VISCOUS CLUTCH WITH FLUID RETURN BORE THROUGH ROTOR |
|||||||
申请号 | EP15178811.4 | 申请日 | 2013-09-20 | 公开(公告)号 | EP2977636B1 | 公开(公告)日 | 2018-08-29 |
申请人 | Horton, Inc.; | 发明人 | Schmidt, Thomas; Brand, Bastian; Miller, Scott; | ||||
摘要 | The present invention relates to a viscous clutch (20) comprising a housing assembly (28), a rotor assembly (26), a reservoir (38) to hold a supply of a shear fluid, a working chamber (40) operatively positioned between the housing assembly (28) and the rotor assembly (26), wherein selective introduction of the shear fluid to the working chamber (40) facilitates selective torque transmission between the housing assembly (28) and the rotor assembly (26), and a fluid return bore (26-1B) that extends radially through at least an outer diameter portion of the rotor assembly (26) to the working chamber (40), the fluid return bore (26-1B) forming at least a portion of a fluid return path from the working chamber (40) to the reservoir (38). | ||||||
权利要求 | |||||||
说明书全文 | The present invention relates to clutches, and more particularly to viscous clutches. Viscous clutches are used in a wide variety of automotive applications, such as to drive fans, pumps and the like, as well as in other contexts. These clutches typically employ relatively thick silicone oil (generally called shear fluid or viscous fluid) for the selective transmission of torque between two rotatable components. It is possible to engage or disengage the clutch by selectively allowing the oil into and out of a working area of the clutch located between input and output members. In a typical viscous clutch, the rotational input is a rotor disk connected to a drive shaft or pulley, and the rotational output is a housing or cover that can be connected to a fan, pump, shaft or other output element. A valve is used to control the flow of the oil through the working area between the input and the output. It has become common for the clutch to be controlled electrically. This has been done to increase the controllability of the clutch, and to also have the clutch capable of responding to multiple cooling needs in a vehicle, such as to respond to coolant temperature, intake air temperature, air conditioning pressure, and/or oil temperature. Viscous clutches have been used in the past as a separate device installed on a rotating pulley on the engine front. Rotational inputs to the clutch have been traditionally been engine crankshafts and water pumps. During the past decade, cooling requirements have been increasing as a result of increasingly stringent engine emission reduction requirements. During this time, the use of a belted pulley has become a more common method of providing an input to the fan clutch, with the belted pulley (synonymously called a sheave) capable of increasing the fan speed in order to obtain more cooling air flow for a vehicle's heat exchanger(s). The belted drive is desirable due to its simplicity, low cost and ease of obtaining desired rotational speed. Due to the rotational input to the fan clutch being separated from the water pump or crankshaft, it is possible for the cooling system engineer to choose the exact fan speed required to provide the necessary and desired cooling for a given application. Examples of viscous clutches include those disclosed in commonly-assigned It is therefore desired to provide an alternative clutch design that is suitable for use with relatively high input speeds and torque loads, has relatively low mass, and provides relatively good heat dissipation, among other possible features and benefits. In addition, or in the alternative, it is desired to provide an alternative clutch design that is adaptable to a variety of applications without the need for extensive customization and whole-clutch re-design, among other possible features and benefits. The present invention relates to a viscous clutch and a method for selective torque transmission, as defined in independent claims 1 and 12, respectively. The viscous clutch according to the invention includes a housing assembly, a rotor assembly, a reservoir to hold a supply of a shear fluid, a working chamber operatively positioned between the housing assembly and the rotor assembly, and a fluid return bore that extends radially through at least an outer diameter portion of the rotor assembly to the working chamber. Selective introduction of the shear fluid to the working chamber facilitates selective torque transmission between the housing assembly and the rotor assembly. The fluid return bore forms at least a portion of a fluid return path from the working chamber to the reservoir. The viscous clutch may comprise a pump bore insert having a bore in fluid communication with a fluid return path extending from the working chamber to the reservoir. Persons of ordinary skill in the art will recognize that other aspects and embodiments of the present invention are possible.
While the above-identified drawing figures set forth one or more embodiments of the invention, other embodiments are also contemplated. 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 and spirit of the principles of the invention. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features and components not specifically shown in the drawings. In general, the present invention relates to a viscous clutch capable of selectively transmitting a desired torque output from a provided torque input. The present clutch is "backwards" compared to most other viscous clutches in that an input member (e.g., pulley or sheave) attaches to a housing assembly of the device rather than to a rotor. In this way, the rotor can be attached to an output member, such as a fan, and thereby provide an output of the clutch. Further, the housing assembly connected to the input member can together provide a rotational input to the clutch. Advantages of this approach include allowing finned parts (e.g., the housing assembly or other input member(s)) to spin at a relatively high input speed whenever a rotational input is provided, not just when the output is selectively driven. In that way, cooling fins of the clutch can more effectively dissipate heat due to the greater interaction with ambient air that is possible at higher rotational speeds. Also, a reservoir of the clutch can be located in the housing assembly, which allows for greater cooling of the operating or shear fluid (e.g., silicone oil), due to proximity to an exterior of the clutch and to the cooling fins. Additionally, attaching the input member (e.g., pulley or sheave) to the housing can allow elimination of at least a portion of a center section of the input member, saving a great deal of weight (mass). Despite a reduced weight (mass), the input member-when configured as a pulley or sheave-can still provide a relatively large outer diameter, if desired for particular applications. In addition or in the alternative, a clutch of the present invention can include a detachable/interchangeable wiper, which allows a size of the wiper to be easily changed, to help adjust a pumping rate of the clutch. Further, a pump bore insert can be used that is interchangeable to provide different bore passage sizes, which can also help adjust the pumping rate of the clutch. The adjustable and interchangeable wiper and pump bore insert features can help tune the clutch to operate with a variety of output members (e.g., fans) without requiring complete redesign of the entire clutch. It also allows the clutch to be tuned more readily while in the field, rather than just in a factory or laboratory. Additional features and benefits of the present invention will be recognized by those of skill in the art in view of the entirety of the present disclosure, including the accompanying figures. The journal bracket (or mounting shaft) 22 can be a stationary (i.e., non-rotating) component that is secured to a desired mounting location, such as an engine block in a vehicle's engine compartment. It should be understood that while described as being "stationary" the journal bracket 22 can be installed within a moving vehicle, and the term "stationary" is used herein in relation to the mounting location. In the illustrated embodiment, the journal bracket 22 includes an axially extending shaft portion 22-1 and a generally radially extending flange portion 22-2. A conduit 22-3 can optionally be defined through the journal bracket 22, and can extend along substantially an entire axial length of the shaft portion 22-1. As illustrated, the conduit 22-3 is coaxially aligned with the axis A. Electrical wires or other items can pass through the conduit 22-3, as desired for particular applications. Suitable methods of manufacturing the journal bracket 22 include casting it from metallic material such as iron or steel. In a preferred embodiment, the journal bracket 22 is cast from ductile iron and then machined. The housing assembly 28 of the illustrated embodiment includes a base 28-1 and a cover 28-2. The base 28-1 and the cover 28-2 can be secured together with any suitable means, such as using fasteners, welding, or the like. Cooling fins 28-3 can be provided on an exterior of the housing assembly 28 to help dissipate heat generated by the clutch 20 to ambient air. As shown in the embodiment of In the illustrated embodiment, the housing assembly 28 carries the reservoir 38, which rotates with the housing assembly 28. The reservoir 38 can hold a supply of a shear fluid (e.g., silicone oil) for use by the clutch 20, with a majority of the shear fluid held in the reservoir 38 when the clutch 20 is disengaged. Because the housing assembly 28 is part of an input subassembly, the housing assembly 28 always rotates whenever there is a rotational input to the housing assembly 28. Rotation of the housing assembly 28 in turn keeps the shear fluid under pressure while in the reservoir 38, allowing the shear fluid to be maintained at a relatively high level of kinetic energy to help facilitate quick engagement of the clutch 20. In one embodiment, the reservoir 38 can be provided as a generally annular cavity in the base 28-1 of the housing assembly 28. A reservoir cover 46 can be provided to define part of a boundary of the reservoir 38. In the illustrated embodiment, the reservoir cover 46 is configured as a generally annular plate attached to the base 28-1, such as by a press fit, swaging, the use of fasteners, or the like. One or more outlet bores (also called reservoir bores) 46-1 can be provided in the reservoir cover 46 (or alternatively, on another boundary portion of the reservoir 38) to allow shear fluid out of the reservoir 38, and can be controlled by the valve assembly 30. The location of the reservoir 38 in the housing assembly 28 allows the shear fluid to remain relatively close to the cooling fins 28-3 and/or 28-4 and ambient air, to facilitate heat dissipation. The pulley (or sheave) 24 can be fixedly secured directly or indirectly to the housing assembly 28, such as to the base 28-1, and is configured to accept rotational input from a belt (not shown). The housing assembly 28 can co-rotate with the pulley 24. In the illustrated embodiment, the pulley 24 is axially positioned forward of the flange portion 22-2 of the journal bracket 22. Moreover, in the illustrated embodiment, the pulley 24 is configured as a separate element that is attached, using suitable fasteners, to the housing assembly 28. However, in further embodiments the pulley 24 could be integrally and monolithically incorporated into a portion of the housing assembly 28. A size (i.e., diameter) of a belt engagement portion of the pulley 24 can be selected to help provide a desired rotational input speed to the clutch 20, as will be understood by persons of ordinary skill in the art. In the illustrated embodiment, the pulley 24 provides a relatively large belt engagement diameter, thereby allowing relatively high input speeds, which in turn facilitates relatively high output speeds when the clutch 20 is engaged. Attaching the pulley 24 to the housing assembly 28 can allow a "hollow" center section of the pulley 24, because the pulley 24 need not extend inward beyond a generally radially outward portion of the housing assembly 28, thereby helping to reduce overall mass of the clutch 20. In one embodiment, the pulley 24 can be cast from a metallic material such as iron or steel, and then machined. In an alternative embodiment, the pulley 24 can be spun formed and attached to a separate hub section (not shown) made from a casting. In yet another alternative embodiment, a roll forming or circular forming process in combination with welding or brazing as described in The rotor assembly 26 of the illustrated embodiment includes a disk 26-1, a bearing hub 26-2, and a flow guide 26-3. The disk 26-1 and the bearing hub 26-2 of the rotor assembly 26 can be configured as separate components fixedly secured together with a suitable connection, such as a press-fit, knurled, threaded, splined, or other connection, such that those components rotate together (i.e., co-rotate). In alternative embodiments, the disk 26-1 and the bearing hub 26-2 can be integrally and monolithically formed together. The rotor assembly 26 can be rotatably supported on the shaft portion 22-1 of the journal bracket 22 by the second bearing sets 36. The second bearing sets 36 can include tapered roller bearings, which can provide relatively high load capacity, or other types of bearings as desired. As shown in The disk 26-1 of the rotor assembly 26 can include a number of concentric annular ribs on both front and rear sides near an outer diameter portion in a conventional arrangement. Those annular ribs can complement similar ribs on the cover assembly 28 along the working chamber 40. In the illustrated embodiment, the disk 26-1 is enclosed by the housing assembly 28. One or more fluid openings (not shown) can be formed generally axially through the disk 26-1, such as near an outer diameter portion, in a conventional manner in order to permit shear fluid in the working chamber 40 to pass between front and rear sides of the disk 26-1. A return bore including a first return bore potion 26-1B and a second return bore portion 26-1B' can be provided through the disk 26-1. In the embodiment shown in In the illustrated embodiment of the rotor assembly 26, the bearing hub (also called a fan hub) 26-2 includes a generally axially-extending sleeve portion 26-2A, a generally radially-extending flange portion 26-2B, and a pilot portion 26-2C. The sleeve portion 26-2A can have a generally cylindrical shape, and can be generally axially aligned with both the disk 26-1 and the second bearing sets 36. The seal bearing 42 can be engaged between the bearing hub 26-2 (and specifically the sleeve portion 26-2A) and the cover 28-2 of the housing assembly 28. The seal bearing 42 can also adjoin the disk 26-1, and can be aligned or closely positioned in the axial direction relative to the second bearing sets 36. The flange portion 26-2B can be positioned at or near a forward end of the sleeve portion 26-2A, and the pilot portion 26-2C can be positioned at a central, forward-facing portion of the flange portion 26-2B. The flange portion 26-2B and the pilot portion 26-2C can each at least partially extend beyond (or outside of) the housing assembly 28., such that the flange portion 26-2B, the pilot portion 26-2C and/or other portions of the bearing hub 26-2 of the rotor assembly 26 can provide a mounting surface for an output structure (e.g., fan, pump, shaft, etc.) at or near a front of the clutch 20. It should be noted, however, that in alternative embodiments the output structure could be mounted elsewhere. In this way, the rotor assembly 26 can form part of a selectively controllable output or torque-delivering portion of the clutch 20, as explained further below. Use of the bearing hub 26-2 allows attachment geometry for an output member (e.g., fan, etc.) to be relatively easily adjusted without a need to re-design other components of the clutch 20. For instance, the same basic overall clutch design could be provided with a variety of different bearing hub 26-2 configurations to suit different applications. The working chamber 40 (synonymously called a working area) is defined between the rotor assembly 26 and the housing assembly 28. In the illustrated embodiment the working chamber 40 extends along opposite front and rear sides of the disk 26-1, though in further embodiments the working chamber 40 could be limited to primarily one side of the disk 26-1. The presence of the shear fluid in the working chamber 40 creates a fluid friction coupling between the rotor assembly 26 and the housing assembly 28 to engage the clutch 20 and transmit torque between input and output components. An instantaneous percentage of torque transmission can vary as a function of the amount of shear fluid in the working chamber 40. Generally, the shear fluid is delivered to the working chamber 40 from the reservoir 38 along a fluid delivery path 48, and is returned to the reservoir 38 from the working chamber 40 through the return path 50. The fluid delivery and return paths 48 and 50 are each represented schematically by arrows in The valve assembly 30 can be attached to and carried by the housing assembly 28. In general, the valve assembly 30 is used to selectively cover and uncover the opening outlet bore 46-1 from the reservoir 38. When the outlet bore 46-1 is uncovered (i.e., opened), the shear fluid is allowed to flow from the reservoir 38 to the working chamber 40 along the fluid delivery path 48. The valve assembly 30 can be biased to an open position by default, for instance using a spring bias force. As explained further below, energizing the electromagnetic coil assembly 32 can actuate the valve assembly 30 to at least partially cover the outlet bore 46-1. Further discussion of suitable configurations of the valve assembly 30 is provided below with respect to the discussion of The electromagnetic coil assembly 32 as shown in A variety of alternative control schemes are possible for operating the clutch 20. In one embodiment, the electromagnetic coil assembly 32 can be energized in a coarse on/off manner such that the valve assembly 30 tends to remain in either a fully open position (the default position) or a fully closed position when the coil assembly 32 is selectively energized. In another embodiment, the coil assembly 32 can be energized using pulse width modulated (PWM) signals from an electronic engine controller (not shown). PWM signals allow a dynamically variable average volume of shear fluid to flow out of the reservoir 38. Depending on the pulse width (i.e., duration) and frequency of PWM signals, the valve assembly 30 can variably adjust the amount of shear fluid allowed to pass out of the reservoir 38 through the outlet bore 46-1 to the working chamber 40 over time. That is, the PWM signals cause the coil assembly 32 to open and close the valve assembly 30, and an average amount of time that the valve assembly 30 is open (i.e., uncovering the outlet bore 46-1) dictates the average amount of shear fluid that flows out of the reservoir 38. Greater pulse widths and/or greater frequencies of PWM signals will tend to close the valve assembly 30 more, on average, allowing lower average volumes of shear fluid to pass to the working chamber 40. This PWM control scheme permits the clutch 20 to be operated at selectively variable speeds, such that the rotor assembly 26 can rotate at anywhere from 0% to approximately 100% of the rotational speed of the housing assembly 28 and the pulley 24, rather than merely in a coarse and binary on/off fashion. The speed sensor assembly 44 can include a target wheel carried by and rotating with the bearing hub 26-2 of the rotor assembly 26 that is located in close proximity to a Hall Effect sensor carried by the journal bracket 22. The Hall Effect sensor can detect each revolution of the target wheel in order to determine an output speed of the clutch 20, which can be used to adjust control of the valve assembly 30 and/or for other purposes. In the illustrated embodiment, the sensor assembly 44 can be located, in the axial direction, within the pilot portion 26-2C of the bearing hub 26-2 of the rotor assembly 26. It should be noted that in further embodiments, other types of sensors can be used, or the sensor assembly can be omitted entirely. The pump bore insert 60 can be configured to resemble a bolt modified to include the bore 60-4. Indeed, it is possible to make the pump bore insert 60 by machining (e.g., drilling) the bore 60-4 through a conventional bolt of a suitable configuration. In alternative embodiments, the pump bore insert 60 can have a different configuration. For instance, the head 60-2 can be a separate element, such as a conformable seal strip, block, etc., that is attached to the shank 60-1. As shown in The pump bore insert 60 can be arranged relative to an immediately surrounding structure 62. In one embodiment, the pump bore insert 60 is engaged at an outer diameter portion of the disk 26-1, such that the immediately surrounding structure 62 can be an outer diameter surface of the disk 26-1 (see As best shown in The dimension D2 of the bore 60-4 can be selected as desired for particular applications. Larger dimensions for D2 generally allow for greater pumping rates, while smaller dimensions for D2 can generally allow lower pumping rates. In this way the bore 60-4 provides a pump metering function. The dimension D2 of the bore 60-4 can be varied in size by replacing the interchangeable pump bore insert 60 with a different insert 60 having a different configuration. Persons of ordinary skill in the art will recognize that the interchangeable pump bore insert 60 allows a dimension D2 of the pump bore 60-4 to be easily changed. By adjusting a parameter such as the dimension D2, changes to operational characteristics of the clutch 20 (e.g., shear fluid pressurization for pumping along the fluid return path 50) can be tuned to operate with a variety of output devices (e.g., fans) without requiring complete redesign or disassembly of the entire clutch 20. Further explanation of the method of adjusting the clutch 20 is provided below. It should also be understood that the interchangeable pump bore insert 60 can be utilized with nearly any type of viscous clutch, including those configured differently than the clutch 20. For instance, the interchangeable pump bore 60 can be utilized in a clutch that provides a fluid return path through a housing assembly rather than through a rotor assembly as with the clutch 20. The configuration shown in As shown most clearly in In one embodiment, the field armature 72 can be fixed (i.e., non-translating) at a location proximate the electromagnetic coil assembly 32 and the translating armature 70 can be positioned at least partially inside the field armature 72. The bias spring 74 can bias the translating armature 70 relative to the field armature 72 to a default position, such as rearward against the field armature 72. The rod 78 can be engaged with or secured to the translating armature 70 and can pass through an opening 28-1B in the base 28-1 of the housing assembly 28, with the diaphragm 76 providing fluidic sealing at the opening 28-1B. The control member 80 can be configured as a bolt and can be engaged to the rod 78 generally opposite the translating armature 70. The control member 80 can pass through an opening 46-3 in the reservoir cover 46, and the bellows 82 can provide fluidic sealing at the opening 46-3. The valve element 84 can be attached to the control member 80 generally opposite the rod 78, and can provide a seating surface (not visible in Energizing the coil assembly 32 generates magnetic flux that can pass through the field armature 72 and can cause the translating armature 70 to translate, which in turn translates the rod 78, the control member 80 and the valve element 84. Energizing the coil 32 creates a magnetic force that generally works against a spring force of the bias spring 74. The selective energization of the coil assembly 32 thus allows the translating armature 70, as well as connected structures such as the valve element 84, to move back and forth axially in a linear fashion rather than teetering/pivoting at an angle like most viscous clutch valves. The linear translation action allows the clutch 20 to open and close two or more valve assemblies (only one is visible in In an alternative embodiment, the valve assembly 30 can be configured similarly to that described in Persons of ordinary skill in the art will recognize that various steps described with respect to The following are non-exclusive descriptions of possible embodiments of the present invention. A viscous clutch can include a housing assembly; a rotor assembly; a reservoir to hold a supply of a shear fluid; a working chamber operatively positioned between the housing assembly and the rotor assembly, wherein selective introduction of the shear fluid to the working chamber facilitates selective torque transmission between the housing assembly and the rotor assembly; and a fluid return bore that extends radially through at least an outer diameter portion of the rotor assembly to the working chamber, the fluid return bore forming at least a portion of a fluid return path from the working chamber to the reservoir. 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 for selective torque transmission can include delivering a rotational input to a housing assembly; selectively delivering a shear fluid to a working chamber; transmitting torque to a rotor assembly as a function of volume of the shear fluid selectively delivered to the working chamber; and returning the shear fluid from the working chamber to a reservoir along a substantially radial bore through a disk of the rotor assembly. The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following steps, features, and/or configurations:
A viscous clutch can include a housing assembly; a rotor assembly; a reservoir to hold a supply of a shear fluid; a working chamber operatively positioned between the housing assembly and the rotor assembly, wherein selective introduction of the shear fluid to the working chamber facilitates selective torque transmission between the housing assembly and the rotor assembly; and a pump bore insert having a bore in fluid communication with a fluid return path extending from the working chamber to the reservoir. 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:
Further, a kit for use with the viscous clutch described above can include a replacement pump bore insert of a different configuration, such as having a bore of a different size. A method for using a viscous clutch can include engaging a first pump bore insert along a working chamber of the viscous clutch at a fluid return bore; and replacing the first pump bore insert with a second pump bore insert of a different configuration. The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following steps, features, and/or configurations:
A method for use with a viscous clutch can include positioning a first pump bore insert along a working chamber of the viscous clutch and at least partially within a fluid return bore; removing the first pump bore insert from the viscous clutch; and positioning a second pump bore insert along the working chamber of the viscous clutch and at least partially within the fluid return bore in place of the first pump bore insert. The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following steps, features, and/or configurations:
A method for a viscous clutch can include pumping shear fluid through a bore having a first diameter; and reconfiguring the bore to have a second diameter different from the first diameter. Any relative terms or terms of degree used herein, such as "substantially", "essentially", "generally" 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, temporary alignment or shape variations induced by operational conditions, and the like. Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention. For example, the interchangeable pump bore insert 60 and the wiper 63 disclosed above can each be used in nearly any type of viscous clutch. Moreover, the configuration of the fluid paths 48 and 50 described above can be utilized in clutches having any type of desired pumping assembly. |