Variable displacement pumps

In accordance with at least one aspect of this disclosure, a variable displacement pump system can include, a variable displacement pump disposed in a main line and configured to supply pressure to receive a low pressure fluid and to output a high pressure fluid. The main line can connect a hydraulic fluid source to a plurality of system actuators, where the variable displacement pump is disposed in the main line between the hydraulic fluid source and the plurality of system actuators to pressurize the hydraulic fluid.

TECHNICAL FIELD

The present disclosure relates to variable displacement pumps, and more particularly to methods for controlling variable displacement pumps.

BACKGROUND

Fixed displacement pumps can typically be sized to meet peak demand at a few operating conditions meaning the pump is then oversized for the remainder of conditions. Variable displacement pumps can be used to provide greater efficiency, as the flow can be changed for each operating condition. However, the pump displacement must be controlled to ensure system responsiveness and stability standards are met.

There is always a need in the art for improvements to methods for controlling variable displacement pumps in the aerospace industry. This disclosure provides a solution for this need.

SUMMARY

In accordance with at least one aspect of this disclosure, a variable displacement pump system includes, a variable displacement pump disposed in a main line and configured to receive a low pressure fluid and to output a high pressure fluid. A pressure port can be disposed in the main line downstream of the variable displacement pump configured to port a portion of the high pressure fluid from the main line to a bypass line. A pressure regulating valve can be disposed in the bypass line configured to bypass a portion of the high pressure fluid from the main line to control a pressure of the main line based on an adjustable regulating set point of the pressure regulating valve.

A first controllable valve can be operatively connected to a metering mechanism disposed in a secondary branch of the main line upstream of the pressure regulating valve configured to modulate a pressure of the secondary branch to control the adjustable regulating set point of the pressure regulating valve. A mechanical linkage can be operatively connected to the variable displacement pump configured to be driven by a pressure actuated piston to control displacement of the variable displacement pump. A second controllable valve can be operatively connected to the pressure actuated piston configured to supply a pressure to adjust the position of the piston.

In embodiments, one or more sensors can be operatively connected to sense at least one of a position of the pressure regulating valve and/or a pressure of the main line and configured to output a respective signal indicative of the position of the pressure regulating valve and/or the pressure of the main line. A controller can be operatively connected to receive at least one of the signal indicative of the position of the pressure regulating valve and/or the pressure of the main line

In embodiments, the controller can include machine readable instructions configured to cause the controller to control at least one of the first and/or second controllable valves to achieve an adjustable regulating set point position of the pressure regulating valve, and adjust a position of the pressure actuated piston to drive the mechanical linkage, varying displacement of the variable displacement pump based on at least one of the signal indicative of the position of the pressure regulating valve and/or a pressure of the main line.

In embodiments, the controller can include machine readable instructions configured to cause the controller to control an output pressure set point of the variable displacement pump based on the adjustable regulating set point of the pressure regulating valve. In embodiments, the controller can include machine readable instructions configured to cause the controller to control the at least one of the first and/or second controllable valves to achieve the adjustable regulating set point of the pressure regulating valve in real time to adjust displacement of the variable displacement pump based on the adjustable pressure set point of the pressure regulating valve without stopping flow through the variable displacement pump.

In certain embodiments, the metering mechanism can include a variable metering orifice and the system can further include a fixed metering orifice. In certain such embodiments, the controller can include machine readable instructions configured to cause the controller to control the first controllable valve to align the variable metering orifice in series with the fixed metering orifice to modulate the pressure in the secondary branch to adjust the regulating set point of the pressure regulating valve. In embodiments, the fixed metering orifice is disposed in the secondary branch downstream of the variable metering orifice and configured to bleed a portion of the fluid in the secondary branch back to the main line.

In certain embodiments, the system can include a biasing member operatively connected to the pressure actuated piston and configured to supply an opposing force on the piston to drive the mechanical linkage to adjust displacement of the variable displacement pump. In certain embodiments, the at least one of the first and/or second controllable valves can include an electrohydraulic servo valve. In certain embodiments, the at least one of the first and/or second controllable valves can include a proportional solenoid valve. In certain embodiments, the position sensor can include a linear variable differential transformer. In embodiments, the main line can be configured to supply hydraulic fluid from a hydraulic fluid source to a plurality of actuators.

In accordance with at least one aspect of this disclosure, a control system for a variable displacement pump can include one or more sensors configured to sense one or more of a pressure of a main line, a position of a mechanical linkage operatively connected to the variable displacement pump disposed in the main line, and/or a position of a pressure regulating valve disposed in a bypass line downstream of the variable displacement pump.

A controller can be operatively connected and configured to receive one or more respective signals indicative of the pressure of the main line, the position of the mechanical linkage operatively connected to the variable displacement pump, and/or the pressure regulating valve. In embodiments, the controller can include machine readable instructions configured to cause the controller to perform any one or more of the functions described herein. For example, in embodiments, the machine readable instructions can be configured to, at least, cause the controller control one or more operatively connected controllable valves to control at least one of displacement of the variable displacement pump and/or an adjustable regulating set point of the pressure regulating valve based at least in part on the respective indicative signals.

In accordance with at least one aspect of this disclosure, a method for controlling a variable displacement pump can include, porting a portion of a high pressure fluid from a main line to a bypass line, porting a portion of the high pressure fluid from the main line to a secondary modulating pressure line, metering the high pressure fluid in the secondary modulating pressure line with a one or more metering mechanisms to control a regulating set point of a pressure regulating valve in the bypass line, sensing a position of the pressure regulating valve, and adjusting a position of a mechanical linkage operatively connected to the variable displacement pump to control displacement of the variable displacement pump based at least in part on a signal indicative of the position of the pressure regulating valve.

In certain embodiments, the one or more metering mechanisms can include a variable metering orifice and a fixed metering orifice disposed in the secondary modulating pressure line. In certain such embodiments, the method can include controlling a first controllable valve to align the variable metering orifice in series with the fixed metering orifice to modulate the pressure in the secondary modulating pressure line of to adjust the regulating set point of the pressure regulating valve.

In embodiments, the method can include bleeding a portion of the high pressure fluid in the one or more of the bypass line and/or the secondary modulating pressure line, and returning the portion of the high pressure fluid to the main line.

In certain embodiments, adjusting the position of the mechanical linkage can include controlling the one or more metering mechanisms to achieve the adjustable regulating set point of the pressure regulating valve in real time to adjust displacement of the variable displacement pump based on the adjustable pressure set point of the pressure regulating valve without stopping flow through the variable displacement pump. In certain embodiments, the one or more metering mechanisms can include at least one of: a fixed metering orifice; a variable metering orifice, an electrohydraulic servo valve; and/or a proportional solenoid valve.

DETAILED DESCRIPTION

Fixed displacement pumps may be oversized to meet needs at certain operating conditions but then produce excess output during other operation. Variable displacement pumps can improve efficiency but require a control scheme. Traditional pressure compensated variable displacement pumps operate under at a single pressure set point or used a manual pressure adjustment mechanism. Embodiments described herein allow for the ability to adjust the output pressure set point for given system actuation needs.

In accordance with at least one aspect of this disclosure, a variable displacement pump system100can include, a variable displacement pump102disposed in a main line104and configured to receive a low pressure fluid from an inlet portion106of the main line104and to output a high pressure fluid to an outlet portion108of the main line104. The main line104can connect a hydraulic fluid source110to a plurality of system actuators, where the variable displacement pump102is disposed in the main line104between the hydraulic fluid source110and the plurality of system actuators to pressurize the hydraulic fluid.

A pressure port112can be disposed in the main line104downstream of the variable displacement pump102configured to port a portion (e.g., certain excess flow) of the high pressure fluid from the outlet portion108of the main line104to a bypass line118. The flow through bypass line118can be controlled by a pressure regulating valve120. During normal operation, bypass through bypass line118should be little to none, if the variable displacement pump is operating at a given output pressure set point for the desired system actuators. A second pressure port114can be disposed in the outlet portion108of the main line104configured to port a portion of the high pressure fluid to a secondary modulated pressure branch116.

The pressure regulating valve120can regulate the pressure between a port115on line108and the modulated pressure branch116. For example, a relative increase in pressure at port115would force the pressure regulating valve120to move axially towards an open position, allowing more bypass flow from the main line104to bypass through bypass line118back to the inlet portion106of the main line106. In this scenario, the system pressure in line108to the actuators would decrease. Conversely, an increase in flow through port114would increase the pressure in the modulated pressure branch116, forcing the pressure regulating valve120to move axially towards a closed position, allowing less bypass through bypass line118. Here, the system pressure in line108to the system actuators would increase. The pressure regulating valve can include an adjustable regulating set point, which can determine the amount of flow through the bypass line118, and in turn, the pressure in outlet pressure to the system actuators in line108.

The modulated pressure in branch116can be set by the first controllable valve122(e.g., any suitable valve including an electrohydraulic servo valve and/or a proportional solenoid, for example) by changing a variable flow area124to allow flow from the outlet portion108of the main line to flow to the secondary branch116. An orifice126can be disposed in116downstream of the variable metering orifice124to control the adjustable regulating set point of the pressure regulating valve120. In embodiments, using a hydro-mechanical pressure regulating valve (e.g., such as valve120) can respond quicker to counter system disturbances than by controlling pump displacement alone. The variable metering orifice124can be configured to receive flow from the main line104(e.g., directly via port114), and the fixed metering orifice126can be configured to bleed a portion of the modulated pressure116back to the inlet portion106of the main line104.

A mechanical linkage128can be mechanically, operatively connected to the variable displacement pump102to be driven by a pressure actuated piston130. Movement of the piston130drives the mechanical linkage128to any desired position to control the displacement of the variable displacement pump102. A second controllable valve132(e.g., any suitable valve, including electrohydraulic servo valve, for example) can be operatively connected to the pressure actuated piston130to supply a pressure to adjust the position of the piston130to drive the mechanical linkage128. A biasing member134(e.g., a resilient member or a spring) can be operatively connected to the pressure actuated piston130to counteract the force from the piston130.

One or more sensors136can be operatively connected to sense a plurality of inputs in the system100, including, but not limited to, a position of the pressure regulating valve120and/or a pressure of the main line104. It may also be possible to sense a position or state of either one of the first and/or second controllable valves122,132, the variable metering orifice124, and/or a modulated pressure in branch116. The one or more sensors136can be configured to output a respective signal indicative of the sensed inputs, for example at least a signal indicative of the position of the pressure regulating valve and/or the pressure of the main line (e.g., as indicated by the dashed lines). The one or more sensors136can include any suitable sensors, such as pressure sensors, position sensors (e.g., including a linear variable differential transformer), temperature sensors, and the like.

A controller138can be operatively connected to receive the respective sensed inputs, including at least the signal indicative of the position of the pressure regulating valve120and/or the pressure of the main line104. The controller138can include machine readable instructions configured to cause the controller138to control at least one of the first and/or second controllable valves122to achieve the adjustable regulating set point position of the pressure regulating valve120, or132to adjust a position of the pressure actuated piston130to drive the mechanical linkage128, varying displacement of the variable displacement pump102based on at least one of the signal indicative of the position of the pressure regulating valve120and/or a pressure of the main line104.

In certain embodiments, controlling the displacement of the variable displacement pump102can be based on a desired position of adjustable regulating set point the pressure regulating valve120. In certain embodiments, the machine readable instructions can be configured to cause the controller138to control the first controllable valve122to adjust the variable metering orifice124in series with the fixed metering orifice126to control the modulated pressure116to adjust the regulating set point of the pressure regulating valve120.

In certain embodiments, the machine readable instructions can be configured to cause the controller138to control the at least one of the first and/or second controllable valves122,132to achieve the adjustable regulating set point of the pressure regulating valve120in real time to adjust the output pressure set point of the variable displacement pump102to the system actuators and to control displacement of the variable displacement pump102without stopping flow through the variable displacement pump102.

In accordance with at least one aspect of this disclosure, a control system200for a variable displacement pump (e.g., pump102) can include one or more sensors (e.g., sensors136) operatively connected to sense one or more of a pressure of a main line (e.g., main line104), a position of a mechanical linkage (e.g. linkage128) operatively connected to the variable displacement pump disposed in the main line, and/or a position of a pressure regulating valve (e.g., valve120) disposed in a bypass line (e.g., bypass line118) downstream of the variable displacement pump. A controller (e.g., controller138) can be operatively connected to receive one or more respective signals can be configured to control one or more controllable valves (e.g., valves122,132) to control at least one of displacement of the variable displacement pump and/or a regulating set point of the pressure regulating valve based at least in part on the respective indicative signals. In embodiments, the controller can be configured to adjust the adjustable regulating set point of the pressure regulating valve in real time and to control displacement of the variable displacement pump based on the desired flow without stopping flow through the variable displacement pump (e.g., via controlling controllable valves122,132).

In embodiments, the controller138and/or control system200can be or include both hard wired circuits that cause a logic (e.g., predictive) to be executed, and/or software-based components, for example, simple electric circuits employing analogue components, or the controller can include a CPU, a memory, machine readable instructions in the memory that when executed cause the CPU to perform a method or cause the control system to perform a method, for example as described below. In embodiments, the controller can utilize any suitable algorithm to control the controllable valve as provided herein. In embodiments, the algorithm could be constructed using the functionality as described above in addition to known general engineering principles as applied to the specific characteristics of each particular fuel system to which the technology of the present disclosure is applied.

In accordance with at least one aspect of this disclosure, a method for controlling a variable displacement pump (e.g., pump102) can include porting a portion (e.g., an excess) of a high pressure fluid from a main line (e.g. main line104) to a bypass line (e.g., bypass line118), metering the high pressure fluid in the bypass line with a one or more metering mechanisms (e.g., any one or all of controllable valves122,132and/or metering orifices124,126) to control a regulating set point of a pressure regulating valve (e.g., valve120) in the bypass line. The method can include sensing (e.g., using a sensor136) a position of the pressure regulating valve, and adjusting a position of a mechanical linkage (e.g., linkage128) operatively connected to the variable displacement pump to control the displacement of variable displacement pump102.

In embodiments, the method can include controlling a first controllable valve (e.g., valve122) to align the variable metering orifice in series with the fixed metering orifice to adjust the regulating set point of the pressure regulating valve. In certain embodiments, the method can include bleeding a portion of the high pressure fluid in the modulated pressure branch116and returning the portion high pressure fluid to the main line. In embodiments, adjusting the position of the mechanical linkage can include controlling the one or more metering mechanisms to achieve the adjustable regulating set point of the pressure regulating valve in real time to adjust the predetermined pressure set point of the variable displacement pump system and to control the position of the pressure regulating valve without stopping flow through the variable displacement pump.

Embodiments can utilize a pressure regulating valve to maintain an operating pressure of a main line by bypassing excess flow (e.g., through the pressure regulating valve). The pressure on one side of the pressure regulating valve can be modulated to change an operating set point of the pressure regulating valve. A position feedback sensor can be included on the pressure regulating valve (e.g., to sense a position). In embodiments, the flow output of the variable displacement pump can be altered to set a certain, desired position for the pressure regulating valve, and therefore control the excess bypass flow in the system.

Embodiments can combine a fast response to system disturbances using a pressure regulating valve with the efficiency of a variable displacement pump. Adjustability of the system output pressure therefore can be made possible through modulation on one side of the pressure regulating valve alone. For example, a pressure regulating valve can quickly change bypass flow to handle changes in system flow need. The ability to change pump displacement based on the position of the pressure regulating valve can provide for efficient operation by changing the position of the pressure regulating valve to a low or no bypass position.

Embodiments can include a hydro-mechanical pressure regulating valve used to bypass flow to control system pressure. A set point of the pressure regulating valve can be adjustable through a modulated pressure, for example. The displacement of the variable displacement pump can be actively controlled to set a certain pressure regulating valve position. In embodiments, prior to an anticipated system disturbance, the pump displacement can be increased to better allow the pressure regulating valve to counteract the disturbance, for example. In certain other instances, when low system disturbance is expected, for example, the pump displacement can be reduced so that the pressure regulating valve bypasses little to no flow for better pumping efficiency.

In embodiments, the displacement and/or output pressure of the variable displacement pump can be determined by controlling one controllable valve, and the pressure of the system (e.g., the pressure in the main line output portion) can be determined by controlling the position of the pressure regulating valve (e.g., a hydro mechanical valve) by bypassing excess flow back to the inlet portion of the main line. The position sensor on the pressure regulating valve allows for adjusting the pump displacement to a point where the pressure regulating valve is nearly closed so as to bypass little to no flow. Measuring the position of the pressure regulating valve relates to the amount of flow that is bypassed through the pressure regulating valve. In controlling the first and second controllable valves, the displacement of the variable displacement pump can be adjusted to achieve a desired amount of bypass flow (e.g., increase or decrease bypass flow).

For example, in certain instances, the system actuators may require high displacement or high pressure from the main line (e.g., for a large actuator), the displacement of the pump can be increased with its controllable valve, supplying more pressure on the front side of the pressure regulating valve to drive the pressure regulating valve open, allowing more bypass flow. The same or similar can be true in reverse when less flow and/or pressure may be needed for the system actuators, or for smaller actuators, for example. Controlling the controllable valves can then modulate the pressure in the modulated pressure branch to drive the pressure regulating valve towards the closed position, and decreasing the output pressure and flow of the variable displacement valve to decrease the amount of bypass flow.

Aspects of this disclosure may be described above with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of this disclosure. It will be understood that each block of any flowchart illustrations and/or block diagrams, and combinations of blocks in any flowchart illustrations and/or block diagrams, can be implemented by computer program instructions.

The embodiments of the present disclosure, as described above and shown in the drawings, provide for improvement in the art to which they pertain. While the apparatus and methods of the subject disclosure have been shown and described, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.