Service pack variable displacement pump

A service pack, in certain embodiments, includes an engine, a variable displacement pump coupled to the engine, and a controller configured to control displacement of the variable displacement pump in response to a load condition associated with the engine. A method of managing power of an engine-driven system, in certain embodiments, includes sensing a load associated with an engine coupled to a variable displacement pump. The method also includes adjusting pump displacement of the variable displacement pump in response to the sensed load and one or more limits associated with the engine.

BACKGROUND

The invention relates generally to hydraulic systems. More particularly, this invention relates to the delivery and control of fluid power to a service truck to operate equipment on or near the truck, for example, but not limited to, a crane with multiple functions.

Existing work vehicles often integrate auxiliary resources, such as electrical power, compressor air service, and/or hydraulic service, directly from the mechanical power of the main vehicle engine. Specifically, the main vehicle engine may drive a power take-off (PTO) shaft, which in turn drives the various integrated auxiliary resources. This is common in many applications where the auxiliary systems are provided as original equipment, either standard with the vehicle or as an option. The work vehicles also may include a clutch or other selective engagement mechanism to enable the selective engagement and disengagement of the integrated auxiliary resources.

Unfortunately, these integrated auxiliary resources rely on operation of the main vehicle engine. The main vehicle engine is typically a large engine, which is particularly noisy, significantly over powered for the integrated auxiliary resources, and fuel inefficient. For example, the main vehicle engine may be a spark ignition engine or a compression ignition engine (e.g., diesel engine) having six or more cylinders. The main vehicle engine may have over 200 horsepower, while the integrated auxiliary resources may only need about 20-40 horsepower. Unfortunately, an operator typically leaves the main vehicle engine idling for extended periods between actual use of the integrated auxiliary resources, simply to maintain the option of using the resources without troubling the operator to start and stop the main vehicle engine. Such operation reduces the overall life of the engine and drive train for vehicle transport needs.

Furthermore, the vehicle with integrated auxiliary resources does not control the power consumption, because the main vehicle engine has equal or more power than what is needed under all maximum power consumption circumstances (e.g., full hydraulic flow and pressure). Instead, the main vehicle engine typically runs at a normal condition without any change despite the various loads associated with the integrated auxiliary resources. At this normal condition, the main vehicle engine generally provides a great deal of wasted power.

BRIEF DESCRIPTION

A service pack, in certain embodiments, includes an engine, a variable displacement pump coupled to the engine, and a controller configured to control displacement of the variable displacement pump in response to a load condition associated with the engine. A method of managing power of an engine-driven system, in certain embodiments, includes sensing a load associated with an engine coupled to a variable displacement pump. The method also includes adjusting pump displacement of the variable displacement pump in response to the sensed load and one or more limits associated with the engine.

DETAILED DESCRIPTION

As discussed below, certain embodiments may include control of a pump based on various loads associated with the engine driving the pump. In the present embodiments, the engine may include a spark ignition (SI) engine or a compression ignition (CI) engine other than the main vehicle engine. Thus, the engine may be substantially smaller in size, weight, and power output (e.g., horsepower) as compared to the main vehicle engine. For example, certain embodiments of the engine may provide 20-40 horsepower. Advantageously, the smaller engine provides greater fuel efficiency and costs less for various applications in addition to the clear advantages in reduced size, weight, and so forth.

Unfortunately, the smaller engine can become overloaded by one or more loads during operation. In certain embodiments, the engine may drive an electrical generator, a compressor, a hydraulic pump, or a combination thereof. Thus, the loads may include various electrical tools, lights, a welding torch, a cutting torch, and the like. The loads also may include an air tool, a pneumatic spray gun, and the like. Furthermore, the loads may include a hydraulic lift, a hydraulic crane, a hydraulic stabilizer, a hydraulic tool, and the like. Each of these loads has certain demands, which can overload the prime mover either alone or in certain combinations with one another.

As discussed below, the present embodiments provide a control scheme to tailor or generally match the loads (e.g., hydraulic loads) on the engine to the available power of the engine. Although the disclosed embodiments refer to hydraulic loads, the techniques may be used with other loads such as electrical generators, air compressors, and so forth. Specifically, as discussed below, the disclosed control scheme limits the load created by a hydraulic pump in response to various sensor feedback, such as direct engine load feedback, hydraulic pressure feedback, engine RPMs, and so forth. The disclosed embodiments may be utilized with a variety of portable service packs, work vehicles with service packs or features, or other suitable applications. For example, the disclosed embodiments may be used in combination with any and all of the embodiments set forth in U.S. application Ser. No. 11/742,399, filed on Apr. 30, 2007, and entitled “ENGINE-DRIVEN AIR COMPRESSOR/GENERATOR LOAD PRIORITY CONTROL SYSTEM AND METHOD,” which is hereby incorporated by reference in its entirety. Furthermore, the disclosed embodiments may be used in combination with any and all of the embodiments set forth in U.S. application Ser. No. 11/943,564, filed on Nov. 20, 2007, and entitled “AUXILIARY SERVICE PACK FOR A WORK VEHICLE,” which is hereby incorporated by reference in its entirety.

Embodiments of the control scheme essentially tailor or match the loads on the engine with the power capability of the engine, thereby maximizing use of the engine for more efficient operation. Regarding hydraulic power, the disclosed embodiments are able to satisfy the needs of the operator by providing full pressure at less than full flow, and by providing full flow at less than full pressure (e.g., “power matching”). In order to provide this “power matching” feature, the control scheme functions to control the power consumption of the hydraulic system so as not to overpower the smaller engine.

Turning now to the drawings,FIG. 1illustrates a work vehicle10including a main vehicle engine12, first and second service pack modules18and22, and various equipment in accordance with certain embodiments of the present technique. As discussed in further detail below, the first and second service pack modules18and22may provide various resources, such as electrical power, compressed air, and hydraulic power, with or without assistance from the main vehicle engine12. Thus, in some embodiments, the operator can shut off the main vehicle engine to reduce noise, conserve fuel, and increase the life of the main vehicle engine12, while the service pack modules18and22are self-powered or power one another. However, in some embodiments, the service pack modules18and22may utilize and/or provide some resources of the vehicle10, e.g., use fuel from the vehicle, use hydraulic power from the vehicle, provide hydraulic power to the vehicle, and so forth. The illustrated work vehicle10is a work truck, yet other embodiments of the vehicle may include other types and configurations of vehicles.

The main vehicle engine12may include a spark ignition engine (e.g., gasoline fueled internal combustion engine) or a compression ignition engine (e.g., a diesel fueled engine), for example, an engine with 6, 8, 10, or 12 cylinders with over 200 horsepower. The vehicle engine12includes a number of support systems. For example, the vehicle engine12consumes fuel from a fuel reservoir, typically one or more liquid fuel tanks, which will be addressed later. Further, the vehicle engine12may include or couple to an engine cooling system, which may include a radiator, circulation pump, thermostat controlled valve, and a fan. The vehicle engine12also includes an electrical system, which may include an alternator or generator along with one or more system batteries, cable assemblies routing power to a fuse box or other distribution system, and so forth. The vehicle engine12also includes an oil lubrication system. Further, the vehicle engine12also couples to an exhaust system, which may include catalytic converters, mufflers, and associated conduits. Finally, the vehicle engine12may feature an air intake system, which may include filters, flow measurement devices, and associated conduits.

The service pack modules18and22may have a variety of resources, such as electrical power, compressed air, hydraulic power, and so forth. These service pack modules18and22also may operate alone or in combination with one another, e.g., dependent on one another. In the illustrated embodiment, the first service pack module18includes a service pack engine14and a variable displacement pump16with load sense as discussed in detail below. In particular, the variable displacement pump16may include a hydraulic pump, a water pump, a waste pump, a chemical pump, or any other fluid pump. The service pack engine14may include a spark ignition engine (e.g., gasoline fueled internal combustion engine) or a compression ignition engine (e.g., a diesel fueled engine), for example, an engine with 1-4 cylinders with approximately 10-80 horsepower. In some embodiments, the service pack engine14may have a small engine with approximately 10, 20, 30, 40, or 50 horsepower. Moreover, the service pack engine14may be undersized to improve fuel consumption, while the variable displacement pump16with load sense can satisfy the needs of the operator by providing full pressure at less than full flow or by providing full flow at less than full pressure (e.g., “power matching”). The variable displacement pump16may be configured to provide hydraulic power (e.g., pressurized hydraulic fluid) to one or more devices in the vehicle or elsewhere.

As illustrated in the embodiment ofFIG. 1, the first and second service pack modules18and22are separate from one another and from vehicle engine12. In other words, the first and second service pack modules18and22are stand-alone units relative to the vehicle engine12, such that they do not rely on power from the vehicle engine12. In some embodiments, the first and second service pack modules18and22may be combined as a single standalone unit, while still being separate from the vehicle engine12. However, in the illustrated embodiment, the second service pack module22is driven by hydraulic fluid from the first service pack module18, thereby making the second service pack module22dependent on the first service pack module18or another source of fluid (e.g., hydraulic fluid). Specifically, as illustrated inFIG. 1, the service pack engine14drives the variable displacement pump16, which in turn drives fluid motor24(e.g., hydraulic motor) located in second service pack module22.

The fluid motor24(e.g., hydraulic motor) contained in second service pack module22may be coupled to air compressor26as well as generator28. The air compressor26and the generator28may be driven directly, or may be belt, gear, or chain driven, by the fluid motor24. The generator28may include a three-phase brushless type, capable of producing power for a wide range of applications. However, other generators may be employed, including single phase generators and generators capable of producing multiple power outputs. The air compressor26may also be of any suitable type, although a rotary screw air compressor is presently contemplated due to its superior output to size ratio. Other suitable air compressors might include reciprocating compressors, typically based upon one or more reciprocating pistons.

The first and/or second service pack modules18and22include conduits, wiring, tubing, and so forth for conveying the services/resources (e.g., electrical power, compressed air, and fluid/hydraulic power) generated by these modules to an access panel30. The access panel30may be located on any portion of the vehicle10, or on multiple locations in the vehicle, and may be covered by doors or other protective structures. In one embodiment, all of the services may be routed to a single/common access panel30. The access panel30may include various control inputs, indicators, displays, electrical outputs, pneumatic outputs, and so forth. In an embodiment, a user input may include a knob or button configured for a mode of operation, an output level or type, etc. In the illustrated embodiment, the first and second service pack modules18and22supply electrical power, compressed air, and fluid power (e.g., hydraulic power) to a range of applications designated generally by arrows32.

As depicted, air tool34, torch36, and light38are applications connected to the access panel30and, thus, the resources/services provided by the service pack modules18and22. The various tools may connect with the access panel30via electrical cables, gas (e.g., air) conduits, fluid (e.g., hydraulic) lines, and so forth. The air tool34may include a pneumatically driven wrench, drill, spray gun, or other types of air-based tools, which receive compressed air from the access panel30and compressor26via a supply conduit (e.g., a flexible rubber hose). The torch36may utilize electrical power and compressed gas (e.g., air or inert shielding gas) depending on the particular type and configuration of the torch36. For example, the torch36may include a welding torch, a cutting torch, a ground cable, and so forth. More specifically, the welding torch36may include a TIG (tungsten inert gas) torch or a MIG (metal inert gas) gun. The cutting torch36may include a plasma cutting torch and/or an induction heating circuit. Moreover, a welding wire feeder may receive electrical power from the access panel30. Moreover, a hydraulically powered vehicle stabilizer40may be powered by the fluid system, e.g., variable displacement pump16, to stabilize the work vehicle10at a work site. In the illustration, a hydraulically powered crane42is also coupled to and powered by the variable displacement pump16. Again, the service pack modules18and22provide the desired resources/services to run various tools and equipment without requiring operation of the main vehicle engine12.

As noted above, the disclosed service pack modules18and22may be designed to interface with any desired type of vehicle. Such vehicles may include cranes, manlifts, and so forth, which can be powered by the service pack modules18and/or22. In the embodiment ofFIG. 1, the crane42may be mounted within a bed of the vehicle10, on a work platform of the vehicle10, or on an upper support structure of the vehicle10as shown inFIG. 1. Moreover, such cranes may be mechanical, electrical or hydraulically powered. In the illustrated embodiment, the crane42can be powered by the service pack modules18and/or22without relying on the vehicle engine12. That is, once the vehicle is positioned at the work site, the vehicle engine12may be stopped and the service pack engine14may be started for crane operation and use of auxiliary services. In the embodiment illustrated inFIG. 1, the crane42is mounted on a rotating support structure, and hydraulically powered such that it may be rotated, raised and lowered, and extended (as indicated by arrows44,46and48, respectively) by pressurized hydraulic fluid provided by the service pack output32.

The vehicle10and/or the service pack modules18and22may include a variety of protective circuits for the electrical power, e.g., fuses, circuit breakers, and so forth, as well as valving for the fluid (e.g., hydraulic) and air service. For the supply of electrical power, certain types of power may be conditioned (e.g., smoothed, filtered, etc.), and 12 volt power output may be provided by rectification, filtering and regulating of AC output. Valving for fluid (e.g., hydraulic) power output may include by way example, pressure relief valves, check valves, shut-off valves, as well as directional control valving. Moreover, the variable displacement pump16may draw fluid from and return fluid to a fluid reservoir, which may include an appropriate vent for the exchange of air during use with the interior volume of the reservoir, as well as a strainer or filter for the fluid. Similarly, the air compressor26may draw air from the environment through an air filter.

The first and second service pack modules18and22may be physically positioned at any suitable location in the vehicle10. In a presently contemplated embodiment, for example, the service pack modules18and22may be mounted on, beneath or beside the vehicle bed or work platform rear of the vehicle cab. In many such vehicles, for example, the vehicle chassis may provide convenient mechanical support for the engine and certain of the other components of the service pack modules18and22. For example, steel tubing, rails or other support structures extending between front and rear axles of the vehicle may serve as a support for the service pack modules18and22and, specifically, the components self-contained in those modules. Depending upon the system components selected and the placement of the service pack modules18and22, reservoirs may be provided for storing fluid (e.g., hydraulic fluid) and pressurized air as noted above. However, the fluid reservoir may be placed at various locations or even integrated into the service pack modules18and/or22. Likewise, depending upon the air compressor selected, no reservoir may be used for compressed air. Specifically, if the air compressor26includes a non-reciprocating or rotary type compressor, then the system may be tankless with regard to the compressed air.

In use, the service pack modules18and22provide various resources/services (e.g., electrical power, compressed air, fluid/hydraulic power, etc.) for the on-site applications completely independent of vehicle engine12. For example, the service pack engine14generally may not be powered during transit of the vehicle from one service location to another, or from a service garage or facility to a service site. Once located at the service site, the vehicle10may be parked at a convenient location, and the main vehicle engine12may be shut down. The service pack engine14may then be powered to provide auxiliary service from one or more of the service systems described above. Where desired, clutches, gears, or other mechanical engagement devices may be provided for engagement and disengagement of one or more of the generator28, the variable displacement pump16, and the air compressor26, depending upon which of these service are desired. Moreover, as in conventional vehicles, where stabilization of the vehicle or any of the systems is require, the vehicle may include outriggers, stabilizers, and so forth which may be deployed after parking the vehicle and prior to operation of the service pack modules. The disclosed embodiments thus allow for a service to be provided in several different manners and by several different systems without the need to operate the main vehicle engine12at a service site.

Several different arrangements are envisaged for the components of the first service pack module18and the second service pack module22.FIG. 2illustrates an embodiment of the first and second service pack modules18and22, wherein the first service pack module18includes the service pack engine14, the variable displacement pump16, and a fuel tank50, and wherein the second service pack module22includes the fluid motor24(e.g., hydraulic motor), the air compressor26, and the generator28. As discussed below, the components of each service pack modules18and22are self-contained in respective enclosures49and51, such that the modules18and22are independent and distinct from one another. In other words, the enclosure49of the module18self contains the engine14, the pump16, and the fuel tank50independent of both the module22and various components of the vehicle10. Similarly, the enclosure51of the module22self contains the hydraulic motor24, the air compressor26, and the generator28independent of both the module18and various components of the vehicle10. Again, in alternate embodiments, a single unit may include the components of both service pack modules18and22.

The service pack modules18and22may be used independently or in combination with one another. For example, the first service pack module18may be used to provide fluid (e.g., hydraulic) power for any type of fluid driven (e.g., hydraulically driven) system, which may or may not include the second service pack module22. In certain embodiments, the first service pack module18may be described as dependent only on a source of fuel, such as gasoline or diesel fuel, to operate the engine14and provide the hydraulic power. By further example, the second service pack module22may be hydraulically driven by any suitable source of hydraulic power, which may or may not include the hydraulic pump16of the first service pack module18. Thus, in certain embodiments, the second service pack module22may be described as hydraulically dependent on some source of hydraulic power, or more specifically, only hydraulic power dependence. However, some embodiments may combine the components of these two service pack modules18and22into a single unit.

Turning now to the details ofFIG. 2, the first service pack module18includes a first service access panel52, which includes fluid couplings53to output fluid (e.g., hydraulic fluid) from the variable displacement pump16to various external devices. In the illustrated embodiment, the fluid couplings53couple to the second service pack module22, the hydraulic crane42, a hydraulic tool54, hydraulic equipment56, and the hydraulic stabilizer40. For example, the second service pack module22is connected to the first service pack module18via fluid tubing20(e.g., hydraulic tubing) connected to one of the couplings53.

As further illustrated inFIG. 2, the second service pack module22includes the fluid motor24(e.g., hydraulic motor) coupled to the air compressor26and generator28, which is connected to the welding/cutting circuit58. The circuit58may include one or more circuits configured to provide power, functions, and control for welding, cutting, wire feeding, gas supply, and so forth. The generator28may provide electrical power to the welding circuit58to operate various welding devices, such as those discussed above. The second service pack module22also includes a service pack access panel (e.g.,30), which includes couplings59(e.g., electrical, air, and optionally hydraulic connectors) for various external devices. For example, the service pack module22may or may not provide fluid couplings59(e.g., hydraulic couplings) as a pass through from the fluid received into the system. Connections to access panel30may provide service to several tools, including hydraulic tool60, air tool62, electric tool64, air tool (e.g., wrench)34, torch36, and light38. In addition, the various external devices include electrical cables, air hoses, fluid tubing, and so forth, as illustrated by the lines extending between the devices and their respective couplings59on the panel30. The access panel30also may include one or more controls65for the various services/resources, e.g., electrical power, compressed air, hydraulics, etc. As discussed below, these controls65may include input controls (e.g., switches, selectors, keypads, etc.) and output displays, gauges, and the like.

As appreciated, the generator28and/or circuit58may be configured to provide AC power, DC power, or both, for various applications. Moreover, the circuit58may function to provide constant current or constant voltage regulated power suitable for a welding or cutting application. Thus, the torch36may be a welding torch36, such as a MIG welding torch, a TIG welding torch, and so forth. The torch36also may be a cutting torch, such as a plasma cutting torch. The generator28and/or circuit58also may provide a variety of output voltages and currents suitable for different applications. For example, a 12 volt DC output of the module22may also serve to maintain the vehicle battery charge, and to power any ancillary loads that the operator may need during work (e.g., cab lights, hydraulic system controls, etc.).

FIG. 3illustrates an embodiment of the access panels30and52of the respective first and second service pack modules18and22, as shown inFIGS. 1 and 2. In the illustrated embodiment, the access panel30of the module22includes the various couplings59and controls65shown inFIG. 2. Specifically, the couplings include a set of air couplings59A, a set of electrical power couplings59B, and a set of torch couplings59C. The controls65include a voltage gauge66and associated voltage control knob67, a current gauge68and associated current control knob69, an air pressure gauge70and associated pressure control knob71, and a display screen72(e.g., liquid crystal display) and associated input keys73. The controls65also may include on/off switches or buttons75for each of the couplings59, such that an operator can turn on and off the electrical power, the compressed air, and/or the fluid power (e.g., hydraulic power) linked to the couplings59A,59B, and59C. Optionally, the access panel30may include various fluid couplings (e.g., hydraulic couplings), gauges, and controls in an embodiment that routes at least some of the fluid from the first module18through the second module22to various external hydraulic devices. Furthermore, the access panel30may be used as a central control panel for all resources/services provided by both modules18and22when these modules18and22are used in combination with one another.

In the illustrated embodiment, the access panel52may include several fluid (e.g., hydraulic) output couplings53as well as hydraulic and power controls to monitor and configure settings for service pack engine14and variable displacement pump16. The access panel52may also permit, for example, starting and stopping of the service pack engine14by a keyed ignition or starter button. The access panel52may also include a stop, disconnect, or disable switch that allows the operator to prevent starting of the service pack engine14, such as during transport. The access panel52may also include fluid (e.g., hydraulic) pressure gauge74, engine RPM gauge76, engine fuel gauge78, engine temperature gauge80, and various inputs and outputs as generally depicted by numeral82.

FIG. 4is a diagram illustrating a system for controlling power of the service pack engine14driving the variable displacement pump16in accordance with certain embodiments. In certain embodiments, the pump16may be described as a variable displacement flow compensating piston pump16. In the illustrated embodiment, the system includes the engine14, the variable displacement pump16, a controller100, a valve102, a load sense104, a fluid (e.g., hydraulically) driven system106, and a flow compensator108associated with the pump16.

The illustrated controller100is configured to sense (via load sense104) various load conditions110on the service pack engine14, e.g., throttle/actuator position, fuel flow, engine torque, power output, RPM, exhaust temperature, and so forth. For example, in one specific embodiment, the load sense104monitors the throttle or actuator position on a carburetor or fuel injection system, thereby tracking the amount of fuel injected into the engine14. The amount of fuel injection may be directly correlated to the engine load. For example, greater fuel injection may correlate with greater engine load, whereas lesser fuel injection may correlate with lesser engine load. The illustrated controller100is also configured to sense (via load sense104) various load conditions112on the hydraulically driven system, e.g., hydraulic pressure, hydraulic flow rate, torque, power, and so forth.

As indicated by arrow114, the controller100is configured to control the valve102in response to the load conditions110and/or112received from the load sense104. If the controller100identifies a possible overload condition, then the controller100is configured to control the valve102to reduce the hydraulic-based load on the system and, thus, eliminate the possible overload condition. However, the controller100also may monitor under load conditions (e.g., wasted power), and reduce speed of the service pack engine14, increase the hydraulic-based load on the system, and so forth.

The illustrated variable displacement pump16is configured to respond to the hydraulic pressure in the system via the flow compensator108(e.g., internal pump load sense). For example, the flow compensator108may receive feedback116relating to the pressure drop across the valve102. Specifically, the flow compensator108may control or adjust the variable displacement pump16to increase pump displacement in response to a low hydraulic load (e.g., a low pressure drop) in the system. Similarly, the flow compensator108may control or adjust the variable displacement pump16to decrease pump displacement in response to a high hydraulic load (e.g., a high pressure drop) in the system. Again, the hydraulic load may correspond to a low or high pressure drop across the valve102, which triggers the flow compensator108to adjust the displacement of the pump16. In certain embodiments, the variable displacement pump16may include a piston, a shaft, and a variable displacement mechanism (e.g., a swash plate) disposed between the piston and the shaft. For example, the swash plate may be described as a disk attached to the shaft, wherein the disk has an adjustable angle relative to the shaft (e.g., between 0 and 90 degrees). The swash plate will provide maximum piston displacement at an angle less than 90 degrees between the swash plate and shaft, and will provide minimum piston displacement at an angle of 90 degrees between the swash plate and shaft. Thus, in certain embodiments, the flow compensator108may adjust the angle of the swash plate and, thus the displacement of the piston, to vary the output of the pump16in response to the sensed pressure drop across the valve102. Furthermore, as discussed below, the disclosed embodiments enable control of the valve102in response to load conditions110and/or112from the load sense104. As a result, the control scheme enables control of the variable displacement pump16, such that the service pack engine14is not overloaded beyond its limits. As discussed above, this is particularly important due to the output limits of small engines14.

In the illustrated embodiment, the controller100controls the valve102to induce a change in the hydraulic load (e.g., pressure drop) associated with the variable displacement pump16. Specifically, the valve102may be a variable orifice valve operated by a drive, such as a solenoid. Thus, the valve102can provide a variable opening or path for the hydraulic fluid to pass on to the system106. As a result, the valve102may increase the hydraulic pressure in the system by partially closing the valve102, or the valve102may decrease the hydraulic pressure in the system by partially or fully opening the valve102. As a result of the change in pressure drop across the valve102, the variable displacement pump16may flow compensate via the flow compensator108and variable displacement mechanism (e.g., swash plate).

FIG. 5is a diagram illustrating a variable displacement piston pump circuit120with flow compensator108in accordance with certain embodiments. As illustrated inFIG. 5, the circuit120includes a hydraulic pump16(H-P1) being driven by a prime mover14(e.g., an internal combustion engine), a hydraulic flow control valve102(H-FC1), and a hydraulic filter122(H-F1). The hydraulic pump16has a suction line124(T1) that receives fluid from a reservoir or tank126, a case drain line128(CD1) that returns fluid to the reservoir126, a flow compensation line130(LS1) coupled to the flow compensator108, and a pressure line132(P1).

In the illustrated embodiment, the hydraulic pump16is a variable displacement pump with flow compensator108. The pump16uses the flow compensation line130to maintain a constant, preset, pressure drop across valve102. Regardless of load, the pump16maintains this preset pressure drop, provided the flow compensation line130is placed between the pressure drop control and the load. Greater flowrate creates greater pressure drop across components, and vise-verse, lesser flowrate creates less pressure drop across components. The hydraulic pump16with flow compensator108adjusts flow rate until the preset pressure drop is achieved.

The hydraulic flow control valve102may be a proportional valve that adjust variably from fully closed to fully open and all positions in between. This valve102is used to change the restriction in the pressure line132, which in turn, adjusts the flowrate of the pump16. As illustrated, the valve102includes a solenoid134, a spring136, and a valve member138. The spring136biases the valve member138toward a normally closed position, whereas the solenoid134may be actuated to bias the valve member138toward a partially open or full open position. Thus, in response to the controller100, the valve102may be partially opened or closed to control the pressure drop, which in turn controls the variable displacement of the pump16. In turn, the change in the displacement of the pump16adjusts the load on the engine14.

In general, end users typically have two different types of systems: closed-center and open-center. For a closed-center system, the center (or neutral) position is closed resulting in no flow. For an open-center system, the center (or neutral) position is open and the fluid is allowed to circulate back to the reservoir126. The disclosed embodiments are designed to work with both systems with only minor modifications.

For a closed-center system, fluid is drawn from the reservoir126by the pump16. Most of the fluid drawn to the pump16is delivered to the pressure line132(P1). Minimal fluid is delivered to the case drain line128(CD1), primarily for lubrication purposes. From pressure line132(P1) fluid flows through the flow control valve102(H-FC1) to the end users system106. The fluid then typically passes through a closed-center directional control valve in the end users system106(block140). After the directional control valve, the flow compensation line130is tapped into the system. After the location of the flow compensation line130, the fluid then travels to a load (e.g., a hydraulic cylinder or motor). After the load, the fluid returns from the system106(block142) to the reservoir126through the hydraulic filter122(H-F1).

The operator is able to control the flowrate from the hydraulic pump16to the system106by controlling the pressure drop across the closed-center directional control valve. As the operator closes the directional control valve, pressure drop increases, which in turn, reduces hydraulic pump flow. Hydraulic flow control valve102(H-FC1) is used to induce additional pressure drop as needed to prevent the prime mover14from being overloaded. In other words, the flow compensation line130is measuring the total pressure drop across the hydraulic flow control valve102(H-FC1) plus the directional control valve of the end users system106.

For an open-center system, fluid is drawn from the reservoir126by the pump16to the pump16. Most of the fluid drawn to the pump16is delivered to the pressure line132(P1). Minimal fluid is delivered to the case drain line128(CD1), primarily for lubrication purposes. From the pressure line132(P1), fluid flows through the flow control valve102(H-FC1). After the valve102(H-FC1), the flow compensation line130is tapped into the system. After the location of the flow compensation line130, the fluid then typically passes through a by-pass flow control valve. This valve controls the amount of flow to the system, while the remaining flow is dumped back to the reservoir126. From the by-pass flow control valve, fluid then goes to open-center directional control valves in the end user's system106. After the open-center directional control valve, the fluid then travels to a load (e.g., a hydraulic cylinder or motor). After the load, the fluid returns to the reservoir126through the hydraulic filter122(H-F1).

The operator is able to control the flowrate from the hydraulic pump16by controlling the by-pass flow control valve. As the operator opens the by-pass flow control valve, additional flow is directed to the system, while the remaining flow is dumped to the reservoir126. Hydraulic flow control valve102(H-FC1) is used to induce pressure drop which is read by the flow compensation line130, which in turn, controls the flowrate of the pump16to prevent the prime mover14from being overloaded.

In both the closed-center and open-center systems, flow is controlled by inducing pressure drop across the valve102(H-FC1) until the power consumption of the system is matched by the engine14within a given set of parameters.

The disclosed embodiments may provide several advantages. For example, the disclosed embodiments allow the use of smaller prime mover (e.g., an IC engine) or the addition of other power consuming functions by controlling hydraulic power consumption. With a smaller engine, fuel efficiency and therefore fuel savings are inherent. The disclosed embodiments also may provide flexibility of the hydraulic circuit to be used for both closed-center and open-center systems. The disclosed embodiments also may provide power consumption control that overrides user demands when used with power feedback and control scheme.

Several alternatives are also contemplated. One alternative includes hydraulic flow control (H-FC1) in other locations. For example, it could be placed between the end user's closed-center valve and the load instead of before the end user's closed-center valve. Another alternative includes a plurality of fixed orifices used with directional control to add or subtract orifices, instead of a proportional valve for H-FC1. Another alternative includes a manual valve used with some type of manual or automated adjustment, instead of an electronic valve for H-FC1. Another alternative includes elimination of H-FC1and use of a manual or automated actuation of the pump displacement to match the power consumption with the prime mover.