Electro-hydraulic power unit with variable output flow

Abstract

An example system includes an electric motor (102); a pump (104) coupled to the electric motor; a hydraulic circuit (108) fluidly coupled to the pump and configured to receive a fluid flow from the pump; a hydraulic line (110) fluidly coupled to the hydraulic circuit, wherein the hydraulic circuit is configured to provide a fluid signal to the hydraulic line, wherein the fluid signal is indicative of a fluid flow demand of the hydraulic circuit; a pressure sensor (112) mounted to the hydraulic line and configured to provide sensor information indicative of a pressure level of a fluid within the hydraulic line; and a controller (114) configured to control a speed of the electric motor based on the pressure level indicated by the sensor information to vary a fluid flow rate provided by the pump to the hydraulic circuit to satisfy the fluid flow demand.

Description

[0001] Cross-related applications

[0002] This application claims priority to (i) U.S. Provisional Patent Application No. 63 / 216,620, filed June 30, 2021; (ii) U.S. Provisional Patent Application No. 63 / 226,209, filed July 30, 2021; and (iii) U.S. Provisional Patent Application No. 63 / 248,795, filed September 27, 2021, the entire contents of which are incorporated herein by reference as if they were set forth in the description of this application. Background Technology

[0003] A hydraulic power unit, also known as a hydraulic power pack, is a standalone system that generally includes a motor, a fluid reservoir, and a pump. It provides hydraulic fluid flow to drive the motor, cylinders, and other complementary components of a given hydraulic system.

[0004] The motor can be an internal combustion engine. However, there is a trend toward electrifying hydraulic systems, and electric motors can be used to drive pumps.

[0005] In some applications, to reduce costs, the power unit may include an electric motor that operates at a constant speed and drives a fixed-displacement pump (i.e., a pump configured to provide a specific amount of fluid flow at a given motor speed). In this way, the power unit continuously provides fluid flow regardless of the needs of the hydraulic system, meaning it is not suitable for sensing the characteristics of the external hydraulic system. This configuration can lead to significant energy waste, thereby reducing the efficiency of the hydraulic system. Furthermore, when the hydraulic system does not require fluid flow, the output power of the power unit is often wasted as heat, which reduces the lifespan of both the system and the power unit.

[0006] Power units and hydraulic systems can be manufactured using complex components, pressure compensation, multiple sensors, and sophisticated controls for electric motors. However, such systems can be expensive and unsuitable for a wide range of applications.

[0007] Therefore, it is desirable to have a power unit that can change the fluid flow rate to meet the needs of the hydraulic system without increasing the system's complexity and cost. The disclosure described herein is made precisely in response to these and other considerations. Summary of the Invention

[0008] This disclosure describes embodiments relating to an electro-hydraulic power unit with a variable output flow.

[0009] In a first example embodiment, this disclosure describes a system. The system includes: (i) an electric motor; (ii) a pump coupled to and driven by the electric motor; (iii) a hydraulic circuit hydraulically coupled to the pump and configured to receive fluid flow from the pump; (iv) a hydraulic line hydraulically coupled to the hydraulic circuit, wherein the hydraulic circuit is configured to provide a fluid signal to the hydraulic line, wherein the fluid signal indicates a fluid flow demand in the hydraulic circuit; (v) a pressure sensor mounted to the hydraulic line and configured to provide sensor information indicating a pressure level of fluid within the hydraulic line; and (vi) a controller. The controller is configured to perform operations including: receiving sensor information from the pressure sensor, and controlling the speed of the electric motor to change the fluid flow rate supplied by the pump to the hydraulic circuit based on the pressure level indicated by the sensor information, thereby satisfying the fluid flow demand.

[0010] In a second embodiment, this disclosure describes an electro-hydraulic power unit. The electro-hydraulic power unit includes: (i) an electric motor; (ii) a pump coupled to and driven by the electric motor, wherein the pump is configured to provide fluid flow to a hydraulic circuit outside the electro-hydraulic power unit; (iii) a pressure sensor configured to measure the pressure level of a fluid signal received from the hydraulic circuit, wherein the fluid signal indicates a fluid flow demand of the hydraulic circuit; and (iv) a controller. The controller is configured to perform operations including: receiving sensor information from the pressure sensor indicating the pressure level of the fluid signal, and controlling the speed of the electric motor to change the flow rate of fluid discharged from the pump based on the pressure level indicated by the sensor information, thereby satisfying the fluid flow demand of the hydraulic circuit.

[0011] In a third exemplary embodiment, this disclosure describes a method. The method includes receiving sensor information from a pressure sensor mounted to a hydraulic line at a controller of an electro-hydraulic power unit, the hydraulic line fluidly coupling the electro-hydraulic power unit to a hydraulic circuit outside the electro-hydraulic power unit, wherein the electro-hydraulic power unit includes an electric motor and a pump coupled to and driven by the electric motor, wherein the pump provides fluid flow to the hydraulic circuit, and wherein the hydraulic circuit provides a fluid signal to the hydraulic line, the fluid signal indicating a fluid flow demand in the hydraulic circuit; and controlling the speed of the electric motor to change the fluid flow rate supplied to the hydraulic circuit by the pump based on the sensor information indicating the pressure level of the fluid signal in the hydraulic line, thereby satisfying the fluid flow demand.

[0012] The foregoing summary is merely illustrative and should not be construed as limiting in any way. Other aspects, embodiments, and features, besides those illustrative above, will become clear from the accompanying drawings and the detailed description below. Attached Figure Description

[0013] Figure 1 A block diagram of a system according to an example implementation is shown.

[0014] Figure 2 A system with a hydraulic circuit according to an example embodiment is shown, the hydraulic circuit having a valve assembly configured to provide a load-sensing fluid signal.

[0015] Figure 3 An example embodiment of a device with a pressure relief valve is shown. Figure 2 A partial view of the system.

[0016] Figure 4 An example implementation is shown. Figure 2 A partial view of the system, which has a combination of a spring-loaded one-way valve and parallel orifices.

[0017] Figure 5 A system with a variable displacement pump according to an example embodiment is shown.

[0018] Figure 6 A system according to an example embodiment is shown, the system comprising a hydraulic circuit with a valve assembly having an open center configuration.

[0019] Figure 7 A block diagram of a motor control system for an electric motor according to an example embodiment is shown.

[0020] Figure 8 A block diagram of a proportional-integral controller according to an example implementation is shown.

[0021] Figure 9 This is a flowchart of a method for an operating system according to an example implementation. Detailed Implementation

[0022] This document discloses a system and an electro-hydraulic power unit capable of efficient operation without the need for complex electro-hydraulic components, systems, or configurations. An example power unit includes an electric motor that drives a pump to provide fluid flow to an external hydraulic circuit. A fluid signal is generated by the hydraulic circuit, indicating a fluid flow demand in a desired state (e.g., the fluid flow rate required to operate the hydraulic circuit). A pressure sensor is configured to provide sensor information to a controller of the electric motor, indicating the pressure level of the fluid signal. The controller then adjusts the speed of the electric motor, decreasing or increasing the speed based on the sensor information.

[0023] In one example, a fixed displacement pump is used. A fixed displacement pump is a positive displacement pump, in which the displacement (or the amount of fluid pumped per revolution of the pump's input shaft) cannot be changed when operating at a given speed. In this case, changing the speed of the electric motor is used to change the pump's fluid flow rate output.

[0024] In another example, a variable displacement pump is used. With a variable displacement pump, the displacement, or the amount of fluid pumped per revolution of the pump's input shaft, can be changed during pump operation. For example, the pump can have a swashplate whose angle determines the pump's displacement, and thus changing the swashplate angle changes the pump's displacement. In one example, the swashplate angle can be used to change the amount of fluid flow output by the pump. In another example, an electric motor can be used to change the speed of the input shaft to control the amount of fluid flow, while the swashplate angle can be changed to alter the torque load on the electric motor.

[0025] In this way, the disclosed system and power unit can provide the power output required by the hydraulic circuit without generating excessive wasted power. This improves the system's efficiency.

[0026] Figure 1 A block diagram of a system 100 according to an example embodiment is shown. The system 100 has an electro-hydraulic power unit that includes an electric motor 102 that drives a pump 104 (i.e., the output shaft of the electric motor 102 is coupled to the input shaft of the pump 104).

[0027] Pump 104 draws fluid from fluid reservoir 106, which is configured as a hydraulic fluid tank that stores or contains hydraulic fluid at low pressure levels (e.g., 0-70 pounds per cubic inch (psi)). Pump 104 then provides the fluid flow to hydraulic circuit 108. Hydraulic circuit 108 may include multiple hydraulic components such as valves and actuators (e.g., hydraulic cylinders or motors). Thus, the fluid flow provided by pump 104 drives the actuators of hydraulic circuit 108.

[0028] Hydraulic circuit 108 is configured to generate a fluid signal in hydraulic line 110 coupled to hydraulic circuit 108. The fluid signal is configured such that the pressure level of the fluid signal provides an indication of whether fluid flow is required by hydraulic circuit 108. If fluid flow is required by hydraulic circuit 108, the pressure level of the fluid signal can further provide the amount of fluid flow rate required by hydraulic circuit 108 for operating hydraulic circuit 108 in a desired or commanded state.

[0029] System 100 includes a pressure sensor 112 disposed in a hydraulic line 110 and configured to provide sensor information indicating the pressure level of a fluid signal in the hydraulic line 110. System 100 also includes a controller 114 that receives the sensor information from the pressure sensor 112.

[0030] The fluid signal in hydraulic line 110 can then be provided to fluid reservoir 106. In one example, system 100 includes valve 116 or other components fluidly coupled to hydraulic line 110 and receiving fluid signal from hydraulic circuit 108. As described below, valve 116 is configured to generate back pressure to allow pressure levels to increase in hydraulic line 110. Valve 116 can also be configured to limit the pressure level of the fluid signal and impede (prevent) backflow from fluid reservoir 106 to hydraulic line 110.

[0031] The controller 114 may have a microprocessor, which may include one or more processors. The processor may include a general-purpose processor (e.g., Single-core processor or A processor may be a multi-core processor or a dedicated processor (e.g., a digital signal processor, a graphics processor, or an application-specific integrated circuit (ASIC) processor). The processor may be configured to execute computer-readable program instructions (CRPI) to perform the operations described herein. The processor may be configured to perform hard-coded functions (in addition to soft-coded functions, such as those via CRPI) or as an alternative to soft-coded functions.

[0032] The controller 114 is configured to control the speed of the electric motor 102 via the inverter 118. The inverter 118 may, for example, include a structure comprising semiconductor switching elements (transistors) capable of supporting the conversion of direct current (DC) power supplied by a power source 120 (e.g., a battery or electric motor) into three-phase power suitable for driving the electric motor 102. The power source 120 may also be electrically coupled to the controller 114 to supply electrical energy to it and receive commands from it.

[0033] Specifically, the controller 114 can control the speed of the electric motor 102 in response to or based on the pressure level indicated by sensor information received from the self-pressure sensor 112. In this way, the controller 114 can change the speed of the electric motor 102, thereby causing the pump 104 to produce a specific fluid flow rate required by the hydraulic circuit 108.

[0034] If the hydraulic circuit 108 does not require fluid flow or requires only a small amount of fluid flow, the electric motor 102 is instructed to rotate at a standby speed to avoid excessive fluid flow being wasted as heat. If the hydraulic circuit 108 requires more flow, the pressure level of the fluid signal in the hydraulic line 110 changes, and the controller 114 responsively increases the speed of the electric motor 102 to generate the required fluid flow from the pump 104.

[0035] The components of system 100 can be configured to operate in an interconnected manner and / or in an interconnected manner with other components coupled to the respective system. One or more of the described operations or components of system 100 can be distributed into additional operations or physical components, or combined into fewer operations or physical components. In some other examples, additional operations and / or physical components can be added to system 100. For example, controller 114 and inverter 118 can be combined into a single package. An electro-hydraulic power unit can include electric motor 102, pump 104, and fluid reservoir 106 in a single package, which has fluid and electrical connections to other parts of system 100. The electro-hydraulic power unit can also include controller 114 and inverter 118.

[0036] Based on the configuration of the hydraulic circuit 108, the implementation of system 100 can take different forms. For example, the hydraulic circuit 108 may include a closed-center valve, a load-sensing valve, and an open-center valve. As another example, pump 104 may be a fixed displacement pump or a variable displacement pump. Figure 2 , 5 Sections 1, 2, and 6 provide example implementations of system 100 with different configurations.

[0037] Figure 2 A system 200 according to an example embodiment is shown, the system having a hydraulic circuit 202 having a valve assembly 204 configured to provide a load-sensing fluid signal. System 200 is an example embodiment of system 100 when hydraulic circuit 108 includes a load-sensing valve. Similar components between system 100 and system 200 are designated with the same reference numerals.

[0038] As shown in the figure, the electric motor 102 drives the pump 104, and the pump is in Figure 2 The pump 104 is configured as a fixed displacement pump, and it supplies fluid flow to the hydraulic circuit 202. The hydraulic circuit 202 is an external circuit relative to the power unit and is not part of the power unit. In fact, the power unit, which includes the electric motor 102 and the pump 104, provides hydraulic power to operate the hydraulic circuit 202.

[0039] Valve assembly 204 includes an inlet section 206, a first working section 208, a second working section 210, a third working section 212, a fourth working section 214, and an outlet section 216. The inlet section 206, working sections 208 to 214, and outlet section 216 can be coupled together by fasteners (e.g., bolts, clamps, tie rods, etc.) to provide an assembly of valve sections. The outlet section 216 can receive fluid from any of the inlet section 206 and / or working sections 208 to 214.

[0040] like Figure 2 As shown, pump 104 receives fluid from fluid reservoir 106 to provide fluid flow to valve assembly 204. Specifically, outlet port 217 of pump 104 is fluidly coupled to inlet port 218 provided in inlet section 206 of valve assembly 204, so that output fluid flow from pump 104 is received at inlet port 218.

[0041] Valve assembly 204 is also configured to be fluidly coupled to a fluid reservoir, such as fluid reservoir 106, or a different fluid reservoir. For example, inlet section 206 or outlet section 216 may have a tank port (not shown) fluidly coupled to fluid reservoir 106. In this way, fluid is allowed to return from the valve section of valve assembly 204 to fluid reservoir 106 via the tank port. The tank port and the fluid connection from valve assembly 204 to fluid reservoir 106 are not shown to reduce visual clutter in the figures.

[0042] Each of the working sections 208 to 214 is configured to control the fluid flow back and forth to a hydraulic actuator, such as a hydraulic cylinder or a hydraulic motor. For example, the first working section 208 includes a first working port 220 and a second working port 222, which are fluidly coupled to corresponding ports of a hydraulic cylinder actuator 224. The hydraulic cylinder actuator has a cylinder 219, which is divided into a first chamber 221 and a second chamber 223 via a piston 225, within which the piston is movable. Specifically, as shown, the piston 225 has a piston head and a piston rod, the piston head dividing the cylinder into the first chamber 221 and the second chamber 223, and the piston rod extending from the piston head along the longitudinal axis of the cylinder.

[0043] The piston rod can be coupled to an actuator or other movable part to apply and withstand forces on an object. For example, if hydraulic circuit 202 controls hydraulically mobile machinery such as a backhoe or excavator, the piston rod can be coupled to an actuator such as a bucket or boom to move the actuator and bucket across the ground or move material from one location to another. Thus, the hydraulic actuator applies and withstands forces that introduce pressure into the chambers (e.g., chambers 221, 223) of the hydraulic actuator during operation of the machinery.

[0044] Other working sections 210 to 214 are similarly constructed to control fluid flow back and forth to the corresponding actuators. As shown, working section 210 has a working port that controls fluid flow back and forth to hydraulic cylinder actuator 226; working section 212 has a working port that controls fluid flow back and forth to hydraulic cylinder actuator 228; and working section 214 has a working port that controls fluid flow back and forth to hydraulic cylinder actuator 230. Hydraulic cylinder actuators 226 to 230 are configured similarly to hydraulic cylinder actuator 224. In other examples, hydraulic circuit 202 may contain other types of actuators such as hydraulic motors.

[0045] Each working section 208 to 214 may include a corresponding spool, which is movable within a spool bore in the corresponding working section. The spool can be actuated in either direction via different types of machinery. As an example for illustration, the spool can be manually actuated, wherein an operator can move a lever or handle connected to the spool, and thus manually move the spool. In other examples, the spool can be actuated via a hydraulic pilot fluid signal, wherein the operator moves a lever, and accordingly, a hydraulic fluid signal is supplied to one side of the spool to move the spool in a given direction.

[0046] When the spool valve moves in a given direction, fluid is supplied to the corresponding hydraulic cylinder actuator, causing its piston to move in the first direction. When the spool valve moves in the opposite direction, fluid is supplied to the corresponding hydraulic cylinder actuator, causing the piston to move in a second direction opposite to the first direction. The greater the stroke of the spool valve, the greater the amount of fluid flowing to the hydraulic cylinder actuator. In other words, the greater the stroke of the spool valve, the greater the fluid flow demanded by the hydraulic cylinder actuator.

[0047] As described above, valve assembly 204 is configured as a load-sensing valve. When the piston of the hydraulic cylinder actuator applies or receives a force, the fluid pressure level in at least one chamber of the hydraulic cylinder actuator (e.g., chambers 221, 223) increases. The pressure in the chamber can be referred to as the load-induced pressure. This pressure level in the chamber indicates the force or load applied or received by the piston.

[0048] Each working section contains a corresponding load sensing channel, and when the spool valve of the working section is actuated to supply fluid to the corresponding hydraulic cylinder actuator, the load sensing channel is fluidly coupled to the hydraulic cylinder actuator via the corresponding working port of the working section. Thus, the load sensing channel provides or transmits a pressure feedback signal from the working port, wherein the pressure feedback signal indicates the load on the hydraulic cylinder actuator.

[0049] Thus, the pressure feedback signal can be referred to as the load-sensing fluid pressure signal. When the load-sensing fluid pressure signal is generated or has a non-zero pressure level, the corresponding hydraulic cylinder actuator has been actuated and fluid flow is demanded. Conversely, when the hydraulic cylinder actuator is not commanded to move, the spool valve of the relevant working section is not actuated and no load-sensing fluid pressure signal is generated. In other words, the load-sensing fluid pressure signal has a zero psi pressure level. Therefore, if the load-sensing fluid pressure signal has a zero psi pressure level (e.g., no signal is generated), no fluid flow is demanded by the corresponding hydraulic cylinder actuator. Thus, the load-sensing fluid pressure signal generated by the working section provides an indication of whether fluid flow is demanded by the hydraulic cylinder actuator controlled by the working section.

[0050] Each of the working sections 208 to 214 is configured to provide a corresponding load-sensing fluid pressure signal. Valve assembly 204 may also include a network of check valves and / or directional valves that compare the pressure levels of different load-sensing fluid pressure signals and then output a load-sensing fluid pressure signal with the highest pressure level. This load-sensing fluid pressure signal is a "general" or "global" load-sensing fluid pressure signal that indicates the highest load borne by the hydraulic cylinder actuator controlled by valve assembly 204.

[0051] The load-sensing fluid pressure signal is then provided to hydraulic line 231, which is fluidly coupled to valve assembly 204. Although hydraulic line 231 is attached... Figure 2 The hydraulic line 231 is shown connected to the inlet section 206, but in other example embodiments, the hydraulic line 231 may be fluidly coupled to other sections such as the outlet section 216 or to other modules / manifolds of the valve assembly 204.

[0052] System 100 also includes an unloading valve 232. Although the unloading valve 232 is shown outside of valve assembly 204, in other example embodiments, the unloading valve 232 may be disposed in or integrated into valve assembly 204. For example, the unloading valve 232 may be integrated into inlet section 206. Thus, hydraulic circuit 202 can be considered to include valve assembly 204, hydraulic cylinder actuators 224 to 230, and unloading valve 232.

[0053] The unloading valve 232 has an inlet port 234, which is fluidly coupled to the outlet port 217 of the pump 104. The unloading valve 232 also has a pilot port 236, which is fluidly coupled to the hydraulic line 231 and thus receives a load-sensing fluid pressure signal indicating the highest load among the loads of the hydraulic cylinder actuators 224 to 230.

[0054] The unloading valve 232 also includes an outlet port 238, which is fluidly coupled to valve 116 via hydraulic line 110. A pressure sensor 112 is disposed within hydraulic circuit 110, which fluidly couples outlet port 238 to valve 116. Thus, pressure sensor 112 is configured to provide sensor information indicating the pressure level of the fluid discharged from outlet port 238.

[0055] The unloading valve 232 includes a movable element such as a poppet, spool, or piston, and includes a spring 240 that applies a biasing force toward the valve seat on the movable element. When seated, the movable element obstructs fluid flow from inlet port 234 to outlet port 238.

[0056] The load-sensing fluid pressure signal received at pilot port 236 applies a first fluid force toward the valve seat on the movable element. Thus, the first fluid force of the load-sensing fluid pressure signal cooperates with the bias force of spring 240 to drive the movable element toward the seated position. Therefore, the force or resultant force comprising the first fluid force of the load-sensing fluid pressure signal and the bias force of spring 240 can be referred to as the closing force.

[0057] On the other hand, the fluid received by the pump 104 at the inlet port 234 exerts a second fluid force on the movable element that is opposite to the closing force; that is, the second fluid force tends to act on the movable element that is not yet seated. Therefore, the second fluid force can be referred to as the opening force.

[0058] As long as the opening force of the fluid from pump 104 does not exceed the closing force, unloading valve 232 remains closed and no fluid flow is permitted from inlet port 234 to outlet port 238. In other words, the pressure level within hydraulic line 110 is approximately zero (e.g., between zero and a low pressure value such as 5 to 10 psi).

[0059] When most of the fluid flow from pump 104 is supplied to or consumed by valve assembly 204, the closing force can be maintained greater than the opening force. For example, if multiple spool valves in multiple working sections 208 to 214 are simultaneously actuated (or a spool valve is actuated to its maximum stroke to move the actuator at maximum speed), most of the fluid output from pump 104 is consumed by valve assembly 204 and supplied to the hydraulic cylinder actuator.

[0060] In some cases, the flow demanded by the hydraulic cylinder actuators 224 to 230 may exceed the flow capacity of the pump 104 at a given speed of the electric motor 102. Consequently, all the flow produced by the pump 104 is supplied to the valve assembly 204, and the pressure level of the fluid at the inlet port 234 of the unloading valve 232 is insufficient to overcome the closing force applied by the load-sensing fluid pressure signal and the spring 240. Thus, the pressure level in the hydraulic line 110 remains low (e.g., zero).

[0061] In this situation, pressure sensor 112 indicates to controller 114 that the flow demand exceeds the capacity of pump 104 (at the current motor speed). In response, controller 114 can instruct electric motor 102 to increase its speed and increase the flow output of pump 104. For example, if the pressure level in hydraulic line 110 is zero, controller 114 can instruct electric motor 102 to operate at maximum speed.

[0062] If the pressure level of the fluid received by pump 104 at inlet port 234 increases such that the opening force exceeds the closing force, the movable element of unloading valve 232 disengages (lifts) from its seat, and fluid flows from inlet port 234 to outlet port 238. Unloading valve 232 is configured as a proportional valve, such that the amount of fluid flowing through it is proportional to the pressure difference between the fluid at inlet port 234 and the fluid at pilot port 236.

[0063] Specifically, the greater the pressure difference between the fluid at inlet port 234 and the load-sensing fluid pressure signal at pilot port 236, the greater the movement of the movable element of unloading valve 232, and thus the larger the opening of pressure relief valve 232, allowing a larger amount of fluid to flow to outlet port 238. Conversely, the smaller the pressure difference between the fluid at inlet port 234 and the load-sensing fluid pressure signal at pilot port 236, the smaller the amount of fluid flowing through pressure relief valve 232. Thus, the pressure level of the fluid signal output from outlet port 238 to hydraulic line 110 is based on the difference between the second fluid force and the combination of the first fluid and bias pressure.

[0064] Valve 116 is configured to restrict the fluid flow to fluid reservoir 106. Therefore, the greater the fluid flow rate through hydraulic line 110, the greater the pressure level (back pressure) in hydraulic line 110 due to the presence of valve 116. With this configuration, when pump 104 provides a larger volume of fluid flow than required by valve assembly 204 and hydraulic cylinder actuators 224 to 230, the fluid flow rate through hydraulic line 110 and the pressure level therein increase. This increase in pressure level is provided to controller 114 by pressure sensor 102, which responsively reduces the speed of electric motor 102 to decrease the fluid flow output of pump 104.

[0065] With this configuration, controller 114 modifies, alters, or regulates the speed of electric motor 102 such that the speed of electric motor 102 is inversely proportional to the pressure level indicated by pressure sensor 112 in hydraulic line 110. If the flow demand from hydraulic circuit 202 (e.g., by hydraulic cylinder actuators 224 to 230) increases, the pressure level of the fluid output by pump 104, and thus the pressure level of the fluid supplied to hydraulic line 110, decreases when the fluid demand exceeds the pump capacity at a given motor speed and can reach zero. Responsively, controller 114 increases the speed of electric motor 102 so that pump 104 increases the flow output to meet the flow demand.

[0066] Conversely, if the fluid demand of hydraulic circuit 202 (e.g., by hydraulic cylinder actuators 224 to 230) decreases, the pressure level of the fluid output by pump 104, and thus the pressure level of the fluid supplied to hydraulic line 110 (as pump 104 provides more flow than is consumed by valve assembly 214), increases. In response, controller 114 causes the speed of electric motor 102 to decrease, resulting in pump 104 reducing its flow output to a level sufficient to meet the flow demand. Thus, system 200 operates efficiently when pump 104 provides sufficient flow to operate hydraulic circuit 202 (as opposed to providing a particularly fixed amount of fluid flow output regardless of flow demand).

[0067] In one example, the inverse relationship between the speed of electric motor 102 and the pressure level in hydraulic line 110 can be an inverse proportional relationship. For example, if the hydraulic level in hydraulic line 110 is 280 psi, controller 114 operates electric motor 102 at a standby speed (e.g., 600 revolutions per minute (RPM)). If the pressure level in hydraulic line 110 drops to 0 psi (over-demand scenario, where all flow from pump 104 is consumed by hydraulic cylinder actuators 224 to 230), controller 114 operates electric motor 102 at a maximum speed, e.g., 2000 RPM. This inverse proportional relationship indicates that controller 114 changes speed linearly with pressure level, meaning that as pressure level increases, speed decreases and vice versa. However, in other examples, the inverse relationship is not linear. In fact, an inverse nonlinear relationship, or schedule, can be adjusted as desired.

[0068] Without valve 116, hydraulic line 110 is directly coupled to fluid reservoir 106, and therefore the pressure level in hydraulic line 110 remains at a level approximately equal to the pressure level of the fluid in fluid reservoir 106 (regardless of flow demand). The presence of valve 116 allows the pressure level in hydraulic line 110 to change, thus indicating the amount of flow demanded by hydraulic circuit 202.

[0069] Valve 116 can take various forms. As described above, valve 116 is configured to generate back pressure or reverse pressure and allow an increase in the pressure level in hydraulic line 110. Furthermore, valve 116 can be configured to limit the maximum pressure level within hydraulic line 110. Valve 116 can also be configured to prevent backflow from fluid reservoir 106 to hydraulic line 110. Thus, valve 116 can be a relief valve or a combination of any valve or component that simulates the operation of a relief valve.

[0070] Figure 3 A partial view of a system 200 according to an example embodiment is shown, the system having a valve 116 configured as a pressure relief valve 300. The pressure relief valve 300 is a pressure relief valve (PRV) configured to control or limit pressure within a hydraulic line 110. When the pressure level of the fluid from pump 104 is sufficient to overcome the load-sensing fluid pressure signal and the bias force of spring 140, unloading valve 232 opens and fluid flows into hydraulic line 110.

[0071] The pressure of the fluid within hydraulic line 110 can increase or accumulate until it reaches the pressure setting of pressure relief valve 300. When the pressure setting is exceeded, pressure relief valve 300 opens, and fluid is allowed to flow to fluid reservoir 106. After the pressure level decreases to below the pressure setting (e.g., when the flow demand of hydraulic circuit 202 increases), pressure relief valve 300 closes again. Thus, pressure relief valve 300 allows the pressure level to change within hydraulic line 110, enabling pressure sensor 112 to measure the pressure level within hydraulic line 110 and provide an indication of the flow demand of hydraulic circuit 202 to controller 114 (as described above).

[0072] In addition, the pressure relief valve 300 can limit the pressure level within the hydraulic line 110 so that it does not exceed a threshold (e.g., 300 psi). In this way, the pressure level within the hydraulic line 110 is allowed to change between zero and the maximum pressure level value, and the controller 114 is able to change the speed of the electric motor 102 inversely proportional to the pressure level within the range between the maximum motor speed and the standby speed.

[0073] Additionally, the pressure relief valve 300 prevents backflow from the fluid reservoir 106 into the hydraulic line 110. For example, if the pressure level in the hydraulic line 110 is zero (when the unloading valve 232 is closed) and the pressure level of the fluid in the fluid reservoir 106 is slightly above zero, fluid could flow back into the hydraulic line 110. The pressure relief valve 300 prevents this backflow from the fluid reservoir 106, thus providing an accurate indication of the pressure level in the hydraulic line 110 for the flow required by the hydraulic circuit 202.

[0074] Other configurations can be used to perform the same operation as the pressure relief valve 300 described above. Figure 4 A partial view of a system 200 according to an example embodiment is shown, which has a valve 116 configured as a combination of a spring-loaded check valve 400 and a parallel throttle orifice 402. Both the spring-loaded check valve 400 and the throttle orifice 402 fluidly couple a hydraulic line 110 to a fluid reservoir 106.

[0075] The spring-loaded check valve 400 may have a movable element, such as a ball or cone biased by a spring toward a seated position. As long as the pressure level of the fluid in the hydraulic line 110 is insufficient to overcome the spring, the movable element remains seated, blocking the flow of fluid to the fluid reservoir 106.

[0076] The orifice 402 can be configured to have a small size, thus being "saturated" with a small fluid flow, allowing the pressure level of the fluid in the hydraulic line 110 to increase or accumulate when the orifice 402 restricts the fluid flow to the fluid reservoir 106. The pressure level of the fluid in the hydraulic line 110 is allowed to increase until it reaches a pressure setting determined by the spring of the spring-loaded check valve 400. Once the pressure setting is reached, the spring-loaded check valve 400 opens to allow fluid to flow to the fluid reservoir 106. With this configuration, the combination of the spring-loaded check valve 400 and the orifice 402 can operate similarly to the pressure relief valve 300.

[0077] As described above, in system 200, pump 104 is configured as a fixed displacement pump. Therefore, pump 104 provides a fixed amount of fluid flow at a specific speed of electric motor 102. To change the output flow rate of pump 104, controller 114 changes the speed of electric motor 102. In other example embodiments, a variable displacement pump can be used. In this example, in addition to changing the speed of electric motor 102 to change the fluid flow rate, or as an alternative, controller 104 can change the pump's displacement to change the fluid flow rate output by the pump. In another example, controller 114 is capable of changing the pump's displacement to change the torque load on electric motor 102 in addition to changing the speed of electric motor 102. Thus, controller 114 is able to control the pressure level and flow rate of the fluid output by pump 104.

[0078] Figure 5 A system 500 with a variable displacement pump 502 according to an example embodiment is shown. System 500 is an example embodiment of system 100. Furthermore, system 500 differs from system 200 in that it does not use a fixed displacement pump; instead, an electric motor 102 drives a variable displacement pump.

[0079] The variable displacement pump 502 may have a module or cylinder in which multiple pistons are housed. Springs press each piston against a stationary disk 504. When the disk 504 is not tilted and the cylinder rotates, the variable displacement pump 502 does not discharge fluid. However, when the disk 504 is tilted such that it forms an angle relative to the module containing the pistons, as the module rotates, the pistons draw in fluid during a half-turn and expel fluid during another half-turn. Changing the tilt angle of the disk 504 changes the flow rate of fluid discharged from the variable displacement pump 502. For example, a larger angle results in a farther piston movement and a higher fluid flow rate.

[0080] For a given motor speed of the electric motor 102, changing the angle of the oscillator 504 alters the power output of the power unit. The power output can be determined as the product of the flow rate and the pressure level of the fluid output by the variable displacement pump 502, or the product of the speed of the electric motor 102 and the torque applied by the electric motor 102 to the variable displacement pump 502. Therefore, for a given motor speed, changing the angle of the oscillator 504 controls the torque of the electric motor 102.

[0081] The variable displacement pump 502 may have a control actuator mechanism that controls the angle of the swashplate 504. For example, a cylinder-piston configuration may be used, wherein the piston is coupled to the swashplate 504. A solenoid valve may control the fluid flow to the cylinder to move the piston and the coupled swashplate 504. A controller 114 communicates with and is configured to instruct the solenoid valve. In this way, the controller 114 can change the angle of the swashplate 504, thereby controlling the torque load on the electric motor 102.

[0082] In this way, by controlling both the speed and torque of the electric motor 102, the controller 114 can regulate the output power of the electric motor 102. Thus, the controller 114 can change the power consumption from the power source 120. For example, if the power source 120 is a battery, the controller 114 can increase the lifespan of both the battery and the inverter 118 by reducing power consumption when the temperature level of the battery or inverter 118 exceeds a threshold.

[0083] Systems 200 and 500 are example implementations of system 100. Other examples are possible. For instance, instead of a load-sensing, neutral-position closed valve assembly such as valve assembly 204, the methods and systems described herein can be used with a neutral-position open valve.

[0084] Figure 6 A system 600 with a hydraulic circuit 602 according to an exemplary embodiment is shown, the hydraulic circuit 602 having a valve assembly 604 with a neutral-open configuration. System 600 is an exemplary embodiment of system 100 when hydraulic circuit 108 includes a load-sensing valve configured with a neutral-open valve. Components similar to those in systems 100, 200, and 600 are indicated by the same reference numerals.

[0085] Valve assembly 604 includes an inlet section 606, a first operating section 608, a second operating section 610, a third operating section 612, a fourth operating section 614, and an outlet section 616. The operating sections 608 to 614 are positioned adjacent to each other between the inlet section 606 and the outlet section 616. Depending on the application and the number of actuators controlled by valve assembly 604, valve assembly 604 may have more or fewer valve sections.

[0086] Inlet section 606 has an inlet port 618 configured to be fluidly coupled to outlet port 217 of pump 104 via inlet line 619. Outlet section 616 has a reservoir port 620 configured to be fluidly coupled to fluid reservoir 106 via reservoir line 621.

[0087] Each of the working sections 608 to 614 includes a housing defining a longitudinal orifice configured to receive a spool valve axially movable within the orifice. The housing includes a neutral opening channel that intercepts the longitudinal orifice. Inlet section 606 and outlet section 616 also have corresponding neutral opening channels. The corresponding neutral opening channels of inlet section 606, working sections 608 to 614, and outlet section 616 together form a neutral opening channel 622 of the transverse valve assembly 604.

[0088] The center-opening channel 622 receives fluid supplied to the inlet port 618 via a branch 623, which can be formed in the inlet port 606, as shown below. Figure 6 As shown. As described below, when all spools in all operating sections are in the neutral non-operating position, valve assembly 604 allows continuous flow through neutral-open channel 622. After shifting one or more spools to actuate the associated hydraulic cylinder actuator, the spools vary and restrict or cut off the neutral-open flow.

[0089] Additionally, the housing includes a return channel that intercepts longitudinal orifices. The corresponding return channels of operating sections 608 to 614 together form a return channel 624, which traverses the valve assembly 604. The return channel 624 is fluidly coupled to the reservoir port 620 via the outlet section 616, and thus to the fluid reservoir 106.

[0090] In addition, the housing includes a supply channel that intercepts longitudinal orifices. The corresponding supply channels of the working sections 608 to 614 together form a supply channel 626, which traverses the valve assembly 604. Supply channel 626 is fluidly coupled to inlet port 618 and thus to pump 104.

[0091] Each working section is configured to control fluid flow back and forth to a corresponding hydraulic actuator of hydraulic cylinder actuators 224 to 230. For example, a first working section 608 is fluidly coupled to a first chamber 221 of hydraulic cylinder actuator 224 via a first working port channel 628, and fluidly coupled to a second chamber 223 of hydraulic cylinder actuator 224 via a second working port channel 630. Each working port channel includes an internal channel within the housing of the first working section 608 that is fluidly coupled to a working port, and each working port includes a fluid line that connects the working port to a corresponding chamber of hydraulic cylinder actuator 224.

[0092] Working sections 610 to 614 are similarly configured to correspondingly control the fluid flow of reciprocating hydraulic cylinder actuators 226 to 230. Specifically, as shown, working section 610 has a working port channel that controls the fluid flow of reciprocating hydraulic cylinder actuator 226, working section 612 has a working port channel that controls the fluid flow of reciprocating hydraulic cylinder actuator 228, and working section 614 has a working port channel that controls the fluid flow of reciprocating hydraulic cylinder actuator 230.

[0093] In each operating section, the diameter of the spool valve varies along its length to form shoulders (land) of variable diameter, which are adapted to selectively interconnect different channels of the intercepting longitudinal orifice to control fluid flow to and from the actuator. When the spool valve is in a neutral (e.g., unactuated, centered, or unbiased) position, the neutral opening channel 622 is open or unobstructed. Thus, the neutral opening channel 622 is the path of least resistance, and fluid received at the inlet port 618 flows through the branch 623 and then through the neutral opening channel 622.

[0094] The fluid then exits the neutral-open channel 622 and valve assembly 604 via the neutral-open outlet port 632. The neutral-open outlet port 632 can be referred to as a "power beyond" port, which is connected to other functions of the machine or vehicle to provide flow to them. Furthermore, as... Figure 6 As shown, the hydraulic line 110 is fluidly coupled to the neutral open outlet port 632.

[0095] Therefore, when none of the spool valves in operating sections 608 to 614 are actuated, all the output flow from pump 104 flows through neutral-open channel 622, exits valve assembly 604 via neutral-open outlet port 632, and flows through hydraulic line 110. Valve 116 (or pressure relief valve 300 or a combination of spring-loaded check valve 400 and throttle port 402) allows the pressure level in hydraulic line 110 to increase to the maximum value permitted by valve 116. Pressure sensor 112 thus provides sensor information to controller 114 indicating this high pressure level, and controller 114 responsively instructs electric motor 102 to operate at a standby speed (low speed) to reduce the amount of flow and power loss.

[0096] After the spool valve is shifted to actuate its associated actuator (e.g., when the spool valve in the first operating section 608 is shifted to actuate the hydraulic cylinder actuator 224), the shifted spool valve restricts the fluid flow through the neutral opening channel 622. Because the fluid is restricted to flow through the neutral opening channel 622, the fluid at the inlet port 618 flows through the supply channel 626.

[0097] Furthermore, when the spool valve is displaced, fluid flowing through supply channel 626 flows to one of the multiple working port channels in the working section, based on the direction of the valve's displacement. In this way, fluid is supplied to the corresponding hydraulic cylinder actuator, causing its piston to move. Fluid returning from the hydraulic cylinder actuator is also directed through the spool valve to return channel 624, and then flows to fluid reservoir 106 via reservoir port 620 and reservoir line 621.

[0098] As the displaced spool valve constrains the fluid flow through the neutral opening channel 622, the pressure level downstream of the spool valve in the neutral opening channel 622 decreases. Specifically, the spool valve forms a variable orifice between one or more of its shoulders and the inner surface of the housing of the corresponding operating section. The size of the variable orifice depends on the degree of spool valve movement or stroke.

[0099] As fluid flows through the variable throttle orifice, the pressure level decreases—that is, a pressure reduction occurs from the pressure level of the fluid received at inlet port 618 to the pressure level of the fluid downstream of the spool valve in the neutral opening channel 622. The greater the amount of fluid flow required by the hydraulic cylinder actuator (i.e., the greater the speed of the command to its piston), the greater the displacement of the spool valve. The greater the displacement of the spool valve, the greater the amount of fluid flow diverted to supply channel 626 to supply the hydraulic cylinder actuator, and the greater the constraint on the variable throttle orifice. The greater the constraint on the variable throttle orifice, the greater the pressure drop across it, and thus the further the pressure level downstream of the spool valve in the neutral opening channel 622 and the hydraulic line 110 coupled thereto.

[0100] As the pressure level in hydraulic line 110 decreases and pressure sensor 112 provides sensor information indicating the pressure level to controller 114, controller 114 responsively instructs electric motor 102 to increase its speed, thereby increasing the output flow rate of pump 104 to meet the demand. If the spool valve is fully displaced (i.e., at maximum stroke) (indicating maximum flow demand by the hydraulic cylinder actuator), neutral opening channel 622 can be blocked, and no fluid flow is supplied to neutral opening channel 622 or hydraulic line 110. In this case, the pressure level in hydraulic line 110 can be zero, and controller 114 instructs electric motor 102 to operate at maximum speed.

[0101] Conversely, if the flow demand from the hydraulic cylinder actuator decreases and the spool valve is shifted back towards the neutral position, the variable throttle orifice becomes less constrained, and the pressure level in the neutral opening channel 622 and hydraulic line 110 increases. In response, controller 114 instructs electric motor 102 to reduce its speed to decrease the output flow rate of pump 104 and meet the flow demand without providing excessive flow.

[0102] Although the above description pertains to the displacement of one spool valve, multiple spool valves can be actuated simultaneously. The operation as described above remains the same. In other words, the higher the flow demand by one or more hydraulic cylinder actuators, the lower the pressure level in the neutral opening channel 622 and hydraulic line 110, and the controller 114 increases the speed of electric motor 102, and vice versa.

[0103] With this configuration, controller 114 adjusts, changes, or regulates the speed of electric motor 102 so that the speed of electric motor 102 is inversely proportional to the pressure level in hydraulic line 110 indicated by pressure sensor 112. If the flow demand from hydraulic circuit 602 (e.g., by hydraulic cylinder actuators 224 to 230) increases, the pressure level of the fluid supplied to hydraulic line 110 decreases and can reach zero when the flow demand exceeds the pump capacity at a given motor speed (i.e., when one or more spool valves are shifted to allow maximum flow to be supplied to the hydraulic cylinder actuators). Responsively, controller 114 increases the speed of electric motor 102 so that pump 104 increases flow output to meet the flow demand.

[0104] Conversely, if the flow demand of the hydraulic circuit 602 (e.g., by hydraulic cylinder actuators 224 to 230) is reduced by shifting the spool valve back toward the neutral position, the pressure level of the fluid supplied to the hydraulic line 110 increases. In response, the controller 114 reduces the speed of the electric motor 102 so that the pump 104 reduces its flow output to the amount required to meet the flow demand, without providing excessive flow. Thus, with the pump 104 providing sufficient flow to operate the hydraulic circuit 602, the system 600 operates efficiently, in contrast to a fixed fluid flow rate output (independent of flow demand).

[0105] In one example, the inverse relationship between the speed of electric motor 102 and the pressure level within hydraulic line 110 can be an inverse proportional relationship. For example, if the pressure level within hydraulic line 110 is 280 psi, controller 114 operates electric motor 102 at a standby speed, such as 600 psi. If the pressure level within hydraulic line 110 drops to 0 psi (over-demand scenario, where all flow from pump 104 is consumed by hydraulic cylinder actuators 224 to 230), controller 114 operates electric motor 102 at a maximum speed, such as 2000 psi.

[0106] The inverse proportional relationship indicates that the controller 114 changes the speed linearly. In other examples, the inverse proportional relationship is not linear. In fact, the inverse nonlinear relationship or arrangement can be adjusted as desired.

[0107] In the description of system 600, pump 104 is shown as a fixed displacement pump. However, it should be understood that a variable displacement pump 502 can be used instead. In this case, controller 114 is able to control both the speed of electric motor 102 and the torque output of electric motor 102, which is achieved by controlling the angle of swivel plate 504 (see Appendix). Figure 5 (As mentioned above).

[0108] Controlling the electric motor 102 may involve a closed-loop feedback system for precisely controlling the speed and / or torque of the electric motor 102. The closed-loop feedback system may be implemented in the controller 114 or the inverter 118.

[0109] Figure 7 A motor control system 700 for an electric motor 102 according to an example embodiment is shown. In one example, the motor control system 700 is implemented by or includes an inverter 118. In another example, the motor control system 700 is implemented by a controller 114. In yet another example, a portion of the motor control system 700 (e.g., a speed loop) is implemented by the controller 114 and another portion (e.g., a current loop) is implemented by the inverter 118.

[0110] In such Figure 7In the illustrated embodiment, the motor control system 700 is a closed-loop feedback system that includes two control loops or control modules. The first control module is a speed control module 702, and the second control module is a current control module 704.

[0111] The motor control system 700 receives sensor information from the pressure sensor 112 indicating the pressure level within the hydraulic line 110. The motor control system 700 may have a lookup table 705 or something similar to the inverse relationship between pressure level and the commanded speed of the electric motor 102 described above. The lookup table 705 converts the signal from the pressure sensor 112 into a speed command for the electric motor 102 (i.e., the rotational speed of the output shaft coupled to the rotor of the electric motor 102). The speed command is provided to the speed control module 702 as a speed command signal 706.

[0112] The speed control module 702 then determines a reference current command 708 based on the error or difference between the speed command signal 706 and the speed sensor information signal 714 from a sensor coupled to the electric motor 102. For example, the electric motor 102 includes a speed sensor (e.g., a tachometer) that provides the speed sensor information signal 714 to the speed control module 702, which performs closed-loop speed control to control the speed of the electric motor 102.

[0113] The speed control module 702 provides a reference current command 708 to the current control module 704. The current control module 704 then provides a current command 710 to drive the electric motor 102. The electric motor 102 includes a current sensor, which provides a current sensor information signal 712 to the current control module 704, which performs closed-loop current control to control the current supplied to the electric motor 102.

[0114] As an illustrative example, the speed control module 702 and the current control module 704 may include a proportional-integral (PI) controller. The PI controller may be used herein as an illustrative example; however, it should be understood that other types of closed-loop feedback control systems, such as proportional-integral-derivative (PID) controllers, may be employed.

[0115] Figure 8 A block diagram of a PI controller 800 according to an example embodiment is shown. The PI controller 800 embodies a PI speed controller of a speed control module 702 or a PI current controller of a current control module 704.

[0116] An error signal 802 is determined that reflects the difference between the commanded value (e.g., the commanded speed or current) and the feedback value (the actual speed or actual current provided by the corresponding sensor). Thus, the error signal 802 reflects the difference between the speed command signal 706 and the speed sensor information signal 714, or the difference between the reference current command 708 and the current sensor information signal 712.

[0117] Error signal 802 is multiplied by proportional gain K at module 804. P The error signal 802 is further integrated at module 806 (e.g., accumulated over time). The result of the integration at module 806 is then multiplied by the integration gain K at module 808. I The output of module 808 is then summed with the output of module 804 at summing module 810 to generate a reference instruction 812 (e.g., a reference current instruction 708 or a current instruction 710).

[0118] Figure 9 This is a flowchart of a method 900 for an operating system according to an example implementation. For example, method 900 may be implemented by controller 114 using systems 200, 500, and 600.

[0119] Method 900 may include one or more operations or actions represented by one or more modules 902 to 904. Although the modules are shown in a sequential order, they may also be executed in parallel and / or in a different order than those described herein. Additionally, various modules may be combined into fewer modules, divided into additional modules, and / or cancelled based on the desired implementation. It should be clear that, with respect to the processes and other processes and methods described herein, the flowcharts illustrate the functionality and operation of one possible implementation of the present example. Alternative implementations are included within the scope of the examples of this disclosure, in which functions may be performed out of order with respect to those shown or discussed, including substantially simultaneous or reverse order, depending on the functions involved, as understood by those skilled in the art.

[0120] Additionally, for the method 900 described herein and other processes and operations, a flowchart illustrates the operation of one possible implementation of the present example. In this respect, each block may represent a module, segment, or portion of program code containing one or more instructions executable by a processor (e.g., the processor or microprocessor of controller 114) to perform specific logical operations or steps in the process. The program code may be stored on any type of computer-readable medium or memory, such as storage devices including disks or hard disks. The computer-readable medium may comprise non-transitory computer-readable media or memory, such as computer-readable media for short-term data storage, such as register memory, processor cache, and random access memory (RAM). For example, the computer-readable medium may also include non-transitory media or memory, such as auxiliary or persistent long-term storage, like read-only media (ROM), optical discs or disks, compact disc read-only memory (CD-ROM). The computer-readable medium may also be any other volatile or non-volatile storage system. For example, the computer-readable medium may be considered a computer-readable storage medium, a perceptible storage device, or other manufactured article. Additionally, for the method 900 disclosed herein and other processes and operations, Figure 9 One or more blocks in the array can represent circuitry or digital logic, which are arranged to perform specific logical operations during execution.

[0121] At block 902, the method includes receiving sensor information from pressure sensor 112 at controller 114 of an electro-hydraulic power unit, the pressure sensor being mounted to hydraulic line 110, the hydraulic line fluidly coupling the electro-hydraulic power unit to a hydraulic circuit (e.g., hydraulic circuits 108, 202, 602) outside the electro-hydraulic power unit, wherein the electro-hydraulic power unit includes an electric motor 102 and a pump (e.g., pump 104 or variable displacement pump 502) coupled to and driven by the electric motor 102, wherein the pump provides fluid flow to the hydraulic circuit, and wherein the hydraulic circuit provides a fluid signal to hydraulic line 110, wherein the fluid signal reflects the fluid flow demand of the hydraulic circuit.

[0122] At block 904, method 900 includes controlling the speed of electric motor 102 based on sensor information indicating the pressure level of fluid signals within hydraulic line 110 to change the fluid flow rate supplied by the pump to the hydraulic circuit, thereby meeting fluid flow requirements.

[0123] Method 900 may also include any operation disclosed. For example, controlling the speed of the electric motor may include controlling the speed of the electric motor 102 via an inverse relationship between the pressure level of the fluid signal and the speed of the electric motor 102, such that as the pressure level of the fluid signal decreases, the speed of the electric motor 102 is increased to increase the flow rate of the fluid discharged by the pump.

[0124] In the example, the electro-hydraulic power unit includes a fluid reservoir 106 that holds fluid at a low pressure level, wherein a pump is configured to draw fluid from the fluid reservoir 106 and discharge the fluid to a hydraulic circuit. The electro-hydraulic power unit may also include a valve 116 that fluidly couples a hydraulic line 110 to the fluid reservoir 106, wherein the valve 116 is configured to allow the pressure level within the hydraulic line 110 to increase to a threshold pressure (before opening and releasing fluid to the fluid reservoir 106).

[0125] In the first example, valve 116 includes a pressure relief valve 300. In another example, there is a spring-loaded check valve 400 and a throttle port 402 arranged in parallel with the spring-loaded check valve 400.

[0126] As an example, hydraulic circuits can be designed for... Figure 2 and 6 The different forms described above.

[0127] The detailed description above, with reference to the accompanying drawings, illustrates various features and operations of the disclosed system. The illustrative embodiments disclosed herein are not intended to be limiting. Specific aspects of the disclosed system can be arranged and combined in a wide range of different configurations, all of which are incorporated herein.

[0128] Furthermore, unless the context suggests otherwise, the features disclosed in each figure may be used in combination with each other. Thus, the figures should be viewed generally as constituent aspects of one or more overall embodiments, and understood as not all features shown being necessary for every embodiment.

[0129] Additionally, any elements, modules, or steps listed in the specification and claims are for explicit purposes. Therefore, such listing should not be construed as requiring or implying that these elements, modules, or steps are attached to a particular arrangement or implemented in a particular order.

[0130] Furthermore, the apparatus or system may be used or configured to perform the functions illustrated in the accompanying drawings. In some examples, components of the apparatus and / or system may be configured to perform functions, such that the components are actually configured and constructed (using hardware and / or software) to achieve such performance. In other examples, components of the apparatus and / or system may be arranged to be suited, adapted, or appropriate to perform functions, for example, when operated in a particular manner.

[0131] The use of the terms "approximately" or "about" implies that the characteristic, parameter, or value mentioned does not need to be implemented precisely, but deviations or changes (e.g., including tolerances, measurement errors, measurement accuracy limits, and other factors well known to those skilled in the art) can occur in a quantity that does not preclude the effect that the characteristic will provide.

[0132] The arrangement described herein is merely for illustrative purposes. Thus, those skilled in the art will understand, based entirely on the desired results, that other arrangements and other elements (e.g., mechanisms, interfaces, operations, sequences, and groupings of operations, etc.) may be used, and some elements may be omitted. Furthermore, the various elements described are functional entities that can be implemented as discrete or distributed components or combined with other components (in any suitable combination or location).

[0133] Although various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and are not intended to be limiting, while the true scope is indicated by the appended claims together with the full scope of their equivalents. Furthermore, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0134] The embodiments of this disclosure may therefore be associated with one of the exemplary embodiments (EEE) listed below.

[0135] EEE 1 is a system comprising: an electric motor; a pump coupled to and driven by the electric motor; a hydraulic circuit fluidly coupled to the pump and configured to receive fluid flow from the pump; a hydraulic line fluidly coupled to the hydraulic circuit, wherein the hydraulic circuit is configured to provide a fluid signal to the hydraulic line, wherein the fluid signal indicates a fluid flow demand of the hydraulic circuit; a pressure sensor mounted to the hydraulic line and configured to provide sensor information indicating a pressure level of fluid within the hydraulic line; and a controller configured to perform operations including: receiving sensor information from the pressure sensor and, based on the pressure level indicated by the sensor information, controlling the speed of the electric motor to change the fluid flow rate supplied by the pump to the hydraulic circuit, thereby satisfying the fluid flow demand.

[0136] EEE 2 is a system of EEE 1, wherein controlling the speed of the electric motor includes increasing the speed of the electric motor to increase the fluid flow rate provided by the pump as the pressure level in the hydraulic line decreases.

[0137] EEE 3 is a system of any one of EEE 1 to 2, and further includes: a fluid reservoir containing fluid at a low pressure level, wherein a pump is configured to draw fluid from the fluid reservoir and discharge fluid to a hydraulic circuit; and a valve that fluidly couples a hydraulic line to the fluid reservoir, wherein the valve is configured to allow the pressure level within the hydraulic line to increase to a threshold pressure value before opening and releasing fluid to the fluid reservoir.

[0138] EEE 4 is a system of EEE 3, in which the valves include pressure relief valves.

[0139] EEE 5 is a system of EEE 3, wherein the valves include: a spring-loaded check valve and a throttle port arranged in parallel with the spring-loaded check valve.

[0140] EEE 6 is a system of any of EEE 1 to 5, wherein the hydraulic circuit includes: a valve assembly comprising multiple operating sections, each operating section being configured to control fluid flow to and from a corresponding hydraulic actuator, wherein the valve assembly includes a load-sensing channel traversing the multiple operating sections and configured to transmit a load-sensing fluid pressure signal embodying the pressure caused by the highest load in the corresponding hydraulic actuator controlled by the multiple operating sections; and the hydraulic circuit includes an unloading valve comprising (i) an inlet port configured to receive fluid from a pump; (ii) a pilot port configured to receive the load-sensing fluid pressure signal; and (iii) an outlet port fluidly coupled to a hydraulic line to provide a fluid signal thereto.

[0141] EEE 7 is a system based on EEE 6, wherein the unloading valve further includes: a movable element on which the load-sensing fluid pressure signal applies a first fluid force, and wherein fluid from the inlet port applies a second fluid force on the movable element in opposition to the first fluid force; and a spring on which a bias force is applied, wherein: when the second fluid force overcomes the first fluid force and the bias force, the unloading valve opens to provide a fluid signal to a hydraulic line fluidly coupled to an outlet port, such that the pressure level of the fluid signal is based on the difference between the second fluid force and the combination of the first fluid force and the bias force, and when the force of the combination of the second fluid force and the bias force exceeds the first fluid force, the unloading valve blocks the fluid flow to the hydraulic line, such that the pressure level of the fluid signal is approximately zero.

[0142] EEE 8 is a system of any of EEE 1 to 5, wherein the hydraulic circuit includes: a valve assembly comprising multiple operating sections, each operating section being configured to control fluid flow to and from a corresponding hydraulic actuator, wherein the valve assembly includes: (i) a supply passage fluidly coupled to a pump, and (ii) a neutral-open passage configured to receive fluid from the pump and fluidly coupled to a hydraulic line, wherein: when the multiple operating sections are not actuated, fluid flow from the pump is provided to the neutral-open passage and then to the hydraulic line, and when one or more of the multiple operating sections are actuated, fluid flow to the neutral-open passage and the hydraulic line is constrained, thereby providing fluid flow to the supply passage, thus reducing the pressure level of the fluid signal within the hydraulic line; and a valve disposed downstream of the multiple operating sections and configured to fluidly couple the hydraulic line to a fluid reservoir, wherein the valve is configured to allow the pressure level within the hydraulic line to increase to a threshold pressure value before opening and releasing fluid to the fluid reservoir.

[0143] EEE 9 is an electro-hydraulic power unit comprising: an electric motor; a pump coupled to and driven by the electric motor, wherein the pump is configured to provide fluid flow to a hydraulic circuit outside the electro-hydraulic power unit; a pressure sensor configured to measure the pressure level of a fluid signal received from the hydraulic circuit, wherein the fluid signal indicates a fluid flow demand of the hydraulic circuit; and a controller configured to perform operations including: receiving sensor information from the pressure sensor indicating the pressure level of the fluid signal, and controlling the speed of the electric motor to change the fluid flow rate discharged from the pump to meet the fluid flow demand of the hydraulic circuit based on the pressure level indicated by the sensor information.

[0144] EEE 10 is an electro-hydraulic power unit of EEE 9, wherein controlling the speed of the electric motor includes controlling the speed of the electric motor via an inverse relationship between the pressure level of the fluid signal and the speed of the electric motor, such that as the pressure level of the fluid signal decreases, the speed of the electric motor is increased to increase the fluid flow rate discharged by the pump.

[0145] EEE 11 is an electro-hydraulic power unit of any of EEE 9 to 10, and further includes: a fluid reservoir containing fluid at a low pressure level, wherein a pump is configured to draw fluid from the fluid reservoir and discharge fluid to a hydraulic circuit; and a valve that fluidly couples a fluid signal to the fluid reservoir, wherein the valve is configured to allow the pressure level of the fluid signal to increase to a threshold pressure value before opening and releasing fluid to the fluid reservoir.

[0146] The EEE 12 is an electro-hydraulic power unit of the EEE 11, wherein the valves include a pressure relief valve.

[0147] EEE 13 is an electro-hydraulic power unit of EEE 11, wherein the valves include: a spring-loaded check valve; and a throttle port arranged in parallel with the spring-loaded check valve.

[0148] EEE 14 is a method comprising: receiving sensor information from a pressure sensor at a controller of an electro-hydraulic power unit, the pressure sensor being mounted to a hydraulic line that fluidly couples the electro-hydraulic power unit to a hydraulic circuit outside the electro-hydraulic power unit, wherein the electro-hydraulic power unit includes an electric motor and a pump coupled to and driven by the electric motor, wherein the pump provides fluid flow to the hydraulic circuit, and wherein the hydraulic circuit provides a fluid signal to the hydraulic line, wherein the fluid signal indicates a fluid flow demand in the hydraulic circuit; and controlling the speed of the electric motor based on sensor information indicating a pressure level of the fluid signal within the hydraulic line to change the fluid flow rate supplied to the hydraulic circuit by the pump to meet the fluid flow demand.

[0149] EEE 15 is a method of EEE 14, wherein controlling the speed of an electric motor includes controlling the speed of the electric motor via an inverse relationship between the pressure level of a fluid signal and the speed of the electric motor, such that as the pressure level of the fluid signal decreases, the speed of the electric motor is increased to increase the flow rate of fluid discharged by the pump.

[0150] EEE 16 is a method of any of EEE 14 to 15, wherein the electro-hydraulic power unit further includes: a fluid reservoir containing fluid at a low pressure level, wherein a pump is configured to draw fluid from the fluid reservoir and discharge fluid to a hydraulic circuit; and a valve that fluidly couples a hydraulic line to the fluid reservoir, wherein the valve is configured to allow the pressure level within the hydraulic line to increase to a threshold pressure value before opening and releasing fluid to the fluid reservoir.

[0151] EEE 17 is a method of EEE 16, wherein the valve includes a combination of a pressure relief valve or a spring-loaded check valve and a throttling orifice arranged in parallel with the spring-loaded check valve.

[0152] EEE 18 is a method of EEE 16, wherein the pump is a variable displacement pump with a swashplate, and wherein the method further includes changing the angle of the swashplate of the pump.

[0153] EEE 19 is a method of any of EEE 14 to 18, wherein the hydraulic circuit includes: a valve assembly comprising a plurality of working sections, each working section being configured to control fluid flow to and from a corresponding hydraulic actuator, wherein the valve assembly includes a load-sensing channel traversing the plurality of working sections and configured to transmit a load-sensing fluid pressure signal embodying the pressure caused by the highest load in the respective hydraulic actuators controlled by the plurality of working sections; and the hydraulic circuit includes an unloading valve comprising (i) an inlet port configured to receive fluid from a pump; (ii) a pilot port configured to receive a load-sensing fluid pressure signal; and (iii) an outlet port fluidly coupled to a hydraulic line. (iv) A movable element, wherein the load-sensing fluid pressure signal applies a first fluid force to the movable element, and wherein fluid from the inlet port applies a second fluid force to the movable element in opposition to the first fluid force; and (v) a spring that applies a bias force to the movable element, wherein: when the second fluid force overcomes the first fluid force and the bias force, an unloading valve opens to provide a fluid signal to a hydraulic line fluidly coupled to an outlet port, such that the pressure level of the fluid signal is based on the difference between the second fluid force and the combination of the first fluid force and the bias force, and when the force of the combination of the second fluid force and the bias force exceeds the first fluid force, the unloading valve blocks the fluid flow to the hydraulic line, such that the pressure level of the fluid signal is approximately zero.

[0154] EEE 20 is a method of any of EEE 14 to 18, wherein the hydraulic circuit includes: a valve assembly comprising a plurality of operating sections, each operating section being configured to control fluid flow to and from a corresponding hydraulic actuator, wherein the valve assembly includes: (i) a supply passage fluidly coupled to a pump, and (ii) a neutral-open passage configured to receive fluid from the pump and fluidly coupled to a hydraulic line, wherein: when the plurality of operating sections are not actuated, fluid flow from the pump is provided to the neutral-open passage and then to the hydraulic line, and when one or more of the plurality of operating sections are actuated, fluid flow to the neutral-open passage and the hydraulic line is constrained, thereby fluid flow is provided to the supply passage, thus reducing the pressure level of the fluid signal within the hydraulic line.

Claims

1. A system comprising: Electric motor; A pump coupled to and driven by an electric motor; A hydraulic circuit, the hydraulic circuit being fluidly coupled to a pump and configured to receive fluid flow from the pump; A hydraulic line is fluidly coupled to the hydraulic circuit, wherein the hydraulic circuit is configured to provide a fluid signal to the hydraulic line, wherein the fluid signal indicates the fluid flow demand of the hydraulic circuit; A pressure sensor, wherein the pressure sensor is mounted to a hydraulic line and configured to provide sensor information indicating the pressure level of the fluid within the hydraulic line; and The controller is configured to perform the following operations: The self-pressure sensor receives sensor information, and Based on the pressure level indicated by sensor information, the speed of the electric motor is controlled to change the fluid flow rate supplied by the pump to the hydraulic circuit, thereby meeting the fluid flow demand. The hydraulic circuit includes: A valve assembly comprising multiple operating sections, each operating section configured to control fluid flow to and from a corresponding hydraulic actuator, wherein the valve assembly includes a load-sensing channel traversing the multiple operating sections and configured to transmit a load-sensing fluid pressure signal embodying the pressure caused by the highest load in the respective hydraulic actuator controlled by the multiple operating sections; and An unloading valve includes (i) an inlet port configured to receive fluid from a pump; (ii) a pilot port configured to receive a load-sensed fluid pressure signal; and (iii) an outlet port fluidly coupled to a hydraulic line to provide a fluid signal thereto.

2. The system according to claim 1, wherein, Controlling the speed of an electric motor includes: As the pressure level within the hydraulic lines decreases, the speed of the electric motor is increased to increase the fluid flow rate supplied by the pump.

3. The system according to claim 1, further comprising: A fluid reservoir containing fluid at a low pressure level, wherein a pump is configured to draw fluid from the fluid reservoir and discharge fluid to a hydraulic circuit; and A valve that fluidly couples a hydraulic line to a fluid reservoir, wherein the valve is configured to allow the pressure level within the hydraulic line to increase to a threshold pressure value before opening and releasing fluid into the fluid reservoir.

4. The system according to claim 3, wherein, The valves include pressure relief valves.

5. The system according to claim 3, wherein, The valve includes: Spring-loaded check valve; and A throttling orifice is arranged in parallel with a spring-loaded check valve.

6. The system according to claim 1, wherein, The unloading valve also includes: A movable element, wherein a load-sensed fluid pressure signal applies a first fluid force to the movable element, and wherein fluid from an inlet port applies a second fluid force to the movable element in opposition to the first fluid force; and A spring that applies a biasing force to a movable element, wherein: When the second fluid force overcomes the first fluid force and the bias pressure, the unloading valve opens to provide a fluid signal to the hydraulic line fluidly coupled to the outlet port. The pressure level of the fluid signal is based on the difference between the second fluid force and the combination of the first fluid force and the bias pressure. When the combined force of the second fluid force and the bias pressure exceeds the first fluid force, the unloading valve blocks the fluid flow to the hydraulic line, so that the pressure level of the fluid signal is approximately zero.

7. A system comprising: Electric motor; A pump coupled to and driven by an electric motor; A hydraulic circuit, the hydraulic circuit being fluidly coupled to a pump and configured to receive fluid flow from the pump; A hydraulic line is fluidly coupled to the hydraulic circuit, wherein the hydraulic circuit is configured to provide a fluid signal to the hydraulic line, wherein the fluid signal indicates the fluid flow demand of the hydraulic circuit; A pressure sensor, wherein the pressure sensor is mounted to a hydraulic line and configured to provide sensor information indicating the pressure level of the fluid within the hydraulic line; and The controller is configured to perform the following operations: The self-pressure sensor receives sensor information, and Based on the pressure level indicated by sensor information, the speed of the electric motor is controlled to change the fluid flow rate supplied by the pump to the hydraulic circuit, thereby meeting the fluid flow demand. The hydraulic circuit includes: A valve assembly comprising multiple operating sections, each configured to control fluid flow to and from a corresponding hydraulic actuator, wherein the valve assembly includes: (i) a supply passage fluidly coupled to a pump, and (ii) a neutral-position open passage configured to receive fluid from the pump and fluidly coupled to a hydraulic line, wherein: When multiple operating sections are not activated, fluid flow from the pump is supplied to the neutral open channel, and then to the hydraulic lines, and When one or more of the multiple working sections are actuated, the fluid flow to the neutral opening channel and hydraulic lines is constrained, thereby supplying fluid flow to the supply channel and reducing the pressure level of the fluid signal within the hydraulic lines; and A valve located downstream of multiple operating sections and configured to fluidly couple a hydraulic line to a fluid reservoir, wherein the valve is configured to allow the pressure level within the hydraulic line to increase to a threshold pressure value before opening and releasing fluid to the fluid reservoir.

8. An electro-hydraulic power unit, comprising: Electric motor; A pump coupled to and driven by an electric motor, wherein the pump is configured to provide fluid flow to a hydraulic circuit outside an electro-hydraulic power unit; A pressure sensor configured to measure the pressure level of a fluid signal received from a hydraulic circuit, wherein the fluid signal indicates the fluid flow demand of the hydraulic circuit; and A controller, configured to perform operations, including: Receive sensor information from the pressure sensor indicating the pressure level of the fluid signal, and Based on the pressure level indicated by sensor information, the speed of the electric motor is controlled to change the fluid flow rate discharged from the pump to meet the fluid flow requirements of the hydraulic circuit, wherein the hydraulic circuit includes: A valve assembly comprising multiple operating sections, each operating section configured to control fluid flow to and from a corresponding hydraulic actuator, wherein the valve assembly includes a load-sensing channel traversing the multiple operating sections and configured to transmit a load-sensing fluid pressure signal embodying the pressure caused by the highest load in the respective hydraulic actuator controlled by the multiple operating sections; and An unloading valve includes (i) an inlet port configured to receive fluid from a pump; (ii) a pilot port configured to receive a load-sensed fluid pressure signal; and (iii) an outlet port fluidly coupled to a hydraulic line to provide a fluid signal thereto.

9. The electro-hydraulic power unit according to claim 8, wherein, Controlling the speed of an electric motor includes: The speed of the electric motor is controlled by the inverse relationship between the pressure level of the fluid signal and the speed of the electric motor. As the pressure level of the fluid signal decreases, the speed of the electric motor is increased to increase the flow rate of the fluid discharged by the pump.

10. The electro-hydraulic power unit according to claim 8, further comprising: A fluid reservoir containing fluid at low pressure levels, wherein a pump is configured to draw fluid from the fluid reservoir and discharge fluid to a hydraulic circuit; and A valve that fluidly couples a fluid signal to a fluid reservoir, wherein the valve is configured to allow the pressure level of the fluid signal to increase to a threshold pressure value before opening and releasing fluid into the fluid reservoir.

11. The electro-hydraulic power unit according to claim 10, wherein, The valves include pressure relief valves.

12. The electro-hydraulic power unit according to claim 10, wherein, The valve includes: Spring-loaded check valve; as well as A throttling orifice is arranged in parallel with a spring-loaded check valve.

13. A method comprising: The controller of the electro-hydraulic power unit receives sensor information from a pressure sensor mounted to a hydraulic line that fluidly couples the electro-hydraulic power unit to a hydraulic circuit outside the electro-hydraulic power unit. The electro-hydraulic power unit includes an electric motor and a pump coupled to and driven by the electric motor. The pump provides fluid flow to the hydraulic circuit, and the hydraulic circuit provides a fluid signal to the hydraulic line, indicating the fluid flow demand of the hydraulic circuit. The speed of the electric motor is controlled based on sensor information indicating the pressure level of the fluid signal within the hydraulic line, thereby changing the fluid flow rate supplied to the hydraulic circuit by the pump to meet fluid flow requirements. The hydraulic circuit includes: A valve assembly comprising multiple operating sections, each operating section configured to control fluid flow to and from a corresponding hydraulic actuator, wherein the valve assembly includes a load-sensing channel traversing the multiple operating sections and configured to transmit a load-sensing fluid pressure signal embodying the pressure caused by the highest load in the respective hydraulic actuator controlled by the multiple operating sections; and An unloading valve comprising (i) an inlet port configured to receive fluid from a pump; (ii) a pilot port configured to receive a load-sensing fluid pressure signal; (iii) an outlet port fluidly coupled to a hydraulic line to provide a fluid signal thereto; (iv) a movable element wherein the load-sensing fluid pressure signal applies a first fluid force to the movable element, and wherein fluid from the inlet port applies a second fluid force to the movable element in opposition to the first fluid force; and (v) a spring applying a biasing force to the movable element, wherein: When the second fluid force overcomes the first fluid force and the bias pressure, the unloading valve opens to provide a fluid signal to the hydraulic line fluidly coupled to the outlet port. The pressure level of the fluid signal is based on the difference between the second fluid force and the combination of the first fluid force and the bias pressure. When the combined force of the second fluid force and the bias pressure exceeds the first fluid force, the unloading valve blocks the fluid flow to the hydraulic line, so that the pressure level of the fluid signal is approximately zero.

14. The method according to claim 13, wherein, Controlling the speed of an electric motor includes: The speed of the electric motor is controlled by the inverse relationship between the pressure level of the fluid signal and the speed of the electric motor. As the pressure level of the fluid signal decreases, the speed of the electric motor is increased to increase the flow rate of the fluid discharged by the pump.

15. The method of claim 13, wherein, The electro-hydraulic power unit also includes: A fluid reservoir containing fluid at a low pressure level, wherein a pump is configured to draw fluid from the fluid reservoir and discharge fluid to a hydraulic circuit; and A valve that couples hydraulic line fluid to a fluid reservoir, and wherein the method further includes: Use valves to allow the pressure level within the hydraulic line to increase to a threshold pressure value before opening and releasing fluid into the fluid reservoir.

16. The method according to claim 15, wherein, The valve includes a pressure relief valve or a spring-loaded check valve, as well as a combination of a throttling orifice arranged in parallel with the spring-loaded check valve.

17. The method according to claim 15, wherein, The pump is a variable displacement pump with a swivel disc, and the method further includes: Change the angle of the pump's oscillating disc.

18. The method according to claim 13, wherein, The hydraulic circuit includes: A valve assembly comprising multiple operating sections, each configured to control fluid flow to and from a corresponding hydraulic actuator, wherein the valve assembly includes: (i) a supply passage fluidly coupled to a pump, and (ii) a neutral-position open passage configured to receive fluid from the pump and fluidly coupled to a hydraulic line, wherein: When multiple operating sections are not activated, fluid flow from the pump is supplied to the neutral open channel, and then to the hydraulic lines, and When one or more of the multiple working sections are actuated, the fluid flow to the neutral opening channel and hydraulic line is constrained, thereby providing fluid flow to the supply channel and thus reducing the pressure level of the fluid signal in the hydraulic line.

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