Patent Grant
7121189
The present disclosure relates generally to a drain valve, and more particularly, to a drain valve that is both electronically and hydraulically actuated.
Work machines such as, for example, dozers, loaders, excavators, motor graders, and other types of heavy machinery use one or more hydraulic actuators to accomplish a variety of tasks. These actuators are selectively fluidly connected to a pump on the work machine that provides pressurized fluid to chambers within the actuators, and to a tank to allow the pressurized fluid to drain from the actuators. A valve arrangement is typically fluidly connected between the actuators and the pump and tank to control a flow rate and direction of pressurized fluid to and from the chambers of the actuators.
The portion of the valve arrangement connecting the actuator to the tank is called a drain valve. The drain valve typically includes a solenoid operated electronic flow controlling valve or a hydraulic pressure limiting valve. The electronic flow controlling valve has a valve element that is movable against a spring bias between a flow-passing and a flow-blocking position in response to an electronic signal to control a flow of pressurized fluid to an actuator. The hydraulic pressure limiting valve generally includes a valve element that is spring biased toward a flow-blocking position and movable toward a flow-passing position in response to a fluid pressure exerted against the valve element to limit a maximum pressure within the actuator.
A system having one of the electronic flow controlling and hydraulic pressure limiting valves can be problematic, while a valve arrangement having both the electronic flow controlling and hydraulic pressure limiting valves can be large and expensive. For example, the hydraulic pressure limiting valve does not afford the controllability of the electronic flow controlling valve, while the electronic flow controlling valve can not afford pressure limiting functions during electrical failure or system shut down and is not as responsive as the hydraulic pressure limiting valve. One method of providing the benefits of both the electronic flow controlling and hydraulic pressure limiting valves is described in U.S. Pat. No. 5,878,647 (the '647 patent) issued to Wilke et al. on Mar. 9, 1999. The '647 patent describes a hydraulic circuit having two pairs of valves, a variable displacement pump, a reservoir tank, and a hydraulic actuator. One pair of the valves includes a head-end supply valve and a head-end return valve that connects a head end of the hydraulic actuator to either the variable displacement pump or the reservoir tank. The other pair of solenoid valves includes a rod-end supply valve and a rod-end return valve that connects a rod end of the hydraulic actuator to either the variable displacement pump or the reservoir tank. Each of the head and rod-end return valves includes a solenoid operated pilot valve element that selectively communicates fluid from the hydraulic actuator to a hydraulically operated valve element. When both the solenoid operated pilot valve element and the hydraulically operated valve element are in a flow-passing position, fluid from the hydraulic actuator is allowed to drain from the hydraulic actuator to the reservoir tank.
Although the return valves of the hydraulic circuit described in the '647 patent may provide some of the benefits associated with both electronic flow controlling and hydraulic pressure limiting valves, the return valves of the '647 patent may still be problematic. For example, in the situation of electrical failure or system shut down, the return valves of the '647 patent do not perform any pressure limiting functions. Further, because flow through the return valves can be completely blocked by high fluid pressures acting on the hydraulically operated valve element, the hydraulic circuit of the '647 patent lacks control. In addition, excessive pressures within the hydraulic circuit of the '647 patent tend to move the hydraulically operated valve element toward a flow-blocking position rather than a flow-passing position, thereby allowing the excessive pressures to increase even further.
The disclosed valve is directed to overcoming one or more of the problems set forth above.
In one aspect, the present disclosure is directed to a valve. The valve includes a main valve element with a first end and a second end. The main valve element is movable between a flow-passing and a flow-blocking position in response to fluid pressure exerted on the first and second ends. The valve also includes a solenoid mechanism operatively associated with the main valve element to move the main valve element toward one of the flow-passing and the flow-blocking positions. The valve further includes a main valve spring configured to bias the main valve element in opposition to movement caused by the solenoid mechanism. The valve additionally includes a relief valve element configured to communicate a fluid with the first end of the main valve element in response to a fluid pressure to initiate movement of the main valve element.
In another aspect, the present disclosure is directed to a method of operating a valve. The method includes operating a relief valve element to selectively allow pressurized fluid to flow to an end of a main valve element, thereby moving the main valve element between a flow-passing and a flow-blocking position. The method also includes operating a solenoid to move the main valve element toward one of the flow-blocking and flow-passing positions in opposition to a spring bias.
Frame 12 may include any structural unit that supports movement of work machine 10. Frame 12 may be, for example, a stationary base frame connecting a power source (not shown) to a traction device 18, a movable frame member of a linkage system, or any other frame known in the art.
Work implement 14 may include any device used in the performance of a task. For example, work implement 14 may include a blade, a bucket, a shovel, a ripper, a dump bed, a propelling device, or any other task-performing device known in the art. Work implement 14 may be connected to frame 12 via a direct pivot, via a linkage system with hydraulic cylinder 16 forming one member in the linkage system, or in any other appropriate manner. Work implement 14 may be configured to pivot, rotate, slide, swing, or move relative to frame 12 in any other manner known in the art.
As illustrated in
Hydraulic cylinder 16 may include a tube 36 and a piston assembly 38 disposed within tube 36. One of tube 36 and piston assembly 38 may be pivotally connected to frame 12, while the other of tube 36 and piston assembly 38 may be pivotally connected to work implement 14. It is contemplated that tube 36 and/or piston assembly 38 may alternately be fixedly connected to either frame 12 or work implement 14. Hydraulic cylinder 16 may include a first chamber 40 and a second chamber 42 separated by piston assembly 38. First and second chambers 40, 42 may be selectively supplied with a fluid pressurized by primary source 22 and fluidly connected with tank 32 to cause piston assembly 38 to displace within tube 36, thereby changing the effective length of hydraulic cylinder 16. The expansion and retraction of hydraulic cylinder 16 may function to assist in moving work implement 14.
Piston assembly 38 may include a piston 44 axially aligned with and disposed within tube 36, and a piston rod 46 connectable to one of frame 12 and work implement 14 (referring to
Primary source 22 may be configured to produce a flow of pressurized fluid and may include a pump such as, for example, a variable displacement pump, a fixed displacement pump, a variable flow pump, or any other source of pressurized fluid known in the art. Primary source 22 may be drivably connected to a power source (not shown) of work machine 10 by, for example, a countershaft (not shown), a belt (not shown), an electrical circuit (not shown), or in any other suitable manner. Primary source 22 may be dedicated to supplying pressurized fluid only to hydraulic system 20, or alternately may supply pressurized fluid to multiple hydraulic systems within work machine 10.
Head-end supply valve 24 may be disposed between primary source 22 and first chamber 40 and configured to regulate a flow of pressurized fluid to first chamber 40. Specifically, head-end supply valve 24 may include a two-position spring-biased valve element that is solenoid-actuated and configured to move between a first position at which fluid is allowed to flow into first chamber 40 and a second position at which fluid flow from first chamber 40 is blocked. It is contemplated that head-end supply valve 24 may include additional or different mechanisms such as, for example, a proportional valve element, one or more restricted orifices, a pilot valve element, a pressure relief valve element, or any other valve mechanisms known in the art. It is also contemplated that head-end supply valve 24 may alternately be hydraulically-actuated, mechanically-actuated, pneumatically-actuated, or actuated in any other suitable manner. It is further contemplated that head-end supply valve 24 may be configured to allow fluid from first chamber 40 to flow through head-end supply valve 24 during a regeneration event when a pressure within first chamber 40 exceeds a pressure of the fluid supplied by primary source 22.
Head-end drain valve 26 may be disposed between first chamber 40 and tank 32 and configured to regulate a flow of pressurized fluid from first chamber 40 to tank 32. Specifically, head-end drain valve 26 may include a three-position spring-biased pilot valve element 52, a two-position hydraulically-actuated spring-biased main valve element 54 that is mechanically connected to pilot valve element 52 by way of a spring 56 and fluidly connected to pilot valve element 52 by a fluid passageway 58, and a hydraulically-actuated spring-biased pilot relief valve element 60 that is fluidly connected to main valve element 54 by way of a fluid passageway 62. Pilot valve element 52 may be solenoid-actuated and configured to move between a first position at which fluid from pilot source 34 is allowed to act on pilot valve element 52 and main valve element 54 via fluid passageways 64, 66, and 68, a second position at which the fluid acting on pilot valve element 52 and main valve element 54 is allowed to drain to tank 32 via a drain passageway 70, and a third position at which all fluid through pilot valve element 52 is blocked. Restricted orifices 72 and 74 may be disposed within fluid passageways 66 and 68, respectively, to reduce pressure and/or flow oscillations. It is contemplated that restricted orifices 72 and 74 may be omitted, if desired. Main valve element 54 may be hydraulically-actuated and configured to move between a first position at which fluid from first chamber 40 is allowed to drain to tank 32 via fluid passageways 76 and 78 and a second position where fluid from first chamber 40 is blocked. Main valve element 54 may be biased via fluid within a passageway 80 in a direction opposite the direction caused by fluid within passageway 58. A restricted orifice 82 may be disposed within a fluid passageway 84 that connects pilot source 34 to one end of main valve element 54. Pilot relief valve element 60 may be biased via fluid from first chamber 40 toward a flow-passing position to thereby communicate pressurized fluid from first chamber 40 with fluid passageways 80 and 84. A one-way pressure bypass valve 85 may also be included within head-end drain valve 26 to relieve pressures from between pilot valve element 52 and main valve element 54 during situations where pilot relief valve element 60 has initiated motion of main valve element 54, but pilot valve element 52 is blocking fluid passageway 64 and drain passageway 70.
Rod-end supply valve 28 may be disposed between primary source 22 and second chamber 42 and configured to regulate a flow of pressurized fluid to second chamber 42. Specifically, rod-end supply valve 28 may include a two-position spring-biased valve element that is solenoid-actuated and configured to move between a first position at which fluid is allowed to flow into second chamber 42 and a second position at which fluid is blocked from second chamber 42. It is contemplated that rod-end supply valve 28 may include additional or different valve mechanisms such as, for example, a proportional valve element, one or more restricted orifices, a pilot valve element, a pressure relief valve element, or any other valve mechanism known in the art. It is also contemplated that rod-end supply valve 28 may alternately be hydraulically-actuated, mechanically-actuated, pneumatically-actuated, or actuated in any other suitable manner. It is further contemplated that rod-end supply valve 28 may be configured to allow fluid from second chamber 42 to flow through rod-end supply valve 28 during a regeneration event when a pressure within second chamber 42 exceeds a pressure of the fluid supplied by primary source 22.
Rod-end drain valve 30 may be disposed between second chamber 42 and tank 32 and configured to regulate a flow of pressurized fluid from second chamber 42 to tank 32. Specifically, rod-end drain valve 30 may include a three-position spring-biased pilot valve element 86, a two-position hydraulically-actuated spring-biased main valve element 88 that is mechanically connected to pilot valve element 86 by way of a spring 90 and fluidly connected to pilot valve element 86 via a fluid passageway 92, and a hydraulically-actuated spring-biased pilot relief valve element 94 that is fluidly connected to main valve element 88 by way of fluid passageway 96. Pilot valve element 86 may be solenoid-actuated and configured to move between a first position at which fluid from pilot source 34 is allowed to act on pilot valve element 86 and main valve element 88 via fluid passageways 98, 100, and 102, a second position at which the fluid acting on pilot valve element 86 and main valve element 88 is allowed to drain to tank 32 via a drain passageway 104, and a third position at which all fluid through pilot valve element 86 is blocked. Restricted orifices 106 and 108 may be disposed within fluid passageways 100 and 102, respectively, to reduce pressure and/or flow oscillations. It is contemplated that restricted orifices 106 and 108 may be omitted, if desired. Main valve element 88 may be hydraulically-actuated and configured to move between a first position at which fluid from second chamber 42 is allowed to drain to tank 32 via fluid passageways 110 and 112, and a second position where fluid from second chamber 42 is blocked. Main valve element 88 may be biased via fluid within a passageway 114 in a direction opposite the direction caused by fluid within passageway 92. A restricted orifice 116 may be disposed within a fluid passageway 118 that connects pilot source 34 to one end of main valve element 88. Pilot relief valve element 94 may be biased via fluid from second chamber 42 toward a flow-passing position to thereby communicate pressurized fluid from second chamber 42 with fluid passageway 96. A one-way pressure bypass valve 119 may also be included within rod-end drain valve 30 to relieve pressures from between pilot valve element 86 and main valve element 88 during situations where pilot relief valve element 94 has initiated motion of main valve element 88, but pilot valve element 86 is blocking fluid passageway 98 and drain passageway 104.
Head-end and rod-end supply and drain valves 24–30 may be fluidly interconnected. In particular, head-end and rod-end supply valves 24, 28 may be connected in parallel to a common upstream fluid passageway 120. Head-end supply and return valves 24, 26 may be connected in parallel to a common first chamber fluid passageway 122. Rod-end supply and drain valves 28, 30 may be connected in parallel to a common second chamber fluid passageway 124.
Tank 32 may constitute a reservoir configured to hold a supply of fluid. The fluid may include, for example, a dedicated hydraulic oil, an engine lubrication oil, a transmission lubrication oil, or any other fluid known in the art. One or more hydraulic systems within work machine 10 may draw fluid from and return fluid to tank 32. It is also contemplated that hydraulic system 20 may be connected to multiple separate fluid tanks.
Pilot source 34 may be configured to produce a flow of pressurized fluid and may include a pump such as, for example, a variable displacement pump, a fixed displacement pump, a variable flow pump, or any other source of pressurized fluid known in the art. Pilot source 34 may be drivably connected to a power source (not shown) of work machine 10 by, for example, a countershaft (not shown), a belt (not shown), an electrical circuit (not shown), or in any other suitable manner. Pilot source 34 may be dedicated to supplying pressurized pilot fluid only to hydraulic system 20, or alternatively may supply pressurized fluid to multiple hydraulic systems within work machine 10. A pressure relief valve 125 may be associated with pilot source 34 to facilitate a substantially constant pressure within the fluid supplied by pilot source 34.
As illustrated in
Similar to
The disclosed hydraulic system may be applicable to any work machine that includes a fluid actuator where the benefits of hydraulically actuated and electrically actuated drain valves are desired. The disclosed hydraulic system may provide precise control over fluid flow to the fluid actuator, high response pressure limiting, and fail safe pressure limiting for the components of the hydraulic system in a low-cost space-saving configuration. The operation of hydraulic system 20 will now be explained.
As illustrated in
Movement of main valve elements 54 and 88 may be affected in at least two ways (because main valve element 88 functions substantially identical to main valve element 54 and for purposes of simplicity, only the movement with respect to main valve element 54 will be described). An electronic signal from controller 142 may be received via communication line 152 by the solenoid associated with head-end drain valve 26 that causes the solenoid to energize. Upon actuation of the solenoid, pilot valve mechanism 52 may be magnetically repelled away from the solenoid, thereby communicating cylinder bore 128 with drain passageway 70 via fluid passageway 66, allowing the fluid within cylinder bore 128 to drain to tank 32. Because the opposite end of main valve element 54 is simultaneously exposed to pressurized fluid from pilot source 34 via fluid passageway 84, main valve element 54 may be urged toward pilot valve element 52 by an imbalance of force, thereby communicating fluid passageways 76 and 78 allowing fluid from first chamber 40 to drain to tank 32. The signal from controller 142 causing the solenoid of head-end drain valve 26 may be generated in response to operator input or in response to a pressure within hydraulic cylinder 16 being above a predetermined pressure, as measured by pressure sensor 144. Movement of main valve elements 54 and 88 may also be affected when excessive pressures within first chamber 40 cause pilot relief valve element 60 to move to the flow-passing position, allowing the excessive pressures of first chamber 40 to exert force on one end of main valve element 54. Because the opposite end of main valve element 54 is simultaneously exposed to a lower fluid pressure from pilot source 34, an imbalance of force on main valve element 54 is created that urges main valve element 54 towards pilot valve element 52, again communicating fluid passageways 76 and 78 and allowing the fluid from first chamber 40 to drain to tank 32. During movement of main valve element 54 initiated by movement of pilot relief valve element 60 toward the flow passing position, fluid may be allowed to exit central bore 128 past pressure bypass valve 85 to prevent hydraulic lock.
Because the movement of main valve elements 54 and 88 may be affected electronically, hydraulic system 20 may be precisely controllable. Specifically, opening and closing pressures and flow rates of fluid in communication with main valve elements 54 and 88 may be closely tailored to accommodate a variety of different operating conditions. This tailoring may be software facilitated and implemented with an electronic controller (not shown) to provide system-wide optimization and improved efficiency.
Because the movement of main valve elements 54 and 88 may also be affected hydraulically, hydraulic system 20 may be able to respond to rising fluid pressures and fluid pressure spikes quickly and may provide fail safe pressure relief for hydraulic system 20. In particular, a hydraulically actuated valve mechanism may respond on the order of 5–15 μs, while an electronically actuated valve mechanism may respond much slower, typically on the order of about 100 μs. The increased responsiveness of the hydraulically actuated main valve elements 54 and 88 may help to prevent potentially damaging pressure fluctuations that an electronic-only system might not be able to avoid. Further, even in situations of electronic failure or during power system shutdown, the movement of pilot relief valve element 60 may still cause movement of main valve element 54 from the flow-blocking position to the flow-passing position, thereby providing fail safe protection for hydraulic system 20 that electronic-only valve configurations can not provide.
In addition, because the electronic relief function and the hydraulic relief functions can be embodied into a single valve configuration rather than completely separate stand-alone valve mechanisms, both cost and space savings may be realized. Further space savings may be realized when pilot relief valve elements 60 and 94 are disposed within main valve elements 54 and 88, rather than in separate bores within valve body 126.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed electro-hydraulic valve. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed electro-hydraulic valve. For example, it is contemplated that the solenoid actuation of pilot valve elements 52 and 86 may alternatively include a pull-type actuation where energizing the solenoid attracts pilot valve elements 52 and 86 toward the solenoid rather than repelling. It is further contemplated that pilot valve elements 52 and 86 may be omitted, if desired, and main valve elements 54 and 88 directly acted upon by the solenoids. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
This application claims the benefit of U.S. Provisional Patent Application No. 60/614,343, entitled “Hybrid Electronic/Pilot-Operated Line Relief,” which was filed on Sep. 29, 2004.
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