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 relates to viscous friction clutches including such electromagnetic control systems, as well as methods for manufacturing and using them.

Background Art

[0002] Clutches (also referred to as drives or couplings) are used in various situations to selectively control torque transmission between an input and an output. For example, a fan clutch is used to control the rotation of a fan such as a cooling fan for automotive or industrial applications. Controlling the operation of the cooling fan not only provides all the advantages associated with the cooling flow when the clutch is engaged, but also allows the fan to be stopped when not needed, reducing parasitic losses and improving fuel efficiency. When the cooling fan is stopped, the excess power can be diverted to other uses. In some clutches, instead of a simple on / off alternative, it is possible to control the output speed to selectively vary within a certain range. Full variable clutch control is useful for optimizing performance such as adjusting cooling according to the current state of a cooling fan application.

[0003] Viscous friction clutches (also simply called viscous clutches) are used in a variety of applications, including fan drives in automobiles. These clutches typically use relatively high-viscosity silicone oil (more commonly referred to as shear fluid or viscous fluid) to selectively transmit torque between two rotatable parts. Engagement or disengagement of the clutch is achieved by selectively introducing or releasing the shear fluid into the clutch's working chamber, located between the input and output members (e.g., between the rotor and the housing). In this working chamber, viscous shear coupling by the shear fluid partially transmits torque from the input to the output member. The amount of shear fluid held in the working chamber controls the velocity difference between the primary / input side (input velocity) and the secondary / output side (output velocity) of the clutch. Valve assemblies are used to control the flow of shear fluid introduced into or released from the working chamber.

[0004] Temperature-sensing bimetallic control clutches are known. However, such bimetallic valve control cannot support active control and is therefore unsuitable for some applications (e.g., blower fan applications).

[0005] Solenoid valve control devices that use electromagnetic coils to selectively generate magnetic flux for use in operating valve assemblies are also well known. In typical viscous clutches, all or part of the valve body that controls the flow of shear fluid must be located inside the clutch to regulate the flow of shear fluid introduced into or released into the storage chamber. The electromagnetic coil, on the other hand, is usually located outside the clutch to allow for appropriate external electrical connections. Such typical viscous clutches have a magnetic flux path and / or mechanical connection between the electromagnetic coil and the valve so that the electromagnetic coil operates the valve body while the coil is physically separated from the valve body. However, many conventional viscous clutches have limitations regarding the magnetic flux circuit and / or mechanical connection (e.g., control rods) used for electromagnetic control of the valve assembly. For example, in some clutch designs, while the clutch is disengaged, shear fluid can be stored in a storage chamber that is mounted on or whose rotation is fixed in an input rotor (located inside the housing and always rotating when torque is applied to the clutch). This allows for rapid engagement of the clutch's external output housing from a disengaged and stopped state, and enables the clutch to operate at very low output speeds (e.g., fan speed) when the valve is positioned to limit the amount of shear fluid in the working chamber. However, when the storage chamber is mounted on a rotor disc or the like, the valve body rotates with clutch input, especially when the rotation of the electromagnetic coil is fixed (i.e., not rotating), which significantly limits design freedom. Positioning the valve relative to a rotating storage chamber while providing suitable fluid and magnetic flux paths presents challenging issues, such as the need to seal potential leak paths through which shear fluid may leak. Under these constraints, designers are seeking to provide a relatively small and lightweight clutch package that can handle desired torque loads and function quickly, efficiently, and reliably.

[0006] Patent Document 1 discloses a mechanical connection between an external electromagnetic coil and a valve inside a clutch. Another mechanical connection of a valve assembly is disclosed in Patent Document 2. However, these mechanical connections require additional components to seal against shear fluid leakage from the inside to the outside of the clutch and to electromagnetically control the mechanical connection itself.

[0007] Patent Document 3 describes an insert component embedded in the housing of a clutch for a magnetic flux path connecting the armature and electromagnetic coil of a valve component. However, embedding an iron insert component in a die-cast aluminum housing may cause leakage due to the difference in thermal expansion coefficients between the aluminum housing and the iron insert component. 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 inside of the clutch are disclosed in Patent Documents 5, 6, and 7, and cooling systems for those 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 entirely contained within the housing, or follows multiple separate 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 with any part of the housing, but rather passes back and forth at an internal position within the housing, bypassing the housing). In Cojali's commercial clutches, there is no magnetic flux guide, and the magnetic flux path goes 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 from the valve to the coil without being guided).

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

[0010] Furthermore, depending on the application, a clutch configured to have an "active" central shaft that functions as either an input or output to the clutch is desirable. An "active" central shaft generally refers to a shaft that can rotate during clutch operation, as opposed to a shaft whose rotation is fixed relative to the journal bracket, which is static or whose rotational movement is stationary. An "active" central shaft clutch is useful, for example, in light-load applications. A clutch configured to include an "active" central shaft is even more useful in providing a relatively lightweight and relatively compact clutch package, for example, by potentially eliminating the need for pulleys (or pallets), 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 [Overview of the project] [Problems that the invention aims to solve]

[0012] Thus, it is desirable to provide an electromagnetic control system for a viscous friction clutch, as well as a method for manufacturing and using the same. These aim to reduce or eliminate the need for mechanical connection of the clutch housing and / or insert components of the magnetic flux guide embedded in the housing, while simultaneously providing a relatively small and relatively lightweight clutch package. Furthermore, it is desirable to provide a clutch configuration with an active central shaft. [Means for solving the problem]

[0013] A viscous friction clutch in one embodiment comprises a rotor, a housing rotatable with respect to the rotor, an operating chamber disposed between the rotor and the housing, capable of selectively introducing a predetermined amount of shear fluid to contact both the rotor and the housing, an electromagnetic coil, a valve assembly for controlling the amount of shear fluid introduced into the operating chamber, and a magnetic flux path for magnetically connecting the electromagnetic coil and the valve assembly, wherein the magnetic flux path passes through a magnetic flux guide portion extending through the rotor inside the viscous friction clutch and crosses a magnetic flux gap that traverses both the air gap and the non-magnetic portion of the housing, and passes through a magnetic flux guide portion made of a ferromagnetic material.

[0014] A method for operating a valve assembly by transmitting magnetic flux via a viscous friction clutch in another embodiment is described. The viscous friction clutch comprises a rotor and a housing and a shaft, each of which is fixed to rotate 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 the working chamber. This method comprises the steps of: energizing an electromagnetic coil located outside the housing of the viscous friction clutch and whose rotational movement is stationary; transmitting magnetic flux from the electromagnetic coil to a coil housing surrounding at least a portion of the electromagnetic coil; transmitting magnetic flux from the coil housing to the shaft of the viscous friction clutch across a radial gap; transmitting magnetic flux from the shaft to the armature of the valve assembly across an axial gap in the region affected by the magnetic force; transmitting magnetic flux from the armature to a magnetic flux guide made of a ferromagnetic material across the gap; transmitting magnetic flux along the magnetic flux guide between the front and rear sides of the rotor of the viscous friction clutch that are opposite each other in the axial direction; transmitting magnetic flux from the magnetic flux guide to the coil housing across a magnetic flux gap having a non-ferromagnetic portion of the housing of the viscous friction clutch; and returning magnetic flux from the coil housing to the electromagnetic coil. The magnetic flux guide is made of a ferromagnetic material.

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

[0016] These means are provided as examples only and are not limiting. Other aspects of the present invention will be understood by considering this entire disclosure, including the entire text, the claims, and the accompanying drawings. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a cross-sectional view of one embodiment of the viscous friction clutch according to the present invention. [Figure 2] Figure 2 is a partial cross-sectional view of the viscous friction clutch in Figure 1, with annotations added indicating the magnetic flux path and the region affected by the magnetic force. [Figure 3] Figure 3 is another partial cross-sectional view of a part of the viscous friction clutch of FIGS. 1 and 2. [Figure 4] Figure 4 is a cross-sectional view of the rotor insert assembly alone. [Figure 5] Figure 5 is a front perspective view of the rotor insert assembly of FIG. 4. [Figure 6] Figure 6 is a front perspective view of another embodiment of the rotor insert assembly alone. [Figure 7] Figure 7 is a cross-sectional view of another embodiment of the viscous friction clutch according to the present invention. [Figure 8] Figure 8 is a view in which annotations of the magnetic flux path and the region where the magnetic force acts are added to a partial cross-sectional view of the viscous friction clutch of FIG. 7. [Figure 9] Figure 9 is another partial cross-sectional view of a part of the viscous friction clutch of FIGS. 7 and 8.

[0018] Although the above figures show one or more embodiments of the present invention, as discussed above, other embodiments are also conceivable. In all cases, this disclosure presents the invention as representative and not limiting. Those skilled in the art should understand that numerous other changes and other embodiments within the scope and spirit of the principles of the present invention are possible. The drawings are not necessarily drawn to scale, and the uses and embodiments of the present invention may include features, steps, and / or components not specifically shown in the drawings.

Mode for Carrying Out the Invention

[0019] Generally, embodiments of the present invention provide an electromagnetically controlled system for a viscous friction clutch that can be controlled to selectively transmit torque between a clutch input and a clutch output at a desired speed. Such a viscous friction clutch can be used to selectively drive a cooling fan in a vehicle or to speed-control torque transmission to other devices. The viscous friction clutch may include a valve assembly having a central shaft, a rotor, a housing, a storage chamber, an operating chamber, and an armature actuated by magnetic flux from an electromagnetic coil. The electromagnetic coil can be located outside the viscous friction clutch and its rotation can be fixed, i.e., its movement in the rotational direction can be stationary. In some embodiments, the armature and valve body of the valve assembly can each 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. The central shaft may, in some embodiments, be a “live” central shaft whose rotation is fixed relative to the rotor so as to always rotate together with the rotor at the same speed. The rotor may, in some embodiments, be configured in a disc shape. The storage chamber may be supported by an input to the clutch, such as a rotor, so as to always rotate when there is a torque input to the clutch. In some embodiments, the housing may be a multi-piece assembly including a base and cover surrounding at least a portion of the rotor. Viscous friction may include a rotor insert assembly in a rotor that includes a flux guide portion. The rotor insert assembly serves a variety of functions. A first portion of the rotor insert assembly, at least a portion of which is made of a flux-conducting material such as a ferromagnetic material, acts as a flux path controller or flux guide that guides the flux along a portion of the flux path through the viscous friction clutch (e.g., across or through the rotor), facilitating the electromagnetic control operation of a valve located inside the clutch without incorporating additional flux-conducting insert components into the clutch housing. A second portion of the rotor insert assembly, also called 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 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 magnetic flux guide portion of the rotor insert assembly (which can transmit magnetic flux via a rotor that may be made of a non-ferromagnetic material), and then across the magnetic flux gap 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, and 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 magnetic flux guide portion of the rotor insert assembly, and further across the magnetic flux gap back to the electromagnetic coil. In various embodiments, the magnetic flux gap can traverse a portion of the housing made of a non-ferromagnetic material such as aluminum (such as a portion of the housing base). In some embodiments, a housing cover opening, seals and seal supports, armature stops, and / or other optional components may be further provided. Thus, the disclosed embodiments provide a viscous friction clutch for, for example, driving a cooling fan in a vehicle or controlling the speed of torque transmission to another device, and having an electromagnetic flux path passing through the inside of the clutch. The flux path passes through a ferromagnetic flux guide portion that passes through the rotor inside the clutch, and also passes through both a non-ferromagnetic portion of the housing surrounding at least a portion of the rotor and a flux gap that crosses the air gaps at both ends of the non-ferromagnetic portion of the housing. The flux guide portion can be embedded in or connected to a rotor made of a non-ferromagnetic material. Embodiments of a method for manufacturing and using a viscous friction clutch with an electromagnetic control system are also disclosed and will be apparent to those skilled in the art.

[0020] Further embodiments are conceivable. For example, while the disclosed embodiments show an electromagnetic control system used in a live-center clutch configuration, it will be understood that the electromagnetic control system, rotor insert assembly, and / or related methods are also applicable to other types of clutch configurations. Those skilled in the art will recognize numerous features and advantages by considering the entirety of this disclosure, including the accompanying drawings.

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

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

[0023] As shown in the embodiment in Figure 1, the viscous friction clutch 100 includes an electromagnetic coil 101, a coil housing 102 defining an N pole 102N and an S pole 102S, a rotor insert assembly 103 having a hub portion 104 and a magnetic flux guide portion 105, a rotor 106, a valve assembly 107 (shown in the adsorption position) having an armature 108 and a valve body 109, a shaft 110, a housing 112, a storage chamber 113, a discharge port 114, and an operating chamber 115. Although not specifically shown, the 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] As shown in the illustrated embodiment, the shaft 110 is the "active" central shaft defining the rotation axis CL of the viscous friction clutch 100. The electromagnetic coil 101 is capable of being stationary in rotational motion and can be rotatably mounted on the shaft 110 by a suitable bearing 101X. Furthermore, the coil housing 102 can be rotatably mounted on the shaft 110 using a bearing 101X that also supports the electromagnetic coil 101, and can enclose at least a portion of the electromagnetic coil 101. Both the electromagnetic coil 101 and the coil housing 102 can be positioned outside the housing 112. The shaft 110 may have a mounting function at its rear end. The shaft 110 can function as an input to the viscous friction clutch 100 and receive torque input from a prime mover (not shown), such as an internal combustion engine of a vehicle. In the illustrated embodiment, at least a portion of the shaft 110 is made of a flux-conducting ferromagnetic material.

[0025] At least a portion of the electromagnetic coil 101 is located 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 magnetic flux guide portion 105 (and the base 112b of the housing 112).

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

[0027] In the illustrated embodiment, the rotor insert assembly 103 has a hub portion 104 at a radially inward position and a flux guide portion 105 at a radially outward position (the rotor insert assembly 103 will be further described below in relation to Figures 4 and 5). The hub portion 104 can be positioned on the radially inward portion of the rotor 106 and may be provided as a component for structurally mounting the rotor 106 to the shaft 110. In the illustrated embodiment, the hub portion 104 is a multi-piece assembly including a core 104c and a disk 104d, 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 may include a non-ferromagnetic material such as austenitic stainless steel and / or may be configured to have a flux shielding function that reduces or eliminates magnetic short circuits substantially radially between the flux guide portion 105 and the shaft 110, as will be further described below. In the illustrated embodiment, the core 104c is made of a ferromagnetic material, and the disk 104d is made of a non-ferromagnetic material. The non-ferromagnetic material blocks any flow of magnetic flux along the rotor insert assembly 103 in the radial direction. More generally, the hub portion 104 of the rotor insert assembly 103 in the illustrated embodiment includes a non-ferromagnetic portion, or at least a portion thereof, between its inner diameter and outer diameter.

[0028] The magnetic flux guide portion 105 can be attached to the hub portion 104 on the radially outer portion of the disk 104d. The magnetic flux guide portion 105 extends axially through the rotor 106. The magnetic flux guide portion 105 can be made of a ferromagnetic material so as to conduct magnetic flux through the non-ferromagnetic material of the rotor 106. In the illustrated embodiment, the magnetic flux guide portion 105 has a rear end 105a that projects axially from the rear side of the rotor 106 and assists the magnetic flux to travel to the S pole 102S of the coil housing 102, either in or adjacent to the outer diameter of the coil housing 102, as will be further described below. As in the illustrated embodiment, the rear end 105a of the magnetic flux guide portion 105 overlaps with the S pole 102S of the coil housing 102 in a radial position (so that the magnetic flux path between them can be substantially axial or entirely axial). However, in further embodiments, the rear end 105a can be positioned radially inward from the south pole 102S of the coil housing 102, or in other positions in the radial direction.

[0029] The storage chamber 113 has an internal volume for storing the supplied shear fluid. The outlet 114 allows the shear fluid to flow from the storage chamber 113 to the working chamber 115 and can be selectively covered or uncovered by the valve assembly 107. A return bore (not shown) exits to the storage chamber 113, allowing the shear fluid to be returned to the storage chamber 113 for storage. As in the illustrated embodiment, the storage chamber 113 is supported 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 continuously during periods of torque input to the viscous friction clutch 100. In some embodiments, the magnetic flux guide 105 can be adjacent to and / or constitute at least part of the boundary of the storage chamber 113. As shown in the illustrated embodiment, a storage chamber plate 113a defining a portion of the boundary of the storage chamber 113 is optionally fixed to the rear end 105a of the magnetic flux guide portion 105. The storage chamber plate 113a can be made of a ferromagnetic material and may optionally form a portion of the magnetic flux path. In an alternative embodiment, the storage chamber 113 may optionally further include one or more inner walls, a backflow prevention function or a morning thickness prevention function such as a morning thickness prevention valve.

[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., housing base 112b) is pivotally supported on the shaft 110 by bearings 112X and is rotatable relative to the shaft 110 and also relative to the rotor 106. Since the housing 112 can function as an output of the viscous friction clutch 100, an output device such as a fan (not shown) can be mounted on the housing 112 to receive the torque output that the viscous friction clutch 100 selectively transmits during operation. The housing 112 can be made of a non-ferromagnetic material such as aluminum.

[0031] The working chamber 115 is positioned between the rotor 106 and the housing 112 and, depending on the amount of shear fluid held in the working chamber 115, frictionally contacts both the rotor 106 and the housing 112, thereby transmitting torque between the rotor 106 and the housing 112 at a sliding speed that is largely dependent on the amount of shear fluid held in the working chamber 115. The basic operation of the working chamber in a viscous friction clutch is known in the art.

[0032] The valve assembly 107 includes an armature 108 and a valve body 109. The armature 108 is connected to the valve body 109 and moves the valve body 109 in response to an applied magnetic flux, as will be further described 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 rear side opposite the rotor 106. The valve body 109 is spring-forced in the open position by default, and when an applied magnetic flux generates a valve acting force that exceeds the spring's biasing force, it moves the armature 108 and valve body 109 to the closed position. This is referred to as a “fail-on” configuration, meaning that when power is lost, the spring's biasing force moves the valve assembly 107 back to the default “on” or open position. As shown in the illustrated embodiment, the valve assembly 107, including the armature 108 and valve body 109, is located inside the viscous friction clutch 100 (i.e., inside the housing 112) and is supported by or on the rotor 106. Furthermore, in the illustrated embodiment, the valve body 109 pivots or translates approximately axially during the stroke C (see Figure 3). The stopper 116 is optionally installed on the rotor 106 to restrict the movement of the armature 108 and valve body 109, as well as the stroke C of the valve assembly 107 in the off, open, or disengaged position. The outlet 114 allows shear fluid to flow from the storage chamber 113 to the working chamber 115, and the amount of shear fluid held in the working chamber 115 is regulated by the valve assembly 107 selectively covering or not covering the outlet 114, thereby controlling the operation of the viscous friction clutch 100. While the clutch is operating, the shear fluid is sent back almost continuously from the working chamber 115 to the storage chamber 113 through a return bore (not shown).

[0033] During operation, the electromagnetic coil 101 is selectively excited to generate magnetic flux that travels along the magnetic flux path (or magnetic flux circuit) A through the viscous friction clutch 100, thereby operating the valve assembly 107. Figure 2 schematically shows the magnetic flux path A on one side of the rotation axis CL of the clutch 100 with a dashed line. However, it should be understood that only a portion of the magnetic flux path A is described in Figure 2, and the magnetic flux path A has a three-dimensional shape extending around axis CL. The magnetic flux path A allows the 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 leaves the electromagnetic coil 101 and enters the coil housing 102, and from the north pole 102N of the coil housing 102, it crosses the gap and reaches the shaft 110. The gap between the coil housing 102 and the shaft 110 is constant and is radially arranged in the illustrated embodiment. Next, the magnetic flux can travel across the gap between the shaft 110 and the armature 108 in the region D through which the magnetic force extends. In some embodiments, the magnetic flux may optionally travel through the core 104c of the hub portion 104 of the rotor insert assembly 103, within and / or near the region D through which the magnetic force extends. In some embodiments, the region D through which the magnetic force extends may be located radially outward from the axis of rotation CL. In other embodiments, the region D through which the magnetic force extends may reach the axis of rotation CL. In the illustrated embodiments, the gap between the shaft 110 (and the core 104c) and the armature 108 in the region D through which the magnetic force extends is axially oriented. The dimensions of the gap between the shaft 110 (and the core 104c) and the armature 108 change in accordance with the movement of the armature 108 during the operation of the clutch 100. The distance of the gap between the armature 108 and the shaft 110 (and core 104c) corresponds to the stroke C of the valve assembly 107 (see Figure 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 makes physical contact with the shaft 110 and / or core 104c) while energizing the electromagnetic coil 101.The magnetic flux path A extends from the armature 108 through the gap F (see Figure 3) to the magnetic flux guide portion 105 of the rotor insert assembly 103. In the illustrated embodiment, the radially positioned gap F (located on the outer diameter of the armature 108) is constant. A constant radial gap F allows for a constant flow of magnetic flux, regardless of the open / closed position of the armature 108. A constant flow of magnetic flux in magnetic flux path A helps improve the internal magnetic force to the armature 108. Next, magnetic flux path A passes through the magnetic flux guide portion 105 of the rotor insert assembly 103 and then through the entire rotor 106 from the front to the opposite rear in the axial direction. Next, magnetic flux path A continues from the magnetic flux guide portion 105 of the rotor insert assembly 103 across the magnetic flux gap B (see Figure 3) to the south pole 102S of the coil housing 102, and then returns to the electromagnetic coil 101.

[0034] As shown in the illustrated embodiment, the flux gap B is axially oriented and is larger than the other gaps in the flux path A. The flux gap B can be constant. The flux gap B traverses a portion 112b-1 of the housing 112, as well as the air gaps at both axial ends of the housing 112. More specifically, the flux gap B axially crosses the non-ferromagnetic portion 112b-1 of the base 112b of the housing 112. This non-ferromagnetic portion 112b-1 contains no embedded flux guide inserts or other ferromagnetic components in or near the flux path A that passes through the housing 112 completely (or partially) between the inside and outside of the housing 112. In other words, in some embodiments, since there is no ferromagnetic material in the flux gap B, it can be referred to as a non-ferromagnetic flux gap. The magnetic flux path A can traverse the magnetic flux gap B and pass through or across a portion 112b-1 of the housing 112, and through one or more adjacent voids and the retained shear fluid, without requiring a ferromagnetic flux guide, which could potentially create undesirable leakage paths for shear fluid due to the different thermal expansion coefficients of the ferromagnetic material and the adjacent non-ferromagnetic material (e.g., between iron and aluminum). In various embodiments, the number of voids within the magnetic flux gap B can be limited to two or fewer, and the portion 112b-1 of the housing 112 may be the only non-ferromagnetic component through which the magnetic flux path A intersects within the magnetic flux gap B. In some embodiments, the dimension of the magnetic flux gap B between the rear end 105a of the magnetic flux guide portion 105 and the S pole 102S of the coil housing 102 may be smaller than the distance between the rear end 105a of the magnetic flux guide portion 105 and other adjacent ferromagnetic materials. In yet another embodiment, the axial dimension of the magnetic flux gap B between the rear end 105a of the magnetic flux guide portion 105 and the coil housing 102 may be smaller than the distance between the rear end 105a of the magnetic flux guide portion 105 and other nearby ferromagnetic materials, either in the axial or radially inward direction.Furthermore, in the illustrated embodiment, since the magnetic flux guide portion 105 penetrates the rotor 106 and protrudes rearward, the dimension of the magnetic flux gap B between the rear end 105a of the magnetic flux guide portion 105 and the S pole 102S of the coil housing 102 can be smaller than the distance between the rear side of the rotor 106 and the S pole 102S 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 105a of the magnetic flux guide portion 105 and the S pole 102S of the coil housing 102 can be smaller than the axial distance between the S 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 from the working chamber 115. Note that even if a ferromagnetic material is placed radially outside of the magnetic flux path A, a short circuit of path A will not occur. Therefore, in some embodiments, a ferromagnetic material (e.g., a storage chamber plate 113a made of a ferromagnetic material) can be positioned radially outward from the flux path A, close to or in physical contact with the flux guide portion 105, without significantly affecting the properties of the flux path A in or near the flux gap B. Because the linear distance of the flux gap B is relatively short (although it may be larger than other gaps in the flux path A), there is no need to add any iron insert components embedded in the housing 112. In the illustrated embodiment, the non-ferromagnetic portion 112b-1 of the housing 112 that is included in (and across by) the flux gap B is positioned radially outward from the bearing 112X that supports the housing 112 in the rotational direction on the shaft 110, such that the bearing 112X is located inside the flux path A. Furthermore, in the illustrated embodiment, the bearing 101X that supports the electromagnetic coil 101 and the coil housing 102 on the shaft 110 is also located inside the flux path A.

[0035] To guide the 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 having specific defined characteristics. One embodiment, shown separately in Figures 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. Thus, the magnetic flux guide portion 105 and core 104c, each made of a ferromagnetic material, and the disk 104d, made of a non-ferromagnetic material, can be separate components that engage or connect with each other and are embedded in or otherwise connected to a rotor 106 made of a non-ferromagnetic material, such as by using a die-casting process. The core 104c made of a ferromagnetic material can help improve the performance of the magnetic flux path A. In an alternative embodiment, the core 104c and disk 104d of the hub portion 104 may be a single component made of a non-magnetic material. Embodiments of the rotor insert assembly 103 shown in Figures 4 and 5 also include cuts 118a, 118b, and 118c, which may constitute openings in the hub portion 104 and / or the magnetic flux guide portion 105. In the illustrated embodiment, a plurality of U-shaped cuts 118a, spaced equally in the circumferential direction, extend continuously through the magnetic flux guide portion 105 radially to the front end (opposite the rear end 105a) and open axially forward. A plurality of U-shaped cuts 118b are located on the outer diameter of the disk 104d of the hub portion 104, aligned with the cuts 118a to form a combined opening, and extend continuously to the outer diameter of the disk 104d. Finally, the cuts 118c are a plurality of circular holes spaced equally in the circumferential direction, which axially penetrate the center of the disk 104d. However, in further embodiments, the breaks 118a, 118b, and / or 118c can have other shapes and arrangements. After being fully mounted to the viscous friction clutch 100, the breaks 118a, 118b, and / or 118c can be filled, at least in part, with the nonferromagnetic material of the rotor 106.More specifically, in some embodiments, the cuts 118b and 118c may be completely filled with the nonferromagnetic material of the rotor 106, while the cuts 118a may be only partially filled with the nonferromagnetic material of the rotor 106.

[0036] Alternatively, as shown in Figure 6, the flux guide portion 105' and hub portion 104' of the rotor insert assembly 103' can be fabricated as a single, integrated monolithic component made of ferromagnetic material, and by having flux blocking functions such as openings 118' located in the hub portion 104' (and optionally in the flux guide portion 105' in further embodiments), magnetic short circuits between the flux guide portion 105' and the hub portion 104' (and shaft 110) can be reduced or avoided. In the illustrated embodiment, the flux guide portion 105' has a non-breakable configuration and no openings, etc. The flux blocking functions (openings 118') are preferably as numerous and large as possible. After being fully mounted on the viscous friction clutch 100, the openings 118' of the hub portion 104' (and / or the flux guide portion 105') etc. are filled with the non-ferromagnetic material of the rotor 106 for torque transmission between the rotor 106, the hub portion 104', and the flux guide portion 105'. Alternatively, rotor insert assembly 103' is the same as rotor insert assembly 103 described above and functions essentially the same.

[0037] Figures 7 to 9 show another embodiment of the viscous friction clutch 200. Figure 7 is a cross-sectional view of another 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 region D to which the magnetic force extends, and Figure 9 is a partial cross-sectional view of a portion of the viscous friction clutch 200. In general, the embodiments of the viscous friction clutch 200 shown and described in Figures 7 to 9 are similar to the embodiments of the viscous friction clutch 100 described in Figures 1 to 6. Therefore, the same reference numerals, usually with 100 added, are used. More specifically, the viscous friction clutch 200 as shown in the embodiments of Figures 7 to 9 comprises an electromagnetic coil 201, a coil housing 202 defining an N pole 202N and an S pole 202S, a rotor insert assembly 203 having a hub portion 204 and a magnetic 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 storage chamber 213 (having a storage chamber cover 213a), a discharge port 214, an operating chamber 215, and a rotating shaft CL. Although not specifically shown, the viscous friction clutch 200 further includes suitable return bore and pump components. The magnetic flux path A' includes the magnetic flux gap B, the valve assembly stroke C, and the region D over which the magnetic force extends, which may be similar to or identical to those of the viscous friction clutch 100 in the viscous friction clutch 200. However, the embodiments of the viscous friction clutch 200 shown in Figures 7 to 9 differ from the clutch 100 in terms of the design around the shaft 210.

[0038] As shown in Figures 7 to 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 may open axially forward, as in the illustrated embodiment. The rim of the shaft 210 surrounding the blind hole 220 at the front end 210F of the shaft 210 efficiently transmits magnetic flux from the shaft 210 to the armature 208 along the magnetic flux path A. The blind hole 220 of the shaft 210 provides the option to use a torque or tooling function 223 (e.g., a tool engagement function such as a Torx® bit engagement function) at the front end 210F of the shaft 210 (e.g., the rear or bottom of the blind hole 220), which facilitates mounting the rear end 210R of the shaft 210 to a corresponding component (not shown) with another connection function such as a thread 210t. In the illustrated embodiment, the front end 210F of the shaft 210 and the blind hole 220 are located inside 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 passages to the blind hole 220 and the torque function or tooling function 223. A corresponding central hole 208h can be provided in the armature 208 to enable operation of the blind hole 220 and / or the torque function 223. To protect the internal components of the viscous friction clutch 200 from debris, a removable cap (not shown) can be provided in or inside the opening 228 in the cover 212c of the housing 212. The engagement of the cap 228a with the cover 212c of the housing 212 can be enabled by including suitable features such as engagement grooves in the structure of the opening 228 or its vicinity.

[0039] The carrier 222 is engageable with a blind hole 220 by a connecting function 222c (e.g., a screw thread) that attaches the carrier 222 to the shaft 210, and the connecting function 222c can be located inside the blind hole 220. The carrier 222 may further include tooling functions 222t, such as a flat or slot, to accept a tool bit, screwdriver, or other suitable tool to which torque can be applied. By making the carrier 222 from a non-ferromagnetic material, the carrier 222 can be isolated from the magnetic flux path A, or at least interference with the magnetic flux path A can be avoided. The carrier 222 may extend axially from the shaft 210 through the central hole 208h of the armature 208. The carrier 222 may further include an opening 222a, such as a central opening that extends axially through completely between its ends, to enable the operation of a torque or tooling function 223. This allows a tool to be inserted from the front of the viscous friction clutch 200 through the opening 228 in the cover 212c of the housing 212 (and through the central hole 208h of the armature 208). Furthermore, the carrier 222 is capable of supporting and bearing sealing components 229 (e.g., bearings such as dynamic seals or sealed bearing sets) that contact the housing 212, and helps prevent leakage of shear fluid by sealing against the cover 212c of the housing 212 at the opening 228. In addition, a stopper 230 can be installed on the carrier 222 on the side of the armature 208 opposite the shaft 210. The stopper 230 can limit the stroke C of the valve assembly 207, and in particular, the stopper 230 can limit the axial movement of the armature 208 and valve body 209 under the default spring biasing force. In the illustrated embodiment, the stopper 230 is a flange extending radially outward from the body of the carrier 222.

[0040] The rotor 206 can be fixed in rotation relative to the shaft 210 so that the rotor 206 and the shaft 210 rotate together at the same speed. The housing 212 (e.g., housing base 212b) is supported in the rotational direction on the shaft 210 by suitable bearings 212X and is rotatable relative to the shaft 210 and the rotor 206. The electromagnetic coil 201 and coil housing 202 can be fixed in rotation and can both be mounted on the shaft 210 by suitable bearings 201X with the electromagnetic coil 201 and coil housing 202 positioned outside the housing 212.

[0041] The electromagnetic coil 201 may have an L-shaped cross-section, similar to that disclosed in Patent Document 8. An L-shaped electromagnetic coil 201, 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 housed in a coil housing 202. The coil housing 202 can surround at least a portion of the electromagnetic coil 201 and can be shaped to conform to 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), an intermediate portion 202M located axially rearward (having a U-shape or C-shape), and a north pole 202N located axially forward of the intermediate 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 intermediate portion 202M and the north pole 202N of the coil housing are shaped to provide space for bearings.

[0042] The working chamber 215 is located between the rotor 206 and the housing 212, and is positioned such that the amount of shear fluid held within the working chamber 215 allows for frictional contact with both the rotor 206 and the housing 212, enabling torque transmission between the rotor 206 and the housing 212 at a slip speed that is largely dependent on the amount of shear fluid held within the working chamber 215. The rotor 206 and shaft 210 can function as inputs 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 torque output from the viscous friction clutch 200.

[0043] The valve assembly 207 operates in response to the applied magnetic flux to selectively cover or uncover the outlet 214, thereby regulating the amount of shear fluid in the working chamber 215. Unused shear fluid can be stored in the storage chamber 213. In the illustrated embodiment, the valve assembly 207 is located on the front side of the rotor 206, while the electromagnetic coil 201 and the storage chamber 213 are located on the rear side opposite the rotor 206, respectively.

[0044] In the illustrated embodiment, the rotor insert assembly 203 has a hub portion 204 at a radially inward position and a flux guide portion 205 at a radially outward position (see also Figures 4 and 5). The hub portion 204 can be positioned in the radially inward portion of the rotor 206 and can accommodate structural mounting components between the rotor 206 and the shaft 210. In the illustrated embodiment, the hub portion 204 is a multi-piece assembly including a core 204c and a disk 204d, the disk 204d extending radially outward from the core 204c. The core 204c can be positioned directly on the shaft 210. The hub portion 204 may include a non-ferromagnetic material such as austenitic stainless steel and / or may be configured to have a flux shielding function that reduces or eliminates substantially radial magnetic short circuits between the flux guide portion 205 and the shaft 210, as described above for the previous embodiments. In the illustrated embodiment, the core 204c is made of a ferromagnetic material and the disk 204d is made of a non-ferromagnetic material, blocking the radial flow of magnetic flux along the rotor insert assembly 203. More generally, the hub portion 204 of the rotor insert assembly 203 in the illustrated embodiment includes a non-ferromagnetic portion or at least a portion of a non-ferromagnetic portion between its inner and outer diameters.

[0045] The magnetic flux guide portion 205 can be attached to the hub portion 204 on the radially outer portion of the disk 204d. The magnetic flux guide portion 205 extends axially through the rotor 206. The magnetic 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 magnetic 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, either on or adjacent to the outer diameter of the coil housing 202, as will be further described below. This helps to guide the 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 magnetic flux guide portion 205 is positioned to coincide with the radial position of the south pole 202S of the coil housing 202 (so that the magnetic flux path between them is completely blocked). However, in further embodiments, other relative radial positions can be positioned.

[0046] Similar to the operation of the viscous friction clutch 100 described above, during operation, the electromagnetic coil 201 is selectively excited to generate magnetic flux that travels through the viscous friction clutch 200 along the magnetic flux path (or magnetic flux circuit) A', thereby operating the valve assembly 207. Figure 8 schematically shows the magnetic flux path A' on one side of the rotation axis CL of the clutch 200 with a dashed line. However, it should be understood that only a portion of the magnetic flux path A' is described in Figure 8, and the magnetic flux path A has a three-dimensional shape extending around axis CL. The magnetic flux path A' allows the magnetic flux to travel 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' leaves the electromagnetic coil 201 and enters the coil housing 202, and from the N pole 202N of the coil housing 202, it crosses the gap and reaches the shaft 210. The gap between the coil housing 202 and the shaft 210 is constant and is radially arranged in the illustrated embodiment. Next, the magnetic flux can travel across the gap between the shaft 210 and the armature 208 in the region D through which the magnetic force extends. In some embodiments, the magnetic flux may optionally travel through the core 204c of the hub portion 204 of the rotor insert assembly 203, within and / or near the region D through which the magnetic force extends. In some embodiments, the region D through which the magnetic force extends may be located radially outward from the axis of rotation CL. In other embodiments, the region D through which the magnetic force extends may reach the axis of rotation CL. In the illustrated embodiments, the gap between the shaft 210 (and the core 204c) and the armature 208 in the region D through which the magnetic force extends is axially oriented. The dimensions of the gap between the shaft 210 (and the core 204c) and the armature 208 change in accordance with the movement of the armature 208 during the operation of the clutch 200. The distance of the gap between the armature 208 and the shaft 210 (and core 204c) corresponds to the stroke C of the valve assembly 207 (see Figure 9). In some embodiments, the magnetic flux can attract the armature 208 to the shaft 210 so that the gap between the armature 208 and the shaft 210 is completely closed (i.e., the armature 208 makes physical contact with the shaft 210 and / or core 204c) while energizing the electromagnetic coil 201.The magnetic flux path A' extends 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 positioned gap F (located on the outer diameter of the armature 208) is constant. A constant radial gap F allows for a constant flow of magnetic flux, regardless of the open / closed position of the armature 208. A constant flow of magnetic flux in the magnetic flux path A' helps improve the internal magnetic force to the armature 208. Next, the magnetic flux path A' continues through the magnetic flux guide portion 205 of the rotor insert assembly 203, passing through the entire rotor 206 from the front to the opposite rear in the axial direction. Then, from the magnetic flux guide portion 205 of the rotor insert assembly 203, the magnetic flux path A' continues across the magnetic flux gap B to the south pole 202S of the coil housing 202, and then returns to the electromagnetic coil 201.

[0047] As shown in the illustrated embodiment, the flux gap B is axially positioned and is larger than the other gaps in the flux path A'. The size of the flux gap B can be constant. The flux gap B traverses a portion 212b-1 of the housing 212, as well as the air gaps at both axial ends of the housing 212. More specifically, the flux gap B axially crosses the non-ferromagnetic portion 212b-1 of the base 212b of the housing 212. This non-ferromagnetic portion 212b-1 does not contain any embedded flux guide inserts or other ferromagnetic components in or near the flux path A' that passes through the housing 212 completely (or partially) between the inside and outside of the housing 212. In other words, the flux gap B can be referred to as a gap of non-ferromagnetic flux. The flux path A' can pass through the flux gap B and through or across a portion 212b-1 of the housing 212, as well as through one or more adjacent gaps and the retained shear fluid, without requiring a ferromagnetic flux guide that could potentially create an undesirable leakage path for the shear fluid. In various embodiments, the number of gaps within the flux gap B can be limited to two or fewer, and the portion 212b-1 of the housing 212 may be the only non-ferromagnetic component through which the flux path A' intersects within the flux gap B. In some embodiments, the dimension of the flux gap B between the rear end 205a 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 end 205a of the flux guide portion 205 and other nearby ferromagnetic materials. In yet another embodiment, the axial dimension of the magnetic flux gap B between the rear end 205a of the magnetic flux guide portion 205 and the coil housing 202 may be smaller than the distance between the rear end 205a of the magnetic flux guide portion 205 and other nearby ferromagnetic materials, either in the axial or radially inward direction. Also, in the illustrated embodiment, since the magnetic flux guide portion 205 protrudes rearward through the rotor 206, the dimension of the magnetic flux gap B between the rear end 205a of the magnetic flux guide portion 205 and the S pole 202S of the coil housing 202 may be smaller than the distance between the rear side of the rotor 206 and the S pole 202S of the coil along the magnetic flux path A'.In some embodiments, the axial distance of the flux gap B between the rear end 205a of the flux guide portion 205 and the south pole 202S of the coil housing 202 can 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 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 across by) the flux gap B is positioned radially outward from 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 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 flux path A'.

[0048] It should be noted that in various embodiments, depending on the requirements of a particular application, either the rotor insert assemblies 103 and 103' discussed above and shown in Figures 4 to 6 may be used in the viscous friction clutch 200. Furthermore, other embodiments of the rotor insert assemblies are also possible.

[0049] Considering the entirety of this disclosure, including the accompanying drawings, a person skilled in the art will recognize that the disclosed embodiments of the viscous friction clutch offer many advantages and benefits. For example, the disclosed embodiments provide an electromagnetically controlled viscous friction clutch that is relatively lightweight and relatively easy to manufacture. This clutch transmits magnetic flux across or through the non-ferromagnetic portion of the housing, while not including a magnetic 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 outer diameter, or having at least a portion of a non-ferromagnetic portion, can be used to reduce or minimize magnetic short circuits or short circuits in the electromagnetic flux path through the viscous friction clutch and help increase the magnetic force available to move the armature of a valve assembly, even when there is no magnetic flux insert component embedded in the housing. Note that in some known clutch designs, the magnetic flux path does not pass through the housing; however, instead, the magnetic flux path is either entirely contained within the housing, or follows multiple magnetically isolated paths within the shaft, rotor hub, and / or bearing assembly located radially inward from the housing (i.e., the magnetic flux path does not pass through any part of the housing, but rather bypasses it). A magnetic flux path entirely contained within the housing is generally associated with a fixed (i.e., non-rotating) journal bracket shaft, whereas embodiments of this disclosure disclose a “live” shaft or a driven shaft. Also, having multiple magnetically isolated paths within the shaft, rotor hub, and / or bearing assembly tends to increase the radial dimensions of the entire clutch and may make manufacturing more complex, whereas embodiments of this disclosure may use a shaft that can be a single monolithic part without embedded insert components or embedded magnetic isolation insert components. Furthermore, in certain conventional clutches, the absence of a magnetic flux guide means that the magnetic flux is transmitted inefficiently without and / or through various clutch components, or across them. As a result, a relatively large electromagnetic coil is required to generate sufficient magnetic flux to overcome such inefficiencies.For example, such conventional clutches may require a magnetic flux across a single flux gap that includes three or more air gaps and multiple separate nonferromagnetic components. In contrast, embodiments of the present disclosure allow for limiting the number of air gaps in the flux gap that cross the nonferromagnetic portion of the housing.

[0050] <Discussion of possible embodiments> A viscous friction clutch may include a rotor, a housing rotatable relative to the rotor, an operating chamber positioned between the rotor and the housing, in which a predetermined amount of shear fluid can be selectively introduced to contact both the rotor and the housing, an electromagnetic coil, a valve assembly for controlling the amount of shear fluid held in the operating chamber, and a magnetic flux path for magnetically connecting the electromagnetic coil and the valve assembly, wherein the magnetic flux path passes through a magnetic flux guide portion extending through the rotor inside the viscous friction clutch and crosses a magnetic flux gap that traverses both the air gap and the non-magnetic portion of the housing, and passes through a magnetic flux guide portion made of ferromagnetic material.

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

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

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

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

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

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

[0057] A portion of the magnetic flux guide can protrude axially from the rotor at a position adjacent to the outer diameter of the electromagnetic coil housing separated by the magnetic flux gap, and at least a portion of the electromagnetic coil is located inside the electromagnetic coil housing.

[0058] The rear end of the magnetic flux guide portion is capable of extending axially behind the working chamber.

[0059] The electromagnetic coil can be at least partially positioned within the electromagnetic coil housing, and the rear end of the magnetic flux guide portion can project axially from the rear end of the rotor such that the magnetic flux gap between the rear end of the magnetic 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 does not need to include an embedded insert portion for the ferromagnetic flux guide in the magnetic flux path passing between the inside and outside of the housing.

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

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

[0063] The end of the shaft inside the viscous friction clutch may have a blind hole that extends axially.

[0064] A carrier with a blind hole for the shaft.

[0065] The carriers can consist of non-magnetic materials.

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

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

[0068] The carrier may also have touring capabilities.

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

[0070] The shaft may have a tooling function located within a blind hole.

[0071] The housing cover may include openings that allow the shaft and tooling functions to be operated with tools.

[0072] A cap may be further provided at or inside the opening of the housing cover.

[0073] At least a portion of the electromagnetic coil can be placed inside a coil housing, which may have two opposing magnetic poles and an intermediate portion between those poles.

[0074] One magnetic pole extends radially, while the other magnetic pole can extend axially.

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

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

[0077] A storage chamber supported by a rotor.

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

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

[0080] A bearing that supports the housing in the rotational direction on the shaft. This bearing is located inside the magnetic flux path.

[0081] A method for operating a valve assembly by transmitting magnetic flux via a viscous friction clutch, the viscous friction clutch comprising a rotatable rotor and housing, respectively, and a shaft whose rotation relative to the rotor is fixed, and selectively controlling the degree of viscous friction engagement between the rotor and the housing by controlling the amount of shear fluid held in the working chamber of the valve assembly. This method comprises the steps of: energizing an electromagnetic coil located outside the housing of a viscous friction clutch and whose rotational movement is stationary; transmitting magnetic flux from the electromagnetic coil to a coil housing surrounding at least a portion of the electromagnetic coil; transmitting magnetic flux from the coil housing to the shaft of the viscous friction clutch across a radial gap; transmitting magnetic flux from the shaft to the armature of a valve assembly across an axial gap in the region affected by the magnetic force; transmitting magnetic flux from the armature to a magnetic flux guide made of a ferromagnetic material across the gap; transmitting magnetic flux along the magnetic flux guide between the front and rear sides of the rotor of the viscous friction clutch that are opposite each other in the axial direction; transmitting magnetic flux from the magnetic flux guide to the coil housing across a magnetic flux gap having a non-ferromagnetic portion of the housing of the viscous friction clutch; and returning magnetic flux from the coil housing to the electromagnetic coil.

[0082] The methods described in the preceding paragraph may optionally include, additionally and / or alternatively, one or more of the following features, configurations, and / or additional steps:

[0083] A step in which magnetic flux is transmitted through the core of the hub portion embedded in the rotor.

[0084] The gap between the armature and the magnetic flux guide can be constant and radially positioned.

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

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

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

[0088] The magnetic flux gap between the magnetic flux guide and the coil housing can have the maximum distance in the magnetic flux path that magnetically connects the electromagnetic coil and the armature of the valve assembly.

[0089] The non-ferromagnetic portion of the housing included in the magnetic flux gap may be positioned radially outward from the bearing that supports the housing in the rotational direction on the shaft.

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

[0091] <Summary> Relative terms or terms expressing degree, such as “substantially,” “essentially,” “generally,” and “approximately,” used herein should be interpreted in accordance with the applicable definitions or limitations expressly stated herein. Furthermore, in all examples, relative terms or terms expressing degree used herein should be interpreted to broadly encompass the scope or variations that can be understood by those skilled in the art by referring to the relevant disclosed embodiments and the entirety of this specification. This disclosure includes, for example, variations in normal manufacturing tolerances, accidental changes in alignment, transient changes in alignment or shape induced by operating conditions of heat, rotation, or vibration, and transient variations in electromagnetic fields. Moreover, relative terms or terms expressing degree used herein should be interpreted to encompass the scope expressly included without altering the specified quality, feature, parameter, or value, as in cases where relative terms or terms expressing degree are 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 understand that the form and details can be modified without departing from the spirit and scope of the invention. For example, although it has been disclosed that flux-conducting ferromagnetic housing insert components are not required for the electromagnetic control of the viscous friction clutch, it is conceivable that alternative embodiments could still include such ferromagnetic housing insert components, whether for part of an electromagnetic control system or for one or more other purposes. Furthermore, in another embodiment, the valve assembly can be positioned behind the rotor or mounted in the housing. Furthermore, in yet another embodiment, valve assemblies using control rods, such as a valve assembly that is fully positioned inside the viscous friction clutch and has one or more control rods passing through the rotor disk, are available in the invention. Furthermore, the positions of the north and south poles of the coil housing can be reversed or swapped as needed in various embodiments.

Claims

1. A rotor, a housing rotatable relative to the rotor, an operating chamber disposed between the rotor and the housing, the operating 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 the shear fluid held in the operating chamber, a viscous friction clutch comprising a magnetic flux path magnetically connecting the electromagnetic coil and the valve assembly, wherein the magnetic flux path passes through a magnetic flux guide portion made of a ferromagnetic material extending through the rotor inside the viscous friction clutch and passes through a magnetic flux gap crossing both the air gap portion and the non-magnetic portion of the housing.

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

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

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

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

6. The viscous friction clutch according to claim 1, wherein a part 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 at least a part of the electromagnetic coil is disposed inside the electromagnetic coil housing.

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

8. The viscous friction clutch according to claim 1, wherein the housing does not include an embedded insert component of a ferromagnetic magnetic flux guide in the magnetic flux path passing between the inside and the outside of the housing.

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

10. The viscous friction clutch according to claim 1, further comprising a shaft, wherein the shaft is fixed against rotation with respect to the rotor, and an end portion of the shaft inside the viscous friction clutch has a blind hole extending axially.

11. A carrier attached to the blind hole and made of a non-magnetic material, The viscous friction clutch according to claim 10, further comprising a sealing component held by the carrier and in contact with the housing.

12. The viscous friction clutch according to claim 11, wherein the carrier has a central opening extending axially through the carrier.

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

14. The viscous friction clutch according to claim 11, wherein the shaft has a two-ring function disposed in the blind hole.

15. The viscous friction clutch according to claim 14, wherein a cover of the housing includes an opening enabling the shaft and the two-ring function to be operable with a tool.

16. Further comprising a coil housing, At least a part of the electromagnetic coil is disposed in the coil housing, the coil housing has two opposite magnetic poles and an intermediate portion between the magnetic poles, one of the magnetic poles extends radially, and the other of the magnetic poles extends axially, the viscous friction clutch according to claim 1.

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

18. The viscous friction clutch according to claim 1, wherein the ferromagnetic magnetic flux guide portion extends axially through the rotor between a rear side opposite to a front side of the rotor.

19. Further comprising a storage chamber carried by the rotor, The viscous friction clutch according to claim 1, wherein the rotor acts as an input to the viscous friction clutch, and whenever there is a torque input to the viscous friction clutch, both the rotor and the storage chamber rotate at an input speed.

20. The viscous friction clutch according to claim 1, further comprising a shaft whose rotation with respect to the rotor is fixed, and a bearing that supports the housing in the rotational direction on the shaft, wherein the bearing is disposed inside 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 rotor and a housing each rotatable, and a shaft whose rotation with respect to the rotor is fixed, and selectively controlling the degree of viscous frictional engagement between the rotor and the housing by controlling the amount of shear fluid in which the valve assembly is held in the working chamber. A step of energizing an electromagnetic coil disposed outside the housing of the viscous friction clutch and having a stationary movement in the rotational direction. A step of transmitting magnetic flux from the electromagnetic coil to a coil housing surrounding at least a part of the electromagnetic coil. A step of transmitting magnetic flux from the coil housing to the shaft of the viscous friction clutch across a radial gap. A step of transmitting magnetic flux from the shaft to the armature of the valve assembly across an axial gap in a region where the magnetic force acts. A step of transmitting magnetic flux from the armature across a gap to a magnetic flux guide portion made of a ferromagnetic material. A step of transmitting magnetic flux along the magnetic flux guide portion between the front side and the rear side on the opposite axial side of the rotor of the viscous friction clutch. A step of transmitting magnetic flux from the magnetic flux guide portion to the coil housing across a magnetic flux gap having a non-ferromagnetic portion of the housing of the viscous friction clutch. A method comprising a step of returning magnetic flux from the coil housing to the electromagnetic coil.

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

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

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

25. The magnetic flux gap between the magnetic flux guide portion and the coil housing is arranged axially and crosses two gaps on both axial sides of the non-ferromagnetic portion of the housing of the viscous friction clutch, the method according to claim 21.

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

27. The magnetic flux gap between the magnetic flux guide portion and the coil housing has a maximum interval in the magnetic flux path magnetically connecting the electromagnetic coil and the armature of the valve assembly, the method according to claim 21.

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

29. The interval of the magnetic flux gap between the rear end of the magnetic flux guide portion and the coil housing is narrower than the interval between the rear side of the rotor along the magnetic flux path magnetically connected to the electromagnetic coil and the armature of the valve assembly and the coil housing, the method according to claim 21.

Images