192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
1999-09-27
2001-04-03
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S084940
Reexamination Certificate
active
06209700
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electric clutch for connecting the drive shaft of a prime mover with a driven shaft, such as the input shaft of a refrigeration compressor, characterized in that a movable armature member is supported by spring means for displacement by electromagnetic means from an inactive de-energized spaced position relative to a driven member connected with the driven shaft toward an active energized position in frictional engagement with the driven member, thereby to drive the driven shaft.
2. Brief Description of the Prior Art
As shown by the prior patents to Brownfield, et al., U.S. Pat. No. 5,609,232, Viegas U.S. Pat. No. 5,252,874, and Pardee U.S. Pat. No. 5,119,918, among others, it is well known in the prior art to provide electromagnetic clutches for connecting a drive shaft (for example, an engine shaft) to a driven shaft (for example, the input shaft of a refrigeration compressor).
In conventional electric clutches, the clutch device is driven from an external power source such as an internal combustion engine or an electric motor, or both. In the case of an internal combustion engine, a flywheel is utilized for rotational inertia. The clutch is utilized to couple a secondary device such as a compressor or a pump to the external power source.
In the aforementioned Brownfield, et al., U.S. Pat. No. 5,609,232, a contact or armature member is connected for axial sliding displacement relative to the flywheel by resilient bushing means, whereby upon the activation of electromagnetic means, the armature is slidably displaced to effect clutch engagement. Permanent magnet means bias the armature toward the disengaged position.
One drawback of these known electric clutches is that there is no restriction of the axial movement of the flywheel adapter, thereby producing line-to-line contact between the adapter and the flywheel when the magnet assembly is not excited, thereby generating an unacceptable noise level during operation.
The present invention was developed to avoid the above and other drawbacks of the known electric clutches, and to produce an improved electric clutch that is reliable and positive-acting on the one hand, and is of a cost-effective simple design on the other hand.
SUMMARY OF THE INVENTION
Accordingly, a primary object of the present invention is to provide an improved electric clutch in which an electromagnetically attracted armature is connected with the drive shaft via spring means that support the armature in a normal inactive de-energized position relative to a driven member connected with the driven shaft, and electromagnetic means for displacing the armature axially in the direction of the driven member toward an active energized position in functional engagement with the driven member, thereby to drive the driven shaft.
According to another object of the invention, the improved electric clutch is of a 3-piece modular design including a drive member connected with the drive source, a driven member connected with the driven source, and an electromagnetic armature connected with one of the members by resilient disk biasing means.
According to a more specific object of the invention, the spring means comprises an annular resilient disk formed from spring steel, the inner and outer peripheral portions of said disk being connected with the rotor and with the armature, respectively. To permit distortion of the disk and the axial displacement of the outer peripheral portion relative to the internal peripheral portion, the intermediate portion of the disk is provided with a plurality of spaced circularly arranged slots that partially extend between the openings that receive the fasteners that connect the disk with the rotor and with the armature, respectively.
In common practice, because the external power source and the secondary device are generally commercially available units, it is conventional in the prior art to provide a transitional member between the clutch and the external power source. In this application, the transitional member is the rotor plate. This plate serves the following functions. It is affixed to the flywheel in such a manner as to provide vibration dampening for torque spikes in the normal internal combustion cycle of the engine. This is accomplished by applying vibration dampers and more specifically in this application these dampers are rubber bushings installed to the flywheel adapter plate which are in turn driven from drive pins affixed to the flywheel. It is necessary to allow a clearance between the rotor plate assembly and flywheel otherwise two unacceptable conditions will occur. First, the normal harmonics of the internal combustion engine would create a metallic resonance, which in turn will cause an unacceptable noise level during operation. Secondly, excessive wear between the flywheel and the adapter plate will occur. Both of these conditions are considered a failure mode for this design.
In accordance with a characterizing feature of the present invention. a flat spring plate functions as a transitional member between the rotor plate and the clutch armature plate. This spring incorporates two bolt hole circle patterns. The inner hole circle pattern is affixed radially to the rotor plate and the outer hole circle is affixed radially to an armature plate. The spring functions as the connection device between the two components allowing axial movement of the clutch armature plate in respect to the rotor place. When engaged with the pulley, the armature plate and spring transfers the force vectors from rotor assembly to the pulley.
The rotor is affixed directly to the secondary device and acts as the drive source for said device by coupling to the power source when the clutch is engaged. Clutch coupling of the two devices is accomplished when the armature plate is sufficiently forced into the face of the pulley via magnetic force from an electromagnet. Torque transfer is accomplished when the coefficient of friction of the metal-to-metal surface contact between the clutch armature and the pulley and the force acting on the armature plate is sufficiently strong enough to provide a dynamic clamping force which is in excess of the device torque curves of the external power source and the secondary device. This dynamic clamping force is provided by an electrical magnet.
The electrical magnet assembly comprises a machined iron housing to which a coil of wire is manufactured and affixed within the housing such that the coil is enclosed on three sides of the housing. The coil of wire is encapsulated with a potting compound, such as an epoxy resin, and potted within the magnetic housing. By applying an electrical current to the coil wire ends a magnetic field is created through the magnet housing.
The magnet assembly is affixed to the device housing in such a manner that it is positioned in close proximity to the pulley face. The design of the pulley face includes open slots radially about the hub axis positioned such that the magnetic field flux lines and the magnetic density are optimized in relation to the clutch armature plate. When the coil is excited, the magnetic field is generated around the magnet housing, through the rotor, into the clutch armature plate. The clutch armature plate is the only axially moveable component within the assembly. The magnetic force draws the armature plate toward the rotor causing a specific clamping force.
The design of an electrically operating magnetic clutch has several critical features that must be maintained. Obviously, all of the interface features must be dimensionally correct with the application to which it is applied. the magnetic force of the excited magnet must react sufficiently on the clutch armature to provide a required pull down force known as the normal force on the armature and a dynamic clamping force between the armature and the rotor face known as the frictional torque between the armature and the pulley.
The critical design characteristic referenced as the air gap between the rotor and the hub f
Marx Rodger L.
Wogaman Jason L.
Bonck Rodney H.
Laubscher, Sr. Lawrence E.
Tractech Inc.
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