Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16N—LUBRICATING
  • F16N11/00—Arrangements for supplying grease from a stationary reservoir or the equivalent in or on the machine or member to be lubricated; Grease cups
  • F16N11/08—Arrangements for supplying grease from a stationary reservoir or the equivalent in or on the machine or member to be lubricated; Grease cups with mechanical drive, other than directly by springs or weights

Definitions

• the present invention generally relates to a lubricant delivery system and method and, more particularly, to a lubricant delivery system and method for the bearings that rotationally support a device, such as a control moment gyroscope rotor.
• Attitude control in many spacecraft is implemented using one or more control moment gyros (CMGs).
• CMG is a torque-generating mechanism that may include a rotating flywheel, or rotor, that is mounted in a gimbal frame and that rotates about a spin axis.
• the gimbal frame may be rotationally mounted about one or more gimbal axes, which are perpendicular to the spin axis.
• one or more actuators may be coupled to the gimbal frame and, in response to attitude control commands, may rotate the gimbal frame about one or more of the gimbal axes. By rotating the frame about one or more of the gimbal axes at certain rates, torques can be generated in the spacecraft body to effect spacecraft attitude control.
• one of the components of a CMG is a spinning rotor.
• the rotor is rotationally supported using one or more bearing assemblies.
• the bearing assemblies are predominantly rolling element contact bearings, which are many times the limiting factor in the life of a CMG.
• the bearings are supplied with an initial quantity of lubricant, such as oil, to reduce rotational friction losses and to mitigate bearing wear. Depletion of this lubricant can induce failure.
• lubricant such as oil
• magnetic bearings have been used in some instance, but this results in increased power demand.
• Another way this problem has been addressed is to provide a system to periodically replenish the lubricant.
• an oil delivery system is provided on many CMGs.
• At least one known oil delivery system includes a pressurized oil reservoir, a solenoid valve, and an oil supply line.
• the pressurized oil reservoir is a compressible bellows that is filled with oil.
• the oil within the bellows is continuously pressurized by a spring that biases the bellows toward compression.
• the oil supply line is in fluid communication with the CMG bearing assemblies, and the solenoid valve is in fluid communication with the reservoir and the supply line.
• the solenoid valve is momentarily opened, releasing a volume of oil into, and through, the supply line and to the CMG bearing assemblies.
• linear potentiometers have been incorporated into the system to measure the amount of bellows travel when the solenoid valve is opened.
• a lubricant delivery system and method that reduces the likelihood of delivering excessive amounts of lubricant to the spin bearings, which can increase mission lifetime by having a larger amount of deliverable oil, and that reduces system fabrication and maintenance complexity, time, and associated costs.
• a system and method for delivering lubricant to, for example, control moment gyro (CMG) spin bearings is provided that reduces the likelihood of delivering excessive amounts of lubricant to the spin bearings, and that reduces system fabrication and maintenance complexity, time, and associated costs.
• CMG control moment gyro
• a lubrication medium supply system includes a reservoir, a motor, and a valve.
• the reservoir has an inner volume adapted to receive a lubrication medium therein.
• the motor is coupled to the reservoir and is operable to compress, and thereby pressurize to at least a first pressure magnitude, the lubrication medium.
• the valve has at least a fluid inlet in fluid communication with the reservoir inner volume and a fluid outlet.
• a valve in another exemplary embodiment, includes a valve body and a flow control element.
• the valve body includes at least a fluid inlet and a fluid outlet.
• the fluid inlet is adapted to couple to a selectively pressurized source of a lubrication medium.
• the flow control element is disposed within the valve body and is operable, in response to pressurization of the lubrication medium to at least a first pressure magnitude, to move between at least a closed position and an open position.
• the fluid inlet and fluid outlet are in fluid communication with one another when the flow control element is not in the closed position.
• a method of supplying lubricant contained within a reservoir to a bearing assembly includes providing a valve having a fluid inlet in fluid communication with the lubricant in the reservoir and a fluid outlet in fluid communication with the bearing assembly.
• the valve is operable, in response to pressurization of the lubricant in the reservoir to at least a first pressure magnitude, to couple the fluid inlet and fluid outlet in fluid communication with one another.
• the lubricant is pressurized to at least the first pressure magnitude to thereby move the valve to the open position, whereby lubricant flows from the reservoir to the bearing assembly and substantially simultaneously depressurizes the lubricant.
• FIG. 1 is a simplified schematic diagram of an exemplary control moment gyro system
• FIG. 2 is a cross section view of a lubrication medium supply system according to an exemplary embodiment of the present invention that may be incorporated into the control moment gyro system shown in FIG. 1;
• FIG. 3 is a cross section view of a lubrication medium supply system according to an exemplary alternative embodiment of the present invention that may be incorporated into the control moment gyro system shown in FIG. 1;
• FIG. 1 a simplified schematic diagram of an exemplary control moment gyro (CMG) 100 is shown.
• the CMG 100 may be installed in a spacecraft such as, for example, a satellite, and may be used in conjunction with other CMGs 100 to control spacecraft attitude.
• the CMG 100 includes a flywheel (or rotor) 102 and a gimbal frame 104.
• the flywheel 102 is rotationally supported on the gimbal frame 104 via a plurality of bearing assemblies 106.
• first 106a and second 106b bearing assemblies are provided, though it will be appreciated that other numbers of bearing assemblies could be provided.
• a motive power supply source 108 such as, for example, a motor, is coupled to the flywheel 102 to rotate the flywheel 102 about a spin axis 110.
• the motor 108 could be any one of numerous motor designs known now, or developed in the future including, but not limited to, various types of DC and AC motor designs.
• the gimbal frame 104 is rotationally supported about one or more gimbal axes 112, which are perpendicular to the flywheel spin axis 110, via one or more gimbal actuators 114.
• the gimbal actuators 114 are coupled to receive control signals from, for example, a gimbal controller 116.
• attitude control in a spacecraft may be implemented by changing the angles of each gimbal frame 104 at certain rates (e.g., angular velocities).
• the gimbal controller 116 supplies appropriate control signals to the gimbal actuators 114.
• the gimbal actuators 114 move the gimbal frame 104 at the appropriate angular velocities along the gimbal axes 112.
• One or more sensors 118 that can sense, for example, the position and rate of the gimbal frame 104, may be included to supply position and rate feedback signals to the gimbal controller 116.
• the bearing assemblies 106 are, for example, rolling element bearing assemblies that need periodic lubrication.
• a lubrication medium supply system 120 is also shown in FIG. 1.
• the lubrication medium supply system 120 is used to selectively and/or periodically supply precise quantities of lubricant to the bearing assemblies 106.
• the lubrication medium supply system 120 receives commands from a controller 122 and, in response to the received commands, supplies lubrication to the bearing assemblies 106 via one or more lubrication supply lines 124. Confirmation of the quantity of lubricant delivered is derived from a determination of the amount of reservoir displacement.
• the controller 122 may be a specialized controller that is used solely to control the lubrication medium supply system 120, or a general controller that is used to control other systems in addition to the lubrication supply system 120.
• a cross section view of lubrication medium supply system 120 is shown in FIG. 2, and will now be described in detail.
• the lubrication medium supply system 120 includes a reservoir 202, a motor 204, and a valve 206.
• the reservoir 202 in the depicted embodiment, is a flexible bellows 208 that is made of any one of numerous materials including, but not limited to, various steel alloys. In a particular preferred embodiment, however, the bellows 208 is made of AM350 steel.
• the bellows 208 is contained within a housing 210, and is at least partially filled with a lubrication medium 212.
• the lubrication medium 212 may be any one of numerous types of lubricants useful as a bearing lubricant such as, for example, Pennzane® Nye 2001 liquid lubricant.
• the bellows 208 is coupled at a first end 207 to the a threaded end cap 251 and at a second end 209 to an end plate 214.
• the bellows first 207 and second ends 209 are preferably coupled to the threaded end cap 251 and end plate 214, respectively, by, for example, a welding process, though it will be appreciated that any one of numerous other known methods of coupling could be used.
• the motor 204 is coupled to an end of the housing 210, and includes an input connection 216 such as, for example, a plug connector, that is adapted to receive appropriate commands from the controller 122. As will be described in more detail below, the motor 204 will rotate in either a first direction or a second direction in response to the commands received from the controller 122.
• the motor 204 may be any one of numerous known motor designs known now, or developed in the future, but in a preferred embodiment, it is a stepper motor.
• the motor 204 also includes an output shaft 218 that is coupled to an actuator assembly 220.
• the actuator assembly 220 is in turn coupled to the bellows end plate 209 and, as will be also described in more detail below, is used to compress or decompress the bellows 208.
• the actuator assembly 220 is configured to translate linearly in either a first or a second direction, in response to the rotation of the motor 204 in the first or second direction, respectively.
• the actuator assembly 220 may be any one of numerous known elements that may implement this functionality such as, for example, a leadscrew, or a ballscrew.
• the motor 204 is depicted as being coupled to the housing 210, it will be appreciated that it could be mounted remote from the housing 210. Determining and maintaining a count of steps or revolutions taken by the motor, and knowing the relationship between the steps or revolutions and linear translation of the actuator, provides knowledge of bellows displacement and, therefore, quantity of oil delivered.
• the valve 206 is also coupled to the housing 210, and includes a valve body 222 that has a fluid inlet 224 and a fluid outlet 226.
• the valve body 222 is constructed of two sections, a first section 228 and a second section 230.
• the valve body first section 228, which includes the fluid inlet 224, extends into the reservoir 202 and is sealingly coupled to the threaded end cap 251 by, for example, threaded fasteners 232 and one or more seals 234.
• the valve body second section 230 which includes the fluid outlet 226, is sealingly coupled to the valve body first section 228 by, for example, an O-ring, and one or more seals 236.
• the valve 206 also includes a poppet 240, which is slidably mounted within an inner volume 242 of the valve body 222 and is moveable between a closed position and an open position. In the closed position, which is shown in FIG. 2, a seal element 244, which is coupled to a first end 246 of the poppet 240, fluidly seals the valve body inner volume 242 from the valve body fluid inlet 224.
• a spring element 248 such as, for example, a coil spring, is disposed between the valve body second section 230 and a second end 250 of the poppet 240 and biases the poppet toward the closed position.
• One or more flow passages 252 are formed through the poppet 240 and fluidly communicate the valve body fluid outlet 226 with the valve body inner volume 242. In the open position, when the poppet 240 and seal element 244 are moved in a direction that unseals the valve body fluid inlet 224, the valve body fluid inlet 224 and fluid outlet 226 are in fluid communication with one another via the flow passages 252.
• the controller 122 When lubricant is to be delivered to the bearing assemblies 106, the controller 122 will supply an appropriate command to the motor 204 which will in turn rotate a commanded number of steps or revolutions in the commanded direction. As the motor 204 rotates, the actuator assembly 220 will in turn translate a predetermined amount in a direction that will compress the bellows 208. The controller 122 can use this translation amount to quantify the amount of lubricant delivered, and to determine the total amount of lubricant delivered, and thus the amount of lubricant remaining. The compression of the bellows 208 will in turn pressurize the lubrication medium 212.
• the valve 206 opens, coupling the fluid inlet 224 and fluid outlet 226 in fluid communication with one another.
• the poppet 240 is moved to the left (as viewed from the perspective of FIG. 2). As the poppet 240 moves left, the pressurized lubricant 212 flows into and through the fluid inlet 224, and into the valve body inner volume 242.
• the pressurized lubricant 212 in the valve body inner volume 242 flows through the poppet flow passages 252, into and through the fluid outlet 226, and into and through the fluid supply line 124 to the bearing assemblies 106.
• the pressure of the lubrication medium 212 in the reservoir 202 will decrease.
• the force of the spring element 248 will move the valve 206 to the closed position.
• the spring element 248 moves the poppet 240 to the right (as viewed from the perspective of FIG. 2) toward the closed position. In the closed position, the spring element 248 fluidly seals the fluid inlet 224, and no more lubricant flows into and through the valve 206.
• the first and second pressure magnitudes, at which the valve 206 opens and closes, respectively, is adjustable by adjusting the force supplied to the poppet 240 from the spring element 248. This may be done in any one of numerous ways, in the depicted embodiment, however, the number and/or size of the adjustment shims 238 is varied to adjust the spring force. It will additionally be appreciated that the system 120 may be configured and calibrated to dispense a particular volume of lubricant in response to a particular amount of movement of the actuator assembly 220.
• the system is configured and calibrated such that compressing the bellows 208 0.0005 -inches will result in 4 milligrams of lubricant being dispensed from the reservoir 202.
• the lubrication medium supply system may be implemented with a different type of reservoir.
• the alternative system 300 uses a substantially solid reservoir 302.
• the reservoir 302 may be formed in any one of numerous shapes, but in a preferred embodiment it has an inner peripheral surface 304 that is substantially cylindrical in cross section.
• the actuator assembly 220 is coupled to a plunger 306, which is moveable within the reservoir 302.
• the plunger 306 has an outer peripheral surface 308 that preferably is shaped substantially similar to the cross section of the reservoir inner peripheral surface 304.
• the plunger outer peripheral surface 308 contacts, in a substantially fluid-tight fashion, the reservoir inner peripheral surface 304.
• one or more fluid seals 310 may be coupled to, or formed integrally on, the plunger outer peripheral surface 308.
• FIG. 3 The embodiment depicted in FIG. 3 and described above functions substantially similar to the embodiment depicted in FIG. 2. However, rather than compressing the bellows 208 to pressurize the lubrication medium 212, the plunger 306 is displaced linearly to compress, and thereby pressurize, the lubrication medium 212.
• the alternate system 300 may be configured and calibrated to dispense a particular volume of lubricant in response to a particular amount of movement of the actuator assembly 220.
• the system 300 is configured and calibrated such that displacing the plunger 306 0.0005-inches into the reservoir 302 will result in 4 milligrams of lubricant being dispensed from the reservoir 302.
• the lubrication medium supply systems described herein include reservoirs that are not continuously pressurized. Rather, the lubricant in the reservoirs is pressurized momentarily, when lubricant is to be dispensed. Hence, the likelihood of delivering excessive amounts of lubricant to the spin bearings is reduced, and the volume of lubricant that may be stored in the reservoir can be increased.
• the systems can also reduce fabrication and maintenance complexity, time, and associated costs.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Magnetic Bearings And Hydrostatic Bearings (AREA)
• Rolling Contact Bearings (AREA)

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• 2003
  • 2003-05-07 US US10/431,794 patent/US7152712B2/en not_active Expired - Fee Related
• 2004
  • 2004-05-07 WO PCT/US2004/014267 patent/WO2004102062A2/en not_active Ceased
  • 2004-05-07 EP EP04751600A patent/EP1620675B1/en not_active Expired - Lifetime
  • 2004-05-07 DE DE602004031211T patent/DE602004031211D1/de not_active Expired - Lifetime
  • 2004-05-07 JP JP2006532849A patent/JP2007501924A/ja active Pending

Patent Citations (5)

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