Patent Application
20100122528
The present disclosure relates generally to a hydraulic system, and more particularly, to a hydraulic system having regeneration and supplemental flow.
Hydraulic machines such as, for example, dozers, loaders, excavators, motor graders, and other types of heavy equipment use one or more hydraulic actuators to accomplish a variety of tasks. These actuators are fluidly connected to a pump of the machine that provides pressurized fluid to chambers within the actuators. As the pressurized fluid moves into or through the chambers, the pressure of the fluid acts on surfaces of the chambers to affect movement of the actuators and a connected work tool. When the pressurized fluid is drained from the chambers, it is returned to a low pressure sump of the machine.
One problem associated with this type of hydraulic arrangement involves efficiency. In particular, the fluid draining from the actuator chambers to the sump often has a pressure greater than a pressure of the fluid already within the sump, especially when the actuators are moving in a direction aligned with the pull of gravity (i.e., when actuator movement is being assisted by a weight of the tool and any associated load). As a result, the higher pressure fluid draining into the sump still contains some energy that is wasted upon entering the low pressure sump. This wasted energy reduces the efficiency of the hydraulic system.
Another problem associated with the hydraulic arrangement described above involves flow capacity. That is, the various valves and passageways of the system that control flow to and from the actuators place restrictions on fluid supplying and draining from the actuators. As a result of the restrictions, the flow to and from the actuators may be limited, thereby causing the actuators to move slower than desired.
One attempt to alleviate the problems described above is disclosed in U.S. Patent Application Publication No. 2007/0186548 (the '548 publication) by Smith et al. published on Aug. 16, 2007. Specifically, the '548 publication discloses a hydraulic system including a first actuator, a second actuator, a pump, and a tank. The hydraulic system further includes a first arrangement of valves associated with control of fluid flow from the pump to the first actuator and from the first actuator to the tank, and a second arrangement of valves associated with control of fluid flow from the pump to the second actuator and from the second actuator to the tank. The hydraulic system also includes an independent metering valve connected between the first and second arrangements of valves. During a retraction of the first actuator, the independent metering valve is opened to allow fluid forced from the first actuator to enter and move the second actuator during a regeneration event, and/or to enter and be stored within an accumulator for later use. The fluid stored within the accumulator may then be directed to a suction side of the pump to selectively supplement pump flow that is directed to the first and second actuators.
Although the hydraulic system described in the '548 publication may help improve efficiency and flow capacity by implementing regeneration and supplementing pump flow, it may be suboptimal. Specifically, the hydraulic system may utilize a large number of components to supports its operations, thereby increasing a cost and a complexity of the system. Further, because the supplemental flow from the accumulator is directed into the pump before passing to the first and second actuators, the flow may still be restricted and be flow limited by the number of valves and passageways within the system.
The disclosed hydraulic system is directed to overcoming one or more of the problems set forth above.
In one aspect, the present disclosure is directed to a hydraulic system. The hydraulic system may include pump, a tank, a first actuator having a head-end and a rod-end, and a first valve arrangement configured to control fluid flow from the pump to the first actuator and from the first actuator to the tank. The hydraulic system may also include a second actuator having a head-end and a rod-end, and a second valve arrangement configured to control fluid flow from the pump to the second actuator and from the second actuator to the tank. The hydraulic system may further include a third valve arrangement fluidly connected between the first and second valve arrangements to receive pressurized fluid from the pump in parallel with the first and second valve arrangements, the third valve arrangement being configured to facilitate fluid regeneration of and supplemental flow to at least one of the first and second actuators.
In another aspect, the present disclosure is directed to a method of operating a hydraulic system. The method may include pressurizing a fluid, directing a first flow of the pressurized fluid to move a first actuator, and directing a second flow of the pressurized fluid to move a second actuator. The method may further include directing a third flow of the pressurized fluid in parallel with at least one of the first and second flows of pressurized fluid to move at least one of one of the first and second actuators at an increased velocity, and directing pressurized fluid from the first actuator to the second actuator.
Linkage system 12 may include structure affected by fluid actuators to move work tool 14. Specifically, linkage system 12 may include a boom member (i.e., a lifting member) 17 vertically pivotal about a horizontal axis 28 relative to a work surface 18 by a pair of adjacent, double-acting, hydraulic cylinders 20 (only one shown in
For purposes of simplicity,
As shown in
First and second pressure chambers 38, 40 may each be selectively supplied with pressurized fluid and drained of the pressurized fluid to cause piston assembly 36 to displace within tube 34, thereby changing an effective length of hydraulic cylinders 20, 26. A flow rate of fluid into and out of first and second pressure chambers 38, 40 may relate to a velocity of hydraulic cylinders 20, 26, while a pressure differential between the first and second pressure chambers 38, 40 may relate to a force imparted by hydraulic cylinders 20, 26 on the associated linkage members. An expansion (represented by arrow 46) and a retraction (represented by an arrow 47) of hydraulic cylinders 20, 26 may function to assist in moving work tool 14.
To help regulate filling and draining of first and second chambers 38, 40, machine 10 may include a hydraulic system 48 having a plurality of interconnecting and cooperating fluid components. In particular, hydraulic system 48 may include valve stack 50 at least partially forming a circuit configured to receive pressurized fluid from an engine-driven pump 52 and to discharge fluid to a tank 53 or other low pressure reservoir. Valve stack 50 may include a lift valve arrangement 54, a tilt valve arrangement 56, and an auxiliary valve arrangement 58 fluidly connected to receive pressurized fluid from pump 52 in parallel fashion. In one embodiment, valve arrangements 54-58 may include bodies bolted to each other to form valve stack 50. In another embodiment, each of valve arrangements 54-58 may be stand-alone arrangements, connected only by way of fluid conduits, if desired. It is contemplated that a greater number, a lesser number, or a different configuration of valve arrangements may be included within valve stack 50, if desired. For example, a swing valve arrangement (not shown) configured to control a swinging motion of linkage system 12, one or more attachment valve arrangements (not shown), one or more travel valve arrangements, and other suitable valve arrangements may be included in valve stack 50.
Each of lift, tilt, and auxiliary valve arrangements 54-58 may regulate the motion of their associated fluid actuators. Specifically, tilt valve arrangement 54 may have elements movable to control the motion of hydraulic cylinder 20 associated with boom member 17; tilt valve arrangement 56 may have elements movable to control the motion of hydraulic cylinder 26 associated with work tool 14; and auxiliary valve arrangement 58 may have elements movable to affect the motion of any or both of hydraulic cylinders 20, 26.
Valve arrangements 54-58 may be connected to regulate flows of pressurized fluid to and from hydraulic cylinders 20, 26 via common passages. Specifically, valve arrangements 54-58 may be connected to pump 52 by way of a common supply passage 60, and to tank 53 by way of a common drain passage 62. Lift, tilt, and auxiliary valve arrangements 54-58 may be connected in parallel to common supply passage 60 by way of individual fluid passages 66, 68, 70, respectively, and in parallel to common drain passage 62 by way of individual fluid passages 72, 74, and 76, respectively. A pressure compensating valve 78 and/or a check valve 79 may be disposed within each of fluid passages 66-70 to provide a unidirectional supply of fluid having a substantially constant flow to valve arrangements 54-58. Pressure compensating valves 78 may be movable in response to a differential pressure between a flow passing position and a flow blocking position, such that a substantially constant flow of fluid is provide to valve arrangements 54-58, even when a pressure of the fluid directed to pressure compensating valves 78 varies. It is contemplated that, in some applications, pressure compensating valves 78 and/or check valves 79 may be omitted, if desired. For example, pressure compensating valve 78, in one embodiment, may be omitted from auxiliary valve arrangement 56 to increase a flow capacity thereof.
Each of lift, tilt, and auxiliary valve arrangements 54-58 may be substantially identical, and each may include four independent metering valves (IMVs). Of the four IMVs, two may be generally associated with fluid supply functions, while two may be generally associated with drain functions. For example, lift valve arrangement 54 may include a head-end supply valve 80, a rod-end supply valve 82, a head-end drain valve 84, and a rod-end drain valve 86. Similarly, tilt valve arrangement 56 may include a head-end supply valve 88, a rod-end supply valve 90, a head-end drain valve 92, and a rod-end drain valve 94. And, although not specific to a head-end or a rod-end of a particular cylinder, auxiliary valve arrangement 58 may include a first supply valve 96, a second supply valve 98, a first drain valve 100, and a second drain valve 102.
Head-end supply valve 80 may be disposed between fluid passage 66 and a fluid passage 104 leading to first chamber 38 of hydraulic cylinder 20 to regulate a flow of pressurized fluid to first chamber 38. Head-end supply valve 80 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow into first chamber 38, and a second end-position, at which fluid flow is blocked from first chamber 38. It is contemplated that head-end supply valve 80 may include additional or different elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that head-end supply valve 80 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner. It is further contemplated that head-end supply valve 80 may be configured to allow fluid from first chamber 38 to flow through head-end supply valve 80 during a regeneration event when a pressure within first chamber 38 exceeds a pressure of pump 52 and/or a pressure of the chamber receiving the regenerated fluid.
Rod-end supply valve 82 may be disposed between fluid passage 66 and a fluid passage 106 leading to second chamber 40 of hydraulic cylinder 20 to regulate a flow of pressurized fluid to second chamber 40. Rod-end supply valve 82 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow into second chamber 40, and a second end-position, at which fluid is blocked from second chamber 40. It is contemplated that rod-end supply valve 82 may include additional or different valve elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that rod-end supply valve 82 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner. It is further contemplated that rod-end supply valve 82 may be configured to allow fluid from second chamber 40 to flow through rod-end supply valve 82 during a regeneration event when a pressure within second chamber 40 exceeds a pressure of pump 52 and/or a pressure of the chamber receiving the regenerated fluid.
Head-end drain valve 84 may be disposed between fluid passage 104 and fluid passage 74 that leads to common drain passage 62 to regulate a flow of pressurized fluid from first chamber 38 of hydraulic cylinder 20 to tank 53. Head-end drain valve 84 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow from first chamber 38, and a second end-position, at which fluid is blocked from flowing from first chamber 38. It is contemplated that head-end drain valve 84 may include additional or different valve elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that head-end drain valve 84 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner.
Rod-end drain valve 86 may be disposed between fluid passage 106 and fluid passage 72 that leads to common drain passage 62 to regulate a flow of pressurized fluid from second chamber 40 of hydraulic cylinder 20 to tank 53. Rod-end drain valve 86 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow from second chamber 40, and a second end-position, at which fluid is blocked from flowing from second chamber 40. It is contemplated that rod-end drain valve 86 may include additional or different valve elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that rod-end drain valve 86 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner.
Head-end supply valve 88 may be disposed between fluid passage 68 and a fluid passage 108 leading to first chamber 38 of hydraulic cylinder 26 to regulate a flow of pressurized fluid to first chamber 38. Head-end supply valve 88 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow into first chamber 38, and a second end-position, at which fluid flow is blocked from first chamber 38. It is contemplated that head-end supply valve 88 may include additional or different elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that head-end supply valve 88 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner. It is further contemplated that head-end supply valve 88 may be configured to allow fluid from first chamber 38 to flow through head-end supply valve 88 during a regeneration event when a pressure within first chamber 38 exceeds a pressure of pump 52 and/or a pressure of the chamber receiving the regenerated fluid.
Rod-end supply valve 90 may be disposed between fluid passage 68 and a fluid passage 110 leading to second chamber 40 of hydraulic cylinder 26 to regulate a flow of pressurized fluid to second chamber 40. Specifically, rod-end supply valve 90 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow into second chamber 40, and a second end-position, at which fluid is blocked from second chamber 40. It is contemplated that rod-end supply valve 90 may include additional or different valve elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that rod-end supply valve 90 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner. It is further contemplated that rod-end supply valve 90 may be configured to allow fluid from second chamber 40 to flow through rod-end supply valve 90 during a regeneration event when a pressure within second chamber 40 exceeds a pressure of pump 52 and/or a pressure of the chamber receiving the regenerated fluid.
Head-end drain valve 92 may be disposed between fluid passage 108 and fluid passage 74 that leads to common drain passage 62 to regulate a flow of pressurized fluid from first chamber 38 of hydraulic cylinder 26 to tank 53. Specifically, head-end drain valve 92 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow from first chamber 38, and a second end-position, at which fluid is blocked from flowing from first chamber 38. It is contemplated that head-end drain valve 92 may include additional or different valve elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that head-end drain valve 92 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner.
Rod-end drain valve 94 may be disposed between fluid passage 110 and fluid passage 74 leading to common drain passage 62 to regulate a flow of pressurized fluid from second chamber 40 of hydraulic cylinder 26 to tank 53. Rod-end drain valve 94 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow from second chamber 40, and a second end-position, at which fluid is blocked from flowing from second chamber 40. It is contemplated that rod-end drain valve 94 may include additional or different valve element such as, for example, a fixed-position valve element or any other valve elements known in the art. It is also contemplated that rod-end drain valve 94 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner.
First supply valve 96 may be disposed between fluid passage 70 and fluid passage 108 leading to first chamber 38 of hydraulic cylinder 26 to regulate a flow of pressurized fluid to first chamber 38. First supply valve 96 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow into first chamber 38, and a second end-position, at which fluid flow is blocked from first chamber 38. It is contemplated that first supply valve 96 may include additional or different elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that first supply valve 96 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner. It is further contemplated that first supply valve 96 may be configured to allow fluid from first chamber 38 to flow through first supply valve 96 during a regeneration event when a pressure within first chamber 38 exceeds a pressure of pump 52 and/or a pressure of the chamber receiving the regenerated fluid.
Second supply valve 98 may be disposed between fluid passage 70 and fluid passage 104 leading to first chamber 38 of hydraulic cylinder 20 to regulate a flow of pressurized fluid to first chamber 38. Second supply valve 98 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow into first chamber 38, and a second end-position, at which fluid is blocked from first chamber 38. It is contemplated that second supply valve 98 may include additional or different valve elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that second supply valve 98 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner. It is further contemplated that second supply valve 98 may be configured to allow fluid from first chamber 38 to flow through second supply valve 98 during a regeneration event when a pressure within first chamber 38 exceeds a pressure of pump 52 and/or a pressure of the chamber receiving the regenerated fluid.
First drain valve 100 may be disposed between fluid passage 108 and fluid passage 76 leading to common drain passage 62 to regulate a flow of pressurized fluid from first chamber 38 of hydraulic cylinder 26 to tank 53. First drain valve 100 may include a variable-position, spring-biased valve element, for example a poppet or spool element, that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow from first chamber 38, and a second end-position, at which fluid is blocked from flowing from first chamber 38. It is contemplated that first drain valve 100 may include additional or different valve elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that first drain valve 100 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner.
Second drain valve 102 may be disposed between fluid passage 104 and fluid passage 76 leading to common drain passage 62 to regulate a flow of pressurized fluid from first chamber 38 of hydraulic cylinder 20 to tank 53. Specifically, second drain valve 102 may include a variable-position. spring-biased valve element that is solenoid actuated and configured to move to any position between a first end-position, at which fluid is allowed to flow from first chamber 38, and a second end-position, at which fluid is blocked from flowing from first chamber 38. It is contemplated that second drain valve 102 may include additional or different valve elements such as, for example, a fixed-position valve element or any other valve element known in the art. It is also contemplated that second drain valve 102 may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner.
The disclosed hydraulic system may be applicable to any machine that includes multiple fluid actuators where flow capacity, cost, and efficiency are issues. The disclosed hydraulic system may provide high flow capacity by supplementing flow to and from hydraulic actuators of the system, and low cost by providing the supplemental flow with relatively few components. The disclosed hydraulic system may provide increased efficiency by facilitating cylinder-to-cylinder and in-cylinder regeneration, and by minimizing a pressure drop associated with filling or draining of the cylinders. The operation of hydraulic system 48 will now be explained.
As shown in
For example, if an extension of hydraulic cylinder 26 is requested (i.e., if movement of hydraulic cylinder 26 in the direction of arrow 46 is requested), head-end supply valve 88 may be moved toward the open position to direct pressurized fluid from pump 52 to first chamber 38. Substantially simultaneous to the directing of pressurized fluid to first chamber 38, rod-end drain valve 94 may be moved toward the open position to allow fluid from second chamber 40 to drain to tank 53. The high pressure within first chamber 38 and the low pressure within second chamber 40 may together create a force differential across piston assembly 36 that causes piston assembly 36 to move and extend from tube 34. During the extension of hydraulic cylinder 26, head-end drain valve 92 and rod-end supply valve 90 may be maintained in their closed positions.
If a retraction of hydraulic cylinder 20 is requested (i.e., if movement of hydraulic cylinder 20 in the direction of arrow 47 is requested), rod-end supply valve 82 may be moved toward the open position to direct pressurized fluid from pump 52 to second chamber 40. Substantially simultaneous to the directing of pressurized fluid to second chamber 40, head-end drain valve 84 may be moved toward the open position to allow fluid from first chamber 38 to drain to tank 53. The high pressure within second chamber 40 and the low pressure within first chamber 38 may together create a force differential across piston assembly 36 that causes piston assembly 36 to move and retract back into tube 34. During the retraction of hydraulic cylinder 20, head-end supply valve 80 and rod-end drain valve 86 may be maintained in their closed positions.
As shown in
Auxiliary valve arrangement 58 may also be utilized to increase a velocity of hydraulic cylinders 20, 26 during a retraction by supplementing flow from head-ends 42. For example, during the retraction of hydraulic cylinder 20, fluid already within first chamber 38 may be drained to tank 53 by way of fluid passage 104, head-end drain valve 84, fluid passage 72, and common drain passage 62. Simultaneously, fluid may be directed in parallel from first chamber 38 to tank 53 via fluid passage 104, second drain valve 102, fluid passage 76, and common drain passage 62 During the supplemented retraction of hydraulic cylinder 20, head-end supply valve 80, rod-end drain valve 86, first supply valve 96, second supply valve 98, and first drain valve 100 may be maintained in their closed positions. The additional flow of fluid from first chamber 38 may help to speed up the retracting movement of hydraulic cylinder 20. The retraction speed of hydraulic cylinder 26 may be increased in a similar manner.
As shown in
As shown in
The inclusion of auxiliary valve arrangement 58 may afford several benefits. In particular, auxiliary valve arrangement 58 may facilitate supplemental flow to any of the hydraulic cylinders included within machine 10, and from those cylinders to tank 53. The supplemental flow may allow for increased velocity movements of work tool 14. Further, auxiliary valve arrangement 58 may facilitate both cylinder-to-cylinder and in-cylinder regeneration, thereby increasing an efficiency of machine 10.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed hydraulic system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed hydraulic system. For example, although head-ends 42 of hydraulic cylinders 20, 26 are shown and described as being connected to receive supplemental flow from pump 52 by way of auxiliary valve arrangement 58, one or both of hydraulic cylinders 20, 26 could be connected in an inverse manner such that the supplemental flow is alternatively directed to rod-ends 44, if desired. Further, although pre-pressure compensating valves are described as being included in one exemplary embodiment, it is contemplated that post-compensating valves, makeup valves, relief valves, bypass valves, and other commonly known elements may additionally or alternatively be included within hydraulic system 48, if desired. 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.
