Liquid-cooled high-torque and high-power devices for magnetically transferring torque

Abstract

The invention relates to an improved liquid cooled device for magnetically transferring large torques with a primary rotating member and a secondary rotating member as stated in US 7294947. The primary rotating member has permanent magnets and the secondary rotating member has electrically conductive material. Both rotors are encapsulated in a liquid tight housing enclosure and both rotors are liquid cooled to allow power transfer of over 260 KW and 1000 ft. lb. torques to be achieved.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority from U.S. Application No. 16909989, filed June 23, 2020. BACKGROUND

[0003] The present invention is directed to an improvement over the prior art more specifically set forth in U.S. Patent No. 7,294,947 and its related patents in other jurisdictions, which is incorporated herein by reference, wherein the prior art is for a rotating magnetic torque transfer device utilizing two coaxial cylinders that overlap each other, one cylinder contains a row(s) of permanent magnets and the other cylinder contains a coil of electrically conductive material, but the problem is that the prior art has a maximum power transfer limit due to the induction rotor bar air cooling in the atmosphere, which causes both the induction rotor bar and the magneto circuit material to reach temperatures above the specific power transfer rating point that destroys the magnetic properties of the materials. The challenge is to develop a modified geometry and structure that will allow for direct liquid injection cooling within the coaxial cylinders without increasing the magnetic circuit reluctance or electrical conductor shorting within the device. The prior art is limited to less than 1000 KW of power transfer, otherwise the internal operating temperature of the unit will cause the magnetic field of the permanent magnets to fail.

[0004] It is desirable to design a liquid cooled permanent magnet excitation mechanism for transferring variable torque in drive applications. Specifically, there is a need to couple a constant speed device such as an electric motor or engine to a high power variable output speed and torque device such as a pump impeller, fan, propeller, wheel set, etc. As set forth in the prior U.S. Patent No. 7,294,947, the specific individual electrically conductive rotor bar geometry of this device along with the similarly shaped permanent magnet similar geometry placed directly opposite the rotor conductive bar taken together creates a torque transfer device that is not a traditional eddy current device that creates circular eddy currents in a relatively broad electrically conductive material. The improvement to the specific narrow rotor electrically conductive rotor bar and narrow cross section permanent magnet of the U.S. Patent No. 7,294,947 device is to design a way to maintain this non eddy current rotor bar efficiency in a way that maintains the effective magneto circuit of the prior art (U.S. Patent No. 7,294,947) but also to develop a way to quickly remove the high heat that is generated in the electrically conductive bar for high power transfer.

[0005] The present invention discloses and claims an improvement that allows for great power transfer by injecting a liquid directly into the electrically conductive bar, which then exits and impinges on the magnetic bar rotor, the liquid does not interfere with the magnetic field or the permeability of the magneto circuit.

[0006] The described device is an apparatus that uses permanent magnets and conductors arranged in an optimal manner to produce magnetic flux in a power transmission drive, and uses direct liquid injection for cooling both rotors. The described embodiments utilize mechanical means to change the flux density between the two rotating assemblies to change the torque transmitted by the device and thereby change the output speed of the device. SUMMARY

[0007] As disclosed in U.S. Patent No. 729,947, the present invention utilizes permanent magnets to transmit variable or fixed torque between two rotating elements. The aforementioned permanent magnets are positioned on only one of the two rotating elements (also referred to as "rotors" or "rotating members"), and in certain embodiments, the other rotating element does not contain permanent magnets but does have what is referred to as "conductive" elements. Additionally, what is referred to as "permeable magnetic" material is also included on the non-permanent magnet rotor, which includes a substance that allows magnetic flux to penetrate. The torque between the aforementioned two rotating elements is adjusted by changing the amount of magnetic flux transferred between the elements by changing the degree of axial overlap of the elements. In the preferred embodiment of the device, two concentric cylinders, one containing one or more rows of permanent magnets, is axially moved so as to gradually axially overlap the second cylinder element, which contains conductive and permeable magnetic elements but no permanent magnets. This gradual axial overlap of the two cylinders allows the amount of magnetic flux intersecting the two concentric cylinders to change. This causes the amount of induced current in the cylinder containing the conductive elements to change, which in turn causes the induced diamagnetic force to change. The magnetic force, and thus the transmitted torque, will change based on the amount of axial overlap.

[0008] The prior art is air cooled only by the atmospheric air present around the two rotors. The electrically conductive rotors have induced currents that increase with the increase in the relative angular velocity difference between the two rotors; the currents generate heat whereby the unit is limited to transferring about 260 KW (at 1,000 ft-lb of torque). Therefore, to transfer thousands of kilowatts of power, a liquid cooling system is designed wherein the cooling liquid will travel very close to the current carrying / heating surface of the electrically conductive rotor bars, and wherein the amount of liquid flowing through each rotor bar can be adjusted with a threaded end plug at the end of each electrically conductive rotor bar cooling liquid channel. Furthermore, to cool the surface of the magnet rotor that runs very close to the induced rotor bars through a very narrow gap, as the cooling liquid reaches the flow adjustment screw plug, the liquid coolant is directed radially to the magnet rotor so that the liquid coolant hits directly on the surface of the magnet bars. The proposed invention overcomes the previous limitations of the invention disclosed in US Patent No. 7,294,947 because there is no limit to the amount of power that the device can transfer, the amount of power being limited only by the structural strength of the various materials. There is no longer any limit due to the heat generated in the electrically conductive bars in the electrically conductive rotors. The liquid coolant does not interfere with the magnetic field circuit magnetic flux flow, the coolant also does not allow internal short circuits of the components in and around the electrically conductive elements. Furthermore, the induced rotor rotation itself acts as a second centrifugal booster pump to help circulate the liquid coolant. To properly adjust the amount of liquid coolant flow needed for proper cooling and not to permit additional liquid cooling flow that would reduce the net power transfer efficiency of the unit, the new geometry of the new liquid cooled induced rotor has an adjustment screw plug at the end of each electrically conductive rotor bar (504).

[0009] The proposed invention overcomes the previous limitations by utilizing new technology in the magnet material and provides a stable means of mechanically changing the amount of torque transferred without the need for large external current controls. BRIEF DESCRIPTION OF DRAWINGS

[0010] The drawings constitute a part of this specification and include exemplary embodiments of the present invention, which can be embodied in various forms. It is understood that in some instances various aspects of the

[0011] The description of selected embodiments of the present invention included herein is set forth in the following enumerated clauses:

[0012] Figure 1 is an isometric view of the exterior of a preferred embodiment of the present invention.

[0013] Figure 2 is an exploded isometric view of Figure 1

[0014] Figure 3 is an exploded isometric view of a liquid cooled electrically conductive rotor of a preferred embodiment of the present invention.​

[0015] Figure 4 is an isometric view of a liquid cooled electrically conductive rotor.

[0016] Figure 5 is an isometric view of a detail of a passage for a flow of liquid that cools an electrically conductive rotor bar immediately adjacent to Figure 4 and flows parallel along the electrically conductive rotor bar. DETAILED DESCRIPTION

[0017] A detailed description of preferred embodiments is provided herein. However, it is to be understood that the present application can be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present application in virtually any appropriately detailed system, structure or manner.

[0018] Referring to Figures 1 to 5 , the preferred embodiment of the present application is shown and described as applied to a liquid cooled high power variable speed drive application. Two coaxial rotors [one rotor having an axially placed electrically conductive bar (201) and one rotor having an axially placed permanent magnet bar (202)] with their respective support bearing cylinder systems (200 and 203) are shown in exploded view outside of their housing (100). Also shown is an automatic control system actuator (204) that moves one of the two rotors relative to the other to adjust the axial overlap of the two rotors while they are rotating to vary the amount of torque and power transferred through the unit. The embodiment housing (100) when assembled is completely liquid tight in order to capture the cooling liquid pumped through the cooling liquid passages (501) located directly adjacent to the electrically conductive rotor bar (504). The bearing support cylinders (200 and 203) are oil lubricated and cooled and sealed from the outside and from the housing so that the oil does not mix with the rotor cooling liquid. The purpose of using a magnetically permeable material is to provide a continuous magnetic flux path between the magnetic poles, thereby allowing the optimal magnetic flux arrangement to exist. The magnetically permeable material need not be ferromagnetic.

[0019] The cooling system is a closed system consisting of an external liquid storage tank, a centrifugal circulation pump, a heat exchanger that rejects the heat drawn in the magnetic drive unit, a thermometer, a pressure gauge, a filter and interconnecting pipes. The cooling liquid can consist of a mixture of distilled water and a glycol compound.

[0020] The prior art is air cooled only by the atmospheric air that exists around the two rotors. The electrically conductive rotors have induced currents that increase with the increase in the relative angular velocity difference between the two rotors; the currents generate heat whereby the unit is limited to transferring about 260 KW (at 1,000 ft-lb of torque). Therefore, in order to transfer thousands of kilowatts of power, a liquid cooling system is designed wherein the cooling liquid will travel very close to the current carrying / heat generating surfaces of the electrically conductive rotor bars, and wherein the amount of liquid that flows through each rotor bar can be adjusted with a threaded end plug at the end of each electrically conductive rotor bar cooling liquid channel (502 and 503). Furthermore, in order to cool the surface of the magnet rotor that runs very close to the inductive rotor bars through a very narrow gap, when the cooling liquid reaches the flow adjustment screw plug (503), the liquid coolant is directed radially to the magnet rotor so that the liquid coolant hits directly on the surface of the magnet bars. The proposed invention overcomes the previous limitations of the invention disclosed in US Patent No. 7,294,947 because there is no limit to the amount of power that the device can transfer, the amount of power is limited only by the structural strength of the various materials. There is no longer any limit due to the heat generated in the electrically conductive bars in the electrically conductive rotors. The liquid coolant does not interfere with the magnetic field circuit magnetic flux flow, the coolant also does not allow internal short circuits of the components in and around the electrically conductive elements. Furthermore, the inductive rotor rotation itself acts as a second centrifugal booster pump to help circulate the liquid coolant. In order to properly regulate the amount of liquid coolant flow that is needed for proper cooling and not to permit additional liquid cooling flow that would decrease the net power transfer efficiency of the unit, the new geometry of the new liquid cooled inductive rotor has an adjustment screw plug (502 and 503) at the end of each electrically conductive rotor bar (504).

[0021] While the application has been described in connection with preferred embodiments thereof, it will be understood that the scope of the application is not limited to those preferred embodiments, and that further modifications and / or rearrangements of the preferred embodiments set forth herein can occur to those skilled in the art to which the application pertains without departing from the spirit and scope of the application as defined by the following claims.

Claims

1. A liquid cooled high torque and high power device for magnetically transferring torque comprising: a primary rotating component and a secondary rotating component; said primary rotating component axially overlaps said secondary rotating component; said secondary rotating component is surrounded by said primary rotating component; said primary rotating component has permanent magnets mounted thereon; said secondary rotating component has electrically conductive elements and magnetically permeable material and no permanent magnets; said electrically conductive elements are cooled by liquid coolant flowing in axial liquid cooling channels immediately adjacent to and parallel to said secondary rotating component's electrically conductive elements, said liquid coolant flow is further adjustable to optimize the amount of liquid coolant flow required to achieve optimal device efficiency, said liquid coolant is delivered to said device by a closed liquid cooling system having an external storage tank, an external pump, an external heat exchanger to reject heat generated in said electrically conductive elements, said secondary rotating component is axially overlapped by said primary rotating component, including means for changing the axial position of said primary rotating component relative to said secondary rotating component; and said primary rotating component is connected to and driven by a torque generating device, and said secondary rotating component is connected to a torque utilizing device, whereby rotation of said primary rotating component causes rotation of said secondary rotating component by cutting through said electrically conductive elements on said secondary rotating component with some or all of the magnetic flux emanating from said permanent magnets mounted on said primary rotating component, whereby torque and rotation are generated in said secondary rotating component based on the percentage of the total area of said secondary rotating component that is axially overlapped by said primary rotating component, and said permanent magnets are cooled by direct liquid coolant impingement from the ends of said liquid cooling channels positioned immediately adjacent to said electrically conductive elements of said secondary rotating component.

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