Patent Description:
There are several alternatives available to allow for controllability of torque output from a motor or the like. For example, a variable frequency drive (VFD) can be used with an electric motor. The VFD effectively changes the frequency of the alternating current (AC) power delivered to the electric motor. The motor speed is directly linked to the frequency of the AC power. VFDs are relatively complex to install and operate, particularly in a harsh environment. For instance, the VFD power electronics are sensitive to heat and moisture, making them difficult and expensive to protect in outdoor and harsh operating environments. In many cases, VFD's are not employed due to these complexities and limitations.

Friction clutches have been used for a long time to connect and disconnect rotating processes from their respective rotating input power sources. Friction clutches are a good choice when the process can benefit from being disconnected for substantial periods of time. When a process needs to be connected frequently or when a reduced (but non-zero) output speed would be beneficial, friction clutches are often not a preferred choice. This is due to the substantial wear on the friction material and mating surfaces that results in reliability concerns and relatively high maintenance costs.

Variable speed clutches are used in a variety of applications for controlling an output speed of rotating equipment. For example, viscous (or fluid friction) clutches have been successfully deployed in automotive applications to drive cooling fans and pumps, among other uses. Examples of viscous clutches are disclosed in commonly-assigned <CIT> and <CIT> and <CIT>. Viscous clutches are desirable because they are able to control an output torque over a wide speed range. They are also desirable due to the use of a shearing fluid as the torque transfer means. The shearing fluid has a long service and life and is generally maintenance-free. However, stationary (i.e., non-rotating) mounting brackets used with many viscous clutches can undesirably add mass, occupy large amounts of space, and limit mounting locations for the associated clutch. Moreover, there is a need to provide a configuration with a shaft output at the mounting location of the clutch, rather than spaced from the clutch as disclosed in <CIT>, while maintaining ease of installation. A convenient way of monitoring clutch output and/or input speed is also desired, while maintaining easy access to a belt, chain or the like that transfers torque to the clutch.

It is therefore desired to provide a viscous clutch with an alternative configuration.

In one aspect, a viscous clutch includes a housing, an input device, a rotor, a working chamber, a reservoir, a valve, and a quick disconnect bushing. The housing can have a base, a cover, and a housing hub connected in a rotationally fixed configuration so as to rotate together. The input device can be a pulley, a sprocket, and/or a gear rotationally fixed to the housing. The rotor can have a rotor disk, a rotor hub, and a central opening. The rotor disk and the rotor hub are connected in a rotationally fixed configuration so as to rotate together, and the central opening extends entirely through the rotor hub. The working chamber is arranged between the housing and the rotor disk. The reservoir can hold a supply of a shear fluid, and is fluidically connected to the working chamber by a fluid circuit. The reservoir can be carried by the housing and can be arranged to overlap the input device in an axial direction. The valve is actuatable to selectively control a flow of the shear fluid between the reservoir and the working chamber along the fluid circuit such that a torque coupling between the housing and the rotor disk is selectively created based upon a volume of the shear fluid present in the working chamber. The quick disconnect bushing can be removably secured to the rotor hub at the central opening and can be configured so as to permit a rotationally fixed engagement between the rotor and a component driven by the viscous clutch, such as an output shaft.

In another aspect, a method of assembling a viscous clutch having a housing, a rotor, a working chamber arranged between the housing and the rotor, a reservoir to hold a supply of a shear fluid with the reservoir fluidically connected to the working chamber by a fluid circuit, and a valve, wherein the valve is actuatable to selectively control a flow of the shear fluid between the reservoir and the working chamber along the fluid circuit includes positioning a shaft in a central opening located in a rotor hub of the rotor, such that the shaft extends into the central opening from a rear side of the viscous clutch, and removably securing a quick disconnect bushing to the shaft and the rotor hub to create a rotationally fixed engagement between the rotor and the shaft.

In yet another aspect, a viscous clutch includes a housing, an input device, a rotor, a working chamber, a reservoir, a valve, a first sensor, and a second sensor. The housing can have a base, a cover, and a housing hub connected in a rotationally fixed configuration so as to rotate together. The input device can be a pulley, a sprocket, and/or a gear rotationally fixed to the housing. The rotor can have a rotor disk and a rotor hub connected in a rotationally fixed configuration so as to rotate together, and a central opening can extend entirely through the rotor hub. The working chamber can be arranged between the housing and the rotor disk. The reservoir can hold a supply of a shear fluid, and can be fluidically connected to the working chamber by a fluid circuit. The valve is actuatable to selectively control a flow of the shear fluid between the reservoir and the working chamber along the fluid circuit such that a torque coupling between the housing and the rotor disk is selectively created based upon a volume of the shear fluid present in the working chamber. The first sensor can be located rearward of the input device and configured to measure a speed of the housing. The second sensor can be located rearward of the input device and configured to measure a speed of the rotor.

The present summary is provided only by way of example, and not limitation. Other aspects of the present invention will be appreciated in view of the entirety of the present disclosure, including the entire text, claims and accompanying figures.

While the above-identified figures set forth one or more embodiments of the present invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope of the invention as defined by the appended claims. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features, steps and/or components not specifically shown in the drawings.

In general, the present invention provides a viscous clutch that allows for a torque input and output to be located on the same side of the clutch, and associated methods of assembling and using such a clutch. In some embodiments, a reservoir can be located on an input to the clutch, so as to rotating whenever there is a torque input. Additionally, in some embodiments a quick disconnect (QD) bushing or other securing mechanism can be provided to allow a relatively easy connection and disconnection of the viscous clutch to a shaft. Additionally, or in the alternative, in some embodiments, one or more speed sensors can be provided that sense an input and/or output speed associated with the viscous clutch. Embodiments according to the present invention can provide a viscous clutch that is relatively compact (particularly in an axial direction), relatively low in mass, and that is relatively easy to install and remove, while also providing relatively easy access to replace a dive belt, chain or the like while still installed. Persons of ordinary skill in the art will appreciate numerous other advantages and benefits in view of the entirety of the present disclosure, including the accompanying figures.

The present application is based on and claims the benefit of <CIT>, the content of which is hereby incorporated by reference in its entirety.

<FIG> is a cross-sectional view of an embodiment of a viscous clutch <NUM> (also referred to simply as clutch <NUM>) that includes an input device <NUM>, a housing <NUM>, a rotor <NUM>, a working chamber <NUM>, a reservoir <NUM>, a valve assembly <NUM>, a control coil assembly <NUM> (including an electromagnetic coil <NUM>-<NUM>), and a QD bushing <NUM> that functions as a securing mechanism. The viscous clutch <NUM> is configured to rotate about an axis A. <FIG> is an exploded cross-sectional view of the viscous clutch <NUM>.

The input device <NUM> is removably connected to and rotationally fixed to the housing <NUM> in the illustrated embodiment, and rotates with the housing <NUM> at all times. A prime mover (not shown in <FIG> and <FIG>), such as an electric motor, internal combustion engine, or the like, can generate torque that is delivered to the input device <NUM> through a belt, chain, or the like during operation. The amount of input torque can vary over time, by intent (e.g., as a result of motor throttling) and/or as a result of unintended fluctuations. In the illustrated embodiment, the input device <NUM>, which accepts torque input, is a pulley (or sheave) configured to accept torque input from a belt (not shown in <FIG> and <FIG>), and includes a body <NUM>-<NUM> and multiple lugs <NUM>-<NUM>. The body <NUM>-<NUM> as shown is generally annular and is configured to directly engage the belt. The lugs <NUM>-<NUM> protrude from the body <NUM>-<NUM>, and in the illustrated embodiment are generally equally circumferentially spaced and extend radially inward from the body <NUM>-<NUM>. The input device <NUM> can be removably affixed to the housing <NUM> (e.g., to the base <NUM>-<NUM>) at the lugs <NUM>-<NUM>, such as with suitable fasteners. As shown in <FIG> and <FIG>, at least a portion of the body <NUM>-<NUM> is spaced from the housing <NUM> by the lugs <NUM>-<NUM> such that cooling airflow can pass between the body <NUM>-<NUM> and the housing <NUM> (e.g., near the reservoir <NUM>) in between the lugs <NUM>-<NUM>. In further embodiments, the input device <NUM> can be a sprocket that accepts torque from a chain, a gear that accepts torque from another gear, or another suitable type of input device. Using a gear, sprocket, pulley or the like as the input device <NUM> allows a process speed (that is, clutch output speed) to be tailored using a transmission ratio established through the number of teeth on a sprocket or gear or with a diameter of a pulley or gear. Because the input device <NUM> (sprocket, gear, pulley, etc.) is removable from the remainder of the clutch <NUM>, a relatively high degree of application flexibility is provided, and the same basic clutch <NUM> can be easily adapted to a variety of uses by simply swapping the input device <NUM> for a different size or type. The input device <NUM> can in this way be configured to rotate at a desired speed for a given torque input from a prime mover, thereby allowing the input speed to the viscous clutch <NUM> to be adjusted as desired for particular applications.

The housing <NUM> includes a base <NUM>-<NUM>, a cover <NUM>-<NUM>, and a housing hub <NUM>-<NUM>. The base <NUM>-<NUM> and the cover <NUM>-<NUM> are attached together to form an enclosure or shell of the clutch <NUM>, and are located at an exterior of the clutch <NUM>. One or more interior surfaces of the base <NUM>-<NUM> and/or cover <NUM>-<NUM> can include a number of ribs and grooves to increase a surface area exposed to the working chamber <NUM>. Because torque transmission is achieved by the clutch <NUM> via shearing of a viscous shear fluid in the working chamber, there is heat generated in the shear fluid that needs to be dissipated to atmosphere. External surfaces of the base <NUM>-<NUM> and/or the cover <NUM>-<NUM> can include cooling fins <NUM>-<NUM> to facilitate heat dissipation to ambient air. As shown in the illustrated embodiment, the cover <NUM>-<NUM> includes a radially outward portion and a radially inner spacer portion that are secured tougher in a rotationally fixed relationship. In further embodiments, the cover <NUM>-<NUM> can be made as a single integral and monolithic piece, or have other suitable configurations. In the illustrated embodiment, the housing hub <NUM>-<NUM> is attached to the base <NUM>-<NUM> at an interior of the clutch <NUM> at a generally rearward portion of the base <NUM>-<NUM>, and extends axially forward toward the cover <NUM>-<NUM>. The housing hub <NUM>-<NUM> can alternatively be integrally and monolithically formed with the base <NUM>-<NUM>. Further, in the illustrated embodiment, the housing hub <NUM>-<NUM> is located at a radially inward portion of the housing <NUM>, near the axis A, and tapers in the axial direction from a rear end toward a forward end. The housing hub <NUM>-<NUM> is also located radially inward of the reservoir <NUM> in the illustrated embodiment. As shown in <FIG> and <FIG>, the housing <NUM> is configured as the driving (or input) mechanism of the viscous clutch <NUM>, along with the input device <NUM>. In this way, the housing <NUM> of the illustrated embodiment rotates at all times at the full rotational speed of the input device <NUM> whenever there is a torque input to the clutch <NUM>. The full speed rotation of the housing <NUM> helps increase heat transfer to cool the clutch <NUM>, because convective heat transfer is related to a velocity of ambient cooling air over the housing <NUM> (including the cooling fins <NUM>-<NUM>).

The rotor <NUM> in the illustrated embodiment includes a rotor disk <NUM>-<NUM> and a rotor hub <NUM>-<NUM> having a central opening <NUM>-<NUM>. The rotor disk <NUM>-<NUM> and the rotor hub <NUM>-<NUM> are rotationally fixed to each other so as to rotate together. The rotor disk <NUM>-<NUM> can be positioned within the housing <NUM> formed by the base <NUM>-<NUM> and the cover <NUM>-<NUM>, and can extend in generally the radial direction. At least a portion of the rotor disk <NUM>-<NUM> adjoins the working chamber <NUM>, and can include a number of ribs and grooves on one or both sides to increase the surface area exposed to the working chamber <NUM>. The ribs and grooves of the rotor disk <NUM>-<NUM> can be interspersed with corresponding ribs and grooves on the housing <NUM>. One or more openings (not specifically shown in <FIG> and <FIG>) can be provided in the rotor disk <NUM>-<NUM> to allow shear fluid present in the working chamber <NUM> to pass between opposite sides of the rotor disk <NUM>-<NUM>. In the illustrated embodiment, the rotor hub <NUM>-<NUM> includes a first portion <NUM>-2R and a second portion <NUM>-2F. The first portion <NUM>-2R extends axially rearward relative to the rotor disk <NUM>-<NUM> and can be substantially cylindrical in shape. In the illustrated embodiment, the first portion <NUM>-2R is located at a radially inward region of the rotor <NUM> near the axis A, and is located radially inward of the housing hub <NUM>-<NUM> in a concentric relationship while overlapping the housing hub <NUM>-<NUM> in the axial direction. Further, in the illustrated embodiment the first portion <NUM>-2R extends axially rearward beyond both the base <NUM>-<NUM> of the housing <NUM> and the input device <NUM>. The second portion <NUM>-2F extends axially forward relative to the rotor disk <NUM>-<NUM>, in a direction opposite from the first portion <NUM>-2R, and can be substantially cylindrical in shape. In the illustrated embodiment, the second portion <NUM>-2F is axially shorter than the first portion <NUM>-2R and does not extend axially beyond the cover <NUM>-<NUM> of the housing <NUM>. The central opening <NUM>-<NUM> is located at the axis A and extends axially through the entire rotor hub <NUM>-<NUM>, exposing the central opening <NUM>-<NUM> at a rear end of the first portion <NUM>-2R and at a front end of the second portion <NUM>-2F. The central opening <NUM>-<NUM> is configured to accept both a shaft <NUM> and a securing mechanism (e.g., QD bushing <NUM>), as explained further below. For instance, the central opening <NUM>-<NUM> can further include one or more regions at the second portion <NUM>-2F of the rotor hub <NUM>-<NUM> that are enlarged or otherwise specifically shaped to accept and engage the QD bushing <NUM>.

Bearings <NUM>, which are shown in the illustrated embodiment as one set of tapered roller bearings, are positioned in between the housing hub <NUM>-<NUM> and the rotor hub <NUM>-<NUM>. The bearings <NUM> thereby allow the housing hub <NUM>-<NUM> to be rotationally supported on the rotor hub <NUM>-<NUM>, with the base <NUM>-<NUM> and cover <NUM>-<NUM> of the housing <NUM> cantilevered relative to the housing hub <NUM>-<NUM>, and allow relative rotation between the housing <NUM> and the rotor <NUM>. In this way the bearings <NUM> allow the rotor <NUM> to rotate at a different speed than the housing <NUM>, depending upon the selected degree of engagement (or slip speed) of the clutch <NUM>. The bearings <NUM> can be substantially axially aligned with the input device <NUM>. Moreover, the bearings <NUM> are located radially inward from and axially aligned with the reservoir <NUM> in the illustrated embodiment. Other types of bearings (e.g., conventional non-tapered roller bearings, needle bearings, double row ball bearings, etc.) can be used in further embodiments. Moreover, any suitable number of bearing sets can be used, as desired for particular applications. Gaps between the housing <NUM> and the rotor <NUM> can be blocked with suitable seal elements.

The working chamber <NUM> is defined between the housing <NUM> and the rotor <NUM>. Ribs and grooves can be provided along the housing <NUM> and the rotor <NUM>, as previously discussed, in order to increase the surface area along the working chamber <NUM>. During operation, the presence of a shear fluid (e.g., silicone oil) in the working chamber <NUM> creates a fluid friction shear coupling to transmit torque from the housing <NUM> (input) to the rotor <NUM> (output). A degree of coupling between the housing <NUM> and the rotor <NUM> varies as a function of an amount (that is, volume) of the shear fluid present in the working chamber <NUM>. In this way, varying the amount of the shear fluid present in the working chamber <NUM> allows selective control of the clutch <NUM>, to vary the torque transmission and a rotational speed of the rotor <NUM>.

The reservoir (or storage chamber) <NUM> can hold a supply of the shear fluid not needed in the working chamber <NUM>. In the illustrated embodiment, the reservoir <NUM> is carried by and/or in the housing <NUM>. More particularly, in the illustrated embodiment the reservoir <NUM> is carried by and at least partially bounded by the base <NUM>-<NUM> and the housing hub <NUM>-<NUM>, with the reservoir <NUM> positioned to the rear side of the rotor disk <NUM>-<NUM>. A reservoir cover <NUM>-<NUM> can further be provided at a boundary of the reservoir <NUM>, to help retain the shear fluid therein. In the illustrated embodiment, the reservoir cover <NUM>-<NUM> is a plate-like wall attached to the base <NUM>-<NUM> near the rotor disk <NUM>-<NUM>. The location of the reservoir in the housing <NUM>, which acts as the input of the clutch <NUM>, allows the reservoir to rotate whenever there is a torque input to the clutch <NUM>. When the clutch <NUM> is disengaged, but a torque input is provided to the clutch <NUM> via the input device <NUM>, the shear fluid is still spinning at relatively high speed and under pressure in the reservoir <NUM>. Thus, when actuation of the clutch <NUM> is required, there is significant pressure available to force the shear fluid into the working area <NUM> quickly, which allows for relatively fast clutch response. The reservoir <NUM> can also be contained in the housing <NUM> which forms an outer shell of the clutch <NUM>. Because torque transmission is achieved via the frictional shearing of the shear fluid, there is heat generated in the shear fluid that needs to be dissipated to atmosphere. The full input speed rotation of the housing <NUM> allows for efficient heat transfer, as the velocity of the air over the housing <NUM> is related to the ability to convectively transfer heat. Thus, because the shear fluid is stored in the reservoir <NUM> near the outside or exterior of the clutch <NUM>, the shear fluid is in closer proximity to relatively cool ambient air allowing the heat transfer a direct and relatively short path to conduct through the housing <NUM> (including and cooling fins <NUM>-<NUM>) to the outside of the clutch <NUM>. Additionally, in the illustrated embodiment, the reservoir <NUM> is located at the rear side of the clutch <NUM>, substantially axially aligned with the input device <NUM> (e.g., pulley), and is located radially inward from the input device <NUM>. The illustrated arrangement of the reservoir <NUM> thus allows for a relatively axially compact clutch <NUM>, while still allowing cooling air to flow near the reservoir <NUM> (e.g., allowing the reservoir to remain near an exterior of the clutch <NUM>) and to pass between the input device <NUM> and the reservoir <NUM>.

A fluid circuit is defined by the viscous clutch <NUM>, including a fluid delivery path that extends from the reservoir <NUM> to the working chamber <NUM>, and a fluid return path that extends from the working chamber <NUM> back to the reservoir <NUM>. In the illustrated embodiment, the fluid delivery path passes through a bore in the reservoir cover <NUM>-<NUM> and the fluid return path extends radially through the rotor disk <NUM>-<NUM>, similar to the fluid circuit disclosed in commonly-assigned <CIT>, though other arrangements are possible in further embodiments. In alternative embodiments, the fluid return path can be defined in the housing <NUM>, for example. A pump element along the working chamber <NUM> can continually pump the shear fluid back to the reservoir <NUM> when there is a torque input to the clutch <NUM>, such as in a manner known in the art.

The valve assembly <NUM> (which may also be referred to simply as valve <NUM>) can be an electromagnetically-actuated valve assembly that regulates flow of the shear fluid between the reservoir <NUM> and the working chamber <NUM>, thereby controlling the degree of engagement of the clutch and an associated clutch output speed. In the illustrated embodiment, the valve assembly <NUM> is positioned at a rear side of the clutch <NUM>, proximate the control coil assembly <NUM>. The valve assembly <NUM> in the illustrated embodiment includes a movable (e.g., axially translatable or pivotal) armature <NUM>-<NUM>, a control rod <NUM>-<NUM>, a valve element <NUM>-<NUM>, and a flux guide (or flux ring) <NUM>-<NUM>. The valve assembly <NUM> can control flow of the shear fluid along the delivery path (or at another point along the fluid circuit in alternative embodiments). For instance, movement of the armature <NUM>-<NUM> can translate the control rod <NUM>-<NUM>, which in turn can axially pivot or translate the valve element <NUM>-<NUM> to selectively cover or uncover (that is, selectively obstruct or open) part of the fluid circuit. The control rod <NUM>-<NUM> allows the valve element <NUM>-<NUM> to be spaced a significant distance from the armature <NUM>-<NUM> but still moved in response to actuation of the armature <NUM>-<NUM>. In one embodiment, actuation of the valve assembly <NUM> can be similar to that described in commonly-assigned <CIT>, and can cover and uncover an outlet bore in the reservoir cover <NUM>-<NUM>. However, it should be noted that the particular configuration of the valve assembly <NUM> disclosed herein is provided merely by way of example and not limitation. The valve assembly <NUM> can be actuated by the control coil assembly <NUM>, which is described further below. Because the valve assembly <NUM> can be carried by the housing <NUM> (e.g., by the base <NUM>-<NUM>) on a rear side of the clutch <NUM>, and can further be located entirely on the rear side of the rotor disk <NUM>-<NUM> in close proximity to the electromagnetic coil <NUM>-<NUM>, a relatively short magnetic flux circuit can operatively link the electromagnetic coil <NUM>-<NUM> of the control coil assembly <NUM> with the valve assembly <NUM>. Such a flux circuit need not pass through any walls of the housing <NUM> or the rotor <NUM>, which can avoid the need for flux conducting inserts to pass through structures like the base <NUM>-<NUM> or the rotor disk <NUM>-<NUM> that are typically made from non-magnetic flux conducting (or simply poorly flux conductive) materials like aluminum, which otherwise have desirable mass and thermal conductivity properties. Yet the relatively small flux guide <NUM>-<NUM> can be positioned in between and directly adjacent to the armature <NUM>-<NUM> and the electromagnetic coil <NUM>-<NUM>, with a suitable shape to accommodate generally radial air gaps separating the rotationally fixed electromagnetic coil <NUM>-<NUM>. In this respect, the flux circuit can be external to both the housing <NUM> (including the base <NUM>-<NUM> and the cover <NUM>-<NUM>) and the rotor <NUM> (including the rotor disk <NUM>-<NUM>). The control rod <NUM>-<NUM> can also be located outside or independent from the flux circuit. This allows the electromagnetic coil <NUM>-<NUM> to be relatively small and lightweight, due to operability of the armature <NUM>-<NUM> of the valve assembly <NUM> with relatively small (that is, low intensity) magnetic fields. In alternate embodiments, a thermally-sensing bi-metal controlled valve or a direct electrically-actuated valve can be used instead of the electromagnetically-actuated valve <NUM> (and the electromagnetic coil <NUM>-<NUM> and other control coil assembly <NUM> components omitted).

The control coil assembly <NUM> as shown in the illustrated embodiment includes electromagnetic coil (or control coil) <NUM>-<NUM> and a coil bearing <NUM>-<NUM>. The control coil assembly <NUM> is generally rotationally fixed, while the coil bearing <NUM>-<NUM> allows an adjacent component supporting the assembly <NUM> to rotate independently. A controller <NUM>-<NUM> with suitable control circuitry can further be provided to govern the selective energization of the electromagnetic coil <NUM>-<NUM>, and, in turn, the output speed of the clutch <NUM> to a desired target speed. The electromagnetic coil <NUM>-<NUM> can be relatively small and therefore require only a small amount of power to control operation of the valve <NUM> and the clutch <NUM> as a whole. This allows for the controller <NUM>-<NUM> to be relatively small as well. Because of the small amount of power needed for the electromagnetic coil <NUM>-<NUM>, and the relatively small amount of heat generated by such relatively low power operation, electrical circuitry of the controller <NUM>-<NUM> can be enclosed and sealed in a protective enclosure to protect the controller <NUM>-<NUM> from exposure to the elements without concern for heat damage. In some embodiments, the electromagnetic coil <NUM>-<NUM> can be secured to and supported on the clutch <NUM>, for instance on the rotor hub <NUM>-<NUM> (e.g., on the first portion <NUM>-2R) by the coil bearing <NUM>-<NUM>, such that mounting and engaging the clutch <NUM> on the output shaft <NUM> (or other output device) simultaneously mechanically mounts the control coil assembly <NUM>, thereby avoiding the need to separately mount the electromagnetic coil <NUM>-<NUM>. The control coil assembly <NUM> can be located at a rear side of the clutch <NUM>, generally rearward of the input device <NUM>. Further, the control coil assembly <NUM> be located at the same side of the clutch <NUM> as both the torque input and output. As shown in the illustrated embodiment, the electromagnetic coil <NUM>-<NUM> is positioned adjacent to the flux guide <NUM>-<NUM> of the valve assembly <NUM>. Further, in the illustrated embodiment, the control coil assembly <NUM> is located at or near the rearmost portion of the clutch <NUM>, which allows a cable (and a tether, bracket or other rotation-fixing device) to be located rearward of the input device <NUM> (e.g., pulley) as well as associated belts, chains, etc. that attach to the input device <NUM>. Such a cable location facilitates removal and/or replacement of the belt, chain, etc. of the input device <NUM> without interference from the cable (or tether) of the control coil assembly <NUM>, for instance.

A securing mechanism can removably attach and engage the clutch mechanism to the out shaft in a rotationally fixed manner. In the illustrated embodiment, the securing mechanism is configured as a quick detachable (QD) bushing <NUM>. QD bushings generally have a keyed (that is, splined) engagement feature on an inner surface and a tapered outer surface (that is, a frusto-conical outer grip surface). In this way, a keyway on the securing mechanism can engage a protruding key or spline on the output shaft <NUM> while a tapered surface can form a tight fit against the rotor hub <NUM>-<NUM> (e.g., within a stepped notch of the central opening <NUM>-<NUM> at the second portion <NUM>-2F). The keyway and tapered surface can each be generally located on a sleeve portion of the QD bushing <NUM>, and a flange with openings to accept suitable fasteners (e.g., bolts, screws or the like) protrudes radially outward from the sleeve portion, typically at an end of the sleeve portion. The fasteners allow the securing mechanism to be tightly engaged with the rotor hub <NUM>-<NUM> (e.g., with the second portion <NUM>-2F). The QD bushing <NUM> can further have a split configuration, with a split line passing through both the sleeve portion and the flange. The split line can be arranged circumferentially opposite the keyway. In alternate embodiments, another type of bushing or other suitable type of securing mechanism can be utilized.

A cap (or cover) <NUM> can be provided, secured to the housing <NUM> of the clutch <NUM> for co-rotation therewith in a rotationally fixed manner. The cap <NUM> can protect the securing mechanism (e.g., QD bushing <NUM>) as well as a cavity in which the securing mechanism and the end of the shaft <NUM> are located. The cap <NUM> can, for instance, be a lightweight, generally planar plate removably secured to the housing <NUM> with suitable fasteners. Removal of the cap <NUM> allows for easy access to the securing mechanism. The cap <NUM>, as well as the securing mechanism, can be located at a front side of the clutch <NUM> opposite from both the torque input and output, as well as generally opposite the input device <NUM> and the control coil assembly <NUM>.

One or more seals can be provided to seal gaps between components that rotate relative to each other, such as to seal a gap between the housing <NUM> and the rotor <NUM>. Such seals can help retain the shear fluid within the clutch <NUM> in a manner well known in the art.

The shaft <NUM> can be separate from the clutch <NUM>. For instance, the shaft <NUM> can be an input shaft of an external device or process that is powered by torque output from the clutch <NUM>. In this sense the shaft <NUM> accepts torque output of the clutch <NUM> and acts as the output. The shaft <NUM> can be removably inserted into the central opening <NUM>-<NUM> (e.g., as a "live" center output shaft), and can be engaged and rotationally fixed to the rotor <NUM> (e.g., to the rotor hub <NUM>-<NUM>) by the securing mechanism (e.g., QD bushing <NUM>). The clutch <NUM> can be supported on the shaft <NUM> in a cantilevered manner in some embodiments. In the illustrated embodiment, the shaft <NUM> enters the central opening <NUM>-<NUM> from the rear of the clutch <NUM> and extends entirely through the rotor hub <NUM>-<NUM> and the central opening <NUM>-<NUM>. Because the shaft <NUM> is not a part of the clutch <NUM>, the shaft <NUM> need not be part of a magnetic flux circuit to operate the valve <NUM> and need not have any openings to accept wires or the like.

<FIG> is a schematic cross-sectional view of an embodiment of a torque transmission system <NUM> utilizing the viscous clutch <NUM>. As shown in the illustrated embodiment, the system <NUM> includes the clutch <NUM>, a prime mover <NUM> (e.g., a motor, engine or the like), a driveshaft <NUM>, a pulley <NUM>, a belt <NUM>, the shaft <NUM>, and an output device <NUM> (e.g., fan, pump, machine, or the like). The prime mover <NUM> generates torque, which is transmitted through the driveshaft <NUM> to the pulley <NUM> and then to the belt <NUM>. The belt <NUM> transmits the torque to the input device <NUM> of the clutch <NUM> at a given input speed. The clutch <NUM> selectively transmits torque to the shaft <NUM> at a desired output speed, as governed by the controller <NUM>-<NUM>. The shaft <NUM> then transmits the output toque to the output device <NUM> and the desired output speed. In this way, the clutch <NUM> allows for modulation of the rotational speed of the output device <NUM> largely independent of the speed of the prime mover <NUM>. It should be noted that the configuration of the system <NUM> in <FIG> is shown merely by way of example. Numerous other configurations are possible in further embodiments, such as systems with more complex drivetrains. Moreover, instead of the pulley <NUM> and the belt <NUM>, a sprocket and chain, gear and shaft assembly, or other suitable types of drivetrain components can be utilized in further embodiments.

Installation and use of the clutch system <NUM> can include the following steps, in some embodiments. A desired input device <NUM> (e.g., pulley) can be attached to a clutch <NUM> (e.g., at or near a rear face of the shell or housing <NUM>). The clutch <NUM> (including the attached input device <NUM>) can then be slid onto the output shaft <NUM> (e.g., the input shaft of an output device <NUM> powered by torque output from the clutch <NUM>), which can include engaging and securing a hub <NUM>-<NUM> of an output member <NUM> (e.g., output rotor) to the output shaft <NUM>. This securing step can include securing the hub <NUM>-<NUM> to the output shaft <NUM> in a rotationally fixed manner with a securing mechanism (e.g., a QD bushing <NUM> or other suitable bushing). A cap <NUM> is then secured over the securing mechanism. A cable can be attached to a control coil assembly <NUM>, to transmit power and control signals between the clutch system <NUM> and external source(s). The control coil assembly <NUM> can be integrated with the clutch <NUM>, thereby avoiding the need for a separate attachment of an electromagnetic coil <NUM>-<NUM> and associated structures. A belt, chain or other transmission element <NUM> is engaged to the input device <NUM> (e.g., pulley) on the input (e.g., housing <NUM>) of the clutch <NUM>. The belt <NUM>, the input device <NUM>, and the output shaft <NUM> can each be located on the same side (e.g., rear side) of the clutch <NUM> (though the output shaft <NUM> can pass mostly or entirely through the clutch <NUM>). The belt <NUM> can in turn be coupled to suitable additional components (e.g., another pulley <NUM>, another shaft, a prime mover, etc.) to allow torque input to the clutch <NUM>. Likewise, the output device <NUM> can be connected to a drivetrain or other components that accept torque output from the clutch <NUM> and transmit that torque to the output device <NUM>.

Once assembled, the clutch <NUM> can be operated by selectively energizing an electromagnetic coil <NUM>-<NUM> of a control coil assembly <NUM> in order to actuate a valve assembly <NUM>. A controller <NUM>-<NUM> can govern the operation of the control coil assembly <NUM> and, in turn, the valve <NUM>, such as by establishing a pulse width modulated (PWM) duty cycle. Actuation of the valve assembly <NUM> can regulate the flow of shear fluid to a working chamber <NUM> from a reservoir <NUM>. The reservoir <NUM> can be rotated whenever there is a torque input to the clutch <NUM>, that is, whenever the input device <NUM> rotates. The presence of the shear fluid in the working chamber <NUM> transmits torque between the input member and the output member, as a function of the amount or volume of the shear fluid present. As explained further below, feedback from a speed sensor assembly can optionally be utilized by the controller <NUM>-<NUM> to adjust the control of the valve <NUM> and the degree of engagement of the clutch <NUM> based on current operating conditions.

<FIG> and <FIG> illustrate another embodiment of a viscous clutch <NUM>' that includes a speed sensor assembly <NUM>. <FIG> is a cross-sectional view of the viscous clutch <NUM>', and <FIG> is rear perspective view of the viscous clutch <NUM>'. In general, the clutch <NUM>' has a configuration similar to that of the clutch <NUM> described above, with like reference numbers identifying like parts, and adds the speed sensor assembly <NUM>. In order to control the speed of the clutch output (e.g., the rotor <NUM>, and, in turn, the shaft <NUM>) relative to the clutch input (e.g., the input device <NUM> and the housing <NUM>) with relatively high precision, the speed of both the input and output of the clutch <NUM>' need to be monitored. To achieve this, the sensor assembly <NUM> can provide at least two sensors (e.g., Hall Effect sensors). These sensors can be secured to the clutch <NUM>' at or near the rotationally stationary control coil assembly <NUM>.

A first (or input) sensor <NUM> can be aimed at a first target <NUM> that is rotationally fixed relative to the input (e.g., the housing <NUM> and the input device <NUM>) in order to sense a rotational speed of the clutch input. The first sensor <NUM> can include a Hall Effect sensor element <NUM>-<NUM> and a circuit board <NUM>-<NUM>, and can be rotationally fixed to the rotationally stationary control coil assembly <NUM>. The first target <NUM> can be an array or one or more notches in or on the flux guide <NUM>-<NUM> that co-rotates with the input (e.g., housing <NUM>). In the illustrated embodiment, the first target <NUM> is an array of circumferentially spaced, generally rectangularly shaped notches that pass entirely radially through a distal end of an axially extending flange of the flux guide <NUM>-<NUM> located radially outward of the electromagnetic coil <NUM>-<NUM>.

The second (or output) sensor <NUM> can be aimed at a second target <NUM> that is rotationally fixed relative to the output (e.g., the rotor <NUM> and, in turn, the shaft <NUM>) in order to sense a rotational speed of the clutch output. The second sensor <NUM> can include a Hall Effect sensor element <NUM>-<NUM> and a circuit board <NUM>-<NUM>, and can be rotationally fixed to the rotationally stationary control coil assembly <NUM>. The second target <NUM> can be an array of one or more notches in or on the rotor hub <NUM>-<NUM> that co-rotates with the output (e.g., the rotor <NUM> and, in turn, the shaft <NUM>). In the illustrated embodiment, the second target <NUM> is an array of circumferentially spaced, generally rectangularly shaped notches that pass entirely radially through a distal end of the first portion <NUM>-2R of the rotor hub <NUM>-<NUM> located radially inward of the electromagnetic coil <NUM>-<NUM> (and the coil bearing <NUM>-<NUM>) and the first sensor <NUM>.

The use of notches to form the first and second targets <NUM> and <NUM> allows those targets <NUM> and <NUM> to be integrated into existing components (e.g., the flux guide <NUM>-<NUM> and the rotor hub <NUM>-<NUM>), thereby avoiding the need to add mass and/or manufacturing/assembly complexity associated with the use of separate, additional target structures. Though in further embodiments, one or both of the first and second targets <NUM> and <NUM> can be provided as a separate disk, wheel, sleeve or the like that is rotationally fixed to desired clutch input and/or output structures.

In the illustrated embodiment, the first and second sensors <NUM> and <NUM> are both supported by a common support structure <NUM>, which can have a generally L-shaped configuration. The support structure <NUM> allows the sensor assembly <NUM> to be installed on the control coil assembly <NUM> in essentially a single attachment operation, and integrally forming the targets <NUM> and <NUM> requires no further attachment operations, thus simplifying manufacturing/assembly of the clutch <NUM>'. In further embodiments the first and second sensors <NUM> and <NUM> can be mounted separately, without a common mounting structure.

The rotational speed measurement of the first sensor <NUM> provides a measurement of the input speed of the clutch <NUM>', and the rotational speed measurement of the second sensor <NUM> provides a measurement of the output speed of the clutch <NUM>'. A comparison of the output speed to a desired output speed is possible with use of only the second sensor <NUM>. However, it is further useful to measure both the input and output speeds in order to accurately control the clutch output (e.g., the rotor <NUM> and, in turn, the shaft <NUM>) relative to the clutch input (e.g., the input device <NUM> and the housing <NUM>). For instance, variations in input torque can be compensated for through control of the clutch <NUM>' to provide a substantially constant output speed. In this way, unintended variations in input torque from a prime mover (see <FIG>), whether periodic and predictable or essentially random and unpredictable, can be compensated for and smoothed out by the clutch <NUM>', thereby helping to minimize variations in rotational speed of an output device that receives torque from the clutch <NUM>' (see <FIG>).

A viscous clutch can include a housing having a base, a cover, and a housing hub, with the base, the cover and the housing hub are connected in a rotationally fixed configuration so as to rotate together; an input device rotationally fixed to the housing, with the input device being a pulley, a sprocket, a gear, or the like; a rotor having a rotor disk, a rotor hub, and a central opening, with the rotor disk and the rotor hub connected in a rotationally fixed configuration so as to rotate together, and with the central opening extending entirely through the rotor hub; a working chamber arranged between the housing and the rotor disk; a reservoir to hold a supply of a shear fluid, the reservoir fluidically connected to the working chamber by a fluid circuit, the reservoir carried by the housing and arranged to overlap the input device in an axial direction; a valve, the valve being actuatable to selectively control a flow of the shear fluid between the reservoir and the working chamber along the fluid circuit such that a torque coupling between the housing and the rotor disk is selectively created based upon a volume of the shear fluid present in the working chamber; and a quick disconnect bushing removably secured to the rotor hub at the central opening and configured so as to permit a rotationally fixed engagement between the rotor and an output shaft.

The viscous 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:.

A method of assembling a viscous clutch having a housing, a rotor, a working chamber arranged between the housing and the rotor, a reservoir to hold a supply of a shear fluid with the reservoir fluidically connected to the working chamber by a fluid circuit, and a valve, with the valve being actuatable to selectively control a flow of the shear fluid between the reservoir and the working chamber along the fluid circuit, the method can include positioning a shaft in a central opening located in a rotor hub of the rotor, with the shaft extending into the central opening from a rear side of the viscous clutch; and removably securing a quick disconnect bushing to the shaft and the rotor hub to create a rotationally fixed engagement between the rotor and the shaft.

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

A viscous clutch can include a housing having a base, a cover, and a housing hub, where the base, the cover and the housing hub can be connected in a rotationally fixed configuration so as to rotate together; an input device rotationally fixed to the housing, with the input device being a pulley, a sprocket, a gear, or the like; a rotor having a rotor disk and a rotor hub, the rotor disk and the rotor hub can be connected in a rotationally fixed configuration so as to rotate together, and the rotor hub can have a central opening that extends entirely through the rotor hub; a working chamber arranged between the housing and the rotor disk; a reservoir to hold a supply of a shear fluid, the reservoir fluidically connected to the working chamber by a fluid circuit; a valve, actuatable to selectively control a flow of the shear fluid between the reservoir and the working chamber along the fluid circuit such that a torque coupling between the housing and the rotor disk is selectively created based upon a volume of the shear fluid present in the working chamber; a first sensor located rearward of the input device, the first sensor configured to measure a speed of the housing; and a second sensor located rearward of the input device, the second sensor configured to measure a speed of the rotor.

Any relative terms or terms of degree used herein, such as "substantially", "essentially", "generally", "approximately" and the like, should be interpreted in accordance with and subject to any applicable definitions or limits expressly stated herein. In all instances, any relative terms or terms of degree used herein should be interpreted to broadly encompass any relevant disclosed embodiments as well as such ranges or variations as would be understood by a person of ordinary skill in the art in view of the entirety of the present disclosure, such as to encompass ordinary manufacturing tolerance variations, incidental alignment variations, transient alignment or shape variations induced by thermal, rotational or vibrational operational conditions, transitory signal fluctuations, and the like. Moreover, any relative terms or terms of degree used herein should be interpreted to encompass a range that expressly includes the designated quality, characteristic, parameter or value, without variation, as if no qualifying relative term or term of degree were utilized in the given disclosure or recitation.

Claim 1:
A viscous clutch (<NUM>; <NUM>') comprising:
a housing (<NUM>) having a base (<NUM>-<NUM>), a cover (<NUM>-<NUM>), and a housing hub (<NUM>-<NUM>), wherein the base, the cover and the housing hub are connected in a rotationally fixed configuration so as to rotate together;
an input device (<NUM>) rotationally fixed to the housing, wherein the input device is selected from the group consisting of a pulley, a sprocket, and a gear;
a rotor (<NUM>) having a rotor disk (<NUM>-<NUM>), a rotor hub (<NUM>-<NUM>), and a central opening (<NUM>-<NUM>), wherein the rotor disk and the rotor hub are connected in a rotationally fixed configuration so as to rotate together, and wherein the central opening extends entirely through the rotor hub;
a working chamber (<NUM>) arranged between the housing and the rotor disk;
a reservoir (<NUM>) to hold a supply of a shear fluid, the reservoir fluidically connected to the working chamber by a fluid circuit, wherein the reservoir is carried by the housing and is arranged to overlap the input device in an axial direction; and
a valve (<NUM>), wherein the valve is actuatable to selectively control a flow of the shear fluid between the reservoir and the working chamber along the fluid circuit such that a torque coupling between the housing and the rotor disk is selectively created based upon a volume of the shear fluid present in the working chamber, characterized in that it further comprises
a quick disconnect bushing (<NUM>) removably secured to the rotor hub at the central opening and configured so as to permit a rotationally fixed engagement between the rotor and an output shaft (<NUM>).