Patent Application
20230113348
The present disclosure generally relates to electric motor driven pump systems and more specifically, to pump systems providing desired and optimized performance characteristics by leveraging high speed motor input while limiting the rotational speed of the pump.
Pump systems of apparatus such as vehicles and other equipment and machinery, move fluids and/or generate pressures for a variety of purposes. Many types of pumps are available and each generally requires a motive input device (motor), such as one that operates on electric, pneumatic, hydraulic, or mechanical power to drive moving parts of the pump. The type of pump selected is driven by the operational requirements of the pump system and the load services by the pump. The design and operating conditions of the pump determine the amounts of torque or force required to drive the moving parts. The amount of torque/force required influences the cost, weight and type of the motive input device that is appropriate for use. For example, when an electric motor is used to drive the pump, the types and the design of the electric motor is dictated by the input requirements and performance capabilities of the selected pump.
In a given fluid system, the pump that is selected and the work done by the fluid influences the selection of a paired motor that will achieve the performance requirements for a given application. In applications such as those for vehicles, size and its impact on weight may have an influence on factors such as fuel economy. The amount of electric power consumed is also preferably minimized. In addition, motor cost is an ongoing concern. As a result, in designing pump systems, the type of motor used and operational capabilities of the motor are considered.
Accordingly, it is desirable to provide a pump system for a given application that results in appropriate performance characteristics such as torque/force requirements and provides a desired level of efficiency at minimized cost. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
Systems and methods are provided for pump systems that deliver desirable performance characteristics such as operating the motor at a relatively high speed while operating the pump at a lower, limited speed. In a number of embodiments, a method includes selecting a pump for the pump system. A maximum operating speed of the pump is determined, and its torque requirements are evaluated. A motor is selected to meet the torque requirements and a speed target is set for the motor. A speed reducer is sized for operation of the motor at the speed target and operation of the pump below the maximum speed, and the motor is coupled with the pump through the speed reducer.
In additional embodiments, determining the maximum speed includes determining a high speed fill limit of the pump above which fluid flow of the pump is independent of speed change, and the maximum speed is set at a threshold below the high speed fill limit.
In additional embodiments, sizing the speed reducer includes selecting a gear ratio of the speed reducer that results in operating the pump below the high speed fill limit when the motor is operated at the speed target.
In additional embodiments, evaluating the torque requirements includes evaluating the torque requirements for the pump through a range of operating temperatures and flow rates of the pump system.
In additional embodiments, setting the speed target includes evaluating, simultaneously, speed and torque requirements of the motor.
In additional embodiments, selecting the speed reducer includes selecting the speed reducer that reduces speed from the motor to the pump and that increases torque transferred from the motor to the pump.
In additional embodiments, selecting the motor includes selecting a brushless direct-current motor. Selecting the speed reducer includes selecting a planetary gearset for the speed reducer. The motor is coupled to the planetary gearset, and the pump is coupled to the planetary gearset.
In additional embodiments, the pump is fluid coupled with a load, and the pump is sized to meet flow requirements of the load.
In additional embodiments, sizing the pump includes evaluating flow requirements of the load over a range of operating temperatures.
In additional embodiments, a maximum torque required to drive the pump is determined over an operating temperature range of the pump.
In a number of other embodiments, a pump system includes a pump configured to operate at a maximum speed and with torque requirements. A motor is configured to meet the torque requirements and to operate at a speed target. A speed reducer is coupled with the motor and the pump, and is configured to operate the pump below the maximum speed when the motor is operated at the speed target.
In additional embodiments, the pump is configured to operate at the maximum speed, which is lower than a high speed fill limit of the pump above which fluid flow of the pump is independent of speed change.
In additional embodiments, the speed reducer includes gearing with a ratio that results in operating the pump below the high speed fill limit when the motor is operated at the speed target.
In additional embodiments, the motor and the speed reducer are configured to deliver torque requirements for the pump through a range of operating temperatures and flow rates of the pump system.
In additional embodiments, the motor is configured to operate at the speed target and simultaneously to meet the torque requirements of the pump over a range of operating temperatures.
In additional embodiments, the speed reducer reduces speed from the motor to the pump and increases torque transferred from the motor to the pump.
In additional embodiments, the motor is a brushless direct-current motor, and the speed reducer includes a planetary gearset. The motor is coupled to the planetary gearset, and the pump is coupled to the planetary gearset.
In additional embodiments, a load serviced by the pump, the pump is fluid coupled with the load, and the pump is configured to meet flow requirements of the load.
In additional embodiments, the pump is configured to deliver flow requirements of the load over a range of operating temperatures.
In a number of additional embodiments, a method of manufacturing a pump system includes selecting a pump for the pump system. The pump is fluid coupled in a fluid system with a load that is operated using fluid supplied by the pump. A high speed fill limit of the pump above which fluid flow of the pump is independent of speed change of the pump is determined. A maximum operating speed of the pump is set at a threshold below the high speed fill limit. Torque requirements of the pump are evaluated through a range of operating temperatures and flow rates of the fluid system. A motor is selected to meet the torque requirements. A speed target is set for the motor above ten-thousand revolutions per minute. A speed reducer is selected and sized for operation of the motor at the speed target and operation of the pump below the maximum speed. The motor is coupled with the pump through the speed reducer. The pump is coupled with the load to supply the load with fluid from the pump.
The exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
The following detailed description is merely exemplary in nature and is not intended to limit the application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding introduction, brief summary or the following detailed description.
For the systems and methods disclosed herein, mated pump and motor performance requirements and characteristics are jointly considered and balanced for benefits such as to maximize efficiency and reduce cost. The pump moves a fluid to flow by increasing pressure so that the pressurized fluid moves to a lower pressure region of the system and to power operation of a load such as a drive unit. The characteristics of the pump are determined by considering the requirements of the load that will use the pumped fluid, and of the system through which the fluid is pumped. Therefore, a pump is selected with flow and pressure ratings selected and sized to match the flowrate and pressure required for the application's load and system. The rotational speed at which the pump will be operated is considered, and the system is configured so the pump's operating speed is maintained below a maximum desirable threshold.
The currently disclosed embodiments may employ a high speed electric motor coupled with the pump in an optimized system that may include a specifically tailored speed reduction in the coupling between the motor and the pump. The motor performs with higher efficiency when spinning at higher speeds with relatively low torques. System torque requirements are evaluated to ensure the maximum required torque is provided when needed in driving the pump, while motor speed is maintained for efficiency. In certain embodiments, such as vehicle applications, the high speed motor is supplied with electric power by a forty-eight volt power source for efficiently driving the motor at high speed, and the pump operates at robust functional speed for durability, noise minimization, and to avoid outcomes such as cavitation.
Referring to
The motor 24 may be any of various types of electric motors. In some embodiments such as for automotive applications, a brushless direct current (BLDC) motor 24 may be employed. Employing a BLDC motor 24 provides a relatively small and compact package that may be desirable for applications where space and weight are considered, such as automotive applications. A BLDC motor may be particularly desirable for electric vehicle applications where battery power is limited, and relatively high voltage is available. Therefore, the use of BLDC motors 24 in automotive and other applications may be desirable in driving various types of pumps 22 to provide motive fluid power for various types of loads 28. In general, the current disclosure may be applicable in any application where high speed operation of the electric motor 24 is desirable, without overdriving the pump 22. The motor 24 generally includes a stator 34 and a rotor 35, with a shaft 36 connected with the rotor 35.
The load 28 may be any unit that uses a flow of fluid to do work. In an embodiment, the load 28 is the fluid system for operating a drive unit of a vehicle. For example, a hydraulic drive unit may employ fluid power for actuation to effect control, shifting and/or to transfer torque. In other embodiments, the load 28 may be an actuator that provides power/motion for any use.
The speed reducer 26 may be any of various types of torque transferring and input-output ratio defining mechanisms. For example, the speed reducer 26 may be a geartrain arrangement, a sprocket and chain arrangement, a pulley and belt arrangement, a combination therefor, or another type of mechanism that transfers torque and defines the input-output speed ratio. In the current embodiment, the speed reducer 26 includes a planetary gear arrangement with a sun gear 40, planet gears 42, a ring gear 44, and a planet carrier 46. To provide a speed reduction, the input from the motor shaft 36 is delivered to the sun gear 40, output to the pump shaft 33 is provided from the ring gear 44, and the planet carrier 46 is fixed, such as to a case 48. The various gears are sized to provide the input-output ratio desired.
Also shown in
The pump system 20 includes an electrical system 60, a mechanical system 62 and a fluid system 64. The electrical system 60 includes the motor 24, the power supply 50, the controller 52 and the driver and power electronics module 54. Other elements such as various sensors, actuators and other conventional elements are not shown. The mechanical system 62 includes the motor shaft 36, the speed reducer 26 and the pump shaft 33. Other elements, such as the rotor 30, 35 may be considered a part of the mechanical system for various purposes. The fluid system 64 includes the pump 22, the load 28 and the fluid circuit 68. The fluid circuit 68 includes the fluid passageways in the pump 22 and in the load 28 and includes the conduits 70 interconnecting the various elements. Other elements such as heat exchangers, valves and reservoirs are not shown.
Referring to
Referring to
A process 100 for developing and manufacturing the pump system 20 is illustrated in
In the current embodiment, a fixed displacement pump 22, such as an internal gear pump is selected. The process 100 continues with a determination 108 of the maximum pump speed. As a fixed displacement pump 22, a fixed amount of fluid is delivered per revolution of the pump 22. In general, flow-rate is increased in proportion to the rotational speed increase of the pump. A high speed fill limit is reached when the pump chambers can no longer be completely filled with fluid due to the high speed at which the rotor 30 is moving, and may be determined by system performance testing and/or modelling, such as using available fluid dynamics software. In determining 108 the maximum pump speed, the high speed fill limit conditions are evaluated throughout the range of operation speeds of the pump 22 and for the range of operating temperatures of the fluid circuit 68. The evaluation may be conducted through performance testing and/or through analysis such as by using available fluid dynamics software. When the maximum pump speed threshold is determined, the system 20 is configured to maintain speeds below the threshold. At the same time, pump speeds are implemented to deliver the fluid flow requirements of the fluid circuit 68. The speed target may be evaluated with reference to pump performance curves available from the manufacturer or developed by characteristic testing and/or modelling. Pump sizing may be re-evaluated is consideration of the limited speed threshold to ensure requirements of the load at achieved.
In coordination with the determination 108 of the maximum pump speed, pump input torque requirements are evaluated 110. Input torque requirements for the pump 22 are evaluated 110 through the range of operating temperatures and flow rates of the fluid circuit 68. The highest torque required may occur under certain conditions. For example, due to fluid viscosity increases with lower temperatures, the maximum torque required to drive the pump 22 may occur at the lowest operating temperatures of the system 20. In other cases, the maximum torque required may be required at the highest flow requirements of the fluid circuit 68, including of the load 28. Accordingly, flow requirements are evaluated over the range of operating temperature and over the range of system flow rates. Iteration may be used to determine where the maximum torque requirement exists within the range of temperature and flow rate variables.
Given the maximum torque requirement, the motor 24 is selected 112 to meet those requirements, with consideration of desirable speeds. Speed-torque characteristics of the motor 24 are aligned with requirements of the pump 22. For example, a BLDC motor 24 that matches the requirements may be selected. With a BLDC motor 24, size (and torque) considerations have an impact on cost due to a number of factors. The use of rare earth materials in the magnets of the motor 24 are minimized by reducing size. Smaller size also leads to less mass and cost of the motor and vehicle wiring. Lower torque and cost may be accomplished by operating at higher speeds, above those at which the pump 22 may be preferably operated. Commercially available finite element method based-based software may be used to assist in motor specification.
The operational speed target of the motor 24 is set 114, based on efficiency and a balance of torque and speed. For example, and with reference to
Iteration 118 may be used to consider speed and torque requirements in sizing the motor 24 and the gearing in the speed reducer 26. In the evaluation, consideration may be given to the characteristic that operating at high torque may result in the motor 24 heating up and losing efficiency. In addition, mechanical power is the product of torque and speed and so the torque and speed are balanced so that the high speed fill limit threshold of the pump 22 is not exceeded and so that the motor 24 is right sixed to meet torque requirements while operating at efficient speeds. With the motor 24, speed reducer 26 and pump 22 selected, the system 20 is assembled 120 and may be operated to service the load 28. In a number of embodiments, the order of the steps in the process 100 may differ from those described herein, other steps may be added, and some steps may be omitted.
Accordingly, pump systems and methods are provided with an electric motor that spins at efficient speeds, such as greater than 10,000 revolutions per minute. Using speed reduction, the pump spins at speeds below its high speed fill limit, such as below 5000-6000 revolutions per minute. The system has high efficiency, low cost, low electrical current requirements, with more capability (higher pressure and flow).
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.
