Valve control system for viscous friction clutch

Abstract

A viscous friction clutch (100, 00) includes a rotor (106, 206), a housing (112, 212) rotatable relative to the rotor, a working chamber (115, 215) between the rotor and the housing such that a volume of shear fluid can be selectively introduced into the working chamber to contact both the rotor and the housing, an electromagnetic coil (101, 201), a valve assembly (107, 207) that controls the volume of shear fluid present in the working chamber, and a flux path (A, A') that magnetically joins the electromagnetic coil with the valve assembly. The flux path passes through a flux guide portion (105, 105', 205) made of a ferromagnetic material that extends through the rotor in the interior of the viscous friction clutch and across a flux gap (B) that traverses both an air gap and a non-ferromagnetic portion (112b-1, 212b-1) of the housing.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to viscous friction clutches, and more particularly to electromagnetic control systems for viscous friction clutches, viscous friction clutches including such electromagnetic control systems, and methods of making and using the same. BACKGROUND

[0002] Clutches, also referred to as drives or couplings, are used in a variety of environments to selectively control the transmission of torque between an input and an output. For example, fan clutches are used to control the rotation of a fan, such as a cooling fan for automotive or industrial applications. Controlled operation of a cooling fan provides all the benefits associated with cooling flow when the clutch is engaged, but also allows the fan to be turned off when not needed, thereby reducing parasitic losses and increasing fuel efficiency. Turning off the cooling fan can also allow additional power to be diverted to other uses. Some clutches can allow selective control of variable output speed across a range, rather than just in a binary on / off fashion. Full variable clutch control can help optimize performance, such as customizing cooling for current conditions in a cooling fan application.

[0003] Viscous friction clutches, also referred to simply as viscous clutches, are used in a wide variety of applications, such as for automotive fan drive applications. These clutches typically employ a relatively thick silicone oil, more generally referred to as a shear fluid or viscous fluid, for selectively transmitting torque between two rotatable components. Engagement or disengagement of the clutch is made possible by selectively allowing the shear fluid to enter and exit a working region of the clutch located between the input member and the output member (e.g., between a rotor and a housing), in which viscous shear coupling can be created by the shear fluid to frictionally transmit torque from the input member to the output member. The volume of shear fluid present in the working chamber controls the speed differential between the primary / input side (input speed) and the secondary / output side (output speed) of the clutch. A valve assembly is used to control the flow of shear fluid into and / or out of the working region.

[0004] Temperature-sensing bimetal-controlled clutches are known. But such bimetal valve control does not allow active control and can not be suitable for some applications (e.g., blower applications).

[0005] Electromagnetic valve control is also known, which uses an electromagnetic coil to selectively generate a magnetic flux for operating a valve assembly. In a typical viscous clutch, a valve element that controls shear fluid flow must be located either entirely or partially within the clutch in order to regulate shear fluid flow into and / or out of a reservoir, while the electromagnetic coil is typically placed at the exterior of the clutch outside of the clutch in order to allow for proper external electrical connections. Such typical viscous clutches have a magnetic flux path and / or mechanical connection between the electromagnetic coil and the valve in order to operate the valve element with the electromagnetic coil physically spaced apart from the valve element. However, many prior art viscous clutches have limitations associated with the magnetic flux loop and / or mechanical connection (e.g., control rod) for electromagnetic control of the valve assembly. For example, while the clutch is disengaged, some clutch designs allow for shear fluid to be stored in a reservoir carried on or otherwise rotationally fixed to an input rotor (located inside the housing and typically rotating whenever there is a torque input to the clutch), in order to maintain the kinetic energy available in the shear fluid to allow for a quick engagement of the outer output housing of the clutch from a disengaged / off state, as well as to allow for the clutch to have very low output speeds (e.g., fan speeds), while the valve is positioned to limit the volume of shear fluid in the working area. However, carrying the reservoir on a rotor disk or similar substantially limits design flexibility, especially where the valve element is electromagnetic with the coil rotationally fixed (i.e., not rotating) as the clutch input rotates. Positioning the valve relative to the rotating reservoir while still providing suitable fluid and flux paths presents a difficult challenge, including the need to seal potential leak paths through which shear fluid can escape. These limitations are typically applicable, while designers also seek to provide a relatively compact and low mass clutch package that can accommodate desired torque loads and also function quickly, efficiently, and reliably.

[0006] U.S. Patent No. 6,419,064 Bl (with German counterpart Patent No. DE 19940099 B4) describes a mechanical connection between an external electromagnetic coil and a valve inside the clutch. PCT International Patent Application Publication No. WO 2014 / 047430 Al describes another mechanical connection of a valve assembly. However, mechanical connections require additional components for sealing to prevent leakage of shear fluid from the interior to the exterior of the clutch, as well as electromagnetic control for the mechanical connection itself.

[0007] U.S. Patent No. 6,443,283 Bl describes an embedded insert in a clutch housing for engaging a flux path of a valve element armature and an electromagnetic coil. However, there is a risk of leakage from the embedded iron insert in the die cast aluminum housing due to the different coefficients of thermal expansion between the aluminum housing and the iron insert. This leakage problem is known in the art and described, for example, in U.S. Patent No. 5,511,643.

[0008] Other viscous clutch designs that provide a flux path through the interior of the clutch include those disclosed in U.S. Patent No. 5,992,594 (with German counterpart Patent No. DE 19753725 C2), U.S. Patent No. 7,886,886 B2 (disclosed in U.S. Patent Application Publication No. 2008 / 0257677 Al), and PCT International Patent Application Publication No. WO 2011 / 062856 A2, and the Cooltronic® clutch available from Cojali S.L. (Real City, Spain). These clutch designs generally have a flux path that does not pass through the housing, but rather the flux path is entirely contained within the interior of the housing, or otherwise the flux path follows multiple isolated paths in a shaft, rotor hub, and / or bearing assembly that is positioned radially inward from the housing (i.e., the flux path does not pass through any portion of the housing but rather passes back and forth through at locations inward from the housing). In the case of the commercial Cooltronic® clutch from Cojali, the flux path passes from the inner diameter of the coil through a central shaft to the valve, and then returns to the outer diameter of the coil in any manner without any flux guides (i.e., the magnetic flux returns from the valve to the coil in an unguided manner).

[0009] Additional considerations include the need to provide a relatively compact and relatively low mass overall clutch package. The electromagnetic coil generally must be large enough to produce a sufficient magnetic field to actuate the valve assembly. A relatively large amount of magnetic flux is needed to actuate the control system of the valve element, which requires a correspondingly large electromagnetic coil, but such a large electromagnetic coil occupies a considerable amount of space and also has a relatively high mass. Thus, a control system that can reliably operate with lower overall magnetic flux requirements (i.e., a control system that can relatively efficiently use the magnetic flux for valve actuation) can help provide a relatively compact and low mass clutch package.

[0010] Further, clutches configured with a "live" center shaft that serves as the clutch input or output are desirable for some applications. A "live" center shaft generally refers to a shaft that is rotatable during clutch operation, as opposed to a stationary or rotationally stationary shaft, such as a mounting shaft of a rotationally fixed journal carrier. For example, a "live" center shaft clutch can be used for light duty applications. Clutches configured with a "live" center shaft can further help provide a relatively compact overall clutch package with relatively low mass, such as by potentially eliminating the need for a pulley (or sheave), journal carrier, or the like.

[0011] Accordingly, it is desirable to provide an electromagnetic control system for a viscous friction clutch and associated methods of making and using the electromagnetic control system that reduces or eliminates the need for mechanical connections through the clutch housing and / or flux guiding inserts embedded in the housing, while at the same time providing a relatively compact and low mass clutch package. It is further desirable to provide such a clutch configured with a "live" center shaft. SUMMARY

[0012] In one aspect, a viscous friction clutch includes a rotor, a housing that is rotatable relative to the rotor, a working chamber located between the rotor and the housing such that a volume of shear fluid can be selectively introduced into the working chamber so as to contact both the rotor and the housing, an electromagnetic coil, a valve assembly that controls the volume of shear fluid present in the working chamber, and a flux path that magnetically interfaces the electromagnetic coil with the valve assembly. The flux path passes through a flux guiding portion made of a ferromagnetic material that extends through the rotor and across a flux gap in an interior of the viscous friction clutch, the flux gap traversing both an air gap and a non-ferromagnetic portion of the housing.

[0013] In another aspect, a method of transmitting magnetic flux to operate a valve assembly through a viscous friction clutch is presented. The viscous friction clutch includes a rotor and a housing, each of which is rotatable, and a shaft that is rotationally fixed to the rotor. The valve assembly controls a volume of shear fluid present in a working chamber to selectively control a degree of viscous friction engagement between the rotor and the housing. The method includes energizing a stationary electromagnetic coil located outside of the housing of the viscous friction clutch, transmitting magnetic flux from the electromagnetic coil to a coil housing at least partially surrounding the electromagnetic coil, transmitting the magnetic flux from the coil housing to the shaft of the viscous friction clutch across a radial gap, transmitting the magnetic flux from the shaft to an armature of the valve assembly across an axial gap in a magnetic attraction region, transmitting the magnetic flux from the armature to a flux guide portion across a gap, transmitting the magnetic flux along the flux guide portion between axially opposite front and back sides of the rotor of the viscous friction clutch, transmitting the magnetic flux from the flux guide portion to the coil housing across a flux gap that includes a non-ferromagnetic portion of the housing of the viscous friction clutch, and transmitting the magnetic flux from the coil housing back to the electromagnetic coil. The flux guide portion is made of a ferromagnetic material.

[0014] In still further aspects, a method of manufacturing a viscous friction clutch is also provided.

[0015] This Summary is provided merely for purposes of summarizing the application so as to provide a basic understanding of it. As will be appreciated, there are at least some aspects of the present application that are not set forth in this Summary. The objectives attendant with this application, including those objects herein described, will be understood by persons skilled in the art in view of the disclosure, as provided in the entire text, including the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a cross-sectional view of an embodiment of a viscous friction clutch according to the present application.

[0017] Figure 2 is Figure 1 a partial cross-sectional view of the viscous friction clutch of

[0018] Figure 3 is Figure 1 and Figure 2 another partial cross-sectional view of a portion of the viscous friction clutch of

[0019] Figure 4 is a cross-sectional view of a rotor insert assembly shown separately.

[0020] Figure 5 is a front perspective view of the rotor insert assembly of Figure 4

[0021] Figure 6 is a perspective view of another embodiment of a rotor insert assembly shown separately.

[0022] ​Figure 7 is a cross-sectional view of another embodiment of a viscous friction clutch according to the present invention.

[0023] Figure 8 is Figure 7 is a partial cross-sectional view of a viscous friction clutch of

[0024] Figure 9 is Figure 7 and Figure 8 is another partial cross-sectional view of a portion of a viscous friction clutch of

[0025] While the above-identified drawings set forth one or more embodiments of the application, other embodiments are also contemplated, as noted in the discussion. Such changes and modifications can be carried out without departing from the scope and spirit of the application. The drawings described are not intended to be to scale as human height, vehicle height, and other dimensions are not to scale. The application and embodiments can include features, steps, and / or components not specifically shown in the drawings. The application encompasses all such modifications and embodiments. DETAILED DESCRIPTION

[0026] Generally, embodiments of the present invention provide an electromagnetic control system for a viscous friction clutch that can be controlled to selectively transmit torque between a clutch input and a clutch output at a desired speed. Such a viscous friction clutch can be used to selectively drive a cooling fan in a vehicle or for speed controlled torque transmission to other devices, among other possible uses. The viscous friction clutch can include a center shaft, a rotor, a housing, a reservoir, a working chamber, and a valve assembly having an armature operated by magnetic flux from an electromagnetic coil. The electromagnetic coil can be located outside of the viscous friction clutch and can be rotationally fixed, i.e., stationary in rotation. In some embodiments, the armature and valve elements of the valve assembly can each be positioned within the interior of the viscous friction clutch. In some embodiments, the valve assembly and electromagnetic coil can be located on opposite sides of the rotor. In some embodiments, the center shaft can be a "live" center shaft rotationally fixed to the rotor so as to always co-rotate at the same speed as the rotor. In some embodiments, the rotor can be configured like a disc. The reservoir can be carried by the input of the clutch, such as on the rotor, so as to rotate whenever there is torque input to the clutch. In some embodiments, the housing can be a multi-piece assembly including a base and a cover at least partially surrounding the rotor. The viscous friction can include a rotor insert assembly in the rotor that includes a magnetic flux guiding portion. The rotor insert assembly performs multiple functions. A first portion of the rotor insert assembly, made at least in part of a magnetic flux conducting material, such as a ferromagnetic material, operates as a magnetic flux path controller or guide that guides magnetic flux along a portion of the flux path through the viscous friction clutch (e.g., across or through the rotor) to assist in the operation of the electromagnetic control of the valve located within the clutch without the need for additional embedded magnetic flux guide inserts in the housing of the clutch. A second portion of the rotor insert assembly, also referred to as the hub of the insert assembly, provides a structural connection to transmit torque between the center shaft and the rotor while reducing or avoiding magnetic shorting between the shaft and the first portion of the rotor insert assembly (i.e., the flux guiding portion of the rotor insert assembly). The flux path through the clutch can extend from the electromagnetic coil to the center shaft, then to the armature of the valve assembly, then to the first flux guiding portion of the rotor insert assembly (which can transmit the magnetic flux through the rotor, which can be made of a non-ferromagnetic material), and then across a flux gap back to the electromagnetic coil. In alternative embodiments, the rotor insert assembly includes a multi-piece hub portion having a ferromagnetic hub core and a non-ferromagnetic disc portion; in such alternative embodiments, the flux path through the clutch can extend from the electromagnetic coil to the center shaft, then to the hub core, then to the armature of the valve assembly, then to the first flux guiding portion of the rotor insert assembly, and then across a flux gap back to the electromagnetic coil.In various embodiments, the flux gap can extend through a portion of a housing made of a non-ferromagnetic material, such as aluminum, such as a portion of the housing's base. In some embodiments, a housing cover access opening, a seal and seal carrier, an armature stop, and / or other optional components can further be provided. Thus, for example, the disclosed embodiments provide a viscous friction clutch for driving a cooling fan in a vehicle or for speed-controlled torque transmission to other devices, having an electromagnetic flux path through the clutch interior, the flux path passing through both a ferromagnetic flux guiding portion and a flux gap, the ferromagnetic flux guiding portion passing through a rotor within the clutch interior, the flux gap extending through a non-ferromagnetic portion of the housing at least partially surrounding the rotor and an air gap on each side of the non-ferromagnetic portion of the housing; the flux guiding portion can be embedded in or attached to the rotor, which can be made of a non-ferromagnetic material. Also disclosed, or as will be apparent to one of ordinary skill in the art, are embodiments of methods of making and using a viscous friction clutch with an electromagnetic control system.

[0027] Further embodiments are also contemplated. For example, while the disclosed embodiments illustrate an electromagnetic control system for use with a live center clutch configuration, it should be understood that the electromagnetic control system, rotor insert assembly, and / or associated methods may also be used with other types of clutch configurations. In view of the entirety of this disclosure, including the accompanying drawings, one of ordinary skill in the art will recognize numerous features and benefits.

[0028] This application is based upon and claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 024,592, filed on May 14, 2020, the contents of which are incorporated herein by reference in their entirety.

[0029] Figures 1-5 One embodiment of a viscous friction clutch 100 is shown. Figure 1 is a cross-sectional view of the viscous friction clutch 100; Figure 2 is another cross-sectional view of the viscous friction clutch 100 , with schematic annotations illustrating the magnetic flux path A and the magnetic attraction area D; and Figure 3 is a partial cross-sectional view of a portion of the viscous friction clutch 100 . Figure 4 and Figure 5 Components that are part of the viscous friction clutch 100 are shown individually.

[0030] like Figure 1The viscous friction clutch 100 shown in the embodiment of FIG. 1 includes an electromagnetic coil 101, a coil housing 102 defining a north pole 102N and a south pole 102S, a rotor insert assembly 103 having a hub portion 104 and a flux guiding portion 105, a rotor 106, a valve assembly 107 (shown in an attracted position) having an armature 108 and a valve element 109, a shaft 110, a housing 112, a reservoir 113, a release orifice 114, and a working chamber 115. Although not specifically shown, the viscous friction clutch 100 further includes a suitable return orifice and a pumping element, both of which are well known in the art of viscous friction clutches.

[0031] As shown in the illustrated embodiment, the shaft 110 is a shaft that defines the rotational axis C of the viscous friction clutch 100. L The electromagnetic coil 101 can be rotationally stationary and can be rotatably mounted on the shaft 110 via suitable bearings 101X. In addition, the coil housing 102 can be rotatably mounted on the shaft 110 via bearings 101X, which also support the electromagnetic coil 101 and can at least partially surround the electromagnetic coil 101. Both the electromagnetic coil 101 and the coil housing 102 can be located outside the housing 112. The shaft 110 can have attachment features at the rear end. The shaft 110 can be used as an input member of the viscous friction clutch 100 to accept torque input from a prime mover (not shown), such as an internal combustion engine of a vehicle. In the illustrated embodiment, the shaft 110 is at least partially made of a ferromagnetic material that conducts magnetic flux.

[0032] Electromagnetic coil 101 is at least partially positioned within coil housing 102. In the illustrated embodiment, north pole 102N of coil housing 102 extends radially inward toward axis 110, and south pole 102S of coil housing 102 extends axially toward flux guiding portion 105 (and base 112b of housing 112).

[0033] The rotor 106 can be rotationally fixed to the shaft 110 so that the rotor 106 and the shaft 110 rotate together at the same speed (e.g., at the input speed of the torque input to the clutch 100). In the illustrated embodiment, the rotor 106 is configured as a disk and can be made of a non-ferromagnetic material such as aluminum. At least a portion of the hub portion 104 and the flux guiding portion 105 of the rotor insert assembly 103 are embedded in the rotor 106, as shown in the illustrated embodiment.

[0034] In the illustrated embodiment, the rotor insert assembly 103 includes a hub portion 104 at a radially inner position and a flux guiding portion 105 at a radially outer position (the rotor insert assembly 103 is described below with respect to FIG. Figure 4 and Figure 5The hub portion 104 can be located at a radially inner portion of the rotor 106 and can provide structural attachment between the rotor 106 and the shaft 110. In the illustrated embodiment, the hub portion 104 is a multi-piece assembly including a core 104c and a disk 104d, with the disk 104d extending radially outward from the core 104c. The core 104c can be positioned directly on the shaft 110. The hub portion 104 can include a non-ferromagnetic material such as austenitic stainless steel, and / or can be configured with a magnetic flux interruption feature that reduces or eliminates magnetic shorting in the generally radial direction between the flux guide portion 105 and the shaft 110, as explained further below. In the illustrated embodiment, the core 104c is made of a ferromagnetic material, and the disk 104d is made of a non-ferromagnetic material that interrupts any magnetic flux flow in the radial direction along the rotor insert assembly 103. More generally, the hub portion 104 of the rotor insert assembly 103 of the illustrated embodiment includes a non-ferromagnetic or at least partially non-ferromagnetic portion between its inner diameter and its outer diameter.

[0035] The flux guide portion 105 can be attached to the hub portion 104 at a radially outer portion of the disk 104d. The flux guide portion 105 extends axially through the rotor 106. The flux guide portion 105 can be made of a ferromagnetic material in order to guide magnetic flux through the non-ferromagnetic material of the rotor 106. In the illustrated embodiment, the flux guide portion 105 includes a back end 105a that extends and protrudes in the axial direction from the back side of the rotor 106, which helps to guide magnetic flux to the south pole 102S of the coil housing 102, such as at or near the outer diameter of the coil housing 102, as explained further below. As shown in the illustrated embodiment, the back end 105a of the flux guide portion 105 is located at a radial position that overlaps the radial position of the south pole 102S of the coil housing 102 (such that the flux path therebetween can be substantially axial or entirely axial), but in further embodiments other relative radial positions are possible, such as the back end 105a being located radially inward from the south pole 102S of the coil housing 102.

[0036] The reservoir 113 has an internal volume for storing a supply of shear fluid. The release orifice 114 allows shear fluid to flow from the reservoir 113 to the working chamber 115 and can be selectively covered and uncovered by the valve assembly 107. A return orifice (not shown) exits to the reservoir 113 so that shear fluid can return to the reservoir 113 for storage. As shown in the illustrated embodiment, the reservoir 113 is carried by or on the rotor 106. When the rotor 106 is part of the input member of the viscous friction clutch 100, the reservoir 113 rotates as long as there is torque input onto the clutch 100. In some embodiments, the flux guide portion 105 can abut and / or form at least a portion of the boundary of the reservoir 113. As shown in the illustrated embodiment, a reservoir plate 113a that defines a portion of the boundary of the reservoir 113 is optionally secured to the back end 105a of the flux guide portion 105. The reservoir plate 113 can be made of a ferromagnetic material and can optionally form part of the flux path. In alternative embodiments, the reservoir 113 can optionally further include an anti-backlash or anti-morning sickness feature, such as one or more internal walls, a morning sickness prevention valve, etc.

[0037] The housing 112 is a multi-piece assembly in the illustrated embodiment and includes a base 112b and a cover 112c. In the illustrated embodiment, the housing 112 at least partially surrounds the rotor 106. The housing 112 (e.g., the housing base 112b) is rotationally supported on the shaft 110 by a bearing 112X so that the housing 112 can rotate relative to the shaft 110 and relative to the rotor 106. The housing 112 can function as the output member of the viscous friction clutch 100 and an output device such as a fan (not shown) can be attached to the housing 112 so as to receive the torque output selectively transmitted by the viscous friction clutch 100 during operation. The housing 112 can be made of a non-ferromagnetic material such as aluminum.

[0038] The working chamber 115 is located between the rotor 106 and the housing 112 so that the volume of shear fluid present in the working chamber 115 can frictionally contact both the rotor 106 and the housing 112 so as to transmit torque between the rotor 106 and the housing 112 at a slip speed that is generally dependent on the volume of shear fluid present in the working chamber 115. The basic operation of a working chamber in a viscous friction clutch is known in the art.

[0039] The valve assembly 107 includes an armature 108 and a valve element 109. The armature 108 is connected to the valve element 109 and moves the valve element 109 in response to an applied magnetic flux, as explained further below. In the illustrated embodiment, the valve assembly 107 is located on the front side of the rotor 106, while the solenoid 101 is located on the opposite rear side of the rotor 106. The valve element 109 can be spring-biased to an open position by default, such that the applied magnetic flux generates a valve actuation force that overcomes the spring biasing force and moves the armature 108 and valve element 109 to the closed position. This is referred to as a "fail-open" configuration, in which any loss of power means that the spring biasing force defaults to moving the valve assembly 107 to the "on" or open position. As shown in the illustrated embodiment, the valve assembly 107 (including the armature 108 and valve element 109) is positioned within the viscous friction clutch 100 (i.e., within the housing 112) and is carried by or on the rotor 106. Furthermore, in the illustrated embodiment, the valve element 109 is Figure 3 ) pivots or translates generally in an axial direction during operation. A stop 116 may optionally be provided on the rotor 106 to limit the movement of the armature 108 and valve element 109 and the travel C in the closed, open, or non-attractive positions of the valve assembly 107. A release orifice 114 allows shear fluid to flow from the reservoir 113 to the working chamber 115 and can be selectively covered and uncovered by the valve assembly 107 to adjust the volume of shear fluid present in the working chamber 115 and thereby control the operation of the viscous friction clutch 100. The shear fluid is typically continuously pumped from the working chamber 115 back to the reservoir 113 through a return orifice (not shown) during clutch operation.

[0040] During operation, the solenoid coil 101 may be selectively energized to generate magnetic flux that travels along a magnetic flux path (or flux loop) A through the viscous friction clutch 100 to operate the valve assembly 107 . Figure 2 The diagram schematically shows the rotation axis C of the clutch 100. L There is a dashed flux path A on one side, but it should be understood that even in Figure 2 Only a portion of the flux path A is marked, and the flux path A also has a direction around the axis C. LExtended three-dimensional shape. Flux path A allows magnetic flux to pass from the electromagnetic coil 101 to the armature 108 of the valve assembly 107 and then back to the electromagnetic coil 101. The magnetic flux path A exits the coil 101 and enters the coil housing 102, then crosses the gap from the north pole 102N of the coil housing 102 to the shaft 110. The gap between the coil housing 102 and the shaft 110 is constant and is arranged radially in the illustrated embodiment. The magnetic flux can then travel in the attraction region D across the gap between the shaft 110 and the armature 108. In some embodiments, this magnetic flux can optionally travel through the core 104c of the hub portion 104 of the rotor insert assembly 103 in and / or near the attraction region D. In some embodiments, the attraction region D can be located radially outward of the rotational axis C L but in other embodiments, the attraction region D can reach the rotational axis C L In the illustrated embodiment, the gap between the shaft 110 (and core 104c) and the armature 108 in the attraction region D is arranged axially. The size of the gap between the shaft 110 (and core 104c) and the armature 108 changes during operation of the clutch 100 according to the movement of the armature 108. The gap distance between the armature 108 and the shaft 110 (and core 104c) corresponds to the stroke C (see Figure 3 ) of the valve assembly 107. In some embodiments, the magnetic flux can attract the armature 108 to the shaft 110 such that the gap between the armature 108 and the shaft 110 is completely closed (i.e., the armature 108 physically contacts the shaft 110 and / or core 104c) when the electromagnetic coil 101 is energized. Flux path A continues from the armature 108 across the gap F to the flux guide portion 105 of the rotor insert assembly 103 (see Figure 3 ). In the illustrated embodiment, the gap F is constant and is arranged radially (and is located at the outer diameter of the armature 108). The constant radial gap F allows for a constant magnetic flux flow independent of the open or closed position of the armature 108. The constant magnetic flux flow in flux path A helps to improve the internal magnetic force to the armature 108. Flux path A then continues through the flux guide portion 105 of the rotor insert assembly 103, axially through the entire rotor 106 between the opposing front and back sides. The magnetic flux path A then continues from the flux guide portion 105 of the rotor insert assembly 103 across the magnetic flux gap B (see Figure 3 ) to the south pole 102S of the coil housing 102 and then back to the electromagnetic coil 101.

[0041] As shown in the illustrated embodiment, flux gap B is disposed axially and is a larger gap than the other gaps of flux path A. The size of flux gap B can be constant. Flux gap B traverses a portion 112b-1 of housing 112, as well as air gaps on axially opposite sides of housing 112. More specifically, flux gap B axially traverses a non-ferromagnetic portion 112b-1 of a base 112b of housing 112 that lacks any embedded flux guiding inserts or other ferromagnetic components that fully (or even partially) traverse housing 112 between its interior and exterior in or near flux path A. In other words, in some embodiments, there is no ferromagnetic material in flux gap B, and thus it can be referred to as a non-ferromagnetic flux gap. Flux path A can cross flux gap B, traverse or cross portion 112b-1 of housing 112, as well as one or more adjacent air gaps and any shear fluid, without requiring any ferromagnetic flux guides that would potentially create undesirable leakage paths for the shear fluid, particularly due to different coefficients of thermal expansion of ferromagnetic and adjacent non-ferromagnetic materials (e.g., between steel and aluminum materials). In various embodiments, the number of air gaps within flux gap B can be limited to no more than two air gaps, and portion 112b-1 of housing 112 can be the only non-ferromagnetic component that flux path A crosses within flux gap B. In some embodiments, the size of flux gap B between rear end 105a of flux guide portion 105 and south pole 102S of coil housing 102 can be less than the distance between rear end 105a of flux guide portion 105 and any other nearby ferromagnetic material; and, in further embodiments, the axial size of flux gap B between rear end 105a of flux guide portion 105 and coil housing 102 can be less than the distance between rear end 105a of flux guide portion 105 and any other nearby ferromagnetic material in the axial or radially inward direction. Moreover, because flux guide portion 105 extends through rotor 106 and projects rearward in the illustrated embodiment, the size of flux gap B between rear end 105a of flux guide portion 105 and south pole 102S of coil housing 102 can be less than the distance between the backside of rotor 106 and south pole 102S of coil housing 102 along flux path A. In some embodiments, the axial distance of flux gap B between rear end 105a of flux guide portion 105 and south pole 102S of coil housing 102 can be less than the axial distance between south pole 102S of coil housing 102 and working chamber 115, that is, rear end 105a of flux guide portion 105 can extend axially rearward from working chamber 115.It should be noted that the presence of any ferromagnetic material radially outward of flux path A would not tend to create any short circuit of flux path A, and thus in some embodiments, ferromagnetic material (e.g., a reservoir plate 113a made of ferromagnetic material) can be present proximate to or in physical contact with flux guide portion 105, radially outward of flux path A, without significantly impacting the performance of flux path A at or near flux gap B. Due to the relatively short and direct distance of flux gap B (even though it can be larger than other gaps in flux path A), no additional embedded ferrous inserts are needed in housing 112. The non-ferromagnetic portion 112b-1 of housing 112 included in (and traversed by) flux gap B is positioned radially outward of bearing 112X, which in the illustrated embodiment rotationally supports housing 112 on shaft 110, such that bearing 112X is positioned in the interior of flux path A. Further, in the illustrated embodiment, bearing 101X that supports electromagnetic coil 101 and coil housing 102 on shaft 110 is also located within magnetic flux path A.

[0042] In order to direct magnetic flux path A from shaft 110 into armature 108 and then into flux guide portion 105 of rotor insert assembly 103, it is important to avoid a magnetic short circuit between flux guide portion 105 and shaft 110, which can be achieved by using rotor insert assembly 103 with certain defined characteristics. In one embodiment, illustrated separately in Figure 4 Figure 5 In one embodiment, illustrated separately in Figs. 10A and 10B, this can be achieved by using a non-ferromagnetic material for disk 104d of hub portion 104 of rotor insert assembly 103. In this way, flux guide portion 105 and core 104c, each made of ferromagnetic material, and disk 104d, made of non-ferromagnetic material, can be separate pieces that are joined or connected together and embedded or otherwise connected to rotor 106, made of non-ferromagnetic material, such as using a die casting process. Having core 104c made of ferromagnetic material can help improve the performance of flux path A. Although in alternative embodiments, core 104c and disk 104d of hub portion 104 can be a single piece made of non-magnetic material. Figure 4 Figure 5 ​​The embodiment of the rotor insert assembly 103 shown in FIG also includes interruptions 118a, 118b, and 118c, which may be configured as openings in the hub portion 104 and / or the flux guiding portion 105. In the illustrated embodiment, a plurality of circumferentially equally spaced U-shaped interruptions 118a radially extend through the flux guiding portion 105 and extend all the way to the front end (opposite the rear end 105a) so as to be open in the axial forward direction, a plurality of U-shaped interruptions 118b are positioned at the outer diameter of the disk 104d of the hub portion 104 and aligned with the interruptions 118a to create a combined opening, wherein the interruptions 118b extend axially through the disk 104d and all the way to the outer diameter of the disk 104d, and finally, the interruption 118c is a plurality of equally circumferentially spaced circular holes axially through the middle of the disk 104d. However, in further embodiments, other shapes and arrangements of the interruptions 118a, 118b, and / or 118c are possible. When fully installed in the viscous friction clutch 100, the interruptions 118a, 118b, and / or 118c can be at least partially filled with the non-ferromagnetic material of the rotor 106. More specifically, in some embodiments, the interruptions 118b, 118c can each be completely filled with the non-ferromagnetic material of the rotor 106, while the interruption 118a can each be only partially filled with the non-ferromagnetic material of the rotor 106.

[0043] Alternatively, as Figure 6 As shown, the flux-guiding portion 105' and the hub portion 104' of the rotor insert assembly 103' can be fabricated as a single, unitary piece of ferromagnetic material, and flux-interrupting features, such as openings 118' in the hub portion 104' (and, in further embodiments, optionally also in the flux-guiding portion 105'), can be present to reduce or avoid magnetic shortcuts in a generally radial direction between the flux-guiding portion 105' and the hub portion 104' (and the shaft 110). Although in the illustrated embodiment, the flux-guiding portion 105' has an uninterrupted configuration without any openings or the like, the flux-interrupting features (openings 118') are preferably as numerous and large as possible. When fully installed in the viscous friction clutch 100, such openings 118' in the hub portion 104' (and / or the flux-guiding portion 105') are filled with non-ferromagnetic material of the rotor 106 for torque transmission between the rotor 106, the hub portion 104', and the flux-guiding portion 105'. The rotor insert assembly 103 ′ is otherwise similar to and functions in substantially the same manner as the rotor insert assembly 103 described above.

[0044] Figures 7-9 Another embodiment of a viscous friction clutch 200 is shown. Figure 7is a cross-sectional view of this alternative embodiment of the viscous friction clutch 200; Figure 8 is another cross-sectional view of the viscous friction clutch 200 with various schematic annotations to illustrate the magnetic flux path A' and the magnetic attraction area D; and Figure 9 is a partial cross-sectional view of a portion of the viscous friction clutch 200. In general, Figures 7-9 The embodiment of the viscous friction clutch 200 shown and described is similar to that described above with respect to Figures 1-6 The embodiment of the viscous friction clutch 100 is described herein and accordingly like reference numerals are used generally increased by one hundred. More specifically, as Figures 7-9 The viscous friction clutch 200 shown in the embodiment of FIG includes an electromagnetic coil 201, a coil housing 202 defining a north pole 202N and a south pole 202S, a rotor insert assembly 203 having a hub portion 204 and a flux guiding portion 205, a rotor 206, a valve assembly 207 having an armature 208 and a valve element 209, a shaft 210, a housing 212 (including a base 212b and a cover 212c), a reservoir 213 (having a reservoir cover 213a), a release orifice 214, a working chamber 215, and a rotational axis C. L Although not specifically shown, the viscous friction clutch 200 further includes a suitable return hole and pumping element. The magnetic flux path A' including the flux gap B, the valve assembly stroke C, and the magnetic attraction area D in the viscous friction clutch 200 can be similar or the same as that of the viscous friction clutch 100. However, Figures 7-9 The embodiment of the viscous friction clutch 200 differs from the clutch 100 in the design surrounding the shaft 210 .

[0045] like Figures 7-9 As shown in the illustrated embodiment, the front end of the shaft 210 includes a blind hole 220 and a carrier 222 engaged with the blind hole 220. The blind hole 220 can extend axially into the shaft 210 and can be axially open forward, as shown in the illustrated embodiment. The edge of the shaft 210 surrounding the blind hole 220 at the front end 210F of the shaft 210 is sufficient to transmit magnetic flux from the shaft 220 to the armature 208 along the flux path A. The blind hole 220 in the shaft 210 provides a torque or tooling feature 223 (e.g., a tool engaging feature, such as a tool engaging feature) for use at the front end 210F of the shaft 210 (e.g., at the rear or bottom of the blind hole 220). The shaft 210 can further include a rear end 210R and a front end 210F. The rear end 210R can include a threaded feature 210t, such as a threaded hole, for example, to facilitate attachment of the rear end 210R of the shaft 210 to a complementary element (not shown) with another connecting feature, such as a threaded 210t. In the illustrated embodiment, the front end 210F of the shaft 210 and the blind hole 220 are located in an interior portion of the viscous friction clutch 200, inside the housing 212. To provide access to the blind hole 220 and to the torque or tool feature 223, an opening 228 (e.g., a central hole) can be provided in the cover 212c of the housing 212. A corresponding central hole 208h can be provided in the armature 208 to allow access to the blind hole 220 and / or the torque feature 223. A removable cap (not shown) can be provided at or within the opening 228 in the cover 212c of the housing 212 to protect the elements within the viscous friction clutch 200 from debris and the like. The opening 228 or the structure near the opening 228 can include suitable features, such as an engagement groove, to allow engagement of the cap 228a with the cover 212c of the housing 212.

[0046] The carrier 222 can be engaged with the blind hole 220 by a connecting feature 222c (e.g., a thread) that attaches the carrier 222 to the shaft 210 and that can be located within the blind hole 220. The carrier 222 can further include a tool feature 222t, e.g., a flat or a slot, for receiving a tool bit, driver, or other suitable tool that can apply torque. The carrier 222 can be made of a non-ferromagnetic material to isolate the carrier 222 from the flux path A or at least to avoid interference with the flux path A. The carrier 222 can extend axially from the shaft 210 through the central hole 208h in the armature 208. The carrier 222 can further include an opening 222a, such as an axially extending central opening, that extends entirely through the carrier 222 between its opposite ends to allow access to the torque or tool feature 223, such as to allow insertion of a tool through the opening 228 in the cover 212c of the housing 212 (and through the opening 208h in the armature 208) from the front side of the viscous friction clutch 200. In addition, the carrier 222 can support and carry a sealing element 229 (e.g., a dynamic seal or a bearing, such as a sealed bearing set) that contacts the housing 212 and can provide a seal against the cover 212c of the housing 212 at the opening 228 to help prevent leakage of the shear fluid. In addition, a stop 230 can be provided on the carrier 222 on the side opposite the armature 208 and the shaft 210. The stop 230 can limit the travel C of the valve assembly 207, in particular, the stop 230 can limit the range of motion of the armature 208 and the valve element 209 in the axial direction under the default spring biasing force. In the illustrated embodiment, the stop 230 is a radially outwardly extending flange that extends from the body of the carrier 222.

[0047] The rotor 206 can be rotationally fixed to the shaft 210 such that the rotor 206 and the shaft 210 co-rotate together at the same speed. The housing 212 (e.g., the housing base 212b) can be rotationally supported on the shaft 210 by suitable bearings 212X such that the housing 212 can rotate relative to the shaft 210 and relative to the rotor 206. The electromagnetic coil 201 and the coil housing 202 can be rotationally stationary and can both be mounted on the shaft 210 by suitable bearings 201X, with the electromagnetic coil 201 and the coil housing 202 located outside of the housing 212.

[0048] The electromagnetic coil 201 can have an L-shape similar to the cross-section disclosed in PCT International Application Publication No. WO 2018 / 004833 Al. Such an L-shaped electromagnetic coil 201 as shown in the illustrated embodiment can help reduce the overall size and mass of the viscous friction clutch 200. The electromagnetic coil 201 is at least partially positioned in the coil housing 202. The coil housing 202 can at least partially surround the electromagnetic coil 201 and can have a shape that conforms to the L-shape of the electromagnetic coil 201. For example, in the illustrated embodiment, the coil housing 202 has a south pole 202S positioned axially forward (with one end of the south pole 202S extending axially toward the base 212b and the flux guide portion 205 of the housing 212), an intermediate portion 202M positioned axially rearward (and having a U-shape or C-shape), and a north pole 202N positioned axially forward of the intermediate portion 202M but axially rearward of the south pole 202S (with one end of the north pole 202N extending radially inward toward the shaft 210). The shape of the intermediate portion 202M and the north pole 202N of the coil housing can provide space for bearings.

[0049] The working chamber 215 is located between the rotor 206 and the housing 212 such that a volume of shear fluid present in the working chamber 215 can frictionally contact both the rotor 206 and the housing 212 in order to transmit torque between the rotor 206 and the housing 212 at a slip speed that is generally dependent on the volume of shear fluid present in the working chamber 215. The rotor 206 and the shaft 210 can act as an input for the viscous friction clutch 200, while the housing 212 can act as an output. An output device, such as a fan (not shown), can be attached to the housing 212 to receive torque output from the viscous friction clutch 200.

[0050] The valve assembly 207 operates in response to applied magnetic flux in order to selectively cover and uncover the release orifice 214 in order to regulate the volume of shear fluid in the working chamber 215. When not in use, the shear fluid can be stored in the reservoir 213. In the illustrated embodiment, the valve assembly 207 is located on the forward side of the rotor 206, while the electromagnetic coil 201 and the reservoir 213 are both located on the opposite rear side of the rotor 206.

[0051] In the illustrated embodiment, the rotor insert assembly 203 includes a hub portion 204 at a radially inner location and a flux guide portion 205 at a radially outer location (see also Figure 4 and Figure 5 ). The hub portion 204 can be located at a radially inner portion of the rotor 206 and can provide structural attachment between the rotor 206 and the shaft 210. In the illustrated embodiment, the hub portion 204 is a multi-piece assembly including a core 204c and a disk 204d extending radially outward from the core 204c. The core 204c can be positioned directly on the shaft 210. The hub portion 204 can include a non-ferromagnetic material, such as austenitic stainless steel, and / or can be configured with magnetic flux interruption features that reduce or eliminate magnetic shorting in a generally radial direction between the flux guide portion 205 and the shaft 210, as explained above with respect to prior embodiments. In the illustrated embodiment, the core 204c is made of a ferromagnetic material and the disk 204d is made of a non-ferromagnetic material that interrupts any magnetic flux flow in a radial direction along the rotor insert assembly 203. More generally, the hub portion 204 of the rotor insert assembly 203 of the illustrated embodiment includes a non-ferromagnetic portion or at least partially non-ferromagnetic portion between its inner diameter and its outer diameter.

[0052] The flux guide portion 205 can be attached to the hub portion 204 at a radially outer portion of the disk 204d. The flux guide portion 205 extends axially through the rotor 206. The flux guide portion 205 can be made of a ferromagnetic material in order to guide magnetic flux through the non-ferromagnetic material of the rotor 206. In the illustrated embodiment, the flux guide portion 205 includes a rear end 205a that extends and protrudes in an axial direction from the rear side of the rotor 206, which helps to direct magnetic flux to the south pole 202S of the coil housing 202, such as at or near the outer diameter of the coil housing 202, as explained further below. As shown in the illustrated embodiment, the rear end 205a of the flux guide portion 205 is located at a radial position that overlaps the radial position of the south pole 202S of the coil housing 202 (such that the flux path therebetween can be entirely axial), although other relative radial positions are possible in further embodiments.

[0053] During operation, the electromagnetic coil 201 can be selectively energized to generate magnetic flux that travels along a magnetic flux path (or flux loop) A through the viscous friction clutch 200 to operate the valve assembly 207, similar to the operation of the viscous friction clutch 100 described above. Figure 8 The flux path A is shown schematically with dashed lines on one side of the rotational axis C L of the clutch 200, but it will be understood that even inFigure 8 Only a portion of flux path A’ is labeled, flux path A’ also has a portion that wraps around axis C L extends. Flux path A’ allows magnetic flux to pass from the electromagnetic coil 201 to the armature 208 of the valve assembly 207 and then back to the electromagnetic coil 201. The magnetic flux path A’ exits the coil 201 and enters the coil housing 202, then crosses the gap from the north pole 202N of the coil housing 202 to the shaft 210. The gap between the coil housing 202 and the shaft 210 is constant and is arranged radially in the illustrated embodiment. The magnetic flux can then travel in the attraction region D through the gap between the shaft 210 and the armature 208. In some embodiments, the magnetic flux can optionally travel through the core 204c of the hub portion 204 of the rotor insert assembly 203 in and / or near the attraction region D. In some embodiments, the attraction region D can be located radially outward of the rotational axis C L but in other embodiments, the attraction region D can reach the rotational axis C L In the illustrated embodiment, the gap between the shaft 210 (and core 204c) and the armature 208 in the attraction region D is arranged axially. The size of the gap between the shaft 210 (and core 204c) and the armature 208 changes during operation of the clutch 200 according to the movement of the armature 208. The gap distance between the armature 208 and the shaft 210 (and core 204c) corresponds to the stroke C (see Figure 9 ) of the valve assembly 207. In some embodiments, the magnetic flux can attract the armature 208 to the shaft 210 such that the gap between the armature 208 and the shaft 210 is completely closed (i.e., the armature 208 physically contacts the shaft 210 and / or core 204c) when the electromagnetic coil 201 is energized. Flux path A continues from the armature 208 across a gap F to the flux guide portion 205 of the rotor insert assembly 203, the gap F is constant and is arranged radially in the illustrated embodiment (and is located at the outer diameter of the armature 208). The constant radial gap F allows for a constant magnetic flux flow independent of the open or closed position of the armature 208. The constant magnetic flux flow in flux path A’ helps to improve the internal magnetic force on the armature 208. Flux path A’ then continues through the flux guide portion 205 of the rotor insert assembly 203, axially through the entire rotor 206 between the opposing front and back sides. Flux path A’ then continues from the flux guide portion 205 of the rotor insert assembly 203 across the magnetic flux gap B to the south pole 202S of the coil housing 202, and then back to the electromagnetic coil 201.

[0054] As shown in the illustrated embodiment, flux gap B is axially disposed and is a larger gap than the other gaps of flux path A'. The size of flux gap B can be constant. Flux gap B traverses portion 212b-1 of housing 212, as well as air gaps on axially opposite sides of housing 212. More specifically, flux gap B axially spans a non-ferromagnetic portion 212b-1 of base 212b of housing 212 that lacks any embedded flux guiding inserts or other ferromagnetic components that fully (or even partially) pass through housing 212 between the interior and exterior of housing 212 in or near flux path A', meaning that flux gap B can be referred to as a non-ferromagnetic flux gap. Flux path A' can span flux gap B, pass through or across portion 212b-1 of housing 212, and one or more adjoining air gaps and any shear fluid present, without requiring any ferromagnetic flux guides that would potentially create undesirable leakage paths for shear fluid. In various embodiments, the number of air gaps within flux gap B can be limited to no more than two air gaps, and portion 212b-1 of housing 212 can be the only non-ferromagnetic component that flux path A' spans within flux gap B. In some embodiments, the size of flux gap B between rear end 205a of flux guide portion 205 and south pole 202S of coil housing 202 can be less than the distance between rear end 205a of flux guide portion 205 and any other nearby ferromagnetic material; and, in further embodiments, the axial size of flux gap B between rear end 205a of flux guide portion 205 and coil housing 102 can be less than the distance between rear end 205a of flux guide portion 205 and any other nearby ferromagnetic material in the axial or radially inward direction. Moreover, because flux guide portion 205 extends through rotor 206 and protrudes rearward in the illustrated embodiment, the size of flux gap B between rear end 205a of flux guide portion 205 and south pole 202S of coil housing 202 can be less than the distance between the rear side of rotor 206 and south pole 202S of coil housing 202 along flux path A'. In some embodiments, the axial distance of flux gap B between rear end 205a of flux guide portion 205 and south pole 202S of coil housing 202 can be less than the axial distance between south pole 202S of coil housing 202 and working chamber 215, that is, rear end 205a of flux guide portion 205 can extend axially rearward of working chamber 215. In the illustrated embodiment, non-ferromagnetic portion 212b-1 of housing 212 that is included in (and traversed by) flux gap B is positioned radially outward from bearing 212X that rotationally supports housing 212 on shaft 210, such that bearing 212X is positioned in the interior of flux path A'.Furthermore, in the illustrated embodiment, the bearings 201X that support the electromagnetic coil 201 and the coil housing 202 on the shaft 210 are located outside of the magnetic flux path A'.

[0055] It should be noted that any of the rotor insert assemblies 103 and 103' discussed above and illustrated in FIGS. 1-3 can be used with the viscous friction clutch 200, as desired for a particular application. Furthermore, in additional embodiments, other embodiments of rotor insert assemblies are possible. Figures 4-6

[0056] ​In view of the overall disclosure, including the drawings, those of ordinary skill in the art will recognize that the disclosed embodiments of viscous friction clutches provide a number of advantages and benefits. For example, the disclosed embodiments provide an electromagnetically controlled viscous friction clutch that can be relatively compact, have a relatively low mass, and be relatively simple to manufacture, that lacks any magnetic flux guides through the housing that would potentially create a shear fluid leak path, while still transmitting magnetic flux across and through the non-ferromagnetic portion of the housing. For example, a rotor insert assembly that includes a non-ferromagnetic or at least partially non-ferromagnetic portion between its inner diameter and its outer diameter can be used in order to reduce or minimize magnetic short-cuts or short-circuits through the electromagnetic flux path of the viscous friction clutch and help increase the magnetic power available to move the armature of the valve assembly, all without any embedded flux inserts in the housing. It has been noted that some known clutch designs have flux paths that do not pass through the housing, but rather are completely contained within the interior of the housing, or the flux path follows multiple isolated paths in the shaft, rotor hub, and / or bearing assembly positioned radially inward from the housing (i.e., the flux path does not pass through any portion of the housing but rather avoids the housing). But flux paths that are completely contained within the housing are generally associated with fixed (i.e., non-rotating) journal bearing shafts, whereas the presently disclosed embodiments provide a "live" shaft or driven shaft. And having multiple magnetic isolation paths in the shaft, rotor hub, and / or bearing assembly tends to increase the overall radial size of the clutch and can also make manufacturing more complex, whereas the presently disclosed embodiments allow for the use of a shaft that can be a single monolithic piece without any embedded inserts or embedded magnetic isolation inserts. Moreover, the lack of any flux guides in certain prior art clutches means that the magnetic flux is not and / or is transmitted through or across different clutch components in an inefficient manner, which results in the need for relatively large electromagnetic coils to generate sufficient flux to overcome such inefficiencies. For example, such prior art clutches can require magnetic flux to cross a single flux gap that includes three or more air gaps and multiple separate non-ferromagnetic components, whereas the presently disclosed embodiments can limit the number of air gaps in the flux gap across the non-ferromagnetic portion of the housing. Moreover, those of ordinary skill in the art will recognize that the present disclosure includes methods of manufacturing and using the disclosed viscous friction clutches.

[0057] Discussion of possible embodiments

[0058] A viscous friction clutch can include: a rotor; a housing rotatable relative to the rotor; a working chamber located between the rotor and the housing such that a volume of shear fluid can be selectively introduced into the working chamber so as to contact both the rotor and the housing; an electromagnetic coil; a valve assembly that controls the volume of shear fluid present in the working chamber; a flux path that magnetically interfaces the electromagnetic coil with the valve assembly, the flux path passing through a flux guide portion made of a ferromagnetic material, the flux guide portion extending through the rotor and across a flux gap in an interior of the viscous friction clutch, the flux gap traversing both an air gap and a non-ferromagnetic portion of the housing.

[0059] The viscous friction clutch of the preceding paragraph can optionally include (additionally and / or alternatively) any one or more of the following features, configurations, and / or additional components:

[0060] The flux guide portion can be embedded in the rotor;

[0061] The rotor can be made of a non-ferromagnetic material, such as aluminum;

[0062] The flux guide portion can be part of a multi-piece rotor insert assembly that further includes a hub portion made at least partially of a non-ferromagnetic material;

[0063] The rotor insert assembly can include the flux guide portion and at least a partially non-ferromagnetic hub portion between an inner diameter and an outer diameter, and the flux guide portion can be located at or near the outer diameter;

[0064] The hub portion can include a core made of a ferromagnetic material and a disk made of a non-ferromagnetic material, the disk extending radially outward from the core;

[0065] A portion of the flux guide portion can axially protrude from the rotor at a location proximate to an outer diameter of an electromagnetic coil housing that is separated by the flux gap, wherein the electromagnetic coil is at least partially located within the electromagnetic coil housing;

[0066] A back end of the flux guide portion can axially extend behind the working chamber;

[0067] The electromagnetic coil can be at least partially located within an electromagnetic coil housing, and a back end of the flux guide portion can axially protrude from a back side of the rotor such that a flux gap between the back end of the flux guide portion and the coil housing is less than a distance between the back side of the rotor and the coil housing along the flux path;

[0068] The housing can lack any embedded ferromagnetic flux guide insert in (or near) the flux path between an interior and an exterior of the housing;

[0069] The flux path can include a radial gap between an armature of the valve assembly and the flux guide portion, and the radial gap can be located at an outer diameter of the armature;

[0070] a shaft rotationally fixed to the rotor;

[0071] An end of the shaft in the interior of the viscous friction clutch can include an axially extending blind hole;

[0072] A carrier attached to the shaft at the blind hole;

[0073] The carrier can be made of a non-ferromagnetic material;

[0074] A sealing element (e.g., a dynamic seal or a sealed bearing) carried by the carrier in contact with the housing;

[0075] The carrier can include an axially extending central opening that extends completely through the carrier;

[0076] The carrier can further include a tool feature;

[0077] The carrier can further include a stop arranged to contact an armature of the valve assembly during a stroke of the valve assembly;

[0078] The shaft can include a tool feature located in the blind hole;

[0079] The cover of the housing can include an opening to allow access to the shaft and the tool feature by a tool (e.g., a wrench, a drill, a screwdriver, etc.);

[0080] A cap can be further provided at or within the opening in the cover of the housing;

[0081] The electromagnetic coil can be positioned at least partially in a coil housing having opposite magnetic poles and an intermediate portion between the opposite magnetic poles;

[0082] One of the magnetic poles can extend radially and the other of the magnetic poles can extend axially;

[0083] The intermediate portion of the coil housing can be U-shaped;

[0084] The flux guide portion extends axially through the entire rotor between opposite front and back sides of the rotor;

[0085] A reservoir carried by the rotor;

[0086] The rotor can act as an input to the viscous friction clutch, and both the rotor and the reservoir rotate at an input speed whenever there is a torque input to the viscous friction clutch;

[0087] a shaft rotationally fixed to the rotor; and / or

[0088] The bearing rotatably supports the housing on a shaft, wherein the bearing is located in the interior of the flux path.

[0089] A method for transmitting magnetic flux through a viscous friction clutch to operate a valve assembly, the viscous friction clutch including a rotor and a housing, both of which are rotatable, and a shaft, the shaft being rotationally fixed to the rotor, wherein the valve assembly controls the volume of shear fluid present in a working chamber to selectively control the degree of viscous friction engagement between the rotor and the housing; the method can include energizing an electromagnetic coil located outside of the housing of the viscous friction clutch, wherein the electromagnetic coil is rotationally stationary; transmitting magnetic flux from the electromagnetic coil to a coil housing at least partially surrounding the electromagnetic coil; transmitting the magnetic flux from the coil housing to the shaft across a radial gap; transmitting the magnetic flux from the shaft to an armature of the valve assembly across an axial gap in a magnetic attraction region; transmitting the magnetic flux from the armature to a flux guide portion across a gap, wherein the flux guide portion is made of a ferromagnetic material; transmitting the magnetic flux along the flux guide portion between axially opposite front and back sides of the rotor of the viscous friction clutch; transmitting the magnetic flux from the flux guide portion to the coil housing across a flux gap, the flux gap including a non-ferromagnetic portion of the housing of the viscous friction clutch; and transmitting the magnetic flux from the coil housing back to the electromagnetic coil.

[0090] The method of the preceding paragraph can optionally additionally and / or alternatively include any one or more of the following features, configurations, and / or additional steps:

[0091] The magnetic flux is transmitted through a core of a hub portion embedded in the rotor;

[0092] The gap between the armature and the flux guide portion can be radially arranged and can be constant;

[0093] The radial gap between the coil housing and the shaft can be constant;

[0094] The flux gap between the flux guide portion and the coil housing can be axially arranged and can traverse two air gaps at axially opposite sides of the non-ferromagnetic portion of the housing of the viscous friction clutch;

[0095] The flux gap between the flux guide portion and the coil housing can be constant;

[0096] The flux gap between the flux guide portion and the coil housing can be the largest gap in the flux path that magnetically engages the electromagnetic coil with the armature of the valve assembly;

[0097] The non-ferromagnetic portion of the housing included in the flux gap can be located radially outward from a bearing that rotatably supports the housing on a shaft; and / or

[0098] The size of the flux gap between the rear end of the flux guide portion and the coil housing is smaller than the distance along the flux path between the rear side of the rotor and the coil housing.

[0099] SUMMARY

[0100] Any relative or degree terms used herein, such as "substantially", "essentially", "generally", "approximately", and the like, should be construed in accordance with any applicable definitions or limitations expressly set forth herein and governed by such, in all cases. Any relative or degree terms used herein should be interpreted in the broadest possible way consistent with the specific context as would be understood by those of ordinary skill in the art in light of the whole of the disclosure, such as to encompass ordinary manufacturing tolerances, incidental alignment variations, transient alignment or shape variations caused by thermal, rotational, or vibrational operating conditions, transient electromagnetic field fluctuations, and the like. Moreover, any relative or degree terms used herein should be interpreted to include a range expressly including the specified quality, characteristic, parameter, or value without variation, as if the qualifying relative or degree term or terms were not utilized in the given disclosure or recitation.

[0101] While the application has been described with reference to preferred embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the application. For example, while it has been disclosed that the ferromagnetic housing insert for flux conduction is not necessary for electromagnetic control of the viscous friction clutch, it is contemplated that alternative embodiments can still include such a ferromagnetic housing insert, whether as part of an electromagnetic control system or for one or more other purposes. Moreover, in additional embodiments, the valve assembly can be positioned at the rear side of the rotor or attached to the housing. Furthermore, in additional embodiments, a valve assembly using a control rod or the like can be used with the present application, such as a valve assembly having one or more control rods positioned entirely within the interior of the viscous friction clutch and through the rotor disk. Moreover, in different embodiments, the positions of the north and south magnetic poles of the coil housing can be reversed or swapped as desired.

Claims

1. A viscous friction clutch comprising: rotor; a housing, wherein the housing is rotatable relative to the rotor; a working chamber located between the rotor and the housing such that a volume of shear fluid can be selectively introduced into the working chamber to contact both the rotor and the housing; electromagnetic coil; a valve assembly that controls the volume of the shear fluid present in the working chamber; and A flux path magnetically engaging the solenoid coil and the valve assembly passes through a flux guiding portion made of a ferromagnetic material, the flux guiding portion extending through the rotor within the interior of the viscous friction clutch and across a flux gap that traverses both the air gap and the non-ferromagnetic portion of the housing.

2. The viscous friction clutch according to claim 1, wherein: The flux guiding portion is embedded in the rotor, and wherein the rotor is made of a non-ferromagnetic material.

3. The viscous friction clutch according to claim 1, wherein: The flux guiding portion is part of a multi-piece rotor insert assembly that also includes a hub portion that is at least partially made of a non-ferromagnetic material.

4. The viscous friction clutch according to claim 1, wherein: The rotor insert assembly includes the flux guiding portion and an at least partially non-ferromagnetic hub portion between an inner diameter and an outer diameter, and wherein the flux guiding portion is located at or near the outer diameter.

5. The viscous friction clutch according to claim 4, wherein: The hub portion includes a core made of a ferromagnetic material and a disk made of a non-ferromagnetic material extending radially outward from the core.

6. The viscous friction clutch according to claim 1, wherein: A portion of the flux guiding portion protrudes axially from the rotor at a location adjacent an outer diameter of an electromagnetic coil housing separated by the flux gap, and wherein the electromagnetic coil is at least partially located within the electromagnetic coil housing.

7. The viscous friction clutch according to claim 1, wherein: The rear end of the flux guiding portion extends axially behind the working chamber.

8. The viscous friction clutch according to claim 1, wherein: The housing lacks any embedded ferromagnetic flux guiding inserts in the flux path passing between the interior and exterior of the housing.

9. The viscous friction clutch according to claim 1, wherein: The flux path includes a radial gap between an armature of the valve assembly and the flux guiding portion, and wherein the radial gap is located at an outer diameter of the armature.

10. The viscous friction clutch according to claim 1, further comprising: A shaft, wherein the shaft is rotationally fixed to the rotor, and wherein an end of the shaft within the interior of the viscous friction clutch includes an axially extending blind bore.

11. The viscous friction clutch according to claim 10, further comprising: a carrier attached to the shaft at the blind hole, wherein the carrier is made of a non-ferromagnetic material; and A sealing element is carried by the carrier, wherein the sealing element contacts the housing.

12. The viscous friction clutch according to claim 11, wherein: The carrier includes an axially extending central opening extending completely through the carrier.

13. The viscous friction clutch according to claim 11, wherein: The carrier includes a stopper arranged to contact an armature of the valve assembly during travel of the valve assembly.

14. The viscous friction clutch according to claim 11, wherein: The shaft includes a tool feature located in the blind hole.

15. The viscous friction clutch according to claim 14, wherein: The cover of the housing includes an opening to allow access to the shaft and the tool features using a tool.

16. The viscous friction clutch of claim 1 , further comprising: A coil housing wherein the electromagnetic coil is at least partially positioned in the coil housing, and wherein the coil housing has opposing poles and a middle portion between the poles, wherein one of the poles extends radially and the other extends axially.

17. The viscous friction clutch according to claim 16, wherein: The middle portion of the coil housing is U-shaped.

18. The viscous friction clutch according to claim 1, wherein: The ferromagnetic flux guiding portion extends axially across the rotor between opposite front and rear sides of the rotor.

19. The viscous friction clutch of claim 1 , further comprising: A reservoir is carried by the rotor, wherein the rotor acts as an input to the viscous friction clutch, and wherein both the rotor and the reservoir rotate at an input speed whenever there is a torque input to the viscous friction clutch.

20. The viscous friction clutch of claim 1, further comprising: a shaft, wherein the shaft is rotationally fixed to the rotor; and A bearing rotatably supports the housing on the shaft, wherein the bearing is located within an interior of the flux path.

21. A method of transmitting magnetic flux through a viscous friction clutch to operate a valve assembly, the viscous friction clutch comprising a rotor and a housing, the rotor and the housing both being rotatable, and the viscous friction clutch further comprising a shaft rotationally fixed to the rotor, wherein: The valve assembly controls the volume of shear fluid present in the working chamber to selectively control the degree of viscous frictional engagement between the rotor and the housing, the method comprising: energizing an electromagnetic coil located external to a housing of the viscous friction clutch, wherein the electromagnetic coil is rotationally stationary; transmitting magnetic flux from the electromagnetic coil to a coil housing at least partially surrounding the electromagnetic coil; transmitting magnetic flux from the coil housing to the shaft of the viscous friction clutch across a radial gap; an armature that transmits magnetic flux from the shaft to the valve assembly across an axial gap in the magnetic attraction region; transmitting magnetic flux from the armature to a flux guiding portion across a gap, wherein the flux guiding portion is made of a ferromagnetic material; transmitting magnetic flux along the flux guiding portion between axially opposite front and rear sides of a rotor of the viscous friction clutch; transmitting magnetic flux from the flux guiding portion to the coil housing across a flux gap including a non-ferromagnetic portion of a housing of the viscous friction clutch; and Magnetic flux is transferred from the coil housing back to the electromagnetic coil.

22. The method according to claim 21, further comprising: The magnetic flux is transmitted through the core of the hub portion embedded in the rotor.

23. The method according to claim 21, wherein A gap between the armature and the flux guiding portion is arranged radially and is constant.

24. The method according to claim 21, wherein The radial gap between the coil housing and the shaft is constant.

25. The method according to claim 21, wherein The flux gap between the flux guiding portion and the coil housing is axially arranged and crosses two air gaps at axially opposite sides of the non-ferromagnetic portion of the housing of the viscous friction clutch.

26. The method according to claim 21, wherein The flux gap between the flux guiding portion and the coil housing is constant.

27. The method according to claim 21, wherein The flux gap between the flux guiding portion and the coil housing is the largest gap in the flux path that magnetically engages the electromagnetic coil and the armature of the valve assembly.

28. The method according to claim 21, wherein The non-ferromagnetic portion of the housing included in the flux gap is located radially outward from a bearing that rotationally supports the housing on the shaft.

29. The method according to claim 21, wherein The flux gap between the rear end of the flux guiding portion and the coil housing is sized smaller than a distance between the rear side of the rotor and the coil housing along a flux path that magnetically engages the electromagnetic coil and an armature of the valve assembly.

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