GB2533034A

GB2533034A - Systems and methods for flow summation in a hydraulic system with open center control valves

Info

Publication number: GB2533034A
Application number: GB1518971.5A
Authority: GB
Inventors: Jervis Mark
Original assignee: Husco International Inc
Current assignee: Husco International Inc
Priority date: 2014-11-03
Filing date: 2015-10-27
Publication date: 2016-06-08
Anticipated expiration: 2035-10-27
Also published as: GB2533034B; GB201518971D0

Abstract

A control valve assembly 12 to be integrated into a hydraulic system 10 is provided. The hydraulic system 10 includes a variable displacement pump 14 that draws fluid from a reservoir. The control valve assembly 12 includes at least one valve section to control a hydraulic function of a machine 32,34,36 and having a control valve(s) 26 28 30. The control valve includes an inlet port in fluid communication with a supply conduit and a bypass passage in fluid communication with a bypass conduit 92. The control valve assembly further includes a supply node 82, a control orifice to provide a restriction in the bypass conduit and arranged upstream of the bypass passage and downstream of the supply node, and a pressure and flow control device 68 arranged downstream of the supply node and upstream of the valve section and moveable between a first control position and a second control position.

Description

SYSTEMS AND METHODS FOR FLOW SUMMATION IN A HYDRAULIC

SYSTEM WITH OPEN CENTER CONTROL VALVES

BACKGROUND

10001] The present invention relates generally to hydraulic systems for use on mobile machinery and, more specifically, to systems and methods for flow summation in a hydraulic system with open center control valves.

100021 The use of variable displacement pumps in hydraulic systems on mobile machines is becoming more prevalent. Typically, variable displacement pumps generate only a required flow of the hydraulic system. Generating only a required flow of the hydraulic system can reduce the power requirements and fuel use by the pumps for functions controlled by the hydraulic system. However, in most configurations, variable displacement pumps can require the use of complex valves which have a high cost. The combination of the variable displacement pump and more complex valves can add a large cost to the machine.

100031 Flow summation is a significant innovation in hydraulic control valve technology. Flow summation can enable the use of a pressure compensating, load-sensing (PCLS) variable displacement pump. The combination of the PCLS pump and a control valve utilizing flow summation can significantly improve efficiency in mobile hydraulic machines. But, in order to implement flow summation in a control valve, typically, each valve section of the control valve requires additional galleries when compared to traditional load-sensing control valve sections. The additional galleries inevitably increase a physical size of the flow summation control valve and, as a consequence, increase cost. Since the galleries are added to each valve section in the flow summation control valve, the increased cost can be proportional to the number of valve sections (i.e., increase for each function controlled by the mobile machine).

SUNIMARY OF THE INVENTION

100041 The aforementioned short comings can be overcome by providing a control valve assembly having open center control valves that can achieve the control mechanism, and performance benefits, of flow summation.

10005] In one aspect, the present invention provides a control valve assembly to be integrated into a hydraulic system. The hydraulic system includes a variable displacement pump that draws -1 -fluid from a reservoir. The control valve assembly includes at least one valve section to control a hydraulic function of a machine and having a control valve. The control valve includes an inlet port in fluid communication with a supply conduit and a bypass passage in fluid communication with a bypass conduit. The control valve assembly further includes a supply node in fluid communication with and arranged downstream of a pump outlet of the variable displacement pump, a control orifice to provide a restriction in the bypass conduit and arranged upstream of the bypass passage and downstream of the supply node, and a pressure and flow control device arranged downstream of the supply node and upstream of the valve section and moveable between a first control position and a second control position. The pressure and flow control device includes a first control inlet port in fluid communication with the supply node and a first control outlet port in fluid communication with the supply conduit. The first control position provides a greater restriction to fluid flow between the first control inlet port and the second control inlet port than the second flow control position. The control valve assembly further includes a load sense line which communicates a pressure downstream of the pressure and flow control device and upstream of the inlet port of the control valve to a pump control port. The pressure and flow control device moves between the first control position and the second control position in response to a change is a restriction to fluid flow in the bypass conduit.

100061 In some embodiments, the change in the restriction to fluid flow in the bypass conduit is communicated to the pressure and flow control device via a change in a pressure downstream of the control orifice and upstream of the bypass passage.

10007] In some embodiments, the pressure and flow control device further includes a second control inlet port and a second control outlet port.

100081 In some embodiments, the second control inlet port provides fluid communication from a location downstream of the first control outlet port to the second control outlet port, and the second control outlet port is in fluid communication with the reservoir.

[0009] In some embodiments, the second control position provides a greater restriction to fluid flow between the second control inlet and the second control outlet than the first control position. [0010] In some embodiments, the bypass conduit is in fluid communication with the reservoir downstream of the bypass passage.

10011] In some embodiments, the pressure and flow control device is biased towards the first control position by a spring and a pressure in bypass conduit downstream of the bypass passage. -2 -

100121 In some embodiments, the pressure in the bypass conduit downstream of the bypass passage biasing the pressure and flow control device towards the first control position is substantially equal to a pressure in the reservoir.

100131 In some embodiments, the control valve assembly further includes a pressure regulating device arranged upstream of the control orifice and downstream of the supply node, and the pressure regulating device is movable between a first regulating position and a second regulating position.

100141 In some embodiments, the pressure regulating device moves between the first regulating position and the second regulating position to maintain a fixed and constant pressure upstream of the control orifice.

100151 In some embodiments, the pressure regulating device is biased into the first regulating position by a spring and a pressure in the reservoir.

100161 In some embodiments, the pressure regulating device moves between the first regulating position and the second regulating position in response to a pressure upstream of the control orifice.

100171 In some embodiments, the pressure regulating device ncludes electrically operated solenoid.

100181 In some embodiments, the pressure regulating device includes a first regulating inlet port, a second regulating inlet port, and a regulating outlet port.

100191 In some embodiments, the first regulating inlet port is in fluid communication with the supply node, the second regulating inlet port is in fluid communication with the reservoir, and the regulating outlet port is in fluid communication with the control orifice.

10020] In some embodiments, when the pressure regulating device is in the first regulating position, fluid communication is provided between the first regulating inlet port and the regulating outlet port, and when the pressure regulating device is in the second regulating position, fluid communication is provided between the second regulating inlet port and the regulating outlet port.

100211 In some embodiments, the bypass conduit is in fluid communication with the load sense line downstream of the bypass passage. -3 -

10022] In some embodiments, the pressure and flow control device is biased towards the first control position by a spring and a pressure in the bypass conduit downstream of the bypass passage.

10023] In some embodiments, the pressure in the bypass conduit downstream of the bypass passage biasing the pressure and flow control device towards the first control position is substantially equal to a pressure in the load sense line.

10024] In some embodiments, the restriction to fluid flow in the bypass conduit is at a minimum value when the control valve is in a center, neutral position.

10025] In some embodiments, the restriction to fluid flow in the bypass conduit increases in response to movement of the control valve away from the central, neutral position.

10026] In some embodiments, the control valve assembly comprises a plurality of control valve sections each controlling a hydraulic function of the machine and each including a control valve having an inlet port in fluid communication with the supply conduit and a bypass passage in fluid communication with the bypass conduit.

10027] In some embodiments, the control valve is an open-center, three position valve.

100281 The foregoing and other aspects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims and herein for interpreting the scope of the invention

DESCRIPTION OF DRAWINGS

100291 The invention will be better understood and features, aspects and advantages other than those set forth above will become apparent when consideration is given to the following detailed description thereof Such detailed description makes reference to the following drawings 10030] Fig. 1 shows a schematic illustration of a hydraulic circuit including a control valve assembly having open center control valves in accordance with one embodiment of the present invention.

10031] Fig. 2 shows a pressure reducing device of a hydraulic system in accordance with one embodiment of the present invention. -4 -

10032] Fig. 3 shows a schematic illustration an alternative configuration of the hydraulic circuit of Fig. 1 in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

10033] The use of the terms "downstream" and "upstream" herein are terms that indicate direction relative to the flow of a fluid. The term "downstream" corresponds to the direction of fluid flow, while the term "upstream" refers to the direction opposite or against the direction of fluid flow.

100341 Fig. 1 shows a hydraulic system 10 for controlling one or more functions of a mobile machine (e.g., an excavator, a mini-excavator, a tractor loader, a backhoe, etc.) in accordance with one embodiment of the present invention. The hydraulic system 10 can include a control valve assembly 12, a pump 14, and a reservoir 16. The control valve assembly 12 can include three valve sections 20, 22, and 24 arranged downstream of an inlet section 18. It should be known that the number of valve sections is not meant to be limiting in any way and it should be appreciated that the control valve assembly 14 can include any number of valve sections in communication with any number of functions as required by the mobile machine. The control valve assembly 12 may have a single monolithic body or comprise physically separate valve sections attached side by side.

10035] Each of the valve sections 20, 22, and 24 can include a corresponding control valve 26, 28 and 30 each configured to selectively control, based on a desired operation of the mobile machine, when fluid communication is provided between a corresponding function 32, 34, and 36 and both the pump 14 and the reservoir 16. It should be known that although the functions 32, 34, and 36 are shown as piston-cylinder type actuators, the functions 32, 34 and/or 36 may be in the form of any mechanical movement mechanism (e.g a motor) as required by the mobile machine.

100361 As will be described in detail below, each of the control valves 26, 28 and 30 can also control a flow rate of fluid from the fluid source 14 to the functions 26,28 and 30. Each of the control valves 26, 28 and 30 can each be an open center, three position valve in the form of a spool. It should be known that the number of positions of the control valves 26, 28, and 30 is not meant to be limiting in any way and open center control valves with more or less than three positions could be used. The control valves 26, 28, and 30 may be manually actuated, -5 -hydraulically actuated, electrohydraulically actuated or actuated by any other actuation mechanism known in the art or developed in the future.

[0037] The pump 14 can be a variable displacement pump which draws fluid, such as oil, from the reservoir 16 and furnishes that fluid under increased pressure at a pump outlet 38. The pressure of the fluid provided by the pump 14 at the pump outlet 38 can be responsive to a pressure signal at a pump control port 40. The pump 14 can be configured to maintain the pressure at the pump outlet 38 to be a constant pressure differential, known as margin pressure, greater than the pressure at the pump control port 40. The pump 14 can increase or decrease its displacement in order to maintain the margin pressure between the pump outlet 38 and the pump control port 40.

100381 The pump outlet 38 can be in fluid communication with a supply conduit 42 which extends through the inlet section 18 and each of the valve sections 20 and 22, and can terminate in the valve section 24. In other embodiments, the supply conduit 42 can extend through the valve section 24 to one or more additional valve section(s), as required by the mobile machine. A return conduit 44 can provide fluid communication between each of the control valves 26, 28, and 30 and the reservoir 16.

[0039] As shown in Fig. I, each of the control valves 26, 28 and 30 can include similar features which are identified with like reference numerals and distinguished using the letters "a," "b," and "c" for the control valves 26, 28, and 30, respectively. The following description of the control valve 26 also applies to the control valves 28 and 30. The control valve 26 can include an inlet port 46a and an outlet port 48a. The inlet port 46a can be in fluid communication with the supply conduit 42. A load check valve 50a can be arranged upstream of the inlet port 46a to inhibit fluid flow from the inlet port 46a back into the supply conduit 42 (e.g., when a large load acts on the associated function 32). The outlet port 48a can be in fluid communication with the return conduit 44. Based on the direction that the control valve 26 can be moved from a center, neutral position, shown in Fig. 1, the inlet port 46a can be in fluid communication with one of a first workport 52a or a second workport 54a of the control valve 26, and the outlet port 48a can be in fluid communication with the other of the first workport 52a or the second workport 54a. The first workport 52a and the second workport Ma are each in fluid communication with a different port on the function 32. The control valve 26 can be biased into the center, neutral position, shown in Fig. 1, where both the first workport 52a and the second workport 54a are closed (i.e., -6 -fluid flow can be inhibited from the inlet and outlet ports 46a and 48a to the first and second workports 52a and 54a). As the control valve 26 is moved from the center, neutral position, the inlet and outlet ports 46a and 48a can open according to a valve displacement vs. workport flow area relationship which can be customized to meet specific operational requirements of the mobile machine.

100401 The control valve 26 can also include a bypass inlet port 56a, a bypass outlet port 58a, and a bypass passage 60a arranged therebetween. When the control valve 26 is in the center, neutral position, the bypass passage 60a can be open, as shown in Fig. 1. As the control valve 26 is moved from the center, neutral position, in a desired direction, the bypass passage 60a can begin to close (i.e., provide a greater restriction to fluid flow). The amount that the bypass passage 60a closes can be governed by a valve displacement vs. bypass flow area relationship which can be customized to meet specific operational requirement of the mobile machine. The bypass passages 60a, 60b, and 60c of each of the control valves 26, 28, and 30 can be connected in series via a bypass conduit 62. Downstream of the bypass outlet port 58c, the bypass conduit 62 can be in fluid communication with the reservoir 16.

100411 The inlet section 18 can include a supply node 64, a pressure regulating device 66, a pressure and flow control device 68, and a control orifice 70. It should be known that the pressure regulating device 66 and the pressure and flow control device 68 may be integrated into a separate valve, or they could each have their own valves (remote from the control valve assembly 12). The supply node 64 can be arranged downstream of the pump outlet 38 and upstream of the pressure regulating device 66 and the pressure and flow control device 68. The bypass conduit 62 can tee off from the supply conduit 42 at the supply node 64. The pressure regulating device 66 can be arranged downstream of the supply node 64 and upstream of the control orifice 70, and configured to maintain a pressure upstream of the control orifice 70 to be a constant and fixed value, as described below. The pressure regulating device 66 can include a first regulating inlet port 72, a second regulating inlet port 74, and a regulating outlet port 76. The first regulating inlet port 72 can be in fluid communication with the supply node 64, and the second regulating inlet port 74 can be in fluid communication with the reservoir 16. The regulating outlet port 76 of the pressure regulating device 66 can be in fluid communication with the control orifice 70 -7 - [0042] The pressure regulating device 66 can be biased into a first pressure regulating position, as shown in Fig. 1, by a spring 78 and a pressure from the reservoir 16. When the pressure regulating device 66 is in the first pressure regulating position, the first regulating inlet port 72 can be in fluid communication with the regulating outlet port 76 thereby enabling fluid to flow from the supply node 64 to the regulating outlet port 76, and the second regulating inlet port 74 can be closed. Once a pressure at a location downstream of the regulating outlet port 76 and upstream of the control orifice 70 is greater than the pressure provided by the spring 78 and the reservoir 16, the pressure regulating device 66 can begin to move towards a second pressure regulating position. When the pressure regulating device 66 is in the second pressure regulating position, the first regulating inlet port 72 can be closed, and the second regulating inlet port 74 can be in fluid communication with the regulating outlet port 76 thereby placing the regulating outlet port 76 in fluid communication with the reservoir 16. This operation of the pressure regulating device 66 (i.e., moving between the first pressure regulating position and the second regulating position) can enable the pressure regulating device 66 to maintain a pressure at the regulating outlet port 76 at a fixed and constant value irrespective of the pressure upstream of the pressure regulating device 66 (i.e., at the first regulating inlet port 72). That is, the pressure regulating device 66 can maintain a pressure at the regulating outlet port 76 to be a fixed and constant value irrespective of the pressure at the pump outlet 38. It should be known that the pressure regulating device 66 may include only the first regulating inlet port 72 and the regulating outlet port 76 (i.e., a 2 port valve) and may accomplish the same functionality.

[0043] In other embodiments, as shown in Fig. 2, the pressure regulating device 66 may include a solenoid 80. In this embodiment, the solenoid 80 can be electronically controlled and move the pressure regulating device 66 between the first pressure regulating position and the second pressure regulating position in response to the pressure downstream of the regulating outlet port 76 and upstream of the control orifice 70. It should be known that, the specific arrangement of the solenoid 80 (i.e., whether the solenoid 80 can be configured to push or pull the pressure regulating device 66) is not meant to be limiting in any way.

[0044] With reference back to Fig. 1, the pressure and flow control device 68 can be arranged downstream of the supply node 64 and upstream of the inlet port 46a and the load check valve 50a. The pressure and flow control device 68 can be configured to control a flow rate of fluid in the supply conduit 42 to one or more of the functions 32, 34, and 36 in response to a -8 -displacement of one or more of the control valves 26, 28, and 30, as will be described below. The pressure and flow control device 68 can include a first control inlet port 82, a first control outlet port 84, a second control inlet port 86, and a second control outlet port 88. The first control inlet port 82 can be in fluid communication with the supply node 64, and the first control outlet port 84 can be in fluid communication with the inlet port 46a and the load check valve 50a. The second control inlet port 86 can provide fluid communication from a location downstream of the first control outlet port 84 to the second control outlet port 88, and the second control outlet port 88 can be in fluid communication with the reservoir 16.

[00451 The pressure and flow control device 68 can be biased into a first control position by a spring 90 and a pressure in the bypass conduit 62 downstream of the bypass outlet port 58c. As described above, the bypass conduit 62 can be in fluid communication with the reservoir 16 downstream of the bypass outlet port 58c and, thus, the pressure in the bypass conduit 62 downstream of the bypass outlet port 58c, communicated to the pressure and flow control device 68, can be substantially equal to the pressure in the reservoir 16. When the pressure and flow control device 68 is in the first control position, the first control inlet port 82 can be in fluid communication with the first control outlet port 84, and the second control inlet port 86 can be in fluid communication with the second control outlet port 88. Once a pressure downstream of the control orifice 70 and upstream of the bypass inlet port 56a is greater than the pressure provided by the spring 90 and the pressure in the bypass conduit 62 downstream of the bypass outlet port 58c, the pressure and flow control device 68 can begin to move towards a second control position. When the pressure and flow control device 68 is in the second control position, the first control inlet port 82 can be in fluid communication with the first control outlet port 84, and the second control inlet port 86 and the second control outlet port 88 can be closed.

100461 Whether the pressure and flow control device 68 is in the first control position or the second control position, the first control inlet port 82 can be in fluid communication with the first control outlet port 84, as described above. However, as shown in Fig. 1, a flow restriction between the first control inlet port 82 and the first control outlet port 84 can be increased (i.e., a smaller flow area) when the pressure and flow control device 68 is in the first control position compared to the second control position. Accordingly, as the pressure and flow control device 68 moves from the first control position towards the second control position, a flow restriction between the first control inlet port 82 and the first control outlet port 84 can decrease (i.e., the -9 -flow area can increase). Simultaneously, the flow restriction between second control inlet port 86 and the second control outlet port 88 can increase (i.e., the flow area can decrease).

100471 In other embodiments, the pressure and flow control device 68 can comprise multiple components (e.g., two or more valves) that collectively perform the same function as the pressure and flow control device 68 of Fig. 1.

100481 The control orifice 70 can be arranged downstream of the regulating outlet port 76 and upstream of the bypass inlet port 56a. As shown in Fig. 1, the control orifice 70 can be a fixed orifice. In other embodiments, the control orifice 70 may be a variable orifice or a solenoid operated variable orifice.

[0049] A load sense line 92 can communicate a pressure downstream of the pressure and flow control device 68, specifically, a pressure downstream of the first control outlet port 82 and upstream of the inlet port 46a and the load check valve 50a, to the pump control port 40. Since the pump 14 is configured to maintain the margin pressure between the pump outlet 38 and the pump control port 40, the pressure drop across the pressure and flow control device 68 can be approximately equal to the margin pressure. With the pressure drop across the pressure and flow control device 68 substantially fixed, the portion of the fluid flow from the pump 14 that travels through the pressure and flow control device 68 can be proportional to a restriction (i.e., a flow area) between the first control inlet port 82 and the first control outlet 84.

[0050] Operation of the hydraulic system 10 during different modes of operation will be described with reference to Fig. I. It should be known that the hydraulic system 10 is not limited to the modes of operation described below and alternative modes of operation are within the scope of the present invention. In one non-limiting example, each of the control valves 26, 28, and 30 can be in the center, neutral position, shown in Fig. 1. In this non-limiting example, the flow area through the bypass passages 60a, 60b, and 60c can be a fixed maximum value (i.e., the restriction in the bypass conduit 62 can be a minimum value). Therefore, the pressure downstream of the control orifice 70, sensed by the pressure and flow control device 68, can be sufficiently low to ensure the pressure and flow control device 68 can be in the first control position (i.e., a spring 90 biased position). As described above, when the pressure and flow control device 68 is in the first control position, a maximum flow restriction can occur between the first control inlet port 82 and the first control outlet port 84. Also, when the pressure and flow control device 68 is in the first control position, a restriction between the second control inlet -10-port 86 and the second control outlet port 88 can be less than a restriction between the first control inlet port 82 and the first control outlet port 84. This can prevent the pressure sensed by the load sense line 92 from building (i.e., continually increasing). As the pressure and flow control device 68 is moved from the first control position, the balance of restrictions between the two paths through the pressure and flow control device 68 (i.e., the restriction between the first control inlet port 82 and the first control outlet port 84, and the restriction between the second control inlet port 86 and the second control outlet port 88) can prevent a step change in the pressure in the load sense line 92 from occurring, as described below.. The flow through the bypass passage 62 can be a fixed, predetermined value since a restriction across the control orifice 70 and each of the bypass passages 60a, 60b and 60c can be fixed, when the control valves 26, 28, and 30 are in the center, neutral position. At this non-limiting operating condition, the flow supplied at the pump outlet 38 and the pressure at the pump outlet 38 can be relatively low compared to when a function is commanded. This can reduce a power requirement of the hydraulic system 10 when the control valves 26, 28, and 30 are in the center, neutral position.

100511 In another non-limiting example, the control valve 26 can be partially moved from the center, neutral position. When the control valve 26 is partially moved from the center, neutral position, a flow area defined by the bypass passage 60a can be partially closed (i.e., increase a flow restriction) according to the displacement vs. area relationship which can be customized to meet specific operational requirements of the mobile machine. The partial closing of the bypass passage 60a can increase a restriction in the bypass conduit 62 and can reduce a flow rate of fluid through the bypass conduit 62. Simultaneously, a pressure downstream of the control orifice 70, sensed by the pressure and flow control device 68, can increase in proportion to the increased restriction (i.e., decrease in flow area) in the bypass conduit 62. The pressure upstream of the control orifice 70 can be maintained at the fixed and constant value set by the pressure regulating device 66.

100521 The increased pressure in the bypass conduit 62 downstream of the control orifice 70 can cause the pressure and flow control device 68 to move against the spring 90 to a predetermined position between the first control position and the second control position. In this way, the movement of the control valve 26 can change (i.e., increases) a restriction in the bypass conduit 62 and can result in a servo-like action of the pressure and flow control device 68. That is, the movement of the control valve 26 can substantially simultaneously induce a movement of the pressure and flow control device 68. As described above, movement of the pressure and flow control device 68 from the first control position towards the second control position can increase the flow area between the first control inlet port 82 and the first control outlet 84. Since the pump 14 can maintain a pressure drop (i.e., the margin pressure) across the pressure and flow control device 68, the increased flow area between the first control inlet port 82 and the first control outlet port 84 can result in an increase flow rate of fluid through the supply conduit 42. At the same time, as described above, the flow area between second control inlet port 86 and the second control outlet port 88 can decrease, which can cause the pressure at the pump outlet 38 to increase (i.e., the pressure sensed by the load sense line 92 and communicated to the pump control port 40 can increase). This increased pressure can be prevented from being an abmpt step change in pressure by the flow of fluid from the second control outlet port 88 to the reservoir 16 and, as a result, the operation of the mobile machine can be smooth (i.e., less stressful for the operator of the mobile machine).

[0053] In this non-limiting example, if the control valve 26 as been sufficiently displaced to at least partially open the inlet port 46a and the pressure at the pump outlet 38 is greater than a pressure at the inlet port 46a, then fluid can flow through the pressure and flow control device 68, the load check valve 50a, and on to the function 32. The amount of fluid flow passing to the inlet port 46a can be proportional to a pressure drop between the supply node 64 and the inlet port 46a, and a flow area defined at the inlet port 46a. Similarly, if the outlet port 48a is at least partially open, then fluid can flow from the function 32 through the outlet port 48a and on to the reservoir 16.

[0054] As the fluid flow increases through the supply conduit 42, the flow of fluid through the bypass conduit 62 can decrease, and continue to decrease as the control valve 26 is further moved from the center, neutral position. This can result in reduced quiescent power losses for the hydraulic system 10. It should be known that although the above described non-limiting example was described with reference to the partial displacement of the control valve 26, the operation would be the same if, instead, the control valve 28 or the control valve 30 were partially displaced.

[0055] In another non-limiting example, the control valve 26 can be fully selected (i.e., fully moved away from the center, neutral position and into one of the other two positions). When the control valve 26 is fully selected, the flow area defined by the bypass passage 60a can be -12 -generally closed according to the displacement vs. area relationship. The closing of the bypass passage 60a can cause the flow through the bypass conduit 62 to reduce, or cease due to the increased restriction in the bypass conduit 62. Simultaneously, the pressure downstream of the control orifice 70, sensed by the pressure and flow control device 68, can increase in proportion to the increased restriction (i.e., decrease in flow area) in the bypass conduit 62. In the non-limiting case where the bypass passage 60a is completely closed, the pressure downstream of the control orifice 70, sensed by the pressure and flow control device 68, can be substantially equal to the fixed and constant value set by the pressure regulating device 66.

100561 The increased pressure downstream of the control orifice 70 can cause the pressure and flow control device 68 to move against the spring 90 to a predetermined position between the first control position and the second control position. Movement of the pressure and flow control device 68 from the first control position towards the second control position can increase the flow area between the first control inlet port 82 and the first control outlet 84. Since the pump 14 can maintain a pressure drop (i.e., the margin pressure) across the pressure and flow control device 68, the increased flow area between the first control inlet port 82 and the first control outlet port 84 can result in an increase the flow rate of fluid through the supply conduit 42. At the same time, as described above, the flow area between second control inlet port 86 and the second control outlet port 88 can decrease, which can cause the pressure at the pump outlet 38 to increase (i.e., the pressure sensed by the load sense line 92 and communicated to the pump control port 40 can increase). In the non-limiting case where the bypass passage 60a is completely closed, the pressure and flow control device 68 can be moved fully into the second control position. As described above, in the second control position, the second control inlet 86 and the second control outlet 88 can be closed and the flow area between the first control inlet port 82 and the first control outlet 84 can be at a maximum value. This can enable the hydraulic system 10 to provide all the demanded pump flow, via the supply conduit 42, to the function 32. It should be known that although the above described non-limiting example was described with reference to the full selection of the control valve 26, the operation would be the same if, instead, the control valve 28 or the control valve 30 were fully selected.

[0057] In yet another non-limiting example, two or more of the control valves 26, 28 and 30 can be moved from their center, neutral positions. When two or more of the control valves 26, 28 and 30 are moved, the effective flow area through the bypass conduit 62 can be reduced by the series -13 -effect of each restricted bypass passage 60a, 60b and/or 60c. This can result in the pressure downstream of the control orifice 70, sensed by the pressure and flow control device 68, proportionally increasing. The increased pressure downstream of the control orifice 70 can cause the pressure and flow control device 68 to move against the spring 90 to a predetermined position between the first control position and the second control position. Movement of the pressure and flow control device 68 from the first control position towards the second control position can increase the flow area between the first control inlet port 82 and the first control outlet 84. Since the pump 14 can maintain a pressure drop (i.e., the margin pressure) across the pressure and flow control device 68, the increased flow area between the first control inlet port 82 and the first control outlet port 84 can result in an increase in the flow rate of fluid through the supply conduit 42. At the same time, as described above, the flow area between second control inlet port 86 and the second control outlet port 88 can decrease, which can cause the pressure at the pump outlet 38 to increase (i.e., the pressure sensed by the load sense line 92 and communicated to the pump control port 40 can increase).

100581 The amount of movement of the pressure and flow control device 68 from the first control position towards the second control position can be reflective of an effective sum of the movement of the control valves 26, 28, and 30 so the flow rate of fluid provided at the pump outlet 38 can be greater than if a single control valve 26, 28, or 30 were moved. The commanded flow provided at the pump outlet 38 can be distributed amongst the selected functions 32, 34, and/or 36 according to the load pressures of the selected functions 32, 34, and 36 and the relative movement of the control valves 26, 28, and/or 30, along with the displacement vs. flow area relationships for the inlet ports 46a, 46b, and/or 46c in the control valves 26, 28, and/or 30.

[0059] In still another non-limiting example, the control valve 26 may be moved from the center, neutral position, but the function 32 may not be able to move/actuate. In this non-limiting example, the pressure and flow control device 68 may moved substantially towards the second control position, depending on the amount of movement of the control valve 26 from the center, neutral position. In such a non-limiting case, the pressure sensed by the load sense line 92 and communicated to the pump control port 40 may be greater than a maximum rated pressure of the pump 14. The hydraulic system 10 can be protected from either one or more of a maximum pump pressure limit regulator (not shown), a relief valve (not shown) arranged on the load sense line 92 having a maximum pressure setting less than the maximum rated pressure of the pump -14 - 14, and a main relief valve (not shown) arranged on the supply conduit 42 and/or between the supply node 64 and the pump outlet 38.

100601 Fig. 3 shows an alternative embodiment of the hydraulic system 10. The hydraulic system 10 shown in Fig. 3 is similar to the hydraulic system shown in Fig. 1 except as described below or is apparent from Fig. 3. As shown in Fig. 3, the bypass conduit 62 can be in fluid communication with the load sense line 92 downstream of the bypass outlet port 58c, and the pressure in the load sense line 92 can bias the pressure and flow control device 68 into the first control position along with the spring 90. In this embodiment, the hydraulic system 10 may not include the pressure regulating device 66. Without the pressure regulating device 66, when the control valves 26, 28, and 30 are in the center, neutral position, a pressure drop across the control orifice 70 can be substantially equal to the margin pressure. As one or more of the control valves 26, 28, and 30 are moved from the center, neutral position, the pressure drop across the control orifice 70 can be less than the margin pressure and, therefore, a pressure downstream of the control orifice 70, sensed by the pressure and flow control device 68, can be greater than the pressure in the load sense line 92. Once the pressure downstream of the control orifice 70, sensed by the pressure and flow control device 68, is greater than the pressure in the load sense line 92 and the force of the spring 90, the pressure and flow control device 68 can be biased towards the second control position.

100611 Exemplary advantages of the above-described hydraulic system 10 or other hydraulic systems designed or created using the above-described techniques or properties, will be discussed below with reference to Figs. 1-3. By no means is the following an exhaustive list of the numerous advantages provided by the invention, as will be understood by one of skill in the art.

100621 As described above, the movement of the pressure and flow control device 68 of the hydraulic system 10 between the first control position and the second control position can be governed by a flow restriction through the bypass conduit 62 (i.e., an effective flow area through the bypass passages 60a, 60b and 60c). Since the margin pressure can be maintained across the pressure and flow control device 68, the movement of the pressure and flow control device 68 can dictate a flow rate of fluid through the supply conduit 42 by varying a restriction (i.e., a flow area) between the first control inlet port 82 and the first control outlet 84. This operation can -15 -enable the hydraulic system 10 to harvest the performance benefits (e.g., increased efficiency) of flow summation while using cost effective open-center control valves 26, 28, and 30.

100631 The displacement vs. flow area relationships for the inlet ports 46a, 46b, and 46c can be designed such that if a single control valve is selected, the flow rate of fluid in the supply conduit 42 being supplied to the selected function is less than the maximum pump flow rate. This can be a significant advantage in applications where some functions require a lower flow rate of fluid (e.g., slew on a tractor loader).

100641 The pressure sensed by the load sense line 92 can be prevented from abrupt step changes by the flow of fluid from the second control outlet port 88 to the reservoir 16 provided by the pressure and flow control device 68. As a result, the operation of the mobile machine provided by the hydraulic system 10 can be smooth (i.e., less stressful for the operator of the mobile machine) causing less fatigue during a working day for an operator of the mobile machine.

100651 Whilst the invention has been described above, it extends to any inventive combination of features set out above or in the following description. Although illustrative embodiments of the invention are described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments. Furthermore, it is contemplated that a particular feature described either individually or as part of an embodiment can be combined with other individually described features, or parts of other embodiments, even if the other features and embodiments make no mention of the particular feature. Thus, the invention extends to such specific combinations not already described.

100661 Thus, while the invention has been described in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto. The entire disclosure of each patent and publication cited herein is incorporated by reference, as if each such patent or publication were individually incorporated by reference herein.

100671 Various features and advantages of the invention are set forth in the following claims. -16-

Claims

CLAIMS We claim: 1. A control valve assembly to be integrated into a hydraulic system, the hydraulic system including a variable displacement pump that draws fluid from a reservoir, the control valve assembly comprising: at least one valve section to control a hydraulic function of a machine and including a control valve, the control valve including an inlet port in fluid communication with a supply conduit and a bypass passage in fluid communication with a bypass conduit; a supply node in fluid communication with and arranged downstream of a pump outlet of the variable displacement pump; a control orifice to provide a restriction in the bypass conduit and arranged upstream of the bypass passage and downstream of the supply node; a pressure and flow control device arranged downstream of the supply node and upstream of the valve section and moveable between a first control position and a second control position, the pressure and flow control device including a first control inlet port in fluid communication with the supply node and a first control outlet port in fluid communication with the supply conduit, the first control position providing a greater restriction to fluid flow between the first control inlet port and the second control inlet port than the second flow control position; and a load sense line communicating a pressure downstream of the pressure and flow control device and upstream of the inlet port of the control valve to a pump control port; wherein the pressure and flow control device moves between the first control position and the second control position in response to a change is a restriction to fluid flow in the bypass conduit.
2. The control valve assembly of claim 1, wherein the change in the restriction to fluid flow in the bypass conduit is communicated to the pressure and flow control device via a change in a pressure downstream of the control orifice and upstream of the bypass passage.
3. The control valve assembly of claim 1, wherein the pressure and flow control device further includes a second control inlet port and a second control outlet port. -17-
4. The control valve assembly of claim 3, wherein the second control inlet port provides fluid communication from a location downstream of the first control outlet port to the second control outlet port, and the second control outlet port is in fluid communication with the reservoir.
The control valve assembly of claim 3, wherein the second control position provides a greater restriction to fluid flow between the second control inlet and the second control outlet than the first control position.
6. The control valve assembly of claim 1, wherein the bypass conduit is in fluid communication with the reservoir downstream of the bypass passage.
7. The control valve assembly of claim 6, wherein the pressure and flow control device is biased towards the first control position by a spring and a pressure in bypass conduit downstream of the bypass passage.
8. The control valve assembly of claim 7, wherein the pressure in the bypass conduit downstream of the bypass passage biasing the pressure and flow control device towards the first control position is substantially equal to a pressure in the reservoir.
9. The control valve assembly of claim 7, wherein the control valve assembly further comprises a pressure regulating device arranged upstream of the control orifice and downstream of the supply node, the pressure regulating device movable between a first regulating position and a second regulating position.
10. The control valve assembly of claim 9, wherein the pressure regulating device moves between the first regulating position and the second regulating position to maintain a fixed and constant pressure upstream of the control orifice. -18-
I I. The control valve assembly of claim 9, wherein the pressure regulating device is biased into the first regulating position by a spring and a pressure in the reservoir.
I 2. The control valve assembly of claim 9, wherein the pressure regulating device moves between the first regulating position and the second regulating position in response to a pressure upstream of the control orifice.
13. The control valve assembly of claim 9, wherein the pressure regulating device includes electrically operated solenoid.
14. The control valve assembly of claim 9, wherein the pressure regulating device includes a first regulating inlet port, a second regulating inlet port, and a regulating outlet port.
15. The control valve assembly of claim 14, wherein the first regulating inlet port is in fluid communication with the supply node, the second regulating inlet port is in fluid communication with the reservoir, and the regulating outlet port is in fluid communication with the control orifice.
16. The control valve assembly of claim 15, wherein when the pressure regulating device is in the first regulating position, fluid communication is provided between the first regulating inlet port and the regulating outlet port, and when the pressure regulating device is in the second regulating position, fluid communication is provided between the second regulating inlet port and the regulating outlet port.
17. The control valve assembly of claim 1, wherein the bypass conduit is in fluid communication with the load sense line downstream of the bypass passage.
18. The control valve assembly of claim 17, wherein the pressure and flow control device is biased towards the first control position by a spring and a pressure in the bypass conduit downstream of the bypass passage. -19-
19. The control valve assembly of claim 18, wherein the pressure in the bypass conduit downstream of the bypass passage biasing the pressure and flow control device towards the first control position is substantially equal to a pressure in the load sense line.
20. The control valve assembly of claim I, wherein the restriction to fluid flow in the bypass conduit is at a minimum value when the control valve is in a center, neutral position.
21. The control valve assembly of claim 1, wherein the restriction to fluid flow in the bypass conduit increases in response to movement of the control valve away from the central, neutral position.
22. The control valve assembly of claim 1, wherein the control valve assembly comprises a plurality of control valve sections each controlling a hydraulic function of the machine and each including a control valve having an inlet port in fluid communication with the supply conduit and a bypass passage in fluid communication with the bypass conduit.
23. The control valve assembly of claim I, wherein the control valve is an open-center, three position valve.-20 -