Abstract:
An on/off clutch assembly is disclosed having a simplified method for attaching the drive shaft to the hub portion of the drive pulley. The rotating shaft is formed with an integral external threaded portion that is designed to mate with a corresponding internal threaded portion of the hub. The external threaded portion, in conjunction with the internal threaded portion, replace the holes and corresponding cap screws that are used to attach the drive shaft to the hub in current designs. The new design limits the complexity of design and manufacture of the fan drive.

Description:
TECHNICAL FIELD 
   The present invention relates generally to a cone clutch fan drives and more particularly to a pneumatic cone clutch fan drive having a threaded attachment method for coupling the drive shaft of the clutch to the hub mounting. 
   BACKGROUND OF THE INVENTION 
   Vehicle engines commonly utilize cooling assemblies to remove excess heat from the engine and maintain an optimal operating temperature. The cooling assembly pumps a coolant through the engine and other components in order to control engine temperature. Heat generated within the engine and other components is absorbed by the coolant and dispersed into the surrounding atmosphere through the use of a radiator. In order to improve dispersal by the radiator, it is common to utilize fan assemblies to draw or force air past the radiator to assist in temperature transmission. 
   It is not always desirable for such fan assemblies to be run continuously. At times, it is desirable for the temperature within the coolant to increase rather than decrease. Additionally, continuous operation when unnecessary places a non-required draw on the engine and thereby reduces efficiency. To compensate for this, present fan assemblies utilize fan clutch assemblies that allow for the selective engagement of the fan to the engine such that the fans are engaged only when necessary. 
   The present invention relates to friction coupling devices that drive radiator-cooling fans. A common friction-coupling device is that of the dry friction drive style, otherwise referred to interchangeably hereinafter with a friction clutch assembly. Dry friction drives are used for their simplicity, cool operating temperature, and ability to turn at fully engaged peak operating speeds. 
   Although the present invention may be used advantageously in various configurations and applications, it is especially advantageous in a coupling device of the type used to drive a radiator cooling fan of an internal combustion engine for a over the road truck, such as a class 8 truck, and will be described in connection therewith. 
   Dry friction drives tend to have two operating conditions “ON and OFF”, which refers to when an associated friction clutch is either fully engaged or fully disengaged. When a friction clutch assembly is fully engaged, the assembly provides cooling to an associated engine and is not slipping. When a friction clutch assembly is fully disengaged slippage between the clutch plate and an engagement surface is at a maximum, thus providing little rotational output to drive an associated fan. 
   In order to attach the clutch to the pulley/bracket assembly, a series of holes are first introduced to the drive shaft and hub portion of the pulley/bracket assembly. A cap screw is then inserted within each of the holes to couple the clutch to the pulley/bracket assembly. These holes and cap screws are complex and add costs to the clutch assembly in terms of raw material costs, manufacturing costs, and assembly costs. It would be highly desirable to minimize these costs by simplifying the design of the coupling. 
   SUMMARY OF THE INVENTION 
   It is therefore an object to the present invention to provide a clutch assembly with a simplified method for attaching the drive shaft to the hub portion of the drive pulley. 
   In accordance with the objects of the present invention, the rotating shaft is formed with an integral external threaded portion that is designed to mate with a corresponding internal threaded portion of the hub. The threaded portions replace the holes and corresponding cap screws that are traditionally used to attach the drive shaft to the hub of the drive pulley. The new design limits the complexity of design and manufacture of the fan drive. 
   Other objects and features of the present invention will become apparent when viewed in light of the detailed description and preferred embodiment when taken in conjunction with the attached drawings and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a vehicle utilizing a friction clutch assembly in accordance with an embodiment of the present invention; 
       FIG. 2  is a quarter side cross-sectional view of a friction clutch assembly in accordance with an embodiment of the prior art; 
       FIG. 3  is an illustration of cone clutch fan drive in accordance with the present invention in a clutch engaged position; and 
       FIG. 4  is an illustration of cone clutch fan drive in accordance with the present invention in the clutch-disengaged position. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   In the following figures the same reference numerals will be used to refer to the same components. While the present invention is described primarily with respect to a cone clutch fan drive system, the present invention may be adapted and applied to various systems including: hydraulic systems, electrical systems, pneudraulic systems, mechanical systems, pneumatic systems, vehicle systems, cooling systems, fan drive systems, friction drive systems, or other systems. 
   In the following description, various operating parameters and components are described for one constructed embodiment. These specific parameters and components are included as examples and are not meant to be limiting. 
   Also, in the following description various fan drive components and assemblies are described as an illustrative example. The fan drive components and assemblies may be modified depending upon the application. 
   Referring now to  FIG. 1 , a perspective view of a vehicle  10  utilizing a fluidically controlled fan drive system  12  in accordance with an embodiment of the present invention is shown. The system  12  uses rotational energy from a liquid cooled engine  14  at an increased ratio to turn a radiator-cooling fan  16  to provide airflow through a radiator  18 . The system  12  includes a friction clutch assembly  20  that is fixed to one or more pulleys, such as pulley  22 , which is coupled to and rotates relative to a crankshaft (not shown) of the engine  14 . The pulleys rotate via a pair of belts  24 , within an engine compartment  25 . Of course, the present invention may be relatively operative in relation to various components and via any number of belts or other coupling devices, such as a timing chain. The friction clutch assembly  20  is mounted on the engine  14  via a mounting bracket  26 . The friction clutch assembly  20  pneumatically engages the fan  16  during desired cooling intervals to reduce the temperature of the engine  14 . 
   The fan  16  may be attached to the friction clutch assembly  20  by any suitable means, such as is generally well known in the art. It should be understood, however, that the use of the present invention is not limited to any particular configuration of the system  12 , or fan mounting arrangement, or any particular application for the system  12 , except as is specifically noted hereinafter. 
   Referring now to  FIGS. 2–4 , a quarter side cross-sectional view of the friction clutch assembly  20  having a rotating shaft  27  with a thermal energy transfer portion  28  in an engaged position accordance with an embodiment of the prior art ( FIG. 2 ) and according to a preferred embodiment of the present invention in both the engaged ( FIG. 3 ) and disengaged position ( FIG. 4 ). As will be described further below, a new and simplified method for coupling the transfer portion  28  to the hub portion  37  is disclosed in the present invention as presented in  FIGS. 3 and 4 . 
   The assembly  20  includes a translatable clutch housing  30  and a drive shaft  27  that is coupled to and rotates with the drive pulley  32 . The clutch housing  30  is attached to an engine-cooling fan, such as fan  16 . A friction liner  34  is coupled to the clutch housing  30  using a series of stamped plates  41  and screws  43  (the cross section shows one plate  41  and a pair of screws  43 ) and resides between the clutch housing  30  and the rotating drive shaft  27 . 
   A clutch spring  36  engages the clutch housing  30  with the drive shaft  27  in a friction clutch engagement area  38 . In operation, the drive pulley  32  rotates in turn rotating the drive shaft  27 , which when engaged rotates the translatable clutch housing  30 . The rotation of the housing  30  is translated to a coupled radiator-cooling fan  16  to provide airflow through a radiator  18 . 
   During engagement of the clutch housing  30 , thermal energy is generated by the contact between the friction liner  34  and the shaft  27 , and a certain amount of the thermal energy is transferred through the transfer portion  28  into the drive pulley  32 . 
   The drive shaft  27  has the transfer portion  28 , as well as a friction contact portion  40  and a spring/bearing portion  42 . The transfer portion  28  is generally vertical in orientation, whereas the friction contact portion  40  and the spring/bearing portion  42  are generally horizontal in orientation. A bearing  48  couples the spring/bearing portion  42  to a non-rotating shaft  79 . The transfer portion  28  has a pulley contact surface  44  that corresponds with a shaft contact surface  46  on the drive pulley  32 . 
   The drive pulley  32  includes a center protruding portion  60  and a pulley portion  62 . The center portion  60  extends forward away from the pulley portion  62  and is in contact with the shaft  27 . The center portion  60  includes the shaft contact surface  46  and is coupled to the drive shaft  27 . The pulley  32  performs as a heat sink and as such may be formed of various thermal energy conductive or heat sink materials known in the art. The pulley  32  may, for example, be formed of steel, aluminum, copper, or a combination thereof. 
   The friction clutch assembly  20  also includes a fluidic control circuit  70  that is operated via a main controller  72 . The fluidic control circuit  70  includes a piston rod or pneumatic transfer conduit  74  with a fluid channel  76  residing therein for the transfer of fluid, such as air, into a piston reservoir  78  of a fluid cylinder  80 . The fluid cylinder  80  resides over a piston  82 . A fluid pump  84  and a corresponding valve  85  are fluidically coupled to the fluid channel  76 . The main controller  72  is coupled to the pump  84  and to the valve  85  and adjusts the flow of the fluid into and out of the reservoir  78 . The valve  85  may, for example, be in the form of a solenoid. 
   The main controller  72  may be contained within the system  12  or may be separate from the system  12  as shown. The main controller  72  may be microprocessor based such as a computer having a central processing unit, memory (RAM and/or ROM), and associated input and output buses. The main controller  72  may be a portion of a central vehicle main control unit, an interactive vehicle dynamics module, a cooling system controller, or may be a stand-alone controller as shown. The main controller  72  may be coupled to a plurality of sensors  77  located throughout the engine that give inputs regarding particular engine operating conditions. The main controller  72  interprets these signals to adjust the flow of fluid into and out of the fluid reservoir  78 , therein precisely controlling the engagement or disengagement of the friction clutch assembly and therein precisely controlling the engine operating temperature to achieve a desired balance of engine performance characteristics such as fuel economy and emission. 
   The friction clutch assembly  20  is frequently engaged, as shown in  FIGS. 2 and 3 . When engaged no fluid is pumped into the reservoir  78 . The piston  82  and thus the housing  30  are in a fully engaged position. In the engaged position the spring  36  is decompressed or in an expanded state. 
   When cooling is no longer desired the main controller  72  pumps fluid into the reservoir  78 , which causes the piston  82  to shift rearward (rightward in  FIG. 4 ), towards the shaft  27 . As the piston  82  shifts rearward, the housing  30  also shifts rearward, thereby, compressing the spring  36  and causing the friction liner  34  and thus the housing  30  to disengage with the drive shaft  27 . This is the so-called disengaged position as shown in  FIG. 4 . 
   Of course, in other preferred embodiments, the engagement and disengagement mechanism of a preferred embodiment of the present invention may be reversed, wherein the clutch mechanism is maintained in a disengaged state in the absence of activation from the main controller and still fall within the spirit of the present invention. 
   As shown in  FIG. 2  and known in the prior art, the rotating shaft  27  is coupled within an internal threaded portion  35  of a hub portion  37  of the drive pulley  32 , within the transfer portion  28 , utilizing one or more cap screws  39 . To accomplish this, the transfer portion  28  includes corresponding holes  47  through which the cap screws  39  are inserted. Typically, six cap screws  39  and holes  47  are needed. 
   In the preferred embodiment of the present invention, as shown in  FIGS. 3 and 4 , the transfer portion  28  is formed having one or more external threaded portions  45 . Each respective external threaded portion  45  is secured within the corresponding threaded opening  35  of the hub portion  37  during assembly. The external threaded portion  45  therefore replaces the cap screws  39  of the prior art, and simplifies the manufacture of the transfer portion  28  of the rotating drive shaft  27  by eliminating the need to form holes  47  within the transfer portion  28 . 
   While the invention has been described in connection with one or more embodiments, it is to be understood that the specific mechanisms and techniques which have been described are merely illustrative of the principles of the invention, numerous modifications may be made to the methods and apparatus described without departing from the spirit and scope of the invention as defined by the appended claims.