Patent Application
20140299434
The present disclosure is directed to clutch systems, and more particularly relates to rheological clutches and clutch systems.
Conventional clutches are designed to control torque throughput in a binary regimen (i.e., on and off). Clutch engagement is generally accomplished by applying force to the drive element which presses the drive element against the driven element to transfer torque therebetween. When torque is modulated by regulating the amount of force the drive element exerts against the driven element, rotational slip occurs between communicating friction surfaces of the drive and driven elements. Modulating torque results in heavy component wear, heat generation and potentially catastrophic damage.
Opportunities exist for improving clutch designs to avoid these and other drawbacks associated with existing clutch designs.
The principles described herein may address some of the above-described deficiencies and others. One aspect provides a clutch assembly including an input shaft, an output shaft, at least one first friction plate mounted to the input shaft, and at least one second friction plate mounted to the output shaft and spaced apart from the at least one first friction plate. The clutch assembly also includes a rheological fluid positioned between the at least one first friction plate and the at least one second friction plate, and a fluid activator configured to increase a viscosity of the rheological fluid to provide increased torque transfer from the at least one first friction plate to the at least one second friction plate.
The clutch assembly may include a housing having an internal cavity, wherein the at least one first friction plate, at least one second friction plate, and rheological fluid are positioned in the internal cavity. The at least one first friction plate and at least one second friction plate may include a plurality of surface friction features. The plurality of surface friction features may include a plurality of projections. The plurality of surface friction features may include a plurality of recesses. The plurality of surface friction features may include a plurality of concentric rings. The plurality of surface friction features may be arranged symmetrically relative to each other on a given friction plate. The plurality of surface friction features may be spaced apart circumferentially and radially on at least some of the first and second friction plates. The plurality of surface friction features may be formed by at least one of embossing, rolling, casting and machining. The plurality of surface friction features may increase a surface area of the at least one first friction plate and the at least one second friction plate.
The fluid activator may include a magnet and the rheological fluid may include a plurality of magnetic particles. The fluid activator may include an electrode configured to electrically charge the rheological fluid. The at least one first friction plate may include a plurality of first friction plates grounded together along peripheral edges thereof. The at least one first friction plate may be connected to the input shaft with a splined connection, and the at least one second friction plate may be connected to the output shaft with a splined connection.
Another aspect of the present disclosure relates to a clutch assembly including at least one first friction plate, at least one second friction plate, and a volume of fluid. The at least one first friction plate includes a first primary surface and a plurality of first friction features formed in the first primary surface. The at least one second friction plate includes a second primary surface and a plurality of second friction features formed in the second primary surface, wherein a space is defined between the first and second primary surfaces. The volume of fluid is retained in the space and has a variable viscosity. The volume of fluid, when energized, increases torque transfer from the at least one first friction plate to the at least one second friction plate.
The clutch assembly may include one of a magnet and an electrode configured to energize the volume of fluid. The at least one first friction plate may include a single plate having a plurality of first concentric rings extending from the first primary surface as the plurality of first friction features. The at least one second friction plate may include a single plate having a plurality of second concentric rings extending from the second primary surface as the plurality of second friction features. The plurality of first and second concentric rings may be arranged radially spaced apart from each other and at least partially overlapping in an axial direction.
The at least one first friction plate may include a plurality of first friction plates, and the at least one second friction plate may include a plurality of second friction plates interposed between the plurality of first friction plates. The clutch assembly may include an input shaft connected to the at least one first friction plate and configured to be coupled to a first torque source, and an output shaft connected to the at least one second friction plate and configured to be coupled to a second torque source.
Another aspect of the present disclosure relates to a method of controlling torque transfer. The method includes providing a clutch assembly having input and output shafts, at least one first friction plate connected to the input shaft, at least one second friction plate connected to the output shaft and spaced apart from the at least one first friction plate, and a rheological fluid positioned between the at least one first friction plate and the at least one second friction plate. The method also includes rotating the at least one first friction plate relative to the at least one second friction plate, and energizing the rheological fluid to increase a viscosity of the rheological fluid to increase torque transfer from the input shaft to the output shaft via the first and second friction plates.
The at least one first friction plate and the at least one second friction plate may include a plurality of friction features configured to create increased surface friction with the rheological fluid. The method may include providing at least one of a magnet and an electrode, and energizing the rheological fluid may include activating the magnet or electrode. The method may include providing a torque source coupled to the input shaft and a compressor coupled to the output shaft, operating the torque source, and energizing the rheological fluid to transfer torque from the torque source to the output shaft to apply torque to the compressor. The method may include arranging the at least one first friction plate and at least one second friction plate radially and concentrically.
The accompanying drawings illustrate certain embodiments discussed below and are a part of the specification.
Throughout the drawings, identical reference characters and descriptions indicate similar, but not necessarily identical elements.
Illustrative embodiments and aspects are described below. It will, of course, be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present disclosure is directed to rheological clutches and related clutch system. One application for such clutches and clutch systems is a fixed or variable speed, flow rate controlled compressor, such as the compressors disclosed in U.S. patent application Ser. No. 13/857,918, filed on 5 Apr. 2013, and entitled “Hybridized Compressor,” which application is incorporated herein in its entirety by this reference [the 46265.0131 application]. The compressor may be used to supply compressed air or other oxidant to a fuel preparation system, such as a dual fluid fuel injection system. The compressor may be driven by one of two torque sources and is configured to switch between the two torque sources on command. In one example, one torque source is an electric motor packaged with the compressor components. The second torque source may be an engine driven motor, which operates the compressor remotely via, for example, a belt and pulley drive system. The clutch system of the present disclosure may be operatively coupled between the first and second torque sources (e.g, between an electric motor and engine drive mechanical motor). An example dual fluid injection system and related methods, which may use the flow of compressed air generated by the compressor, is disclosed in U.S. Patent Publication No. 2011/0284652, which application is incorporated herein in its entirety by this reference.
A basic clutch typically consists of drive and driven elements as discussed above. Mechanical clutches utilize friction plates or pads, which are pulled or pressed into communication by an electromagnet. This method of actuation places the drive and driven elements into physical contact at full rotational speed and torque. The physical contact generates heat and friction that reduces a useful life of the clutch and results in other detrimental effects.
In rheological clutches, the drive and driven elements are enclosed in chambers filled with a rheological fluid. A rheological fluid contains small magnetic particles, which when energized, increase an effective viscosity of the fluid. The rheological fluid is energized either magnetically with a field generated around the drive and driven elements, or directly by passing an electrical current through the rheological fluid between the drive and driven elements. Other methods may be possible to energize the rheological fluid. When energized, the rheological fluid's effective viscosity is increased, causing torque to pass from the drive element to the driven element. Rheological fluid clutches may provide progressive engagement, through slip, which essentially yields a variable speed, and thus variable flow compressor output when the clutch is used with one of the compressor assemblies disclosed herein. Heat generated by working the viscous fluid is not the consequence of direct component interface, therefore wear and subsequent damage may be limited. The rheological fluid may interact with a heat exchanger to provide thermal management and increase life of the fluid and torque control components.
Rheological clutches may be employed as alternatives to a standard friction clutch. In the application of a compressor assembly as described herein, rheological clutches may act as or at least operate with variable speed or torque devices due to their ability to be gradually, partially charged, which allows a speed or torque differential between the drive and driven elements.
A rheological clutch may be integrated into the pulley of a mechanical or engine driven input side of a compressor assembly. Energizing the clutch mechanism moves a friction plate attached to the rotating shaft of the compressor against the engine belt driven pulley and connects the compressor to the running engine. Torque is transferred from the belt to the pulley and into the compressor shaft so that the compressor may continue rotation. The clutch may be actuated to transfer rotation of the pulley to rotation of the compressor shaft after turning off the electric motor of the compressor assembly.
A magneto-rheostatic (rheological) clutch may be employed to operatively connect the mechanical (e.g., engine driven) torque source to the compressor. Energizing an electromagnet situated around a closed volume of magneto-rheological fluid in which input and output torque elements are arranged such that when the magneto-rheological fluid is energized, the viscosity of the fluid is increased. The increased viscosity causes the input drive element to transfer torque through the fluid to the output drive element and to the compressor. The output drive of the magneto-rheostatic clutch is attached to the rotating shaft of the compressor against the engine belt driven pulley and connects the compressor to the running engine. This torque is transferred from the belt to the pulley, into the magneto-rheostatic clutch, and then to the compressor shaft. The compressor components are rotated by the compressor shaft to generate compressed air.
An electro-rheostatic (rheological) clutch may be similar to the magneto-rheostatic clutch with the primary difference being how the fluid is energized. An electrical voltage may be passed through the rheological fluid, thus charging the fluid particles. As the charge in the particles is increased, the effective viscosity of the fluid increases, thereby causing torque to be transferred from the drive element to the driven element. The mechanical function of the drive is the same as the magneto-rheological clutch, with the exception being the charging, or control, of the rheological fluid. The rheological fluid may be directly communicated with control electrodes. An electrical current is passed through the rheological fluid to modulate the viscosity, thus controlling clutch engagement and torque throughput.
Alternative geometries for rheological clutch torque input and drive elements can be optimized for increased torque control or transfer and/or improved packaging. This innovation addresses options for parallel rotor and stator plates and introduces a concentric rotor and stator configuration, which may reduce overall package length as well as component complexity.
Referring now to
The housing 12 includes first and second housing members 30, 32, which define a fluid space or cavity to receive the fluid 24. The input shaft 14 extends through the housing 12 and includes first and second ends 36, 38. The output shaft 16 also extends through the housing 12 and includes a shaft portion 40 and a carrier portion 42. The first friction plates 18A,B are mounted to the input shaft 14. The second friction plates 20A,B are mounted to the carrier portion of the output shaft 16. One of the input and output shafts 14, 16 are coupled to a torque source such as an electric motor or an engine driven motor.
The first friction plates 18A,B each include first and second primary surfaces 50, 52 (see
The first friction plates 18A,B may be directly connected to the input shaft 14 at the central portion 56. The central portion 56 may include keyed or splined features that assist in securing the first friction plates 18A,B to the input shaft 14. The input shaft 14 transfers torque to the first friction plates 18A,B to rotate the first friction plates.
The second friction plates 20A,B include first and second primary surfaces 70, 72, a peripheral portion 74, a pair of spacer blocks 76, 78, and a plurality of fasteners 79. A plurality of friction features may be included on at least one of the first and second primary surfaces 70, 72. The friction features may include first and second friction features 58, 59 as shown in
The spacer block 76 may be positioned between the second friction plates 20A,B. The second friction plates 20A,B are mounted to the shaft portion 40 of the output shaft 16 directly or indirectly via a coupling member. The spacer block 76 may be mounted to the second friction plates 20A,B at the peripheral portion 74. The spacer block 76 may be positioned radially outward from the first friction plates 18A,B.
In at least one example, at least one of the second friction plates 20A,B is mounted directly to the shaft portion 40 of the output shaft 16 with a splined connection. Other types of connections are possible for securing the second friction plates 20A,B to the output shaft 16.
The second friction plates 20A,B may be radially spaced outward from a portion of the input shaft 14 (see
The fluid activator 22 may be exposed to the fluid 24 positioned in the housing 12. In some examples, the fluid activator 22 comprises a magnet. In other examples, the fluid activator 22 comprises an electrode. Typically, when the fluid activator 22 is an electrode, the fluid activator 22 is directly exposed to the fluid 24. In embodiments that comprise a magnet for the fluid activator 22, the magnet may be physically spaced apart and isolated from the fluid 24 while being sufficiently close to impose a magnetic field on the fluid 24.
The fluid 24 may comprise a rheological fluid. In one example, the rheological fluid includes magnetic particles or particles that are energized by a magnetic or electrical field. The fluid 24 has a variable viscosity depending on operation of the fluid activator 22. In one example, operating the fluid activator 22 charges or energizes the fluid 24 to increase the viscosity of the fluid 24. The increased viscosity of the fluid 24 provides increased friction with the first and second friction plates 18A,B and 20A,B to create increased torque transfer between the input and output shafts 14, 16 via the first and second friction plates 18A,B and 20A,B.
The bearings 28, 29 may be interposed between the housing 12 and the input and output shafts 14, 16. The bearings 28, 29 may also provide a fluid-tight seal between the housing 12 and the input and output shafts 14, 16, respectively. At least
The first and second friction features 58, 59 formed in the first and second friction plates 18A,B and 20A,B may have various shapes, sizes, orientations, and arrangements on one of the first and second primary surfaces 50, 52 and 70, 72. The first and second friction features 58, 59 shown in
The second friction features 59 are elongate shaped structures extending radially outward from a central axis of the friction plates. The second friction features 59 are spaced apart circumferentially around the central axis. The second friction features 59 also may be formed as recesses along the first primary surfaces 50, 70 and extend as protrusions along the second primary surfaces 52, 72. The second friction features 59 may be interspaced circumferentially in between groups of the first friction features 58.
The first and second friction features 58, 59 provide increased surface friction as the first and second friction plates 18A,B and 20A,B move relative to each other with the fluid 24 spaced therebetween and in contact with the first and second primary surfaces 50, 52, and 70, 72. Typically, the first and second friction plates 18A,B and 20A,B are spaced apart in an axial direction a sufficient distance such that the first and second friction plates 18A,B and 20A,B, including the first and second friction features 58, 59 positioned on each of the friction plates, remain out of contact with each other at all times. The fluid 24, when energized by the fluid activator 22, may have a sufficiently high viscosity to transfer torque from the first friction plates 18A,B to the second friction plates 20A,B, or vice versa.
Referring now to
The friction features shown in
The first and second friction plates 18A,B and 20A,B are typically coupled or grounded to each other along either their inside diameter (see the first friction plates 18A,B) or their outside diameter (see the second friction plates 20A,B) and situated alternately in an interleaved arrangement relative to each other. A coupling or a grounding of the friction plates for direct connection to either the input or output shaft 14, 16 is not mandatory, but may be used in at least some embodiments to provide improved locking together of the friction plates. One advantage to such a configuration is the potential reduction of noise and wear.
Referring now to
The first friction plate 118 includes first and second primary surfaces 150, 152 (see
The first and second friction plates 118, 120 may include friction features formed in either or both of the first and second primary surfaces 150, 152 and 170, 172, or in any of the first and second rings 166A-E and 180A-E. The friction features may include recesses or protrusions such as those described above with reference to
Determining a separation distance (e.g., gap) between the friction plates and associated friction features, whether the friction features of the first and second friction plates are arranged in parallel with each other (see
The clutch assembly 10 may further include a pulley 26 mounted with a pulley fastener 27 (see
When the first friction plates (also referred to as drive elements) are rotating and the rheological fluid is not energized, the low viscosity, off state, of the rheological fluid typically does not communicate sufficient torque to the second friction plate (also referred to as driven elements) to begin rotation (e.g., transfer torque). When the rheological fluid is energized, the viscosity increases and torque is transmitted through the viscous fluid into the second friction plate. The first and second friction plate features, such as the first and second friction features 58, 59 and the first and second rings 166A-E and 180A-E may provide increased surface area for rheological fluid coverage as well as physical flow resistance to enhance torque transfer.
Generally, in a parallel friction plate embodiment such as the one shown in
In the concentric torque configuration of
Referring now to
The first compressor stage 312A includes a drive plate 330A, a piston housing 332A, a housing 334A, an end plate 336A, and a plurality of piston assemblies 338. The drive plate 330A includes a plurality of lobes 340A (e.g., five lobes), and a track 342A. The piston housing 332A includes a central bore 344A and a plurality of piston bores 346A (e.g., three piston bores). The housing 334A includes an air cavity 348A (see
The second compressor stage 312B includes a drive plate 330B, a piston housing 332B, a housing 334B, an end plate 336B, and a plurality of piston assemblies 339. The drive plate 330B includes a plurality of lobes 340B (e.g., five lobes) and a track 342B. The piston housing 332B includes a central bore 344B and a plurality of piston bores 346B (e.g., three bores). The housing 334B includes an air cavity 348B (see
The electric motor 314 includes an output shaft 360 coupled to the transmission 316. The transmission 316 includes an input gear 362, a sun gear 364, a plurality of planet gears 366, and a gear housing 368. The transmission 316 is operably coupled to the drive plate 330A of first compressor stage 312A. The first and second compressor stages 312A, 312B are coupled together with a drive shaft 370 (see
The first and second compressor stages 312A, 312B, electric motor 314 and transmission 316 are positioned within the casing 320. The clutch 100 is interposed between the pulley 126 and the second compressor stage 312B, as shown in
The preceding description has been presented only to illustrate and describe certain aspects, embodiments, and examples of the principles claimed below. It is not intended to be exhaustive or to limit the described principles to any precise form disclosed. Many modifications and variations are possible in light of the above disclosure. Such modifications are contemplated by the inventor and within the scope of the claims. The scope of the principles described is defined by the following claims.
