functions to actuate the 
temperature control valve to pass additional fluid to the space between 
the clutch members to thereby effect engagement of the fan drive and drive 
the fan to cool the engine coolant. 
Whereas this arrangement is generally satisfactory, it embodies an inherent 
operational inaccuracy since the temperature of the air impacting the 
temperature sensing element is typically significantly different than the 
temperature of the coolant in the radiator. Whereas the temperature at 
which the temperature sensing element is actuated may be adjusted to 
accommodate this difference, the adjustment would have to be different for 
different operating conditions of the same vehicle so that the described 
arrangement can, at best, be calibrated to be accurate over only a portion 
of the range of operating conditions encountered by the vehicle. To 
eliminate this inaccuracy, it has been proposed to sense the temperature 
of the engine coolant directly and engage the fan drive upon the sensing 
of a predetermined coolant temperature. However, all such direct coolant 
temperature sensing systems heretofore proposed have been relatively 
complex and expensive and/or have necessitated a major redesign of the 
basic viscous fan drive system. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a fan 
drive system that is directly responsive to engine coolant temperature and 
yet is compatible with existing fan drive technology. 
A more specific object is to provide an actuator for a viscous fan drive 
which actuates the fan drive in direct response to engine coolant 
temperature and does not require modification of the existing viscous fan 
drive structure. 
The invention actuator is intended for use with an engine system of the 
type including an internal combustion engine having cooling passages 
containing liquid coolant, a radiator adapted to receive and cool the 
coolant, a cooling fan disposed adjacent the radiator, a fan drive 
drivingly interconnecting the engine and the fan, and a sensor mechanism 
operative in response to a predetermined ambient air temperature to cause 
engagement of the fan drive to drive the fan and cool the coolant. 
According to an important feature of the invention, the actuator includes 
means for sensing the temperature of the coolant and means operative in 
response to a predetermined sensed coolant temperature to direct air from 
a source of heated air adjacent the engine to the vicinity of the sensor 
mechanism, whereby to actuate the sensor mechanism and engage the fan 
drive to drive the cooling fan. This arrangement has the advantage of 
engaging the fan drive in direct response to sensed coolant temperature 
while totally preserving the existing viscous fan drive mechanism. 
In the preferred embodiment of the invention, the heated air source 
comprises a heat sink defined adjacent the exhaust manifold of the engine, 
a conduit extends from the heat sink to the vicinity of the sensor 
mechanism, and a blower is provided in the conduit which is actuated in 
response to sensing of the predetermined engine coolant temperature to 
direct a positive stream of heated air at the sensor mechanism. This 
arrangement provides a quick, positive system response and yet is 
extremely simple in structure and operation and constitutes a ready add-on 
to existing and known engine and fan drive structure. 
These and other objects, features, and advantages of the invention will 
become apparent from the following detailed description of a preferred 
embodiment of the invention and from the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The illustrated engine system includes an internal combustion engine 10, a 
radiator 12, a fan drive 14, and a fan drive actuator seen generally at 
16. 
Engine 10 is seen schematically and includes a block 18 containing internal 
cooling passages or jackets (not shown) for circulating a coolant; a 
carburetor 20; an air cleaner 22 having a snorkel 24; an exhaust manifold 
26 feeding combustion products to an exhaust pipe 28; a jacket 30 formed 
as a sheet metal stamping and surrounding manifold 26 to trap heat 
emanating from the manifold and create a heat sink 31 around the manifold; 
a flexible heat pipe 32 fitted at its lower end over a fitting 30a formed 
integral with jacket 30 and fitted at its upper end over a fitting 24a 
formed integral with snorkel 24; a vacuum actuator 34 controlling a valve 
(not shown) in snorkel 24 and operative to direct preheated air to 
carburetor 20 from heat sink 31 during engine warm-up and thereafter 
direct cool outside air to the carburetor; and an accessory shaft 36 
including a pulley 38 driven by a belt 40 driven by the engine crankshaft. 
Radiator 12 is positioned in front of engine 10 and receives and cools 
coolant from engine 10 in known fashion. 
Fan drive 14 is carried on the free or forward end of accessory shaft 36 
and includes an input member 42 fixedly secured to shaft 36, an output 
member 44 journaled on input member 42, a fan 46 fixedly secured to output 
member 44, and a temperature sensing element 48 carried on the forward 
face of output member 44. Element 48 comprises a bimetallic coil spring 
mounted on a central shaft. The shaft of element 48 controls an internal 
valve mechanism (not shown) which in turn regulates the amount of fluid in 
the space between the input and output members and thereby the extent to 
which the output member is driven by the input member. Broadly considered, 
element 48 senses changes in ambient temperature and selectively rotates 
its central shaft in response to such changes to selectively regulate the 
valve mechanism and selectively control the extent to which the fan is 
driven. Further details of the fan drive are shown in U.S. Pat. No. 
3,809,197. 
The present invention primarily concerns the fan drive actuator mechanism 
seen generally at 16. Actuator mechanism 16 functions to direct heated air 
from heat sink 31 to temperature sensing element 48 in response to a 
predetermined engine coolant temperature. Mechanism 16 includes a hose or 
conduit 50, a blower 52, a hose or conduit 54, a valve mechanism 56, and a 
coolant temperature sensing switch 58. 
Hose 50, preferably formed of a heat resistant plastic material, is fitted 
at its rearward end over a fitting 30b formed integral with fitting 30a of 
jacket 30 and is fitted at its forward end over a central fitting 60a 
formed integral with the housing 60 of blower 52. 
Blower 52 includes a small D.C. motor 64 driving a "squirrel cage" type 
impeller 66 journaled in blower housing 60. 
Hose 54, preferably formed of the same heat resistant plastic as hose 50, 
is fitted at one end over a tangential fitting 60b formed integral with 
blower housing 60 and extends therefrom transversely across the rear face 
of radiator 12 to the central longitudinal axis of the engine system where 
it terminates in an elbow portion 54a opening immediately in front of 
temperature sensing element 48. 
Valve mechanism 56 includes a flapper 68 journaled in hose 54 on a shaft 70 
and a solenoid 71 having a central shaft or plunger 72 drivingly connected 
to flapper shaft 70 by a crank member 74 pivotally secured to the free end 
of plunger 72 and fixedly secured to flapper shaft 70. Flapper 68 closes 
hose 54 when solenoid 71 is deenergized and moves to a position opening 
hose 54 when solenoid 71 is energized. 
Coolant temperature sensing switch 58 is mounted in engine block 18 and 
communicates at its lower end with the coolant in the coolant passages of 
the block. Switch 58 may take any of several known forms and, for example, 
may be constituted by the coolant temperature sensing switch already 
present in most motor vehicles as the actuator switch for the overheat 
warning light on the instrument panel. 
Switch 58 is arranged as part of an electrical circuit that includes a 
circuit portion 76 connected to motor 64 of blower 52; a parallel circuit 
portion 78 connected to solenoid 71 of valve mechanism 56; and another 
parallel circuit portion 80 connected to the overheat warning light 82 
mounted on the instrument panel of the associated vehicle. All three 
circuit portions pass through and are completed by switch 58 with block 18 
providing the negative or ground for all three circuit portions. Switch 58 
may, for example, be calibrated to close upon the sensing of an engine 
coolant temperature of 230.degree. F. 
In so long as the engine coolant temperature remains below 230.degree. F., 
the invention actuator is inoperative. Specifically, flapper 68 remains in 
a position closing hose 54, blower 52 is dormant, light 82 remains off, 
and fan 46 remains essentially inactive. When the coolant temperature 
reaches 230.degree. F., switch 58 closes to complete circuits 76, 78 and 
80 and respectively turn on blower 52, open flapper 68, and light bulb 82. 
Heated air from heat sink 31 is thus drawn through hose 50 and directed 
through hose 54 against temperature sensing device 48. The air in heat 
sink 31, with a warm engine, will range between 300.degree. and 
350.degree. F.; the air delivered to element 48 through 50 and 54 will be 
somewhat below that temperature due to line losses. The heated air 
delivered against element 48 will cause the element to react to effect a 
rotation of its central shaft to in turn move the internal valve mechanism 
to a position where there is a net gain of viscous fluid in the space 
between the input and output members of the fan drive, whereby to cause 
the fan to be driven. The fan will continue to be driven until the coolant 
temperature, as sensed by switch 58, drops a predetermined amount below 
230.degree. F., whereupon switch 58 will open, breaking circuits 76, 78 
and 80 and respectively turning off blower 52, closing flapper 68, and 
extinguishing light 82. This cuts off the flow of heated air to element 
48, causing the element to cool and effect a rotation of its central shaft 
in a direction to move the internal valve mechanism to a position where 
there is a net loss of viscous fluid in the space between the input and 
output members of the fan drive whereby to substantially reduce the speed 
at which the fan is driven. 
The invention actuator will be seen to provide a positive, fast-acting 
means of turning the fan drive on and off in direct response to coolant 
temperature. And the disclosed actuator accomplishes its direct coolant 
temperature control of the fan drive without need for modification of 
existing viscous fan drive structures. 
Whereas a preferred embodiment of the invention has been illustrated and 
described in detail, it will be apparent that various changes may be made 
in the preferred embodiment without departing from the scope or spirit of 
the invention. For example, the invention actuator has been described, in 
its preferred embodiment, as including both a blower mechanism 52 and a 
valving mechanism 56 with the blower functioning to direct a positive flow 
of heated air against the temperature responsive circuit and the valve 
mechanism functioning upon opening of switch 58 to close off pipe 54 and 
prevent "run-on" of the fan drive due to heated air continuing to be 
sucked through pipes 50 and 54 following shutdown of the blower. However, 
the invention can also be practiced, in given installations, with either 
the blower mechanism alone or the valving mechanism alone. In 
installations where only the blower is used, the blower provides the means 
for positively directing heated air from the exhaust manifold heat sink to 
the temperature sensing element. In installations where only the valving 
element is used, the valving element, and specifically the flapper of the 
valving element, provides the means for directing heated air from the 
exhaust manifold heat sink to the temperature sensing element. The flow of 
heated air through the conduit means in this latter instance would be 
augmented by the suction created by the fan which, even with the invention 
actuator in an "off" condition, tends to continue to rotate albeit at a 
relatively low speed.