Viscous clutch with front mounted electromagnetic coil, modular valve subassembly and front hub subassembly for viscous clutch, and method of manufacture thereof

Abstract

The viscous clutch assembly (20) includes a rotationally fixed center shaft (22-1), a rotor (32) rotatably supported on the center shaft, a housing (30) rotatably supported on the center shaft, a working chamber (34), a reservoir (36) carried by the rotor, an electromagnetic coil (40) disposed at or near a forward end (22-1F) of the center shaft, a valve subassembly (38) magnetically operable to control flow of shear fluid between the reservoir and the working chamber, a flux guide (44) extending axially across a cover (30C) of the housing, and a flux insulating material (62; 46F) disposed radially inwardly adjacent the flux guide. A flux circuit disposed forward of the rotor connects the electromagnetic coil and the valve subassembly, passes through the flux guide and the center shaft, and at least partially surrounds the flux insulating material.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present invention relates to electromagnetically actuated viscous clutches and modular valve subassemblies for viscous clutches, as well as methods of making and using such assemblies and subassemblies. [Background technology]

[0002] Internal combustion engines, including diesel engines, are in very high demand in many applications including mining and power generation. The engines need to be cooled. The generally preferred method of cooling is to fit a cooling fan to the engine. The cooling fan is usually driven by the engine crankshaft via a pulley. In many cases, the cooling fan is always running when the engine is running, regardless of the need for cooling. This is the simplest way to achieve engine cooling. However, the fan can consume a significant amount of power. The fan power required is typically about 10% of the rated power of the engine. Fan clutches are commonly used as a means to disconnect or partially disconnect the fan when peak cooling is not required, thereby allowing selective control of fan operation. The power required for the fan is correspondingly reduced, saving fuel, reducing noise, and increasing the power available to the machine. An example of a conventional viscous fan clutch can be found in PCT International Patent Application No. 2003 / 0133636. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 062856 Summary of the Invention [Problem to be solved by the invention]

[0004] It would be desirable to provide a viscous clutch assembly supported by a rotationally fixed mounting bracket and having a front mounted electromagnetic coil capable of controlling operation of a valve with a relatively small flux circuit as part of an overall assembly that is relatively small and relatively low mass. It would also be desirable to provide an easy to install valve for a viscous clutch, and a relatively simple method of manufacturing and assembling the entire viscous clutch mechanism and the entire viscous clutch assembly. [Means for solving the problem]

[0005] In one aspect, the viscous clutch assembly includes a center shaft that is rotationally fixed and has a forward end and an aft end opposite the forward end, a rotor rotatably supported on the center shaft, a housing disposed adjacent the rotor and rotatably supported on the center shaft, a working chamber having the rotor and the housing defining at least a portion of a boundary of the working chamber, a reservoir carried by the rotor and rotationally fixed to the rotor, an electromagnetic coil disposed at or near the forward end of the center shaft and rotationally fixed, a valve subassembly operable to control flow of shear fluid between the reservoir and the working chamber and controllable using a magnetic flux generated by the electromagnetic coil, a flux guide extending axially across a cover of the housing, and a magnetic flux insulating material disposed adjacent to and radially inward of the magnetic flux guide. A magnetic flux circuit connects the magnetic coil and the valve subassembly, the magnetic flux circuit being disposed forward of the rotor and passing through the magnetic flux guide and a portion of the center shaft. The magnetic flux insulating material may be at least partially surrounded by the magnetic flux circuit.

[0006] In another aspect, a method of manufacturing a viscous clutch includes the steps of providing a mounting bracket having a center shaft, rotatably mounting a rotor to the center shaft and positioning a housing base adjacent to the center shaft and the rotor, assembling a modular valve subassembly, securing the pre-assembled modular valve subassembly to the rotor, rotatably mounting a housing cover to the center shaft and securing the housing cover to the housing base, and securing an electromagnetic coil at or near a forward end of the center shaft, with one or more wires for the electromagnetic coil extending rearwardly through a bore in the center shaft. The modular valve subassembly includes the steps of: securing a reed valve element to an outer pole of ferromagnetic material; and securing a spring to an armature such that when the modular valve subassembly is fully assembled, the armature is movable relative to the outer pole and at least a sealing portion of the reed valve element is axially disposed between the outer pole and the armature.

[0007] In another aspect, a modular valve subassembly for a viscous clutch includes a magnetic pole having a body having an annular shape and formed of a ferromagnetic material, an armature formed of a ferromagnetic material and configured as a plate, a spring securing the armature to the magnetic pole such that the armature is movable relative to the magnetic pole, and a reed valve element secured to the magnetic pole. The reed valve element can have a sealing portion at least partially positionable between the armature and the magnetic pole and movable relative to the magnetic pole. The reed valve element and the spring can be secured to the magnetic pole at spaced apart locations.

[0008] In yet another aspect, a viscous clutch assembly includes a rotationally fixed center shaft, a rotor rotatably supported on the center shaft, a housing disposed adjacent the rotor and rotatably supported on the center shaft, a working chamber having the rotor and housing defining at least a portion of a boundary of the working chamber, where a shear fluid present within the working chamber is capable of transmitting torque between the rotor and the housing, a reservoir carried by and rotationally fixed to the rotor and having an outlet bore, an electromagnetic coil rotationally fixed to the center shaft at or near a forward end of the center shaft, a valve subassembly operable to control flow of the shear fluid between the reservoir and the working chamber through the outlet bore and controllable using magnetic flux generated by the electromagnetic coil, and a front hub subassembly. The valve subassembly may include an outer pole having an annular body, an armature, a spring pivotally securing the armature to the outer pole, and a reed valve element having a sealing portion pivotally secured to the outer pole and disposed adjacent the outlet bore, where an applied magnetic flux selectively actuates the armature to apply a force to the reed valve element to pivot the reed valve element against the spring bias to selectively open and close the outlet bore. The front hub subassembly may include a flux guide, a bearing set, and a flux insulator sleeve adjacent the bearing set and the flux guide and radially disposed between the bearing set and the flux guide. The front hub subassembly is engageable between the center shaft and the housing, with the flux guide extending axially across a portion of the housing, with a forward end of the flux guide separated from the electromagnetic coil by an air gap and an opposite aft end of the flux guide separated from the outer pole by another air gap.

[0009] This disclosure is provided by way of example only and not by way of limitation. Other aspects of the invention will be appreciated upon consideration of the entire disclosure, including the entire disclosure, the claims, and the accompanying drawings. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a front perspective view of a viscous clutch assembly according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the viscous clutch assembly of FIG. 1 taken along line 2-2. [Figure 3A] FIG. 3A is a rear perspective view of the valve subassembly shown alone and separated from the viscous clutch assembly. [Figure 3B] FIG. 3B is a front perspective view of the valve subassembly shown in isolation. [Figure 4] FIG. 4 is a cross-sectional view of the valve subassembly and part of the rotor shown alone and separated from the viscous clutch assembly, and the valve subassembly attached to the rotor. [Figure 5A] FIG. 5A is a rear view of the rotor and part of the valve subassembly in isolation. [Figure 5B] FIG. 5B is a front view of the rotor and part of the valve subassembly in isolation. [Figure 6] FIG. 6 is a partial cross-sectional view of a portion of a viscous clutch assembly annotated to diagrammatically show the magnetic flux circuits.

[0011] While the foregoing figures show one or more embodiments of the present invention, other embodiments are contemplated, as noted in the description. In any case, the disclosure is presented by way of representation, not limitation. Those skilled in the art will appreciate that numerous other modifications and embodiments may be devised within the scope and spirit of the principles of the present invention. The drawings may not be drawn to scale, and applications and embodiments of the present invention may include features, steps, and / or components not specifically shown in the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Generally, the disclosed viscous clutch assembly includes a torque input-driven viscous clutch mechanism supported on a mounting bracket that can be attached to a mounting location, such as the front of an engine or motor. The mounting bracket can have a center shaft that is rotationally stationary or rotationally fixed. The clutch mechanism generally includes a housing (which can be a multi-part assembly including a housing base and a housing cover), a rotor, a reservoir, working chambers adjacent the housing and rotor, respectively, a return pump, a valve subassembly, and an electromagnetic coil. The valve subassembly can be a modular valve subassembly that can be preassembled as a modular unit before being inserted and secured to other components of the clutch assembly. Furthermore, in some embodiments, the valve subassembly can be operable with a valve element actuated in a primarily axial direction, such as a generally axial pivoting motion, in addition to a reed valve element being available. Any or all of them can facilitate, for example, increased tolerance sensitivity and can be more reliable than a circumferentially rotating valve assembly. Furthermore, in some embodiments, the valve subassembly and the electromagnetic coil can each be located outside the reservoir. The flux circuit connects the electromagnetic coil and the valve subassembly. The flux circuit can be relatively small and has a relatively small number of air gaps, including some radial air gaps, to facilitate efficient flux transfer and facilitate an overall relatively small and relatively lightweight clutch mechanism. For example, locating the flux circuit radially inside the reservoir in front of the rotor helps minimize its size and number of air gaps. In some embodiments, a flux insulator sleeve located inside the flux circuit helps to avoid flux shorting. And, a flux guide and / or flux insulator sleeve can be utilized to facilitate constructing a portion of the flux circuit to pass through the flux guide and axially traverse the cover of the housing. A shear fluid (e.g., silicone oil) is also provided inside the clutch mechanism. A pulley or other suitable input mechanism can accept torque input from a belt or the like to the input side of the clutch mechanism.An output device, such as a fan, can be connected to the output side of the clutch mechanism. By controlling the operation of the valve subassembly with an electromagnetic coil, the slip speed of the clutch mechanism can be essentially continuously controlled to deliver an output torque at a desired output speed between approximately 0% and 100% of the input speed. The disclosed viscous clutch assembly is suitable for use in fan cooling applications such as vehicles and other industrial environments, and other applications where controlled torque transfer between an input and an output is desired. Many other features and advantages of the disclosed invention will be apparent to those of skill in the art from consideration of this disclosure in its entirety, including the accompanying drawings.

[0013] Figure 1 is a front perspective view of one embodiment of a viscous clutch assembly 20, and Figure 2 is a cross-sectional view taken along line 2-2 of Figure 1. In the illustrated embodiment, the viscous clutch assembly 20 includes a mounting bracket (or journal bracket) 22 and a viscous clutch mechanism 24. A portion of a fan 26 is shown attached to the viscous clutch mechanism 24 in Figure 2, but is omitted from Figures 1 and 2 onwards. A pulley (sheave) 28 is also attached to the viscous clutch mechanism 24.

[0014] The mounting bracket 22 in the illustrated embodiment includes a center shaft 22-1 and a flange 22-2. The flange 22-2 allows for mounting to a rotationally fixed mounting location. The center shaft 22-1 is rotationally fixed (i.e., the center shaft 22-1 does not rotate) relative to the mounting location and / or the flange 22-2. The center shaft 22-1 defines a rotation axis A of the clutch mechanism 24 and has a forward (or distal) end 22-1F and an opposite rearward end 22-1R. The flange 22-2 is located at or near the rearward end 22-1R. The bore 22-3 can extend through the axial length of the center shaft 22-1 and through the flange 22-2. In the illustrated embodiment, the bore 22-3 is located centrally in the center shaft 22-1, but in other embodiments the bore 22-3 can be located in a different location and need not be completely surrounded by the material of the center shaft 22-1. Additional bores or passages can be provided. For example, as shown in the illustrated embodiment, there is an auxiliary passage 22-3A that extends at an angle connecting to bore 22-3. The mounting bracket 22 is made of a material that has the structural strength to support the entire assembly, typically cast iron or steel, and can be made as a single, integral piece. The mounting bracket 22 is made of a magnetically conductive material, such as a ferromagnetic material, as part of the electromagnetic control flux circuit, as described further below. Cast iron or steel are ferromagnetic materials that are suitable for carrying magnetic flux.

[0015] As shown in FIG. 2, the viscous clutch mechanism 24 of the illustrated embodiment includes a housing 30 , a rotor 32 , a working chamber 34 , a reservoir 36 , a valve subassembly 38 , an electromagnetic coil 40 , an adapter 42 , and a flux guide 44 .

[0016] The housing 30 is disposed adjacent to the rotor 32 and may partially or completely surround the rotor 32. In the illustrated embodiment, the housing 30 is a multi-piece assembly including a base 30B (rear) and a cover 30C (front) that are secured together. The cover 30C may be rotatably supported on the center shaft 22-1 of the mounting bracket 22 at a bearing set 46F via a front hub unit (described further below), and the base 30B may be partially or fully supported in a cantilevered configuration by the cover 30C. A seal may be provided between the base 30B of the housing 30 and the rotor hub. In the illustrated embodiment, the housing 30 serves as the output side of the clutch mechanism 24 that controllably transmits torque output at a selected output speed.

[0017] The rotor 32 includes a disk 32-1 and a hub 32-2 in a rotationally fixed relationship such that the disk 32-1 and the hub 32-2 always rotate at the same speed. The disk 32-1 and the hub 32-2 can be separate components that are mechanically fixed together with appropriate fasteners. Similarly, the disk 32-1 and / or the hub 32-2 can be made of multiple components connected together as desired. The disk 32-1 can be made of aluminum or the like, and the hub 32-2 can be made of aluminum or steel. The disk 32-1 can extend generally radially relative to the axis of rotation A, and the hub 32-2 can extend axially rearward from the disk 32-1, surrounding the center shaft 22-1. In the illustrated embodiment, the hub 32-2 of the rotor 32 is rotatably supported on the center shaft 22-1 of the mounting bracket 22 by a bearing set 46R. The bearing sets 46F and 46R are axially spaced apart from one another, with the bearing set 46F located at or near the distal or forward end 22-1F of the center shaft 22-1. In this manner, the bearings 46F and 46R separately rotatably support the housing 30 and the rotor 32, respectively, on the center shaft 22-1, allowing the housing 30 and the rotor 32 to rotate relative to each other relative to the rotationally fixed mounting bracket 22. In the illustrated embodiment, the rotor 32 (and pulley 28) serves as the input side of the clutch mechanism 24 and receives the torque input.

[0018] Pulley 28 is mounted to hub 32-2 and can be rotationally fixed so that pulley 28 always rotates at the same speed as rotor 32. Pulley 28 can be engaged with a belt (not shown) that provides input torque from an engine, motor, or the like. In the illustrated embodiment, bearing set 46R is substantially axially aligned with pulley 28; that is, pulley 28 can be axially positioned directly above bearing 46R. Bearing 46R is preferably a deep groove ball bearing, but can be substituted with a tapered roller bearing, angular contact ball bearing, or the like. In alternative embodiments, different devices, such as gears, sprockets, or the like, can be used in place of pulley 28 depending on the particular application.

[0019] The working chamber 34 provides a volume within the viscous clutch mechanism 24 that is at least partially bounded by a portion of the housing 30 and the rotor 32. The housing 30 and the rotor 32 each have a series of annular ribs interspersed along the working chamber 34 and separated by small gaps, which beneficially increases the surface area of ​​the working chamber 34. During operation of the clutch mechanism 24, a shear fluid (e.g., silicone oil) present within the working chamber 34 is sheared by fluid friction due to the relative movement of the rotor 32 and the housing 30. This shearing process imparts a tangential force that is transferred from an input, e.g., to the rotor 32, to an output, e.g., to the housing 30. The viscous clutch mechanism 24 allows for selective control of the torque transfer and output slip speed of the viscous clutch assembly 20 by controlling the volume of shear fluid present within the working chamber. The general principles of operation of a viscous clutch will be understood by those skilled in the art.

[0020] The reservoir 36 allows to maintain a supply of shear fluid. In the illustrated embodiment, the reservoir 36 is fixed to and carried by the rotor 32, specifically the disk 32-1 thereof. Part of the boundary of the reservoir 36 can be formed by the disk 32-1 or other parts of the rotor 32, and a reservoir cover 36-1 can be attached to the rotor 32 (e.g., to the disk 32-1) to define further boundaries of the reservoir 36. When the viscous clutch mechanism 24 is in a disengaged state, most or all of the shear fluid is stored in the reservoir 36. Because the rotor 32 and the reservoir 36 are attached together (and to the pulley 28) to the input side of the viscous clutch mechanism 24, they are always rotating at the maximum input speed whenever there is a torque input. Thus, the shear fluid present in the reservoir 36 is also rotating and under pressure. This is desirable for the shear fluid to move rapidly out of the reservoir 36 due to pressure and available kinetic energy when it is discharged (by the valve subassembly) into the working chamber 34. The reservoir 36 includes an outlet bore (or hole) 36-2, which allows the shear fluid to flow from the reservoir 36 into the working chamber 34 (when permitted by the valve subassembly 38). In the illustrated embodiment, the outlet bore 36-2 extends substantially axially and is located at or near the outer diameter of the reservoir 36, with the outlet end facing aft (see also FIG. 5B). Additionally, in some embodiments, a boss 36-3 may be formed in the boundary of the reservoir 36 adjacent the outlet bore 36-2, such as a wall of the reservoir 36 formed by a portion of the disk 32-1 of the rotor 32. The boss 36-3 may project axially or from other portions of the reservoir boundary wall. In an alternative embodiment, boss 36-3 can be omitted by providing a recess in the bounding wall of reservoir 36 on only one side of outlet bore 36-2.

[0021] The pump can utilize at least one wiper 48 and return bore 50 to provide passive pumping of shear fluid from the working chamber 34 to the reservoir 36 when there is a torque input to the viscous clutch mechanism 24. In the illustrated embodiment, two wipers 48 and two corresponding return bores 50 are disposed diametrically opposite one another and are carried by or extend through the disk 32-1 of the rotor 32, with the bores 50 communicating with the reservoir 36 (see FIG. 5B). Operation of such pumps in viscous clutches is well known in the art.

[0022] The valve subassembly 38 is provided for the purpose of selectively controlling the flow of shear fluid between the reservoir 36 and the working chamber 34. In the illustrated embodiment, the valve subassembly 38 controls the flow of shear fluid from the reservoir 36 by opening and closing (or covering and opening, or sealing and unsealing) an outlet bore 36-2 connecting the reservoir 36 to the working chamber 34. The valve subassembly 38 in the illustrated embodiment is configured as a modular unit including an armature 38-1, a spring 38-2, a reed valve element 38-3, and a magnetic pole 38-4. The valve subassembly 38 is fixedly carried by the rotor 32, for example, partially or entirely at the front of the rotor 32, and at least a portion of the reservoir 36 is axially disposed between the valve subassembly 38 and the electromagnetic coil 40, for example.

[0023] 3A and 3B are rear and front perspective views, respectively, of the valve subassembly 38 shown in isolation. FIG. 4 is a cross-sectional view of the valve subassembly 38 attached to the rotor 32, but FIG. 4 omits most of the other components of the clutch mechanism 24. FIG. 5A and 5B are rear and front views, respectively, of the rotor 32 and a portion of the valve subassembly 38 shown in isolation. FIG. 5B omits portions of the valve subassembly 38 to reveal other hidden components, as will be further described below. FIG. 6 is a cross-sectional view of a portion of the viscous clutch mechanism 24 of the viscous clutch assembly 20, annotated to show a schematic representation of the magnetic flux circuit.

[0024] The armature 38-1 may be a substantially planar plate of a magnetically attractive material, such as steel or other ferromagnetic material, and may be substantially rigid. In the illustrated embodiment, the armature 38-1 includes a body 38-1B and a pressing portion 38-1P extending radially outward from the body 38-1B and extending radially outward from the outer circumference of the poles 38-4 when the subassembly 38 is fully assembled. The armature 38-1 (and the spring 38-2) may have an opening (or hole) 38-1H around its center, the opening 38-1H being large enough to axially accommodate the center shaft 22-1 of the mounting bracket 11 (and optionally other components, such as a portion of the rotor 32). Thus, the body 38-1B may have a generally annular shape. The armature 38-1 may have one or more additional holes 38-1A around the central opening 38-1H and within the body 38-1B located radially outward from the central opening 38-1H. Additionally, in some embodiments, a separate opening may be located in the pressing portion 38-1P. In the illustrated embodiment, the opening 38-1H has an irregular shape and extends into the pressing portion 38-1P, allowing the pressing portion 38-1P to have a "U" shape and to space the armature from a particular portion of the reed valve element 38-3. Additionally, the shape of the armature 38-1 may be adjusted to facilitate balancing of the entire valve subassembly 38 as a modular unit.

[0025] The spring 38-2 engages the armature 38-1, such as by connection with one or more suitable mechanical fasteners (e.g., rivets). The spring 38-2 can be, for example, a leaf spring made from an elongated piece of spring steel with a thickness of about 0.5 mm. One end (e.g., protrusion 38-2P) of the spring 38-2 is attached (e.g., via a mechanical fastener such as a rivet or screw) to the pole 38-4. The spring 38-2 allows the armature 38-1 to move relative to the pole 38-4 (and relative to the rotor 32 and reservoir 36). For example, the armature 38-1 is pivotally connected to the pole 38-4 by the spring 38-2, and can essentially pivot in an axial direction. The spring 38-2 can be biased by default to move the armature 38-1 (and its pressing portion 38-1P) away from the pole 38-4. In the illustrated embodiment, the spring 38-2 extends over substantially the entire front surface of the armature 38-1 and further includes a protrusion 38-2P ​​that extends radially beyond the outer periphery of the armature 38-1 at a position generally opposite the pressing portion 38-1P, e.g., at a position diametrically opposite the pressing portion 38-1P relative to the axis of rotation A of the fully assembled clutch mechanism 24.

[0026] The reed valve element (or valve spring) 38-3 can be attached to a pole 38-4 carried by the rotor 32. That is, the reed valve body 38-3 can be indirectly connected to the rotor 32. In the illustrated embodiment, the reed valve element 38-3 is pivotally attached to the pole 38-4 on the same radial side of the axis of rotation A (and center shaft 22-1) as the outlet of the reservoir outlet bore 36-2, but on the opposite side of the axis of rotation A (and center shaft 22-1) from either or both the position at which the spring 38-2 is attached to the pole 38-4 and / or the position of the pivot axis of the spring 38-2 and the armature 38-1. This means that the reed valve element 38-3 and the spring 38-2 can be fixed to the pole 38-4 at positions spaced apart from each other. In the illustrated embodiment, the reed valve element 38-3 rotates essentially axially. The reed valve element 38-3 is typically located axially between the armature 38-1 and the outlet bore 36-2 (which may be located on a portion of the disk 32-1 of the rotor 32). The reed valve element 38-3 includes a sealing portion 38-3S having a flat surface large enough to cover the entire outlet of the outlet bore 36-2 from the reservoir 36 when closed, and has a leaf spring characteristic that biases the sealing portion 38-3S away from the outlet bore 36-2 by default. In some embodiments, the rear of the boundary wall of the reservoir 36 adjacent the outer periphery of the outlet bore 36-2 may be located axially aft of at least a portion of the pole 38-4 adjacent the reed valve element 38-3. For example, in some embodiments, the sealing portion 38-3S may contact the boss 36-3 to cover, close, or seal the outlet bore 36-2. This arrangement allows essentially unimpeded pivoting of the reed valve element 38-3 without contacting and interfering with the wall surrounding the reservoir 36, and provides a relatively good seal with the sealing portion 38-3S to block shear fluid flow through the outlet bore 36-2. Additionally, this arrangement reduces the tolerance sensitivity of the placement of the pole 38-4 and the entire valve subassembly 38 relative to the reservoir 36.

[0027] In this context, the pole 38-4 may also be referred to as an outer pole and is a flux conducting component that may be included in the valve subassembly 38. The pole 38-4 is carried by the rotor 32 and may be connected to the disk 32-1 by suitable mechanical fasteners or the like. The pole 38-4 may be made of a ferromagnetic material, such as steel, to allow for the transmission of magnetic flux. In the illustrated embodiment, the pole 38-4 includes a generally annular body 38-4B having a central opening 38-4H, a radially inner portion 38-4F (e.g., a flange or region of reduced axial thickness), and a radially inwardly extending mounting extension 38-4R to which the reed valve element 38-3 may be secured. As will be further explained below, the inner portion 38-4F allows the pole 38-4 to at least partially axially overlap the flux guide 44 such that a small radial gap exists between the pole 38-4 and the flux guide 44. The rear of the pole 38-4, including the body 38-4B and / or the inner portion 38-4F, may be substantially planar in some embodiments. And the rear may be axially aligned with or axially forward of the outlet end of the outlet bore 36-2 at the boss 36-3 in some embodiments. The central opening 38-4H may be located inward from the inner portion 38-4F and may be large enough to allow the center shaft 22-1 to pass therethrough (and optionally others as well). However, as will be explained further below, the central opening 38-4H may be smaller than a corresponding portion of at least a portion of the circumference of the armature 38-1, such that at least when the valve subassembly 38 is disengaged, a portion of each of the armature 38-1 and the pole 38-4 overlap to provide a small axial gap therebetween (see FIG. 3A). In the illustrated embodiment, the circumference of the pole 38-4 is generally circular and larger than the body 38-1B of the armature 38-1. The interior or upper portion of the pole 38-4, e.g., the body 38-4B, may include one or more countersinks, mass reducing openings, cutouts, etc. Such features may be beneficial in accommodating mechanical fasteners without interference with other nearby components, aid in balancing the overall modular valve subassembly 38, and / or facilitate reducing the weight of the viscous clutch assembly 20.

[0028] As shown in the illustrated embodiment, such as FIG. 2, the pole 38-4 may be disposed adjacent to the flux guide 44, with a front portion of at least a portion of the pole 38-4 (e.g., inner portion 38-4F) facing the rear end 44R of the flux guide 44 and a portion of the pole 38-4 (e.g., body 38-4B) disposed radially outward of the rear end 44R of the flux guide 44. The reed valve element 38-3 may be disposed generally between the armature 38-1 and the pole 38-4. In some embodiments, the spring 38-2 may also be disposed generally between the armature 38-1 and the pole 38-4, with the reed valve element 38-3 disposed between the spring 38-2 and the pole 38-4. The armature 38-1, spring 38-2, reed valve element 38-3, and pole 38-4, in some embodiments, may be assembled and connected together as a pre-assembled modular unit before being inserted and secured to other components of the viscous clutch mechanism 24 of the viscous clutch assembly 20. For example, in some embodiments, the entire modular valve subassembly 38 may be secured to the rotor 32 using only fasteners that directly engage or engage through pole 38-4, with the other components of the valve subassembly 38 being secured to the rotor 32 only indirectly through pole 38-4. Also, in some embodiments, a portion of the valve subassembly 38, such as the reed valve element 38-3, including at least a portion of the armature pressing portion 38-1P and the sealing portion 38-3S, can be inserted into or through the opening 32-1H of the disk 32-1 of the rotor 32 to a position adjacent to the reservoir 36, with portions of the valve subassembly 38 disposed on the front and rear sides of the disk 32-1 (see, for example, FIGS. 5A and 5B. Note that the magnetic poles 38-4 have been omitted and the reservoir cover 36-1 has not been shown in FIG. 5B to reveal structures that were hidden). The use of pre-assembled modular valve subassemblies 38 may facilitate the manufacture of the viscous clutch mechanism 24 of the viscous clutch assembly 20.For example, the entire valve subassembly 38 may be further balanced as a unit by connecting components or using fasteners for the valve subassembly 38 in locations that may be inaccessible or simply difficult to work with in the final installed position of the viscous clutch mechanism 24. The use of an additional pole 52 (which may be referred to in this context as an inner pole) mountable to the center shaft 22-1 allows for the installation of the modular valve subassembly 38 while allowing for additional axial air gaps in the flux circuit at or adjacent to the armature 38-1, as will be explained further below.

[0029] In alternative embodiments, spring 38-2 and / or reed valve element 38-3 can be attached directly to disk 32-1 of rotor 32 and pole 38-4 can be omitted from valve subassembly 38, optionally in a non-modular configuration. In further alternative embodiments, a translating armature and / or translating reed valve configuration can be utilized instead of a pivoting armature and / or reed valve.

[0030] The armature 38-1 is disposed in a region of the viscous clutch mechanism 24 where it may be attracted and moved by the introduction of a magnetic field. When the armature 38-1 is attracted to the magnetic field selectively generated by the electromagnetic coil 40, the armature 38-1 moves (e.g., pivots) axially toward the reservoir outlet bore 36-2. In the illustrated embodiment, when the magnetic field is generated by the electromagnetic coil 40, the armature is attracted generally axially to the magnetic poles 38-4 and / or 52 against the spring bias from the spring 38-2. When the valve subassembly 38 is actuated, the pressing portion 38-1P of the armature 38-1, and possibly also the adjacent portion of the spring 38-2, applies a force to the reed valve element 38-3 to move the sealing portion 38-3S, thereby covering and blocking or sealing the outlet end of the outlet bore 36-2 of the reservoir 36. In some embodiments, the operation of the valves may be similar to that described, for example, in PCT International Patent Application Publication No. WO 2012 / 024497 A2, but the embodiments disclosed herein have associated new advantages and provide a new and different modular structure.

[0031] The electromagnetic coil 40 is disposed in front of the viscous clutch mechanism 24 and may include a coil winding and a coil housing. The coil housing may include a mounting flange that may extend radially inward relative to the coil winding. In operation, the electromagnetic coil may be selectively energized with power to selectively generate a magnetic field that is utilized to control the operation of the valve subassembly 38, as described further below. Such a front mounted electromagnetic coil arrangement is not only easy to install, but is also preferably located in an area with air flow that may keep the temperature of the electromagnetic coil 40 lower. More specifically, the electromagnetic coil 40 may be secured to the center shaft 22-1 of the mounting bracket 11 at or near the front end 22-1F such that the electromagnetic coil 40 is held rotationally stationary and secured to the center shaft 22-1.

[0032] An output speed sensor 54 (shown only diagrammatically in the drawings) can optionally be secured to the electromagnetic coil 40 or to another rotationally fixed component adjacent to the electromagnetic coil 40 to detect the speed of the output of the viscous clutch mechanism 24. As in the illustrated embodiment, the output speed sensor 54 detects the speed of the fan adapter 42 relative to its rotationally fixed mounting location. The output speed sensor 54 can be a Hall Effect sensor or another suitable detection device that detects the passage of one or more targets on an adjacent output clutch component, such as the fan mounting surface of the adapter 42. The wiring for the electromagnetic coil 40 and the output speed sensor 54 can be bundled together and, in the illustrated embodiment, can be located within a bore 22-3 in the center shaft 22-1 that extends axially through the mounting bracket 22.

[0033] In some applications, it may be desirable to also provide a speed sensor (shown only diagrammatically in the drawings) on the input side of the viscous clutch mechanism 24. This may be a fixed input speed sensor 54 mounted at or near the rear end 22-1R of the center shaft 22-1 of the mounting bracket 22 in an area where the speed of the pulley 28 and / or another input component can be detected. This input speed sensor 54 may be a Hall effect sensor or another suitable detection device that detects the passage of one or more targets on an adjacent input clutch component, such as the hub 32-2 or the pulley 28. The wiring for the input speed sensor 54 may be bundled with the electromagnetic coil wiring and the output speed sensor wiring to pass through a portion of the center shaft 22-1 of the mounting bracket 22, such as the auxiliary passage 22-3A and / or bore 22-3 of the center shaft 22-1, for ease of installation.

[0034] The front hub subassembly 60 may be located at or near the forward end 22-1F of the center shaft 22-1 and includes the flux guide 44, the bearing set 46F, and an optional flux insulator sleeve 62 made of a non-magnetically conductive material. The bearing set 46F rotatably supports the front hub subassembly 60 on the center shaft 22-1 of the mounting bracket 22, and the front hub subassembly 60 structurally supports the housing 30 on the bearing set 46F, such as through the cover 30C. In the illustrated embodiment, the outer ring of the bearing set 46F is secured inside the flux insulator sleeve 62. The flux guide 44 and the flux insulator sleeve 62 may be secured together by a snap ring or other suitable retention mechanism. The front hub subassembly 60 is optionally preassembled with the modular unit being installed as a unit on the center shaft 22-1. and secured to both the center shaft 22-1 (e.g., using a threaded nut) and the housing 30 (e.g., using mechanical fasteners). The front hub subassembly 60 can be installed, for example, after the valve subassembly 38 and the pole pieces 52 are installed.

[0035] The flux guide 44 can be disposed on the outer diameter of the flux insulator sleeve 62 (or alternatively, in embodiments in which the flux insulator sleeve 62 is omitted, at or near the outer ring of the bearing set 46F). In the illustrated embodiment, the flux guide 44 is axially longer than the flux insulator sleeve 62 such that the opposing front and rear ends 44F, 44R project axially beyond the ends of the flux insulator sleeve 62 and also project axially beyond the ends of the bearing set 46F. The flux guide 44 is made of a magnetically conductive material, such as a ferromagnetic material like steel, and allows for the magnetic field to be conducted axially from the electromagnetic coil 40 towards the region in which the valve subassembly 38 resides. In the illustrated embodiment, the rear end 44R of the flux guide 44 is disposed adjacent a portion of the pole 38-4 (e.g., body 38-4B) with a small radial air gap therebetween that allows relative rotation between the flux guide 44 carried by the housing 30 and the pole 38-4 carried by the rotor 32. Generally, radial air gaps are preferred over axial air gaps in the clutch flux circuit. Also, the front end 44F of the flux guide 44 is disposed adjacent the electromagnetic coil 40. In the illustrated embodiment, the front end 44F of the flux guide 44 is disposed outwardly from the housing of the electromagnetic coil 40 separated by a small radial air gap that allows rotation of the flux guide 44 relative to the rotationally fixed electromagnetic coil 40. Thus, during operation, the flux guide 44 can transfer magnetic flux from the electromagnetic coil 40 to the valve subassembly 38 (e.g., to pole 38-4) as part of a flux circuit axially across a portion of the housing 30 (e.g., across cover 30C). The flux guide 44 can be secured to the housing, such as the cover 30C, using, for example, mechanical fasteners. The flux guide 44, as well as the optional flux insulator sleeve 62, are thus rotationally fixed to the housing 30 and can rotate at the same speed as the housing 30 at all times.

[0036] When utilized, the flux insulator sleeve 62 is made of a material that is not magnetically conductive, such as austenitic stainless steel. The flux insulator sleeve 62 is disposed radially between the flux guide 44 and the center shaft 22-1 (and radially between the flux guide 44 and the bearing set 46F), which is beneficial in avoiding magnetic shorting of the radial flux circuit. The flux insulator sleeve 62 may also provide structural support for the housing 30 on the bearing set 46F. In an alternative embodiment, magnetic isolation could instead be achieved using non-magnetic rolling elements inside the bearing set 46F, such as ceramic, austenitic stainless steel balls, or rollers, allowing the non-magnetic sleeve 62 to be omitted, if desired.

[0037] An adapter 42 for the fan 26 or other output device can be secured to the flux guide 44 (e.g., using mechanical fasteners) and can be structurally supported by the flux guide 44 as well. The adapter 42 can be provided with a fan mounting pilot as well as a mounting mechanism such as a threaded stud to facilitate fastening the fan 26 or other output device to the output side of the viscous clutch mechanism 24. In the illustrated embodiment, the adapter is essentially the forward-most component of the viscous clutch assembly 20 (excluding the fan 26) and is located at or beyond the forward end 22-1F of the center shaft 22-1, at least partially covering or capping the electromagnetic coil 40, the output speed sensor 54 (if present), and the components of the front hub subassembly 60. Also, in the illustrated embodiment, the electromagnetic coil 40, the fan adapter 42, and the flux guide 44 overlap one another in the axial direction. In an alternative embodiment, the adapter 42 can be omitted and instead, for example, the fan 26 or other output device can be attached to the cover 30C of the housing 30. Additionally, in some applications, the adapter 42 may be configured as a gear, pulley, or other suitable structure that can engage a desired output device.

[0038] The pole 52 is supported on the center shaft 22-1 and is made of a magnetic flux conducting material, such as a ferromagnetic material like steel. In the illustrated embodiment, the inner pole 52 is a sleeve that surrounds the center shaft 22-1 at a location radially inward of the poles 38-4 and abuts against a radially extending shoulder 22-1S of the center shaft 22-1, which acts as an axial stop. The pole 52 can be in direct physical contact with the center shaft 22-1, allowing magnetic flux to pass between the pole 52 and the center shaft 22-1 without crossing an air gap. In this way, the pole 52 aids in the transfer of magnetic flux between the armature 38-1 and the center shaft 22-1 in the magnetic flux circuit. The bearing set 46F can be positioned axially adjacent the pole 52, such that the pole 52 acts as an axial stop for the ring of the bearing set 46F. The pole 52 can be located on the center shaft 22-1 forward of the bearing set 46F and / or the front hub subassembly 60. In the illustrated embodiment, the shoulder 22-1S is located at the rear end of the pole 52, and the inner ring of the bearing set 46F is located at the opposite front end of the pole 52. The pole 52 can protrude radially outward from a portion adjacent to the center shaft 22-1, for example, protruding radially outward from the shoulder 22-1S such that a portion of the armature 38-1 is located adjacent to the protruding portion of the pole 52. In other words, the radial thickness of the pole 52 can be greater than the radial dimension of the shoulder 22-1S of the center shaft 22-1. In the illustrated embodiment, at least when the valve subassembly 38 is opened and the armature 38-1 is biased away from the pole 38-4, the body 38-1B of the armature 38-1 adjacent the rear end of the pole 52 is positioned to have a small axial gap therebetween (see FIGS. 2 and 6). In alternative embodiments, the pole 52 has a smaller radial thickness, but can be configured differently, such as having a radially outward protrusion or flange adjacent the armature 38-1. In addition to functioning as part of the magnetic flux circuit, the pole 52 can function as a spacer that helps hold the bearing set 46F in place under a clamp load.

[0039] 6 shows a portion of the viscous clutch mechanism 24, with dashed lines illustrating a flux circuit through which the magnetic flux generated by the electromagnetic coil 40 may pass through the valve subassembly 38 and return to the electromagnetic coil 40. In the illustrated embodiment, the magnetic flux circuit passes from the radially outer portion of the coil housing of the electromagnetic coil 40 through a radial air gap to the front end 44F of the flux guide 44, then axially along the flux guide 44 across the cover 30C of the housing 30. It then passes from the rear end 44F of the flux guide 44 through a radial air gap to the body 38-4B of the pole 38-4, through the pole 38-4, then through the axial air gap to the body 38-1B of the armature 38-1, and then radially inwardly along the armature 38-1 (i.e., toward its center and the axis of rotation A). The flux circuit then passes through the axial air gap to the pole 52, through a portion of the center shaft 22-1, through a radially inner portion of the coil housing and / or its mounting flange, and back to the electromagnetic coil 40. The three-dimensional shape of the magnetic flux circuit in the illustrated embodiment has an at least partially toroidal (or "donut") shape, with the axis of rotation A serving as the axis of rotation of the toroidal shape, and the surface of rotation being essentially hollow. The magnetic flux insulating material of the magnetic flux insulator sleeve 62, the rolling elements of the bearing set 46F, and / or another suitable component may be positioned inwardly or inwardly from the outer periphery of the toroidal shaped surface of rotation of the magnetic flux circuit, spaced from the axis of rotation (i.e., spaced from the axis of rotation A), thereby reducing or avoiding the possibility of a magnetic short circuit in the magnetic flux path of the magnetic flux circuit, for example, in the radial direction at a location spaced from the axis of rotation A. In the illustrated embodiment, the flux circuit is located entirely forward of the rotor 32, so that the flux circuit does not have to pass axially through or traverse the entire rotor 32. Additionally, in the illustrated embodiment, the flux circuit is located radially inward of the reservoir.

[0040] In operation, when magnetic flux is introduced through the magnetic flux circuit to the armature 38-1, the valve subassembly 38 is engaged and closes the outlet hole 36-2. This causes the armature 38-1 to move toward the electromagnetic coil 40, the magnetic flux guide 44, and the magnetic poles 38-4 and 52. The armature 38-1 then moves the reed valve element 38-3 so that the sealing portion 38-3S covers the outlet hole 36-2. Thus, selective energization of the electromagnetic coil 40 causes the armature 38-1 to move against the spring bias of the spring 38-2 and the reed valve 38-3. The operation of the viscous clutch mechanism 24 and viscous clutch assembly 20 is achieved by selectively energizing the electromagnetic coil 40 to control the valve subassembly 38 to adjust the volume of shear fluid present in the working chamber 34 when there is a torque input, thereby allowing the output speed to be controlled to a desired set point. In some embodiments, pulse width modulation (PWM) can be used to control the energization of the electromagnetic coil 40. Additionally, input sensors 56 and / or output sensors 54 may be used that provide input and / or output speed feedback to a controller (not shown) that can control the energization of the electromagnetic coil 40 and the automated operation of the viscous clutch assembly 20.

[0041] Those skilled in the art will recognize that the present invention provides numerous advantages and benefits. For example, a relatively small magnetic flux circuit with a relatively small number of air gaps (many of which are radially oriented) allows a relatively small electromagnetic coil to be used to actuate the valve, resulting in a relatively small and lightweight clutch assembly. Additionally, locating the electromagnetic coil at the front of the clutch facilitates assembly and wiring, and the overall clutch assembly is relatively easy to manufacture, primarily by stacking components axially. Additionally, embodiments of the present invention permit the use of one or more modular subassemblies, such as a valve subassembly and a front hub subassembly, which may be preassembled as a modular unit prior to attachment to the remainder of the assembly. The use of such subassemblies facilitates axial stacking of components on the center shaft 22-1 of the mounting bracket 22, and preassembly of the subassemblies allows for easier connection of the subassembly components without obstruction or interference from other components supported on or surrounding the center shaft 22-1.

[0042] Consideration of possible implementations

[0043] The viscous clutch assembly may include a rotationally fixed center shaft having a forward end and an aft end opposite the forward end, a rotor rotatably supported on the center shaft, a housing disposed adjacent the rotor and rotatably supported on the center shaft, a working chamber with the rotor and housing defining at least a portion of a boundary of the working chamber, a reservoir carried by the rotor and rotationally fixed to the rotor, an electromagnetic coil disposed at or near the forward end of the center shaft and rotationally fixed, a valve subassembly operable to control flow of shear fluid between the reservoir and the working chamber and controllable using magnetic flux generated by the electromagnetic coil, a flux guide extending axially across a cover of the housing, and a flux insulating material disposed adjacent to and radially inward of the flux guide. A flux circuit connects the electromagnetic coil and the valve subassembly, the flux circuit being disposed forward of the rotor and passing through the flux guide and a portion of the center shaft. The flux insulating material may be at least partially surrounded by the flux circuit.

[0044] The viscous clutch assembly of the preceding paragraph may optionally, additionally and / or alternatively, be

[0045] It may include any one or more of the features, configurations, and / or additional components described in paragraphs

[0054] to

[0055] .

[0045] The valve subassembly includes an outer pole, an armature, a spring securing the armature to the outer pole, and a reed valve element secured to the outer pole, such that actuation of the armature applies a force to the reed valve element, thereby actuating the reed valve element.

[0046] The outer pole may have an annular or substantially annular shape and may include a base and an inner portion, with the rear end of the flux guide disposed forward of the inner portion, and the flux guide may be disposed inwardly of the base, with a radial gap between the flux guide and the base.

[0047] An inner pole is supported on the center shaft and projects radially outwardly from an adjacent portion of the center shaft, the inner pole being disposed adjacent the armature and radially inward from the flux guide.

[0048] The reservoir may include an outlet bore selectively closable by a reed valve element, and the outlet bore may extend through a boss (a part of the rotor disk that functions as a wall forming at least a part of the boundary of the reservoir) protruding from a wall forming at least a part of the boundary of the reservoir.

[0049] There is a bearing set supported on a center shaft which rotatably supports the housing, and an inner pole supported axially on the center shaft between the armature and the bearing set, with the magnetic flux circuit further passing through the inner pole.

[0050] There is a bearing set supported on the center shaft, and the magnetic flux insulating material is configured as a magnetic flux insulator sleeve radially disposed between the bearing set and the magnetic flux guide, and the bearing set can be configured to rotatably support the housing, the magnetic flux guide, and the magnetic flux insulator sleeve on the center shaft.

[0051] The flux guide may be axially longer than the flux insulator sleeve.

[0052] The forward end of the flux guide may be separated from the electromagnetic coil by a radial gap, and the aft end of the flux guide may be separated from the adjacent magnetic flux conducting portion of the valve subassembly by another radial gap.

[0053] A fan adapter may be rotationally secured to the housing adjacent the forward end of the center shaft.

[0054] The magnetic flux circuit may be positioned radially inward from the reservoir.

[0055] A method of manufacturing a viscous clutch may include providing a mounting bracket having a center shaft, rotatably mounting a rotor to the center shaft and positioning a housing base adjacent to the center shaft and the rotor, assembling a modular valve subassembly, securing the pre-assembled modular valve subassembly to the rotor, rotatably mounting a housing cover to the center shaft and securing the housing cover to the housing base, and securing an electromagnetic coil at or near the forward end of the center shaft, with one or more wires for the electromagnetic coil extending rearwardly through the bore in the center shaft. The modular valve subassembly may include securing a reed valve element to an outer pole made of ferromagnetic material, and securing a spring to the outer pole such that when the modular valve subassembly is fully assembled, the armature is movable relative to the outer pole and at least a sealing portion of the reed valve element is axially disposed between the outer pole and the armature.

[0056] The method of the preceding paragraph may optionally additionally and / or alternatively comprise the steps of:

[0057] The present invention may include any one of the features, configurations, and / or additional steps described in paragraphs

[0062] to

[0062] .

[0057] Fixing the fan adapter to the housing cover such that at least a portion of the fan adapter is disposed on an opposite side of the electromagnetic coil from the housing cover.

[0058] Mounting an inner pole on a shoulder of the center shaft such that a portion of the inner pole protruding beyond the shoulder is axially adjacent the armature such that the inner pole is disposed between the armature and the electromagnetic coil.

[0059] Fixing the flux guide, the flux insulator sleeve, and the bearing set between the housing cover and the center shaft.

[0060] The flux guide, flux insulator sleeve, and bearing set are pre-assembled together as a modular front hub assembly prior to being secured to either the housing cover and the center shaft, or at least prior to being secured to either the housing cover and the center shaft.

[0061] Prior to securing the pre-assembled modular valve subassembly to the rotor, inserting at least a portion of the pre-assembled modular valve subassembly into an opening in the rotor such that at least a sealing portion of the reed valve element is located at a rear portion of a reservoir supported by the rotor and a body portion of the armature is located at an opposite front portion of the rotor.

[0062] The modular valve subassemblies may be balanced before being secured to the rotor.

[0063] A modular valve subassembly for a viscous clutch may include a body having an annular shape, a magnetic pole made of a ferromagnetic material, an armature made of a ferromagnetic material and configured as a plate, a spring securing the armature to the magnetic pole such that the armature is movable relative to the magnetic pole, and a reed valve element secured to the magnetic pole and at least partially disposed between the armature and the magnetic pole, the reed valve element having a sealing portion movable relative to the magnetic pole. The reed valve element and the spring may be secured to the magnetic pole at locations spaced apart from one another.

[0064] The modular valve subassembly of the preceding paragraph may optionally, additionally and / or alternatively be

[0065] The present invention may include any one or more of the features, configurations, and / or additional components described in paragraphs

[0070] to

[0071] .

[0065] The armature may include a pressing portion extending radially outward from the body portion, the outer periphery of the body portion may be smaller than the outer periphery of the magnetic pole, the pressing portion may extend radially outward from the outer periphery of the magnetic pole, and the opening may be disposed at the center of the body portion and extend into the pressing portion.

[0066] The spring is capable of pivotally fixing the armature to the pole at a location diametrically opposite the pressure portion.

[0067] The spring can extend across substantially the entire front of the armature facing the poles.

[0068] The spring may be mechanically attached to the armature via a number of fasteners.

[0069] The spring can be configured to bias the armature away from the magnetic pole.

[0070] The reed valve element can be configured to bias the seal portion away from the magnetic pole.

[0071] The viscous clutch assembly may include a rotationally fixed center shaft, a rotor rotatably supported on the center shaft, a housing disposed adjacent the rotor and rotatably supported on the center shaft, a working chamber comprised of the rotor and the housing defining at least a portion of a boundary of the working chamber, where a shear fluid present within the working chamber may transmit torque between the rotor and the housing, a reservoir carried by and rotationally fixed to the rotor and having an outlet bore, an electromagnetic coil rotationally fixed to the center shaft at or near a forward end of the center shaft, a valve subassembly operable to control flow of the shear fluid between the reservoir and the working chamber through the outlet bore and controllable using magnetic flux generated by the electromagnetic coil, and a front hub subassembly. The valve subassembly may include an outer pole having an annular body, an armature, a spring pivotally fixing the armature to the outer pole, and a reed valve element pivotally fixed to the outer pole and having a sealing portion disposed adjacent the outlet bore. The valve subassembly can also be configured such that the applied magnetic flux selectively actuates the armature to apply a force to the reed valve element, pivoting the reed valve element against a spring bias such that the sealing portion selectively opens and closes the outlet bore. The front hub subassembly can include a flux guide, a bearing set, and a flux insulator sleeve adjacent the bearing set and the flux guide and radially disposed between the bearing set and the flux guide. The front hub subassembly can be engaged between the center shaft and the housing, with the flux guide extending axially across a portion of the housing, a forward end of the flux guide separated from the electromagnetic coil by an air gap and an opposite aft end of the flux guide separated from the outer pole by another air gap.

[0072] summary

[0073] Relative or degree terms, such as "substantially," "essentially," "generally," "approximately," and the like, used herein should be interpreted in accordance with and in accordance with any applicable definitions or limitations expressly set forth herein. In all cases, relative or degree terms used herein should be interpreted broadly to encompass the relevant disclosed embodiments, as well as ranges or variations as would be understood by one of ordinary skill in the art in light of the entirety of this disclosure, to encompass normal manufacturing tolerance variations, accidental alignment variations, transient alignment or shape variations induced by thermal, rotational, or vibrational operating conditions, transient signal or magnetic flux variations, and the like. Moreover, relative or degree terms used herein should be interpreted to encompass a range that expressly includes the specified quality, characteristic, parameter, or value without variation, as if no limiting relative or degree term had been utilized in the particular disclosure or description.

[0074] The word "comprise" or variations such as "comprises" or "comprising" are used herein without limitation and should be interpreted to mean the inclusion of a described element, feature, or step, or group of elements, features, or steps, and should not be interpreted to mean the exclusion of any other element, feature, or step, or group of elements, features, or steps. Unless expressly limited further, the use of the word "comprise" or variations thereof does not, by itself, exclude additional elements, steps, or groups of elements or steps that are not described. Furthermore, unless expressly limited, the words "a" and "an" as used herein refer to one or more and are not intended to limit a specified element, feature, step, etc. to only one. However, the use of the words "a" and "an" herein should be interpreted according to any applicable further limitations expressly stated in the context of the particular use instance, and not to extend such context-specific limitations to all other uses in general.

[0075] Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, the disclosed clutch is designed for use with relatively large displacement engines, from 30 to 50 liters, but may be scaled to fit any size engine or motor.

Claims

1. 1. A viscous clutch assembly comprising: a center shaft that is rotationally fixed and has a front end and a rear end opposite the front end; a rotor rotatably supported on the center shaft; a housing disposed adjacent to the rotor and rotatably supported by the center shaft; a working chamber, the rotor and the housing defining at least a portion of a boundary of the working chamber; a reservoir carried by and rotationally fixed to said rotor; an electromagnetic coil disposed at or near the front end of the center shaft and fixed to rotate; a valve subassembly operable to control flow of shear fluid between the reservoir and the working chamber, the valve subassembly being controllable using magnetic flux generated by the electromagnetic coil; a magnetic flux guide extending axially across a cover of the housing; a flux insulating material disposed adjacent to and radially inward from the flux guide; a flux circuit connecting said electromagnetic coil and said valve subassembly, said flux circuit passing through said flux guide and a portion of said center shaft located forward of said rotor, and said flux insulating material being at least partially surrounded by said flux circuit.

2. The outer magnetic pole, Armature and a spring that secures the armature to the outer pole; 2. The viscous clutch assembly of claim 1, further comprising a reed valve element secured to said outer pole, wherein actuation of said armature applies a force to said reed valve element to actuate said reed valve element.

3. 3. The viscous clutch assembly of claim 2, wherein the outer pole has an annular shape and includes a base and an inner portion, the rear end of the flux guide is disposed forward of the inner portion, the flux guide is disposed inward of the base, and the flux guide has a radial gap therebetween.

4. 3. The viscous clutch assembly of claim 2, further comprising an inner pole supported on said center shaft and projecting radially outward from a portion adjacent said center shaft, said inner pole being disposed radially inward from said flux guide adjacent said armature.

5. 3. The viscous clutch assembly of claim 2, wherein said reservoir includes an outlet bore selectively closeable by said reed valve element, said outlet bore extending through a boss projecting from a wall forming at least a portion of a boundary of said reservoir.

6. a bearing set supported by the center shaft which rotatably supports the housing; an inner pole axially supported on the center shaft between the armature and the bearing set; 3. The viscous clutch assembly of claim 2, wherein said flux circuit further passes through said inner pole.

7. A bearing set supported by the center shaft is further provided.

2. The viscous clutch assembly of claim 1, wherein the flux insulating material is configured as a flux insulator sleeve disposed radially between the bearing set and the flux guide, the bearing set rotatably supporting the housing, the flux guide, and the flux insulator sleeve on the center shaft.

8. 8. The viscous clutch assembly of claim 7, wherein said flux guide is axially longer than said flux insulator sleeve, a forward end of said flux guide is separated from said electromagnetic coil by a radial gap, and a rearward end of said flux guide is separated from an adjacent flux conducting portion of said valve subassembly by another radial gap.

9. 2. The viscous clutch assembly of claim 1, further comprising a fan adapter rotationally fixed to said housing adjacent said forward end of said center shaft.

10. 2. The viscous clutch assembly of claim 1, wherein said flux circuit is disposed radially inward from said reservoir.

11. A method for manufacturing a viscous clutch, comprising: providing a mounting bracket having a center shaft; rotatably mounting a rotor on the center shaft, the mounting step further comprising disposing a housing base adjacent the center shaft and the rotor; assembling a modular valve subassembly; fastening the pre-assembled modular valve subassembly to the rotor; a housing cover rotatably attached to the center shaft and fixed to the housing base; fixing an electromagnetic coil at or near a forward end of the center shaft, with one or more wires for the electromagnetic coil extending rearwardly through a bore in the center shaft; The step of assembling a modular valve subassembly includes: fastening a reed valve element to an outer pole of ferromagnetic material; Securing the spring to the armature; and securing the spring to the outer pole such that, when the modular valve subassembly is fully assembled, the armature is movable relative to the outer pole and at least a sealing portion of the reed valve element is axially disposed between the outer pole and the armature. A method for manufacturing a viscous clutch.

12. The method of claim 11 , further comprising: securing the fan adapter to the housing cover such that at least a portion of the fan adapter is disposed on an opposite side of the electromagnetic coil from the housing cover.

13. 12. The method of claim 11, further comprising the step of attaching an inner pole to a shoulder of the center shaft such that a portion of the inner pole protruding beyond the shoulder is axially adjacent the armature such that the inner pole is disposed between the armature and the electromagnetic coil.

14. The method of claim 11 , further comprising the step of securing a flux guide, a flux insulator sleeve, and a bearing set between the housing cover and the center shaft.

15. The method of claim 14 , wherein the flux guide, the flux insulator sleeve, and the bearing set are pre-assembled together as a modular front hub assembly before being secured to either the housing cover or the center shaft.

16. 12. The method of claim 11, further comprising the step of inserting at least a portion of the pre-assembled modular valve subassembly into an opening in the rotor such that at least the sealing portion of the reed valve element is disposed at a rear portion of a reservoir supported by the rotor and a body portion of the armature is disposed at an opposite front portion of the rotor prior to the step of securing the pre-assembled modular valve subassembly to the rotor.

17. The method of claim 11 , wherein the modular valve subassembly is balanced prior to the step of securing to the rotor.

18. 1. A modular valve subassembly for a viscous clutch, comprising: a magnetic pole including a body having an annular shape and made of a ferromagnetic material; an armature made of a ferromagnetic material and configured as a plate; a spring that secures the armature to the magnetic pole so that the armature can move relative to the magnetic pole; a reed valve element secured to the magnetic pole and at least partially disposed between the armature and the magnetic pole, the reed valve element having a sealing portion movable relative to the magnetic pole; The reed valve element and the spring are secured to the pole piece at spaced apart locations.

19. 20. The modular valve subassembly of claim 18, wherein the armature includes a pressing portion extending radially outward from a body portion, an outer periphery of the body portion being smaller than an outer periphery of the poles, the pressing portion extending radially outward from the outer periphery of the poles, and an opening disposed centrally of the body portion and extending into the pressing portion.

20. 20. The modular valve subassembly of claim 19, wherein the spring pivotally secures the armature to the pole at a location diametrically opposite the biasing portion.

21. 20. The modular valve subassembly of claim 18, wherein the spring extends across substantially the entire front of the armature facing the magnetic pole, and the spring is mechanically attached to the armature via a plurality of fasteners.

22. 20. The modular valve subassembly of claim 18, wherein the spring biases the armature away from the magnetic pole and the reed valve element biases the sealing portion away from the magnetic pole.

23. 1. A viscous clutch assembly comprising: A rotationally fixed center shaft; a rotor rotatably supported on the center shaft; a housing disposed adjacent to the rotor and rotatably supported on the center shaft; a working chamber, the rotor and the housing defining at least a portion of a boundary of the working chamber, and a shear fluid present within the working chamber capable of transmitting torque between the rotor and the housing; a reservoir carried by and rotationally fixed to the rotor, the reservoir having an outlet bore; an electromagnetic coil rotatably fixed to the center shaft at or near a front end of the center shaft; a valve subassembly operable to control a flow of shear fluid between the reservoir and the working chamber through the outlet bore, the valve subassembly being controllable using magnetic flux generated by the electromagnetic coil; a front hub subassembly, The valve subassembly includes: an outer pole having an annular body; Armature and a spring pivotally securing the armature to the outer pole; a reed valve element pivotally secured to the outer pole and having a sealing portion disposed adjacent the outlet bore, wherein an applied magnetic flux selectively actuates the armature to apply a force to the reed valve element causing the reed valve element to pivot against a spring bias such that the sealing portion selectively opens and closes the outlet bore; The front hub subassembly includes: A flux guide; A bearing set, a flux insulator sleeve adjacent to and radially disposed between the bearing set and the flux guide; a viscous clutch assembly, the front hub subassembly being engaged between the center shaft and the housing, the flux guide extending axially across a portion of the housing, a forward end of the flux guide being separated from the electromagnetic coil by an air gap and an opposite rear end of the flux guide being separated from the outer pole by another air gap.

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