Viscous friction clutch valve control system

Abstract

The viscous friction clutch (100; 200) comprises a rotor (106; 206), a housing (112; 212) rotatable relative to the rotor, an actuation chamber (115; 215) disposed between the rotor and the housing, capable of selectively introducing a predetermined amount of shear fluid so that the shear fluid contacts both the rotor and the housing, an electromagnetic coil (101; 201), a valve assembly (107; 207) for controlling the amount of shear fluid held in the actuation chamber, and a magnetic flux path (A; A') magnetically connecting the electromagnetic coil and the valve assembly. The magnetic flux path passes through a magnetic flux guide portion (105; 105'; 205) made of a ferromagnetic material extending through the rotor inside the viscous friction clutch, and crosses a magnetic flux gap (B) that traverses both the air gap and the non-ferromagnetic portion (112b-1; 212b-1) of the housing.

Description

[Technical Field]

[0001] The present invention relates to viscous friction clutches, and more particularly to electromagnetic control systems for viscous friction clutches, and to viscous friction clutches including such electromagnetic control systems, as well as methods of making and using the same. [Background technology]

[0002] Clutches (also called drives or couplings) are used in a variety of situations to selectively control torque transfer between an input and an output. For example, fan clutches are used to control the rotation of fans, such as cooling fans in automotive or industrial applications. Controlling the operation of a cooling fan not only provides all the benefits associated with cooling flow when the clutch is engaged, but also allows the fan to be shut off when not needed, reducing parasitic losses and improving fuel efficiency. Shutting down the cooling fan frees up power that can be diverted for other uses. Some clutches allow for control that selectively varies the output speed within a range, rather than simply being on / off. Fully variable clutch control is useful for performance optimization, such as tailoring cooling to the current conditions of the cooling fan application.

[0003] Viscous friction clutches (also simply referred to as viscous clutches) are used in a variety of applications, such as automotive fan drives. These clutches typically use relatively high-viscosity silicone oil (more commonly referred to as shear fluid or viscous fluid) to selectively transfer torque between two rotatable components. The clutch can be engaged or disengaged by selectively introducing or releasing the shear fluid into an actuation chamber of the clutch, which is located between the input and output members (e.g., between the rotor and the housing). In this actuation chamber, viscous shear coupling by the shear fluid partially transfers torque from the input member to the output member. The amount of shear fluid held within the actuation chamber controls the speed differential between the primary / input side (input speed) and secondary / output side (output speed) of the clutch. A valve assembly is used to control the flow of shear fluid into or out of the actuation chamber.

[0004] Temperature-sensitive bimetallic control clutches are known, but such bimetallic valve controls are not suitable for some applications (e.g., blower fan applications) because they are not amenable to active control.

[0005] Solenoid valve control devices that use an electromagnetic coil to selectively generate magnetic flux for operating a valve assembly are also known. A typical viscous clutch requires that the valve disc controlling the flow of shear fluid be located entirely or partially inside the clutch to regulate the flow of shear fluid into or out of a reservoir chamber. The electromagnetic coil, on the other hand, is typically located outside the clutch to allow for appropriate external electrical connections. These typical viscous clutches have a magnetic flux path and / or mechanical connection between the electromagnetic coil and the valve to operate the valve disc while the electromagnetic coil is physically separated from the valve disc. However, many prior art viscous clutches have limitations regarding the magnetic flux circuit and / or mechanical connection (e.g., a control rod) used to electromagnetically control the valve assembly. For example, some clutch designs allow for the storage of shear fluid in a reservoir chamber mounted or fixed to the input rotor (located inside the housing and rotating whenever torque is applied to the clutch) while the clutch is disengaged. This allows for rapid engagement of the clutch's external output housing from a disengaged, stalled state, and allows the clutch to operate at very low output speeds (e.g., fan speeds) when the valve is in a position that limits the amount of shear fluid in the actuation chamber. However, mounting the reservoir to a rotor disk or similar significantly limits design flexibility, particularly because the valve disc rotates with clutch input even when the electromagnetic coil is fixed (i.e., not rotating). Locating the valve relative to a rotating reservoir while providing suitable fluid and magnetic flux paths presents challenges, including the need to seal potential leak paths through which shear fluid could escape. Within these constraints, designers strive to provide a relatively small, lightweight clutch package that can handle desired torque loads and function quickly, efficiently, and reliably.

[0006] U.S. Patent No. 5,629,999 discloses a mechanical connection between an external electromagnetic coil and a valve inside the clutch, and another mechanical connection for a valve assembly is disclosed in U.S. Patent No. 5,629,999. However, these mechanical connections require additional components to seal against leakage of shear fluid from inside to outside the clutch and to electromagnetically control the mechanical connection itself.

[0007] Patent Document 3 describes an insert embedded in a clutch housing for a magnetic flux path connecting the armature of a valve component and an electromagnetic coil. However, embedding an iron insert in a die-cast aluminum housing can cause leakage due to differences in the thermal expansion coefficients between the aluminum housing and the iron insert. This leakage problem is known in the art and is described, for example, in Patent Document 4.

[0008] Various other viscous clutch designs that provide a magnetic flux path through the interior of the clutch are disclosed in U.S. Patent Nos. 5,629,999, 5,729,963, 5,729,973, and 5,729,973, and cooling systems for these clutches are commercially available from Cojali SL (Ciudad Real, Spain). In these clutch designs, the magnetic flux path typically does not pass through the housing, or the magnetic flux path is either completely contained within the housing or follows multiple separated paths within the shaft, rotor hub, and / or bearing assembly located radially inward from the housing (i.e., the magnetic flux path does not intersect any part of the housing, but rather bypasses the housing by passing back and forth at locations inside the housing). In Cojali's commercially available clutch, there is no magnetic flux guide; the magnetic flux path runs from the inner diameter of the coil, through the central axis, to the valve, and back to the outer diameter of the coil (i.e., the magnetic flux returns unguided from the valve to the coil).

[0009] A further consideration is the need to provide a complete clutch package that is relatively small and lightweight. Generally, the electromagnetic coil must be sized to generate a magnetic field sufficient to operate the valve assembly. Control systems that require a relatively large magnetic flux to operate the valve element require a correspondingly large electromagnetic coil. However, such large electromagnetic coils occupy a large amount of space and are relatively heavy. Therefore, a control system that can reliably operate with a lower total magnetic flux requirement, i.e., a control system that utilizes magnetic flux relatively efficiently to operate the valve, is useful in providing a relatively small and lightweight clutch package.

[0010] Additionally, in some applications, it is desirable for a clutch to be configured with a "live" center shaft that functions as either the input or output of the clutch. A "live" center shaft generally refers to a shaft that can rotate during clutch operation, as opposed to a static or rotationally stationary shaft, such as a mounting shaft that is rotationally fixed relative to a journal bracket. "Live" center shaft clutches are useful, for example, in light-duty applications. Clutches configured with a "live" center shaft are further useful for providing a relatively light-weight and relatively small clutch package, such as by potentially eliminating the need for pulleys, journal brackets, etc. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Patent No. 6,419,064 [Patent Document 2] International Publication No. 2014 / 047430 [Patent Document 3] U.S. Patent No. 6,443,283 [Patent Document 4] U.S. Patent No. 5,511,643 [Patent Document 5] U.S. Patent No. 5,992,594 [Patent Document 6] U.S. Patent No. 7,886,886 [Patent Document 7] International Publication No. 2011 / 062856 [Patent Document 8] International Publication No. 2018 / 004833 Summary of the Invention [Problem to be solved by the invention]

[0012] Thus, it would be desirable to provide an electromagnetic control system for a viscous friction clutch, and methods of manufacturing and using the same, which reduce or eliminate the need for mechanical connections in the clutch housing and / or embedded flux guide inserts, while providing a relatively compact and lightweight clutch package. It would also be desirable to provide a clutch configured with a "live" center shaft. [Means for solving the problem]

[0013] In one aspect, a viscous friction clutch includes a rotor, a housing rotatable relative to the rotor, an actuation chamber disposed between the rotor and the housing, the actuation chamber being capable of selectively introducing a predetermined amount of shear fluid so as to contact both the rotor and the housing, an electromagnetic coil, a valve assembly for controlling the amount of shear fluid introduced into the actuation chamber, and a magnetic flux path magnetically connecting the electromagnetic coil and the valve assembly, the magnetic flux path extending through the rotor within the viscous friction clutch. It consists of a ferromagnetic material a magnetic flux gap that passes through the magnetic flux guide portion and crosses both the gap portion and the non-magnetic portion of the housing; Through Pass.

[0014] In another aspect, a method of operating a valve assembly by transmitting magnetic flux through a viscous friction clutch is described. The viscous friction clutch includes a rotor, a housing, and a shaft, each of which is rotationally fixed relative to the rotor. The valve assembly selectively controls the degree of viscous friction engagement between the rotor and the housing by controlling the amount of shear fluid introduced into an actuation chamber. The method includes the steps of energizing an electromagnetic coil disposed outside the housing of the viscous friction clutch and stationary in its rotational movement, transmitting magnetic flux from the electromagnetic coil to a coil housing surrounding at least a portion of the electromagnetic coil, transmitting the magnetic flux from the coil housing across a radial gap to a shaft of the viscous friction clutch, transmitting the magnetic flux from the shaft across an axial gap in a region of magnetic force to an armature of a valve assembly, transmitting the magnetic flux from the armature across the gap to a flux guide portion made of a ferromagnetic material, transmitting the magnetic flux along the flux guide portion between axially opposite front and rear sides of a rotor of the viscous friction clutch, transmitting the magnetic flux from the flux guide portion to the coil housing across a flux gap having a non-ferromagnetic portion of the housing of the viscous friction clutch, and returning the magnetic flux from the coil housing to the electromagnetic coil. The flux guide portion is made of a ferromagnetic material.

[0015] In yet another aspect, a method for manufacturing a viscous friction clutch is also provided.

[0016] These measures are provided by way of example only and not by way of limitation. Other aspects of the invention will be understood in light of this entire disclosure, including the entire text, claims, and accompanying drawings. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view of one embodiment of a viscous friction clutch according to the present invention. [Figure 2] FIG. 2 is a partial cross-sectional view of the viscous friction clutch of FIG. 1, with annotations of the magnetic flux paths and the areas affected by the magnetic forces. [Figure 3] FIG. 3 is another partial cross-sectional view of a portion of the viscous friction clutch of FIGS. [Figure 4] FIG. 4 is a cross-sectional view of a single rotor insert assembly. [Figure 5] FIG. 5 is a front perspective view of the rotor insert assembly of FIG. [Figure 6] FIG. 6 is a front perspective view of another embodiment of a single rotor insert assembly. [Figure 7] FIG. 7 is a cross-sectional view of another embodiment of a viscous friction clutch according to the present invention. [Figure 8] FIG. 8 is a partial cross-sectional view of the viscous friction clutch of FIG. 7, with annotations of the magnetic flux paths and the areas affected by the magnetic forces. [Figure 9] FIG. 9 is another partial cross-sectional view of a portion of the viscous friction clutch of FIGS.

[0018] While the above-described figures depict one or more embodiments of the present invention, as discussed above, other embodiments are contemplated. In all cases, the present disclosure presents the invention by way of representation and not limitation. Those skilled in the art will recognize that numerous other modifications and other embodiments can be devised that fall within the scope and spirit of the principles of the present invention. The drawings are not necessarily 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 INVENTION

[0019] Generally, embodiments of the present invention provide an electromagnetic control system for a viscous friction clutch that can be controlled to selectively transfer 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 to control the speed of torque transfer to other devices. The viscous friction clutch can include a central shaft, a rotor, a housing, a reservoir, an actuation chamber, and a valve assembly having an armature actuated by magnetic flux from an electromagnetic coil. The electromagnetic coil can be located outside the viscous friction clutch and can be rotationally fixed, i.e., motion in a rotational direction can be stationary. In some embodiments, the armature and valve disc of the valve assembly can be located inside the viscous friction clutch. In some embodiments, the valve assembly and the electromagnetic coil can be located on opposite sides of the rotor. In some embodiments, the central shaft can be a "live" central shaft that is rotationally fixed relative to the rotor so that it always co-rotates with the rotor at the same speed. In some embodiments, the rotor can be disk-shaped. The reservoir can be carried by an input to the clutch, such as a rotor, so that it rotates 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 that surround at least a portion of the rotor. The viscous friction can include a rotor insert assembly in the rotor, including a magnetic flux guide. The rotor insert assembly fulfills various functions. The first portion of the rotor insert assembly, at least a portion of which is made of a magnetic flux conducting material, such as a ferromagnetic material, acts as a magnetic flux path controller or magnetic flux guide, guiding magnetic flux along a portion of the magnetic flux path through the viscous friction clutch (e.g., across or through the rotor), facilitating electromagnetic control of valves located within the clutch without incorporating additional magnetic flux conducting insert components into the clutch housing. The second portion of the rotor insert assembly, also referred to as the insert assembly hub, provides a structural connection between the central shaft and the rotor to transmit torque while reducing or avoiding magnetic short circuits between the shaft and the first portion of the rotor insert assembly (i.e., the magnetic flux guide portion of the rotor insert assembly).The magnetic flux path through the clutch can extend from the electromagnetic coil to the central shaft, then to the armature of the valve assembly, then to the first flux guide portion of the rotor insert assembly (capable of transmitting magnetic flux through the rotor, which can be made of a non-ferromagnetic material), then across the flux gap, and back to the electromagnetic coil. In another embodiment, the rotor insert assembly includes a multi-piece hub portion having a ferromagnetic hub core and a non-ferromagnetic disk portion. In such other embodiments, the magnetic flux path through the clutch can extend from the electromagnetic coil to the central shaft, then to the hub core, then to the armature of the valve assembly, then to the first flux guide portion of the rotor insert assembly, then across the flux gap, and back to the electromagnetic coil. In various embodiments, the magnetic flux gap can cross a portion of the housing (e.g., a portion of the housing base) made of a non-ferromagnetic material, such as aluminum. In some embodiments, a housing cover opening, a seal and seal carrier, an armature stop, and / or other optional components can further be provided. Thus, the disclosed embodiments provide a viscous friction clutch, for example for driving a cooling fan in a vehicle or controlling the speed of torque transmission to other devices, having an electromagnetic flux path passing through the interior of the clutch. The flux path passes through both a ferromagnetic flux guide that passes through the rotor within the clutch, and a flux gap that crosses a non-ferromagnetic portion of a housing that surrounds at least a portion of the rotor and air gaps at both ends of the non-ferromagnetic portion of the housing. The flux guide can be embedded in or connected to the rotor, which is made of a non-ferromagnetic material. Methods for manufacturing and using the viscous friction clutch with an electromagnetic control system are also disclosed and will be apparent to those skilled in the art.

[0020] Additional embodiments are contemplated. For example, while the disclosed embodiments show an electromagnetic control system for use in a live center clutch configuration, it will be understood that the electromagnetic control system, rotor insert assembly, and / or related methods may be utilized in other types of clutch configurations. Those skilled in the art will recognize numerous features and advantages upon consideration of this entire disclosure, including the accompanying drawings.

[0021] This application is based on and claims the benefit of U.S. Provisional Patent Application No. 63 / 024,592, filed May 14, 2020, the contents of which are incorporated herein by reference in their entirety.

[0022] Figures 1 through 5 show one embodiment of a viscous friction clutch 100. Figure 1 shows a cross-sectional view of the viscous friction clutch 100. Figure 2 shows another cross-sectional view of the viscous friction clutch 100 with annotations indicating the magnetic flux path A and the magnetic force area D. Figure 3 shows a partial cross-sectional view of a portion of the viscous friction clutch 100. Figures 4 and 5 show a single assembly that is part of the viscous friction clutch 100.

[0023] 1, viscous friction clutch 100 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 guide portion 105, a rotor 106, a valve assembly 107 (shown in the attracted position) having an armature 108 and a valve disc 109, a shaft 110, a housing 112, a reservoir chamber 113, a discharge port 114, and an actuation chamber 115. Although not specifically shown, viscous friction clutch 100 further includes suitable return bore and pump components, all of which are well known in the art of viscous friction clutches.

[0024] In the illustrated embodiment, the shaft 110 is the "live" center shaft that defines the axis of rotation CL of the viscous friction clutch 100. The electromagnetic coil 101 may be rotationally immobilized and rotatably mounted to the shaft 110 by suitable bearings 101X. Additionally, the coil housing 102 may be rotatably mounted to the shaft 110 using bearings 101X that also support the electromagnetic coil 101 and may surround at least a portion of the electromagnetic coil 101. Both the electromagnetic coil 101 and the coil housing 102 may be located outside the housing 112. The shaft 110 may have mounting features at its rear end. The shaft 110 may serve as an input to the viscous friction clutch 100, receiving torque input from a prime mover (not shown), such as a vehicle's internal combustion engine. In the illustrated embodiment, at least a portion of the shaft 110 is made of a magnetically flux-conducting ferromagnetic material.

[0025] The electromagnetic coil 101 is at least partially disposed within the coil housing 102. In the illustrated embodiment, the north pole 102N of the coil housing 102 extends radially inward toward the shaft 110, and the south pole 102S of the coil housing 102 extends axially toward the flux guide portion 105 (and the base 112b of the housing 112).

[0026] The rotor 106 may be rotationally fixed relative to the shaft 110 so that the rotor 106 and shaft 110 co-rotate at the same speed (e.g., at the input speed of the torque input to the viscous friction clutch 100). The rotor 106, in the illustrated embodiment, is configured as a disk and may be formed from a non-ferromagnetic material such as aluminum. At least a portion of the hub portion 104 and flux guide portion 105 of the rotor insert assembly 103 are embedded in the rotor 106, as in the illustrated embodiment.

[0027] In the illustrated embodiment, the rotor insert assembly 103 includes a hub portion 104 at a radially inner location and a flux guide portion 105 at a radially outer location (the rotor insert assembly 103 is further described below in connection with FIGS. 4 and 5). The hub portion 104 can be positioned on a radially inner portion of the rotor 106 and can provide a 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 include a flux blocking feature that reduces or eliminates magnetic shorting between the flux guide portion 105 and the shaft 110 in a generally radial direction, as described further below. In the illustrated embodiment, core 104c is made of a ferromagnetic material and disk 104d is made of a non-ferromagnetic material that blocks any magnetic flux flow radially along rotor insert assembly 103. More generally, hub portion 104 of rotor insert assembly 103 in the illustrated embodiment includes, or at least includes a portion that is non-ferromagnetic, between its inner diameter and its outer diameter.

[0028] 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 to conduct magnetic flux through the non-ferromagnetic material of the rotor 106. In the illustrated embodiment, the flux guide portion 105 has a rear end 105a that extends axially from the rear side of the rotor 106 and is at or adjacent to the outer diameter of the coil housing 102 to assist in directing magnetic flux to the south pole 102S of the coil housing 102, as described further below. As in the illustrated embodiment, the rear end 105a of the flux guide portion 105 overlaps the south pole 102S of the coil housing 102 at a radial position (such that the magnetic flux path therebetween can be substantially axial or entirely axial). However, in further embodiments, the rear end 105a may be located at other radial positions, such as radially inward from the south pole 102S of the coil housing 102.

[0029] The storage chamber 113 has an interior volume that stores a supply of shear fluid. An outlet 114 allows shear fluid to flow from the storage chamber 113 to the actuation chamber 115 and can be selectively covered or uncovered by a valve assembly 107. A return bore (not shown) exits the storage chamber 113, allowing the shear fluid to be returned to the storage chamber 113 for storage. In the illustrated embodiment, the storage chamber 113 is carried by or on the rotor 106. When the rotor 106 forms part of the input to the viscous friction clutch 100, the storage chamber 113 rotates constantly during periods of torque input to the viscous friction clutch 100. In some embodiments, the flux guide 105 can be adjacent to and / or form at least a portion of the boundary of the storage chamber 113. As in the illustrated embodiment, a reservoir plate 113a defining a portion of the boundary of the reservoir 113 is optionally secured to the rear end 105a of the magnetic flux guide portion 105. The reservoir plate 113a may be made of a ferromagnetic material and may optionally form part of the magnetic flux path. In alternative embodiments, the reservoir 113 may optionally further include one or more interior walls, backflow prevention features such as a morning sickness prevention valve, or morning sickness prevention features.

[0030] In the illustrated embodiment, the housing 112 is a multi-piece assembly having a base 112b and a cover 112c. In the illustrated embodiment, the housing 112 surrounds at least a portion of the rotor 106. The housing 112 (e.g., the housing base 112b) is rotationally supported on the shaft 110 by bearings 112X and is rotatable relative to both the shaft 110 and the rotor 106. The housing 112 can function as an output for the viscous friction clutch 100, and thus can be fitted with an output device, such as a fan (not shown), that receives 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.

[0031] The working chamber 115 is disposed between the rotor 106 and the housing 112 and, depending on the amount of shear fluid held in the working chamber 115, is in frictional contact with both the rotor 106 and the housing 112, and is capable of transmitting torque between the rotor 106 and the housing 112 at a sliding speed that is generally dependent on the amount of shear fluid held in the working chamber 115. The basic operation of a working chamber in a viscous friction clutch is known in the art.

[0032] The valve assembly 107 includes an armature 108 and a valve disc 109. The armature 108 is connected to the valve disc 109 and moves the valve disc 109 in response to an applied magnetic flux, as described further below. In the illustrated embodiment, the valve assembly 107 is located on the front side of the rotor 106, and the electromagnetic coil 101 is located on the opposite rear side of the rotor 106. The valve disc 109 is spring-biased to a default open position, and when applied magnetic flux generates a valve-actuating force that exceeds the spring bias, it moves the armature 108 and valve disc 109 to a closed position. This is referred to as a "fail-on" configuration, meaning that when power is lost, the spring bias moves the valve assembly 107 to its default "on" or open position. As in the illustrated embodiment, a valve assembly 107 including an armature 108 and a valve disc 109 is disposed within the viscous friction clutch 100 (i.e., within the housing 112) and is carried by or on the rotor 106. Further, in the illustrated embodiment, the valve disc 109 pivots or translates generally axially during a stroke C (see FIG. 3). A stop 116 is optionally provided on the rotor 106 to limit the movement of the armature 108 and the valve disc 109 and the stroke C in the off, open, or disengaged position of the valve assembly 107. An outlet 114 allows shear fluid to flow from the reservoir chamber 113 to the actuation chamber 115, and the valve assembly 107 selectively covers or uncovers the outlet 114 to regulate the amount of shear fluid retained in the actuation chamber 115, thereby controlling operation of the viscous friction clutch 100. During clutch operation, shear fluid is generally continuously pumped from the actuation chamber 115 back to the reservoir chamber 113 through a return bore (not shown).

[0033] In operation, the electromagnetic coil 101 can be selectively energized to generate magnetic flux that travels through the viscous friction clutch 100 along a magnetic flux path (or magnetic flux circuit) A to operate the valve assembly 107. FIG. 2 shows the magnetic flux path A schematically with a dashed line on one side of the rotational axis CL of the clutch 100. However, it should be understood that FIG. 2 only depicts a portion of the magnetic flux path A, and that the magnetic flux path A has a three-dimensional shape extending around the axis CL. The magnetic flux path A allows magnetic flux to travel from the electromagnetic coil 101 through the armature 108 of the valve assembly 107 and back to the electromagnetic coil 101. The magnetic flux path A exits the electromagnetic coil 101, enters the coil housing 102, and crosses a 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 radially disposed in the illustrated embodiment. The magnetic flux may then travel across the gap between the shaft 110 and the armature 108 in the magnetic field region D. In some embodiments, the magnetic flux may optionally travel through the core 104c of the hub portion 104 of the rotor insert assembly 103, through and / or near the magnetic field region D. In some embodiments, the magnetic field region D may be spaced radially outward from the axis of rotation CL. In other embodiments, the magnetic field region D may extend to the axis of rotation CL. In the illustrated embodiment, the gap between the shaft 110 (as well as the core 104c) and the armature 108 in the magnetic field region D is axially disposed. The size of the gap between the shaft 110 (and core 104c) and the armature 108 changes as the armature 108 moves during operation of the clutch 100. The gap distance between the armature 108 and the shaft 110 (and core 104c) corresponds to the stroke C of the valve assembly 107 (see FIG. 3). 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 is in physical contact with the shaft 110 and / or the core 104c) while the electromagnetic coil 101 is energized.Magnetic flux path A continues from the armature 108 through gap F (see FIG. 3 ) to the magnetic flux guide portion 105 of the rotor insert assembly 103. In the illustrated embodiment, the radially disposed gap F (located at the outer diameter of the armature 108) is constant. The constant radial gap F allows for a constant magnetic flux flow regardless of the open or closed position of the armature 108. The constant magnetic flux flow in magnetic flux path A helps improve the internal magnetic force on the armature 108. Magnetic flux path A then passes through the magnetic flux guide portion 105 of the rotor insert assembly 103 and then axially passes through the entire rotor 106 from the front side to the opposite rear side. Magnetic flux path A then continues from the magnetic flux guide portion 105 of the rotor insert assembly 103 across magnetic flux gap B (see FIG. 3 ) to the south pole 102S of the coil housing 102 and back to the electromagnetic coil 101.

[0034] As in the illustrated embodiment, flux gap B is axially disposed and is a larger gap than the other gaps in flux path A. Flux gap B may be constant. Flux gap B traverses a portion 112b-1 of housing 112, as well as the air gaps at both axial ends of housing 112. More specifically, flux gap B axially traverses a non-ferromagnetic portion 112b-1 of base 112b of housing 112. This non-ferromagnetic portion 112b-1 does not have any embedded flux guide inserts or other ferromagnetic components in or near flux path A, which passes completely (or partially) through housing 112 between the interior and exterior of housing 112. In other words, in some embodiments, flux gap B does not have ferromagnetic material in it and may be referred to as a non-ferromagnetic flux gap. Magnetic flux path A can cross magnetic flux gap B, particularly through or across portion 112b-1 of housing 112, and through one or more adjacent air gaps and retained shear fluid, without the need for a ferromagnetic flux guide, which could potentially create an undesirable leakage path for the shear fluid due to different thermal expansion coefficients between the ferromagnetic material and the adjacent non-ferromagnetic material (e.g., between iron and aluminum materials). In various embodiments, the number of air gaps within magnetic flux gap B can be limited to two or fewer air gaps, and portion 112b-1 of housing 112 can be the only non-ferromagnetic component that magnetic flux path A crosses within magnetic flux gap B. In some embodiments, the dimension of magnetic flux gap B between rear end 105a of magnetic flux guide portion 105 and south pole 102S of coil housing 102 can be smaller than the distance between rear end 105a of magnetic flux guide portion 105 and other nearby ferromagnetic materials. In yet another embodiment, the axial dimension of the flux gap B between the rear end 105a of the flux guide portion 105 and the coil housing 102 may be smaller than the distance in either the axial or radially inward direction between the rear end 105a of the flux guide portion 105 and other nearby ferromagnetic material.Additionally, in the illustrated embodiment, the magnetic flux guide portion 105 penetrates the rotor 106 and protrudes rearward, so that the dimension of the magnetic flux gap B between the rear end 105a of the magnetic flux guide portion 105 and the south pole 102S of the coil housing 102 can be smaller than the distance along the magnetic flux path A between the rear side of the rotor 106 and the south pole 102S of the coil. In some embodiments, the axial distance of the magnetic flux gap B between the rear end 105a of the magnetic flux guide portion 105 and the south pole 102S of the coil housing 102 can be smaller than the axial distance between the south pole 102S of the coil housing 102 and the working chamber 115. That is, the rear end 105a of the magnetic flux guide portion 105 can extend axially rearward of the working chamber 115. Note that even if a ferromagnetic body is disposed radially outside the magnetic flux path A, a short circuit of the path A does not occur. Thus, in some embodiments, a ferromagnetic material (e.g., reservoir plate 113a made of a ferromagnetic material) can be positioned radially outward from magnetic flux path A in close proximity to or physical contact with magnetic flux guide portion 105 without significantly affecting the characteristics of magnetic flux path A at or near magnetic flux gap B. Because the linear distance of magnetic flux gap B is relatively short (although it may be larger than the other gaps in magnetic flux path A), no additional iron inserts need be embedded in housing 112. In the illustrated embodiment, non-ferromagnetic portion 112b-1 of housing 112 included in (and crossed by) magnetic flux gap B is positioned radially outward from bearing 112X, which rotationally supports housing 112 on shaft 110, such that bearing 112X is located within magnetic flux path A. Furthermore, in the illustrated embodiment, bearing 101X, which supports electromagnetic coil 101 and coil housing 102 on shaft 110, is also located within magnetic flux path A.

[0035] To guide magnetic flux path A from the shaft 110 to the armature 108 and further to the magnetic flux guide portion 105 of the rotor insert assembly 103, it is important to avoid a magnetic short circuit between the magnetic flux guide portion 105 and the shaft 110. This can be achieved by using a rotor insert assembly 103 with specifically defined characteristics. One embodiment, shown separately in FIGS. 4 and 5, can be achieved by using a non-ferromagnetic material for the disk 104d of the hub portion 104 of the rotor insert assembly 103. In this manner, the magnetic flux guide portion 105 and the core 104c, each made of a ferromagnetic material, and the disk 104d made of a non-ferromagnetic material, may be separate components that are engaged or connected to each other and embedded or otherwise connected to the rotor 106 made of a non-ferromagnetic material, such as using a die-casting process. The core 104c made of a ferromagnetic material may help improve the performance of magnetic flux path A. In an alternative embodiment, the core 104c and disk 104d of the hub portion 104 may be a single piece made of a non-magnetic material. The embodiment of the rotor insert assembly 103 shown in FIGS. 4 and 5 also includes sections 118a, 118b, and 118c, which may be configured as openings in the hub portion 104 and / or the flux guide portion 105. In the illustrated embodiment, a plurality of circumferentially equally spaced U-shaped sections 118a extend radially through the flux guide portion 105 to the front end (opposite the rear end 105a) and open axially forward. A plurality of U-shaped sections 118b are located on the outer diameter of the disk 104d of the hub portion 104 and align with sections 118a to form a mating opening that extends continuously to the outer diameter of the disk 104d. Finally, sections 118c are a plurality of circumferentially equally spaced circular holes that axially penetrate the center of the disk 104d. However, in further embodiments, other shapes and arrangements of disconnect 118a, disconnect 118b, and / or disconnect 118c are possible. After being fully installed in viscous friction clutch 100, disconnect 118a, disconnect 118b, and / or disconnect 118c can be at least partially filled with the non-ferromagnetic material of rotor 106.More specifically, in some embodiments, the gaps 118b and 118c may each be completely filled with the non-ferromagnetic material of the rotor 106, while the gaps 118a may each be only partially filled with the non-ferromagnetic material of the rotor 106.

[0036] Alternatively, as shown in FIG. 6 , the flux guide portion 105′ and hub portion 104′ of the rotor insert assembly 103′ can be fabricated as a single, integral, monolithic piece of ferromagnetic material, with flux-blocking features, such as openings 118′ located in the hub portion 104′ (and optionally in further embodiments, in the flux guide portion 105′), to reduce or avoid magnetic short-circuiting between the flux guide portion 105′ and the hub portion 104′ (and shaft 110). In the illustrated embodiment, the flux guide portion 105′ has a seamless configuration and is free of openings, etc. Preferably, the flux-blocking features (openings 118′) are as numerous and large as possible. After fully installed in the viscous friction clutch 100, the openings 118′, etc. in the hub portion 104′ (and / or flux guide portion 105′) are filled with the non-ferromagnetic material of the rotor 106 for torque transfer between the rotor 106, the hub portion 104′, and the flux guide portion 105′. Alternatively, rotor insert assembly 103' is similar to rotor insert assembly 103 described above and functions essentially the same.

[0037] Figures 7 through 9 illustrate another embodiment of a viscous friction clutch 200. Figure 7 is a cross-sectional view of the other embodiment of the viscous friction clutch 200, Figure 8 is another cross-sectional view of the viscous friction clutch 200 with annotations showing the magnetic flux path A' and the magnetic force area D, and Figure 9 is a partial cross-sectional view of a portion of the viscous friction clutch 200. In general, the embodiment of the viscous friction clutch 200 shown and described in Figures 7 through 9 is similar to the embodiment of the viscous friction clutch 100 described above in Figures 1 through 6. Accordingly, similar reference numerals, generally increased by 100, are used. 7-9 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 guide portion 205, a rotor 206, a valve assembly 207 having an armature 208 and a valve body 209, a shaft 210, a housing 212 (including a base 212b and a cover 212c), a reservoir 213 (including a reservoir cover 213a), a discharge port 214, an actuation chamber 215, and a rotation axis CL. Although not specifically shown, the viscous friction clutch 200 further includes suitable return bores and pump components. The magnetic flux path A' includes a magnetic flux gap B, a valve assembly stroke C, and a magnetic force region D, which may be similar or identical in viscous friction clutch 200 to viscous friction clutch 100. However, the embodiment of viscous friction clutch 200 of Figures 7-9 differs from clutch 100 in its design around shaft 210.

[0038] As shown in FIGS. 7-9 , the front end of the shaft 210 includes a blind hole 220 and a carrier 222 that engages with the blind hole 220. The blind hole 220 can extend axially within the shaft 210 and open axially forward, as in the illustrated embodiment. A rim of the shaft 210 surrounding the blind hole 220 at the front end 210F of the shaft 210 sufficiently transfers magnetic flux from the shaft 210 to the armature 208 along magnetic flux path A. The blind hole 220 in the shaft 210 provides the option of using a torque or tooling feature 223 (e.g., a tool engagement feature such as a Torx® bit engagement feature) at the front end 210F of the shaft 210 (e.g., at the rear or bottom of the blind hole 220) to facilitate attachment of the rear end 210R of the shaft 210 to a corresponding component (not shown) with another connection feature, such as a screw thread 210t. In the illustrated embodiment, the front end 210F of the shaft 210 and the blind hole 220 are disposed within the viscous friction clutch 200 inside the housing 212. An opening 228 (e.g., a central hole) can be provided in the cover 212c of the housing 212 to provide access to the blind hole 220 and the torque or tooling feature 223. A corresponding central hole 208h can be provided in the armature 208 to allow operation of the blind hole 220 and / or the torque feature 223. A removable cap (not shown) can be provided at or within the opening 228a in the cover 212c of the housing 212 to protect the internal components of the viscous friction clutch 200 from debris and the like. The opening 228 or structure nearby can include a suitable feature, such as an engagement groove, to allow engagement of the cap 228a with the cover 212c of the housing 212.

[0039] The carrier 222 can be engageable with the blind hole 220 by a connection feature 222c (e.g., threads) that attaches the carrier 222 to the shaft 210, and the connection feature 222c can be positioned within the blind hole 220. The carrier 222 can further include tooling features 222t, such as flats or slots, that accept a tool bit, a screwdriver, or other suitable tool capable of applying torque. The carrier 222 can be made of a non-ferromagnetic material to isolate the carrier 222 from, or at least avoid interference with, the magnetic flux path A. The carrier 222 can extend axially from the shaft 210 through a central hole 208h in the armature 208. The carrier 222 can further include an opening 222a, such as a central opening that extends axially completely through the carrier 222 between its opposite ends, to allow for torque or manipulation of the tooling feature 223. This allows a tool to be inserted from the front of the viscous friction clutch 200 through an opening 228 in the cover 212c of the housing 212 (and through the central hole 208h of the armature 208). Additionally, the carrier 222 can support and carry a sealing component 229 (e.g., a dynamic seal or a bearing, such as a sealed bearing set) that contacts the housing 212 and seals against the cover 212c of the housing 212 at the opening 228 to help prevent leakage of shear fluid. Additionally, a stop 230 can be provided on the carrier 222 on the opposite side of the armature 208 from the shaft 210. The stop 230 can limit the stroke C of the valve assembly 207; in particular, the stop 230 can limit the axial movement of the armature 208 and valve disc 209 under a default spring bias. In the illustrated embodiment, the stop 230 is a flange that extends radially outward from the body of the carrier 222.

[0040] Rotor 206 may be rotationally fixed relative to shaft 210 so that rotor 206 and shaft 210 co-rotate at the same speed. Housing 212 (e.g., housing base 212b) is rotationally supported on shaft 210 by suitable bearings 212X and is rotatable relative to shaft 210 and rotor 206. Electromagnetic coil 201 and coil housing 202 may be rotationally fixed and may both be mounted to shaft 210 by suitable bearings 201X, with electromagnetic coil 201 and coil housing 202 located outside of housing 212.

[0041] The electromagnetic coil 201 may have an L-shaped cross section similar to that disclosed in U.S. Patent Application Publication No. 2006 / 0129990. An L-shaped electromagnetic coil 201, such as in the illustrated embodiment, is useful for reducing the overall size and weight of the viscous friction clutch 200. At least a portion of the electromagnetic coil 201 is disposed within a coil housing 202. The coil housing 202 may surround at least a portion of the electromagnetic coil 201 and may be shaped to match the L-shape of the electromagnetic coil 201. For example, in the illustrated embodiment, the coil housing 202 has a south pole 202S located axially forward (the end of the south pole 202S extends axially toward the base 212b of the housing 212 and the magnetic flux guide portion 205), a middle portion 202M located axially rearward (having a U-shape or C-shape), and a north pole 202N located axially forward of the middle portion 202M and axially rearward of the south pole 202S (the end of the north pole 202N extends radially inward toward the shaft 210). The middle portion 202M and the north pole 202N of the coil housing are shaped to provide space for bearings.

[0042] The working chamber 215 is positioned between the rotor 206 and the housing 212 such that the amount of shear fluid held within the working chamber 215 is capable of frictional contact with both the rotor 206 and the housing 212, allowing torque transmission between the rotor 206 and the housing 212 at a slip speed that is generally dependent on the amount of shear fluid held within the working chamber 215. The rotor 206 and shaft 210 can function as an input to the viscous friction clutch 200, and the housing 212 can function as an output. An output device, such as a fan (not shown), can be attached to the housing 212 to receive the torque output from the viscous friction clutch 200.

[0043] A valve assembly 207 operates in response to the applied magnetic flux to selectively cover or uncover an outlet 214 to regulate the amount of shear fluid in the actuation chamber 215. Unused shear fluid may be stored in a storage chamber 213. In the illustrated embodiment, the valve assembly 207 is located on the front side of the rotor 206, and the electromagnetic coil 201 and storage chamber 213 are each located on the opposite rear side of the rotor 206.

[0044] In the illustrated embodiment, rotor insert assembly 203 has a hub portion 204 at a radially inner location and a flux guide portion 205 at a radially outer location (see also FIGS. 4 and 5 ). Hub portion 204 can be positioned on a radially inner portion of rotor 206 and can provide a structural attachment between rotor 206 and shaft 210. In the illustrated embodiment, hub portion 204 is a multi-piece assembly including core 204 c and disk 204 d, with disk 204 d extending radially outward from core 204 c. Core 204 c can be positioned directly on shaft 210. Hub portion 204 can include a non-ferromagnetic material, such as austenitic stainless steel, and / or can be configured with flux blocking features to reduce or eliminate generally radial magnetic shorting between flux guide portion 205 and shaft 210, as described above for the previous embodiment. In the illustrated embodiment, core 204c is made of a ferromagnetic material and disk 204d is made of a non-ferromagnetic material to block the flow of magnetic flux radially along rotor insert assembly 203. More generally, hub portion 204 of rotor insert assembly 203 in the illustrated embodiment includes a non-ferromagnetic portion, or at least a portion thereof, between its inner and outer diameters.

[0045] 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 is made of a ferromagnetic material and can conduct magnetic flux through the non-ferromagnetic material of the rotor 206. The flux guide portion 205 in the illustrated embodiment includes a rear end 205a that extends axially and protrudes from the rear side of the rotor 206 at or adjacent the outer diameter of the coil housing 202, as described further below. This helps to guide magnetic flux to the south pole 202S of the coil housing 202. As in the illustrated embodiment, the radial position of the rear end 205a of the flux guide portion 205 is positioned to overlap the radial position of the south pole 202S of the coil housing 202 (so that the magnetic flux path therebetween is completely blocked). However, other relative radial positions are possible in further embodiments.

[0046] Similar to the operation of the viscous friction clutch 100 described above, during operation, the electromagnetic coil 201 can be selectively energized to generate magnetic flux that travels through the viscous friction clutch 200 along a magnetic flux path (or magnetic flux circuit) A' to operate the valve assembly 207. FIG. 8 shows the magnetic flux path A' schematically in dashed lines on one side of the rotational axis CL of the clutch 200. However, it should be understood that FIG. 8 only depicts a portion of the magnetic flux path A', and that the magnetic flux path A has a three-dimensional shape extending around the axis CL. The magnetic flux path A' allows magnetic flux to pass from the electromagnetic coil 201 through the armature 208 of the valve assembly 207 and back to the electromagnetic coil 201. The magnetic flux path A' exits the electromagnetic coil 201, enters the coil housing 202, and passes from the north pole 202N of the coil housing 202 across the gap to the shaft 210. The gap between the coil housing 202 and the shaft 210 is constant and, in the illustrated embodiment, is radially disposed. The magnetic flux may then travel across the gap between the shaft 210 and the armature 208 in the magnetic field region D. In some embodiments, the magnetic flux may optionally travel through the core 204c of the hub portion 204 of the rotor insert assembly 203, through and / or near the magnetic field region D. In some embodiments, the magnetic field region D may be spaced radially outward from the axis of rotation CL. In other embodiments, the magnetic field region D may extend all the way to the axis of rotation CL. In the illustrated embodiment, the gap between the shaft 210 (as well as the core 204c) and the armature 208 in the magnetic field region D is axially disposed. The size of the gap between the shaft 210 (and core 204c) and the armature 208 changes as the armature 208 moves during operation of the clutch 200. The gap distance between the armature 208 and the shaft 210 (and core 204c) corresponds to the stroke C of the valve assembly 207 (see FIG. 9). 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 is in physical contact with the shaft 210 and / or the core 204c) while the electromagnetic coil 201 is energized.The magnetic flux path A' continues from the armature 208 through the gap F to the magnetic flux guide portion 205 of the rotor insert assembly 203. In the illustrated embodiment, the radially disposed gap F (located at the outer diameter of the armature 208) is constant. The constant radial gap F allows for a constant magnetic flux flow regardless of the open or closed position of the armature 208. The constant magnetic flux flow of the magnetic flux path A' helps improve the internal magnetic force on the armature 208. The magnetic flux path A' then continues through the magnetic flux guide portion 205 of the rotor insert assembly 203 and passes through the entire rotor 206 from the axial front side to the opposite rear side. The magnetic flux path A' then continues from the magnetic 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 back to the electromagnetic coil 201.

[0047] In the illustrated embodiment, flux gap B is axially disposed and is a larger gap than the other gaps in flux path A'. The gap of flux gap B can be constant. Flux gap B traverses a portion 212b-1 of housing 212 as well as the air gaps at both axial ends of housing 212. More specifically, flux gap B axially traverses a non-ferromagnetic portion 212b-1 of base 212b of housing 212. This non-ferromagnetic portion 212b-1 does not have any embedded flux guide inserts or other ferromagnetic components in or near flux path A', which passes completely (or partially) through housing 212 between the interior and exterior of housing 212. That is, flux gap B may be referred to as a non-ferromagnetic flux gap. Magnetic flux path A' can pass through or across portion 212b-1 of housing 212, as well as through one or more adjacent air gaps and retained shear fluid, without the need for a ferromagnetic flux guide that could potentially create an undesirable leakage path for the shear fluid across magnetic flux gap B. In various embodiments, the number of air gaps within magnetic flux gap B can be limited to two or fewer air gaps, and portion 212b-1 of housing 212 can be the only non-ferromagnetic component that magnetic flux path A' crosses within magnetic flux gap B. In some embodiments, the dimension of magnetic flux gap B between rear end 205a of magnetic flux guide portion 205 and south pole 202S of coil housing 202 can be smaller than the distance between rear end 205a of magnetic flux guide portion 205 and other nearby ferromagnetic bodies. In yet another embodiment, the axial dimension of the flux gap B between the rear end 205 a of the flux guide portion 205 and the coil housing 202 may be smaller than the distance, in either the axial direction or the radially inward direction, between the rear end 205 a of the flux guide portion 205 and other nearby ferromagnetic material. Also, in the illustrated embodiment, because the flux guide portion 205 protrudes rearward through the rotor 206, the dimension of the flux gap B between the rear end 205 a of the flux guide portion 205 and the south pole 202S of the coil housing 202 may be smaller than the distance between the rear side of the rotor 206 and the south pole 202S of the coil along the magnetic flux path A′.In some embodiments, the axial distance of the magnetic flux gap B between the rear end 205a of the magnetic flux guide portion 205 and the south pole 202S of the coil housing 202 may be smaller than the axial distance between the south pole 202S of the coil housing 202 and the working chamber 215. That is, the rear end 105a of the magnetic flux guide portion 105 can extend axially rearward of the working chamber 115. The non-ferromagnetic portion 212b-1 of the housing 212 included in (and crossed by) the magnetic flux gap B is positioned radially outward of the bearing 212X that supports the housing 212 in the rotational direction on the shaft 210, such that the bearing 212X is located inside the magnetic flux path A'. Furthermore, in the illustrated embodiment, the bearing 201X that supports the electromagnetic coil 201 and the coil housing 202 on the shaft 210 is also located inside the magnetic flux path A'.

[0048] It should be noted that in various embodiments, as required for a particular application, any of the rotor insert assemblies 103 and 103' discussed above and shown in Figures 4-6 may be utilized in viscous friction clutch 200. Additionally, other embodiments of rotor insert assemblies are possible.

[0049] Upon consideration of the entirety of this disclosure, including the accompanying drawings, those skilled in the art will recognize that the disclosed embodiments of the viscous friction clutch offer numerous benefits and advantages. For example, the disclosed embodiments provide an electromagnetically controlled viscous friction clutch that is relatively lightweight and relatively easy to manufacture. The clutch transmits magnetic flux across or through non-ferromagnetic portions of the housing, while not including a flux guide through the housing that could create a leakage path for shear fluid. For example, a rotor insert assembly having a non-ferromagnetic portion between its inner diameter and its outer diameter, or at least a portion of the non-ferromagnetic portion, can be used to reduce or minimize magnetic shorting or short-circuiting of the electromagnetic flux path through the viscous friction clutch, helping to increase the magnetic force available to move the armature of the valve assembly, even when there is no flux insert component embedded in the housing. It should be noted that in some known clutch designs, the magnetic flux path does not pass through the housing, but instead is contained entirely within the housing, or follows multiple magnetically decoupled paths within the shaft, rotor hub, and / or bearing assemblies positioned radially inward from the housing (i.e., the magnetic flux path does not pass through any portion of the housing, but rather bypasses the housing). While magnetic flux paths contained entirely within the housing are generally associated with a stationary (i.e., non-rotating) journal bracket shaft, embodiments of the present disclosure disclose a “live” or driven shaft. Also, while having multiple magnetically decoupled paths in the shaft, rotor hub, and / or bearing assemblies tends to increase the radial dimension of the overall clutch and can also make manufacturing more complex, embodiments of the present disclosure may use a shaft that can be a single monolithic component without embedded inserts or embedded magnetic insulating inserts. Furthermore, in certain prior art clutches, the absence of a flux guide means that magnetic flux is transferred inefficiently without and / or through or across the various clutch components, resulting in the need for relatively large electromagnetic coils to generate sufficient magnetic flux to overcome such inefficiencies.For example, such prior art clutches may require magnetic flux to traverse a single flux gap that includes three or more air gaps and multiple separate non-ferromagnetic components, whereas embodiments of the present disclosure allow for a limited number of air gaps in the flux gap across the non-ferromagnetic portion of the housing.

[0050] <Discussion of Possible Implementations> The viscous friction clutch may include a rotor, a housing rotatable relative to the rotor, an actuation chamber disposed between the rotor and the housing, the actuation chamber being capable of selectively introducing a predetermined amount of shear fluid into contact with both the rotor and the housing, an electromagnetic coil, a valve assembly for controlling the amount of shear fluid held in the actuation chamber, and a magnetic flux path magnetically coupling the electromagnetic coil and the valve assembly, the magnetic flux path extending through the rotor within the viscous friction clutch. It consists of a ferromagnetic material a magnetic flux gap that passes through the magnetic flux guide portion and crosses both the gap portion and the non-magnetic portion of the housing; Through Pass.

[0051] The viscous friction clutch of the previous paragraph may optionally, additionally and / or alternatively include any one or more of the following features, configurations and / or additional components.

[0052] The flux guides can be embedded in the rotor.

[0053] The rotor may be made of a non-ferromagnetic material such as aluminum.

[0054] The flux guide portion may be part of a multi-piece rotor insert assembly that further includes a hub portion that is at least partially made of a non-ferromagnetic material.

[0055] The rotor insert assembly may include a flux guide portion and an at least partially non-ferromagnetic hub portion between the inner diameter and the outer diameter, and the flux guide portion may be located at or near the outer diameter.

[0056] The hub portion may have a core made of a ferromagnetic material and a disk made of a non-ferromagnetic material extending radially outward from the core.

[0057] A portion of the flux guide can protrude axially from the rotor adjacent an outer diameter of the electromagnetic coil housing separated by a flux gap, and the electromagnetic coil is at least partially disposed within the electromagnetic coil housing.

[0058] The rear end of the magnetic flux guide portion can extend axially rearward of the working chamber.

[0059] The electromagnetic coil can be at least partially disposed within the electromagnetic coil housing, and the rear end of the flux guide portion can protrude axially from the rear end of the rotor such that a flux gap between the rear end of the flux guide portion and the coil housing is smaller than the distance between the rear side of the rotor and the coil housing along the magnetic flux path.

[0060] The housing may not include embedded inserts of ferromagnetic flux guides in the magnetic flux path passing between the interior and exterior of the housing.

[0061] The magnetic flux path may include a radial gap between the armature and the flux guide of the valve assembly, the radial gap being located on an outer diameter of the armature.

[0062] A shaft whose rotation is fixed relative to the rotor.

[0063] The end of the shaft that is internal to the viscous friction clutch may have an axially extending blind hole.

[0064] Shaft blind hole mounted carrier.

[0065] The carrier may be made of a non-magnetic material.

[0066] A sealing component (e.g., a dynamic seal or sealed bearing) carried on a carrier that contacts the housing.

[0067] The carrier may have a central opening extending axially through the carrier.

[0068] The carrier may also have tooling features.

[0069] The carrier may have a stop positioned to contact the armature of the valve assembly during operation of the valve assembly.

[0070] The shaft may have tooling features located within the blind holes.

[0071] The cover of the housing may include an opening that allows the shaft and tooling features to be accessed with a tool.

[0072] A cap may further be included at or within the opening in the cover of the housing.

[0073] At least a portion of the electromagnetic coil can be disposed within a coil housing, and the coil housing can have two opposing magnetic poles and a middle portion between the magnetic poles.

[0074] One of the poles may extend radially and the other of the poles may extend axially.

[0075] The middle section of the coil housing may be U-shaped.

[0076] The magnetic flux guide portion extends axially through the rotor from the front side to the rear side of the rotor on the opposite side.

[0077] A reservoir carried by the rotor.

[0078] The rotor can act as an input to a viscous friction clutch, and whenever there is a torque input to the viscous friction clutch, both the rotor and the reservoir rotate at the input speed.

[0079] A shaft whose rotation is fixed relative to the rotor.

[0080] A bearing that rotationally supports the housing on the shaft, the bearing being positioned within the magnetic flux path.

[0081] A method of operating a valve assembly by transmitting magnetic flux through a viscous friction clutch, the viscous friction clutch having a rotatable rotor and housing, and a shaft fixed in rotation relative to the rotor, wherein the valve assembly selectively controls the degree of viscous friction engagement between the rotor and housing by controlling the amount of shear fluid retained in an actuation chamber. The method includes the steps of energizing an electromagnetic coil disposed outside a housing of the viscous friction clutch and stationary in its rotational movement; transmitting magnetic flux from the electromagnetic coil to a coil housing surrounding at least a portion of the electromagnetic coil; transmitting the magnetic flux from the coil housing across a radial gap to a shaft of the viscous friction clutch; transmitting the magnetic flux from the shaft across an axial gap in a region of magnetic force to an armature of a valve assembly; transmitting the magnetic flux from the armature across the gap to a flux guide portion made of a ferromagnetic material; transmitting the magnetic flux along the flux guide portion between axially opposite front and rear sides of a rotor of the viscous friction clutch; transmitting the magnetic flux from the flux guide portion to the coil housing across a flux gap having a non-ferromagnetic portion of the housing of the viscous friction clutch; and returning the magnetic flux from the coil housing to the electromagnetic coil.

[0082] The method of the preceding paragraph may optionally additionally and / or alternatively include any one or more of the following features, configurations and / or additional steps.

[0083] A step of transmitting the magnetic flux through a core in the hub portion embedded in the rotor.

[0084] The gap between the armature and the flux guide may be radially disposed and constant.

[0085] The radial gap between the coil housing and the shaft may be constant.

[0086] The front flux gap between the flux guide portion and the coil housing is axially arranged and is capable of crossing two air gaps on either axial side of the non-ferromagnetic portion of the housing of the viscous friction clutch.

[0087] The flux gap between the flux guide and the coil housing may be constant.

[0088] The flux gap between the flux guide and the coil housing may have the largest spacing in the magnetic flux path that magnetically couples the electromagnetic coil to the armature of the valve assembly.

[0089] The non-ferromagnetic portion of the housing included in the flux gap may be located radially outward from a bearing that rotationally supports the housing on the shaft.

[0090] The spacing of the flux gap between the rear end of the flux guide and the coil housing may be narrower than the spacing along the flux path between the rear side of the rotor and the coil housing.

[0091] <Summary> Relative or degree terms, such as "substantially," "essentially," "generally," and "approximately," as used herein, should be construed in accordance with any applicable definitions or limitations expressly set forth herein. Furthermore, in all instances, relative or degree terms used herein should be construed to broadly encompass the relevant disclosed embodiments, as well as the range or variations that would be understood by one of ordinary skill in the art in view of the entire specification. This disclosure encompasses normal manufacturing tolerance variations, accidental alignment changes, temporary alignment or shape changes induced by thermal, rotational, or vibrational operating conditions, temporary electromagnetic field fluctuations, and the like. Furthermore, relative or degree terms used herein should be construed to encompass a range that expressly includes, without modification, the specified quality, characteristic, parameter, or value, just as if the relative or degree term were not used in a given disclosure or description.

[0092] While the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes in form and detail may be made without departing from the spirit and scope of the present invention. For example, while a flux-conducting ferromagnetic housing insert is disclosed as unnecessary for the electromagnetic control of a viscous friction clutch, it is contemplated that alternative embodiments may still include such a ferromagnetic housing insert, whether as part of an electromagnetic control system or for one or more other purposes. Furthermore, in other embodiments, a valve assembly may be located behind the rotor or attached to the housing. Furthermore, in still other embodiments, valve assemblies using control rods, such as a valve assembly located entirely within the viscous friction clutch and having one or more control rods passing through the rotor disc, may be utilized with the present invention. Furthermore, the locations of the north and south poles of the coil housing may be reversed or interchanged as desired in various embodiments.

Claims

1. A rotor, a housing that is rotatable relative to the rotor; an actuation chamber disposed between the rotor and the housing, the actuation chamber being capable of selectively introducing a predetermined amount of shear fluid into contact with both the rotor and the housing; An electromagnetic coil; a valve assembly for controlling the amount of shear fluid retained in the working chamber; a magnetic flux path magnetically coupling the electromagnetic coil and the valve assembly, a viscous friction clutch, wherein the magnetic flux path passes through a magnetic flux guide portion made of a ferromagnetic material that extends through the rotor inside the viscous friction clutch, and also passes through a magnetic flux gap that traverses both the air gap portion and the non-magnetic portion of the housing.

2. 2. The viscous friction clutch of claim 1, wherein said flux guide portion is embedded in said rotor, said rotor being made of a non-ferromagnetic material.

3. 2. The viscous friction clutch of claim 1, wherein said flux guide portion is part of a multi-piece rotor insert assembly further including a hub portion made at least in part of a non-ferromagnetic material.

4. 2. The viscous friction clutch of claim 1, wherein the rotor insert assembly includes the flux guide portion and an at least partially non-ferromagnetic hub portion between an inner diameter and an outer diameter, the flux guide portion being located at or near the outer diameter.

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

6. 2. The viscous friction clutch according to claim 1, wherein a portion of the magnetic flux guide portion protrudes axially from the rotor at a position adjacent to an outer diameter of an electromagnetic coil housing separated by the magnetic flux gap, and the electromagnetic coil is at least partially disposed inside the electromagnetic coil housing.

7. 2. The viscous friction clutch according to claim 1, wherein a rear end of said magnetic flux guide portion extends axially rearward of said operating chamber.

8. 2. The viscous friction clutch of claim 1, wherein said housing does not include an embedded insert component of a ferromagnetic flux guide in said flux path passing between the interior and exterior of said housing.

9. 2. The viscous friction clutch of claim 1, wherein said magnetic flux path includes a radial gap between an armature of said valve assembly and said magnetic flux guide portion, said radial gap being located on an outer diameter of the armature.

10. 2. The viscous friction clutch of claim 1, further comprising a shaft, said shaft fixed for rotation relative to said rotor, said shaft having an axially extending blind hole at an end of said shaft that is interior to the viscous friction clutch.

11. a carrier attached to the blind hole and made of a non-magnetic material; The viscous friction clutch of claim 10 further comprising a sealing element carried by the carrier and in contact with the housing.

12. 12. The viscous friction clutch of claim 11, wherein said carrier has a central opening extending axially therethrough.

13. 12. The viscous friction clutch of claim 11, wherein the carrier has a stop positioned to contact the armature of the valve assembly during operation of the valve assembly.

14. The viscous friction clutch of claim 11 , wherein the shaft has tooling features disposed in the blind holes.

15. 15. The viscous friction clutch of claim 14, wherein the housing cover includes an opening that allows the shaft and the tooling feature to be accessed with a tool.

16. Further comprising a coil housing; 2. The viscous friction clutch of claim 1, wherein at least a portion of said electromagnetic coil is disposed within said coil housing, said coil housing having two opposing magnetic poles and a middle portion between said poles, one of said magnetic poles extending radially and the other of said magnetic poles extending axially.

17. 17. The viscous friction clutch of claim 16, wherein the intermediate section of the coil housing is U-shaped.

18. 2. The viscous friction clutch of claim 1, wherein the ferromagnetic flux guide extends axially through the rotor between a front side and an opposite rear side of the rotor.

19. a reservoir carried by the rotor; 2. The viscous friction clutch of claim 1, wherein said rotor acts as an input to said viscous friction clutch, and whenever there is a torque input to said viscous friction clutch, both said rotor and said reservoir rotate at an input speed.

20. 2. The viscous friction clutch of claim 1, further comprising a shaft fixed in rotation relative to the rotor, and a bearing supporting the housing in a rotational direction on the shaft, the bearing being disposed within the magnetic flux path.

21. A method of operating a valve assembly by transmitting magnetic flux through a viscous friction clutch, the viscous friction clutch having a rotatable rotor and housing, and a shaft fixed in rotation relative to the rotor, wherein the valve assembly selectively controls the degree of viscous friction engagement between the rotor and the housing by controlling the amount of shear fluid retained in an actuation chamber; energizing an electromagnetic coil disposed outside the housing of the viscous friction clutch and stationary in its rotational direction; transmitting magnetic flux from an electromagnetic coil to a coil housing that surrounds at least a portion of the electromagnetic coil; transmitting magnetic flux from the coil housing across a radial gap to the shaft of the viscous friction clutch; transmitting magnetic flux from the shaft to an armature of the valve assembly across an axial gap in a region of magnetic force; transmitting magnetic flux from the armature across a gap to a flux guide portion made of ferromagnetic material; transmitting magnetic flux along the magnetic flux guide portion between axially opposite front and rear sides of the rotor of the viscous friction clutch; transmitting magnetic flux from the flux guide portion to the coil housing across a flux gap with a non-ferromagnetic portion of the housing of the viscous friction clutch; and returning magnetic flux from the coil housing to the electromagnetic coil.

22. 22. The method of claim 21, further comprising transmitting magnetic flux through a core in a hub portion embedded in the rotor.

23. 22. The method of claim 21, wherein the gap between the armature and the flux guide portion is constant and radially disposed.

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

25. 22. The method of claim 21, wherein the flux gap between the flux guide portion and the coil housing is axially disposed and traverses two air gaps on either axial side of the non-ferromagnetic portion of the housing of the viscous friction clutch.

26. 22. The method of claim 21, wherein the flux gap between the flux guide and the coil housing is constant.

27. 22. The method of claim 21, wherein the flux gap between the flux guide and the coil housing has a maximum spacing in a magnetic flux path magnetically coupling the electromagnetic coil and the armature of the valve assembly.

28. 22. The method of 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. 22. The method of claim 21, wherein a spacing of the flux gap between the aft end of the flux guide and the coil housing is less than a spacing between the aft side of the rotor and the coil housing along a magnetic flux path magnetically coupled to the electromagnetic coil and the armature of the valve assembly.

Images