Rotary power transmission joint with an integrated wireless sensor

An assembly for acquiring operational data from a machine including a power generating device and a rotating component interconnected with the power generating device for transmitting power from the power generating device. The assembly comprises a sensor assembly for being interconnected with the rotating component for sensing the operational data of the vehicle that includes at least one accelerometer for measuring the rotational speed of the rotating component, a temperature sensor for measuring the temperature of the rotating component, a pressure sensor for measuring the fluid pressure adjacent to the joint, a strain gauge for being interconnected with the rotating component for detecting the strain on the rotating component. The assembly further comprises an energy harvesting assembly for harvesting energy from the rotating component to provide electric power to the sensor assembly.

BACKGROUND OF THE INVENTION

1. Field of the Invention

An assembly for acquiring operational data from a machine including a power generating device and a rotating component interconnected with the power generating device for transmitting power from the power generating device.

2. Description of the Prior Art

Assemblies for acquiring operational data from a machine including a power generating device and a rotating component interconnected with the power generating device for transmitting power from the power generating device are generally known in the art, especially in the field of vehicles using engines to generate power. One such Assembly is disclosed in U.S. Pat. No. 6,632,252 to Christos T. Kyrtsos, which includes a sensor assembly for being interconnected with a vehicle for transmitting temperature data. The sensor assembly includes an energy harvesting assembly for harvesting ambient energy using an inductive configuration for powering the sensor assembly.

There remains a need for improvements in such assemblies to wirelessly monitor additional types of operational data to improve operation of such machines. With regard to vehicles, there remains a need for improvements that lead to increased fuel economy and longer vehicle life. Further there remains a need for more compact wireless assemblies that have components that are protected from ambient forces.

SUMMARY AND ADVANTAGES OF THE DISCLOSURE

An assembly for acquiring operational data from a machine including a power generating device and a rotating component interconnected with the power generating device for transmitting power from the power generating device. The assembly comprises a sensor assembly for being interconnected with the rotating component for sensing the operational data of the machine. The sensor assembly includes a microprocessor for receiving and interpreting the operational data, at least one accelerometer for measuring the rotational speed of the rotating component to determine the horsepower being transmitted through the rotating component and for measuring vibrations of the rotating component, at least one temperature sensor for being interconnected with the rotating component for measuring the temperature of the rotating component, at least one pressure sensor for being interconnected with the rotating component for measuring the pressure of the air adjacent to the joint, at least one strain gauge for being interconnected with the rotating component for detecting the torsional strain on the rotating component and for determining horsepower, and at least one transceiver for communicating data signal and operational instructions to a transceiver base unit. The assembly further comprises an energy harvesting assembly for being interconnected with the rotating component and electrically connected with the sensor assembly for harvesting energy from the rotating component to provide electric power to the sensor assembly.

Thus several advantages of one or more aspects of the disclosure are that the disclosure provides for a wireless assembly that can be incorporated into a rotating component of a machine to monitor torque, RPM's, horsepower, acceleration, temperature and pressure without the need to connect to the primary battery of the machine. Further, the disclosure provides for a pre-calibrated torque joint instrument that can be built and readily installed in shaft power applications without the need for system calibration of strain rate after installation. Furthermore, the disclosure provides for a sensor assembly that is protected from external forces. Additionally, the disclosure provides for real time corrected horsepower of the power generating component through measured horsepower transmitted through the rotating component, by means of air density measurements taken through temperature and pressure sensors. In addition, the disclosure provides for early detection and failure detection of the rotating part through the strain gauges, accelerometer, and temperature sensor.

DETAILED DESCRIPTION OF THE ENABLING EMBODIMENTS

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, an assembly20is generally shown for acquiring operational data such as torque, acceleration, temperature and pressure from a machine that includes power generating device22and a rotating component, such as but not limited to, a driveshaft24, driveshaft yoke, Cardan universal joints28(U-joints), as best presented inFIG. 2, a double Cardan universal joints30, as best presented inFIG. 4, or various transmission joint to determine operational data such as speed, acceleration, torque, horsepower rotational position and vibration due to imbalance. In the enabling embodiments, the assembly20is used with a vehicle that includes an engine, but it should be appreciated that the assembly could be used with other machines such as, but not limited to turbines, pumps or pulleys, with other types of power generating devices.

In the enabling embodiments, the assembly20acquires data from a joint26that transmits rotational movement from the transmission23to the driveshaft24and from the driveshaft24to the rear transaxle at an angle. Typical rear wheel drive applications have two or more such joints26between the transmission output and the rear differential. In the enabling embodiments, the joint26is a Cardan universal joint28, as best presented inFIG. 2, and a double Cardan universal Cardan joint30, as best presented inFIG. 3. It should be appreciated that in power transmission applications, other joints26could be used, such as but not limited to, a Thompson constant velocity joint29, as best presented inFIG. 4, or a Rzeppa constant velocity joint36, as best presented inFIG. 5. Further it, should be appreciated that the assembly20could acquire data from other rotating components of the vehicle such as, but not limited to, a driveshaft24or driveshaft yoke.

The joint26includes an input shaft and an output shaft34and a joining component36for interconnecting the input and output shafts. In the enabling embodiments, the joint26includes a generally cylindrical shaped input shaft32for being interconnected with the engine22, through a transmission23, and a generally cylindrical shaped output shaft34for being interconnected with the driveshaft24of the vehicle, and a joining component36for interconnecting the input shaft32and the output shaft34and for providing for pivotable movement between the input and output shafts32,34. It should be appreciated that the input and output shafts32,34could have other cross-sectional shapes such as, but not limited to, a square cross section.

A sensor assembly38is interconnected with the rotating part of the machine for acquiring the operational data of the machine. In the enabling embodiments, the sensor assembly38is interconnected with the joint26for acquiring the operational data of the vehicle. It should be appreciated that the sensor assembly38could alternatively be attached to other rotating components of the vehicle such as, but not limited to the driveshaft24or driveshaft yoke. Further, a transceiver base unit35is wirelessly connected with the sensor assembly38for receiving the operational data from the sensor assembly38and for sending instructions to the sensor assembly38to change the preferred mode of operation of the sensor assembly38and/or vehicle. The sensor assembly38includes a remote transceiver43for sending data and receiving instructions from the transceiver base unit35. In the enabling embodiments, the transceiver base unit35is interconnected with the vehicle in an accessible location to operators; however, it should be appreciated that the transceiver base unit could be positioned at any location depending on the application of the sensor assembly38.

Data from the remote transceiver43is wirelessly transmitted (typically in the 2.45 Ghz range) to the transceiver base unit35that receives the digital signal and passes it on to either digital via USB, SPI, two-wire, or USART or other form of digital outputs, or converts it back to analog signals for analog outputs. Commands can be sent from the transceiver base unit35to the remote transceiver43to setup active data channels, set data rates, change transmission channel and various other operating characteristics. It should be appreciated that the transceiver base unit35and remove transceiver43could communicate with each other in others ways such as, but not limited to, a Bluetooth connection.

The sensor assembly38includes a circuit board40that is interconnected with the joint26. It should be appreciated that the circuit board40could be interconnected with the joint in various ways such as, but not limited to, an adhesive or nuts and bolts. In the enabling embodiment, the circuit board generally has a rectangular shape and defines a front face. It should be appreciated that the circuit board40could have various shapes, ideally to match a portion of the joint26which it is being connected to. A rechargeable battery42is interconnected with the joint26and is electrically connected with the sensor assembly38for providing electric power to the sensor assembly38. The circuit board40further includes a microprocessor44that is electrically connected with the sensor assembly38and transceiver43for receiving and interpreting the operational data from the sensor assembly38and rotating component and for directing the electric power from the battery42to the sensor assembly38. It should be appreciated that the transceiver43could be positioned on the circuit board40, or disposed at another location. It should be appreciated that a universal Cardan joint28is a good location for installation of such a sensor assembly38as the sensor can be mounted perpendicular to and centered with to the rotation axis, thus, eliminating inertial loads and imbalance due to the sensor weight.

The sensor assembly38also includes at least one accelerometer46for measuring the rotational speed and vibrations of the rotating component. In the enabling embodiments, the accelerometer measures the rotational speed and vibrations of the joint26to determine the horsepower transmitted through the drive shaft and for measuring vibrations of the drive shaft to send an accelerometer signal corresponding to the rotational speed and/or vibrations. In the enabling embodiments, two 3-axis Microelectromechanical Systems (MEMS) accelerometers46are interconnected with the circuit board40. It should be appreciated that different types, and any number of accelerometers46could be used, and they could be disposed at various locations on the rotating component of the automobile. In the enabling embodiment, the circuit board40is placed such that the face of the circuit board40extends perpendicular to the axis A of rotation, such that the accelerometers46are positioned on the circuit board40to negate gravitational or inertial accelerations of the rotating component of the vehicle in order to determine rotational speed, rotational angle, angular accelerations, and radial disturbances. Further, the accelerometers46are positioned adjacent to the radial center of the joint26, at its axis of rotation, in order to keep the radially oriented axes of the accelerometer(s)46from saturating at high engine22speeds due to the inertial forces. For example, at ¼″ radius, a shaft rotating at 8000 rpm will generate 455 G's in the radial direction. The maximum allowable rotational speed for which the device can produce useful radial acceleration data can therefore be determined based on the maximum G-rating of the accelerometer46and the radial placement of the accelerometer46on the circuit board40. Typically for performance vehicle applications, a system would have two 450 G accelerometers46placed at a radius of approximately ˜¼″. Accordingly, it should be appreciated that the circuit board40is positioned such that its face extends perpendicular to the axis A of rotation, and the accelerometers46are positioned radially adjacent to the axis A.

In addition, access to the axis A of rotation allows two accelerometers46to be installed on a single circuit board40with opposite directions of inertial loads acting on their positive radial axes while gravitational loads are acting in the same direction for each. Similarly, the two accelerometers46can be installed on the board such that opposite directions of gravitational loads are acting on their positive radial axes while inertial loads are acting in the same direction. Likewise, the accelerometers46can have opposite directions of rotational accelerations acting on their positive circumferential axes while gravitational loads are acting in the same direction for each. It should further be appreciated that the accelerometers46are capable of sensing rotational direction from the gravitational quadrature signals associated with two perpendicular accelerometer axes.

The two accelerometers46can be installed on the board such that opposite directions of gravitational loads are acting on their positive circumferential axes while rotational accelerations are acting in the same direction. This enables measurement of angular position, velocity and acceleration as different acceleration signatures can be isolated. Angular position measurements, derived solely from rotating components, can be used as a clocking source for spatially resolved Analogue to Digital (A-D) conversions of instantaneous torque measurements. Angular velocity measurements can be used with instantaneous torque measurements to provide real time horsepower supplied to and/or absorbed from the load.

In the enabling embodiments wherein the rotating component of the vehicle is a universal Cardan joint28, the accelerometer signal from the accelerometer46can determine an axial alignment angle between the input and output shafts32,34. Furthermore, the accelerometer signals can be used to determine axial inclination by considering the Direct Current (DC) component of the axially-aligned axis. Accuracy is improved over a wide range of radial acceleration (i.e., shaft rotational speed) as the remote is capable of digitally changing the range of the MEMS accelerometers46dynamically to best resolve the instantaneous magnitude of radial acceleration. As best presented inFIG. 10, dual 3-axis MEMS gyroscopes47can be added to supplement readings from the accelerometer46with angular velocity to provide more accurate position and orientation measurement. It should be appreciated that other gyroscopes could be used.

Angular shaft accelerations/decelerations result from changes in input torque and/or output load, and from changes in upstream and/or downstream inertial loads applied to the driveshaft24. During positive torque events (i.e., input torque exceeds output torque), torque and angular acceleration sensor measurements can be acquired to determine downstream inertia loads from the sensor assembly38. For example, in the vehicle, the downstream inertial loads result from the rear differential, wheels, and road load which can vary with vehicle weight and payload, vehicle inclination, wheel traction, etc. During negative torque events, torque and angular acceleration can be used to determine upstream inertial loads. In another example, the upstream inertial loads are affected by the operating characteristics of the transmission, clutch and engine22which can vary with gear changes, clutch engagement, cylinder fuel/air management, engine accessory loads, etc.

Further, engine speed can be determined from the accelerometers46as illustrated inFIG. 11B. The signal difference between the x-axes as shown inFIG. 11Bis proportional to the square of the engine speed. The proportionality constant equals the radius at which the accelerometer46is mounted on the circuit board40from the center of rotation of the joint26. In the absence of radial disturbances, the period generated as presented inFIG. 12BandFIG. 13Bis measured using a comparator on the microprocessor44to more accurately determine engine22speed. Multiple periods can be measured and averaged to produce an even higher resolution of engine22speed averaged over the duration of the measurement event. Measurement of multiple periods can furthermore be used to eliminate erroneous period measurements (as determined by its standard deviation) resulting from radial disturbances to the rotating component.

Angular acceleration can be determined as further presented inFIG. 14B. The signal difference between the y-axes as presented inFIG. 14Bequals twice the angular acceleration. As presented inFIGS. 12B and 13Ba radial disturbance on the rotating component can be determined. Radial vibrations may be caused by imbalance in the rotating component or by bulk motion of the vehicle that contains the rotating component (e.g. —a vehicle hitting a pothole). The magnitude of the radial disturbance can be found from the root of the sum of the squares of the two signals (i.e. —(SA2+SB2)).

As best presented inFIG. 7, in the enabling embodiment wherein the joint26is a universal Cardan joint28, the universal Cardan joint28includes a body48that has a generally cross shape that includes a central tube50that has a generally tubular shape and extends along an axis A of rotation, and defines an outer wall52that extends between a pair of ends54and defines a cavity56therein. The body48further includes a pair of input trunnions58that extend from opposing sides of the outer wall52of the central tube50in alignment with one another, and a pair of output trunnions60that extend perpendicularly to the input trunnions58on opposing sides of the outer wall52of the central tube50. A bearing cap62is disposed about each of the input and output trunnions58,60for rotating about the trunnions58,60. The outer wall52of the central tube50defines four corner segments64, each between one of the input trunnions58and one of the output trunnions60.

When the accelerometer axes are aligned with the input trunnions58(constant velocity) or output trunnion60(oscillating velocity) of the joint26, a frequency at twice the rotational frequency of the input shaft32will be superimposed on the rotational frequency signature with an amplitude proportional to the angle between the input and output shafts32,34as the output shaft34cyclically accelerates and decelerates through two cycles every revolution. The amplitude can be used to dynamically determine the relative shaft angle between the input and output shafts32,34. It should be appreciated that due to the oscillatory nature of the joint26, when implemented with a non-zero angle between input and output shafts32,34, provides adequate acceleration to detect rotational speeds in either horizontal or vertical shaft orientations.

In the enabling embodiments, as best presented inFIG. 7, the circuit board40is disposed in the cavity56of the central tube50. The battery42is also disposed in the cavity56of the central tube50adjacent to the circuit board40. An end cap66removably seals each of the ends54of the central tube50for sealing the cavity56and housing the pin bearings. It should be appreciated that the circuit board40and battery42could be positioned at other locations of the rotating component.

It should be appreciated that sealing the circuit board40and battery42in the cavity56advantageously protects the circuitry from harsh environmental conditions and minimizes inertial load imbalance resulting from the system installation.

In the first enabling embodiment, the bearing caps62of the input trunnions58are interconnected with the input shaft32through a U-shaped trunnion yoke33for rotating with the input shaft32. Further, the bearing caps62of the output trunnions60are interconnected with the output shaft34for rotating with the output shaft34.

In the second enabling embodiment, as best presented inFIG. 3, the joint26is a double Cardan universal joint30which includes a first body51and a second body53. The bearing caps62of the input trunnions58of the first body48are interconnected with the input shaft32for rotating with the input shaft32. The bearing caps62of the output trunnions60of the second body48are interconnected with the output shaft34for rotating with the output shaft34. Further, a connection cylinder68that has a generally cylindrical shape is interconnected with the output trunnions60of the first body48and the input trunnions58of the second body48for transferring rotational movement from the first body48to the second body48to spin the output shaft34at the same constant velocity as the input shaft32. It should be appreciated that the connection cylinder68could have other cross-sectional shapes such as, but not limited to, a square cross-section.

As best presented inFIG. 6, the sensor assembly38further includes at least one strain gauge70for detecting the strain on the joint26. In the enabling embodiments, a strain gauge70is disposed on each of the corner segments64for detecting the strain at each of the corner segments64for optimal placement in a peak strain location. Opposite diagonal strain gauges70experience similar compressive/tensile forces. The strain gauges70form the four quadrants of a full Wheatstone bridge circuit. It should further be appreciated that inherent compressive and tensile forces in each quadrant of the joint provide optimal compressive/tensile strain fields for subsequent strain gauge70based measurements. In an embodiment of the circuit board40, the strain gauges70can be directly integrated into the four corners of a flexible circuit board40to eliminate wiring, facilitate accurate placement, and reduce the complexity of installation. The entire circuit board40with integrated gauges could be adhesively mounted to the u-joint surface in a single operation. It should be appreciated that the strain gauge70could be positioned at various other locations on the rotating component such as, but not limited to, trunnion yolk33.

It should be appreciated that the strain gauge70components can advantageously be pre-installed on a U-joint and readily installed in a power transmission application without the need for system calibration of strain rate after installation.

The integrated sensor assembly38is capable of transmitting high-speed signals directly to a stationary base unit35, or integrating high speed signals and calculated parameters on-board over a number of rotational events and subsequently performing lower speed transmission of calculated and averaged values. Re-transmission and AES encryption algorithms can be used to assure that data transfer is reliable and safe.

The sensor assembly38further includes at least one temperature sensor72for measuring the temperature of the rotating component. In the enabling embodiments, the temperature sensor72is interconnected with the joint26. It should be appreciated that any type of temperature sensor72could be used such as, but not limited to, thermocouples, and resistance thermometers. It should be appreciated that readings from the temperature sensor72can be used to detect early signs of performance degradation and potential failure of the driveshaft24or other rotating components.

Temperature sensors72placed near each of the trunnions58,60on the back side of the circuit board40can directly measure significant thermal gradients between trunnions58,60, thus, indicating a potential failure of the roller pin bearings within a specific bearing cap62.

The sensor assembly38further includes at least one pressure sensor73for measuring the fluid pressure adjacent to the joint26. It should be appreciated that depending on the application of the assembly20, the pressure sensor73can measure the pressure of any fluid such as, but not limited to, air, water, lubricants, hydraulic fluid. It should further be appreciated that on-board air density measurements, via the temperature and pressure sensors72,73, provide real time corrected horsepower from measured actual horsepower.

The sensor assembly further includes a global positioning system (GPS) sensor75for detecting speed and location data of the vehicle. It should be appreciated that the speed and location data can be used in conjunction with other operational data collected by the sensor assembly75. For example the GPS data could pinpoint what speed the vehicle was traveling at, and the specific location the vehicle was located at during a particular event. It should be appreciated that the GPS sensor75could be positioned on the circuit board40or any other location of the vehicle and rotating component.

An energy harvesting assembly74is interconnected with the joint26and is electrically connected with the battery42and the sensor assembly38for harvesting energy from the joint26to provide electric power to the sensor assembly38and the battery42for charging the battery42. It should be appreciated that the energy harvesting assembly74can provide a continuous power supply for the sensor assembly38.

As best presented inFIG. 8, in an embodiment of the disclosure, the energy harvesting assembly74is an inductive harvesting assembly that includes a coil76that is interconnected with the body48of the joint26, and a magnet78that is interconnected with the bearing cap62of at least one of the joints26, for rotating with the joint26for generating electricity. The magnet78and the coil76are electrically connected with the sensor assembly38for providing electric power to the sensor assembly38. It should be appreciated that the coil76could alternatively be placed on any of the input or output trunnions58,60and the magnet78could alternatively be positioned on the trunnion yoke33.

In the first enabling embodiment using a universal Cardan joint28, the output shaft34does not operate at constant velocity but rather has a periodic velocity that is twice the frequency of the input shaft32rotational speed. The trunnions58,60move cyclically relative to the bearing cap62at twice the frequency of the input shaft32. This relative motion, which occurs even with a constant input shaft32velocity, provides for an ideal source of inductive charging for supplying current to the sensor assembly38and/or a power storage cell. The magnets78mounted on the bearing caps62or trunnion yoke provide a static reference point relative to the motion of the body48for inductive power generation which can then be used to continuously power the sensor or supply energy to a charge storage device. Analogue to Digital (A-D) monitoring of the inductive signal can further provide a clocking and triggering source for spatially-resolved A-D torque acquisitions and speed sensing. Motion of the body48alone can be used as an inertially dynamic source for inductive and piezo-electric harvesting without the need for a relative static mounting location on the bearing cap62or trunnion yoke33. Similarly, motion of the output shaft34(or the body48of a double Cardan universal joint30) can provide an inertially dynamic energy source, as the output shaft34of a u-joint experiences two acceleration/deceleration cycles for each rotational cycle of the input shaft32of the joint26.

In another embodiment of the disclosure, as best presented inFIG. 10, the energy harvesting assembly74is a piezo-electric harvesting assembly that includes a piezoelectric flexible membrane77made of a ceramic material or a polymeric material and is interconnected with the joint26for deflecting in response to movement of the joint26to produce electricity. The energy harvesting assembly74further includes a charge management device85which is electrically connected with the piezoelectric flexible membrane77for receiving electricity from the piezoelectric flexible membrane. The charge management device84is electrically connected with the sensor assembly38for providing electric power to the sensor assembly38. The piezoelectric flexible membrane77can be tuned with an external mass to deflect at resonant frequencies at or near the typical operational frequencies of the rotating shaft. Deflection of the polymer portion of the piezo-electric flexible membrane77as a result of the oscillations creates a charge field which can be rectified and stored as electrical energy using a charge management device. The harvested energy may supply a portion of the required current needed to operate the sensors, thus, extending the duration between battery42charges, or may even supplement the entire load requirement, thus, enabling indefinite operation of the sensor assembly38.

The remote system is equipped with a battery monitoring circuitry39as well as detection circuitry41of active harvesting to enable intelligent charge management and circuit activation upon obtaining adequate energy storage.

In another embodiment of the disclosure, the energy harvesting assembly74is a peltier harvesting assembly which includes a bi-directional peltier controller which is interconnected with the joint26for generating electricity. The peltier controller is electrically connected with the sensor assembly38for providing electric power to the sensor assembly38. Thermal energy generated within the joint26is another viable energy harvesting source by using a Peltier device. With a bi-directional Peltier controller (i.e., gradients in either direction can be harvested) a single 10 mm square Peltier controller has demonstrated the ability to produce adequate charge current to power our integrated sensor device at transmission rates up to 100 Hz with no more than a 5 C temperature difference between the rotating shaft and ambient air. Higher temperature differences can support higher transmission rates. A universal joint26is unique in that it generates heat as a result of its motion. In an embodiment, needle bearings within the bearing cap62generate frictional heat as they roll within a viscous lubricant transferring load between the bearing cap62and trunnion. The slightest increase in temperature between the u-joint and ambient can provide the necessary thermal gradient to power the device. Even when the shaft is inactive, diurnal changes in temperature continuously warm and cool the thermal mass of the rotating device providing a continuously varying gradient for thermal-electric battery42charging. The unique aspect of this charging technique is that power harvesting is not dependent on motion and can occur even when the shaft is not in use. A combined strategy (i.e., thermal-gradient and motion-based) provides a robust charging and supply system that assure functionality over a long operational life.

Obviously, many modifications and variations of the present disclosure are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims. These antecedent recitations should be interpreted to cover any combination in which the inventive novelty exercises its utility. The use of the word “said” in the apparatus claims refers to an antecedent that is a positive recitation meant to be included in the coverage of the claims whereas the word “the” precedes a word not meant to be included in the coverage of the claims.