Patent Publication Number: US-9410560-B2

Title: Control valve assembly

Description:
FIELD 
     Disclosed embodiments relate to power machines that employ a control valve assembly for controlling hydraulic fluid flow provided to various actuators that are operably coupled to the control valve assembly. 
     BACKGROUND 
     Some power machines including skid steer loaders, tracked loaders, steerable axle loaders, excavators, telehandlers, walk behind loaders, trenchers, and the like, employ engine powered hydraulic power conversion systems. In some power machines, the hydraulic power conversion systems utilize an open center series control valve assembly that receives pressurized fluid from a pump. This control valve assembly typically has multiple valve elements to port hydraulic fluid to different work functions on the power machine. For example, on a work machine with a lift cylinder that raises and lowers a lift arm, a tilt cylinder that controls a tilt position of an implement carrier and thus an attached implement with respect to the lift arm, and one or more implement work actuators, the control valve assembly may have three (although any number can be used) valve elements, often in the form of linear spools, to port hydraulic fluid to the different actuators on the power machine and/or implement. The term open center refers to a feature in a valve assembly such that when a valve element is in an unactuated position (such as the center position on a typical spool valve) or a partially actuated position (such as in a proportional spool valve), at least some hydraulic fluid is allowed to flow through the unactuated position to a downstream valve element. 
     The valve elements in an open center control valve assembly are arranged such that the first valve element that receives hydraulic fluid from a pump has priority over subsequent downstream valve elements. A traditional priority in a power machine such as a skid steer loader is that the hydraulic fluid is provided first to a lift valve element, which is used to selectively control the lift cylinder to raise and lower the lift arm. Subsequently hydraulic fluid is provided to the tilt valve element, which is used to control the tilt cylinder and then to the auxiliary or implement valve element and then out of the valve. 
     It is known that in certain open center hydraulic control valve assemblies, when downstream valve elements are actuated to provide fluid to a downstream actuator, back pressures can be raised to a point where functionality of upstream elements can be limited or compromised. 
     The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
     SUMMARY 
     Disclosed embodiments include a power machine and a power conversion system for a power machine. In an exemplary embodiment, the power conversion system includes a pump configured to provide a source of pressurized hydraulic fluid. A control valve assembly is coupled to the pump to receive the hydraulic fluid. The control valve assembly includes a first valve element configured to direct pressurized hydraulic fluid to and receive pressurized hydraulic fluid from an actuator when the first valve element is in first and second actuated positions. The control valve assembly also includes a second valve element downstream of the first valve element. The first valve element is moveable between an unactuated position and the first and second actuated positions. The control valve assembly is configured to direct hydraulic fluid received from the actuator through the second actuated position to the second valve element and direct hydraulic fluid received from the actuator through the first actuated position to bypass the second valve element. 
     This Summary and the Abstract are provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view of a power machine having a power conversion system with a control valve assembly in accordance with exemplary embodiments. 
         FIG. 2  is a block diagram illustrating components of the power machine and power conversion system of  FIG. 1 . 
         FIG. 3  is a block diagram illustrating a power conversion system according to one illustrative embodiment. 
         FIGS. 4-7  are hydraulic circuit diagrams illustrating an exemplary embodiment of a control valve assembly of  FIG. 3  configured to implement disclosed embodiments and concepts. 
     
    
    
     DETAILED DESCRIPTION 
     The concepts disclosed herein are not limited in their application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. That is, the embodiments disclosed herein are illustrative in nature. The concepts illustrated in these embodiments are capable of being practiced or being carried out in various ways. The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Words such as “including,” “comprising,” and “having” and variations thereof as used herein are meant to encompass the items listed thereafter, equivalents thereof, as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
       FIG. 1  is a side elevation view of a representative power machine  100  upon which the disclosed embodiments can be employed.  FIG. 2  is a block diagram illustrating certain features and arrangements of the power machine. The power machine  100  illustrated in  FIG. 1  is a skid loader, but other types of power machines such as tracked loaders, steerable wheeled loaders, including all-wheel steer loaders, excavators, telehandlers, walk behind loaders, trenchers, and utility vehicles, to name but a few examples, may employ the disclosed embodiments. The power machine  100  includes a supporting frame or main frame  102 , which supports a power source  104 , which in some embodiments is an internal combustion engine. A power conversion system  106  is operably coupled to the power source  104 . Power conversion system  106  illustratively receives power from the power source  104  and operator inputs to convert the received power to power signals in a form that is provided to and utilized by functional components of the power machine. In some embodiments, such as with the power machine  100  in  FIG. 1 , the power conversion system  106  includes hydraulic components such as one or more hydraulic pumps and various actuators and valve components that are illustratively employed to receive and selectively provide power signals in the form of pressurized hydraulic fluid to some or all of the actuators used to control functional components of the power machine  100 . For example, a control valve assembly  204  (shown in  FIG. 2 ) can be used to selectively provide pressurized hydraulic fluid from a hydraulic pump  206  (shown in  FIG. 2 ) to actuators  208  (shown in  FIG. 2 ) such as hydraulic cylinders that are positioned on the power machine. In some embodiments, control valve assembly  204  also selectively provides pressurized hydraulic fluid to actuators  210  located on an implement  212  attached to the power machine. Other types of control systems are contemplated. For example, the power conversion system  106  can include electric generators or the like to generate electrical control signals to power electric actuators. For the sake of simplicity, the actuators discussed in the disclosed embodiments herein are referred to as hydraulic or electrohydraulic actuators, but other types of actuators can be employed in some embodiments. 
     Among the functional components that are capable of receiving power signals from the power conversion system  106  are tractive elements  108 , illustratively shown as wheels, which are configured to rotatably engage a support surface to cause the power machine to travel. Other examples of power machines can have tracks or other tractive elements instead of wheels. In an example embodiment, a pair of hydraulic motors (not shown in  FIG. 1 ), are provided to convert a hydraulic power signal into a rotational output. In power machines such as skid steer loaders, a single hydraulic motor can be operatively coupled to both of the wheels on one side of the power machine. Alternatively, a hydraulic motor can be provided for each tractive element in a machine. In a skid steer loader, steering is accomplished by providing unequal rotational outputs to the tractive element or elements on one side of the machine as opposed to the other side. In some power machines, steering is accomplished through other means, such as, for example, steerable axles. 
     The power machine  100  also includes a lift arm structure  114  that is capable of being raised and lowered with respect to the frame  102 . The lift arm structure  114  illustratively includes a lift arm  116  that is pivotally attached to the frame  102  at attachment point  118 . An actuator  120 , which in some embodiments is a hydraulic cylinder configured to receive pressurized fluid from power conversion system  106 , is pivotally attached to both the frame  102  and the lift arm  116  at attachment points  122  and  124 , respectively. Actuator  120  is sometimes referred to as a lift cylinder, and is a representative example of one type of actuator  208  shown in  FIG. 2 . Extension and retraction of the actuator  120  causes the lift arm  116  to pivot about attachment point  118  and thereby be raised and lowered along a generally vertical path indicated approximately by arrow  138 . The lift arm  116  is representative of the type of lift arm that may be attached to the power machine  100 . The lift arm structure  114  shown in  FIG. 1  includes a second lift arm and actuator disposed on an opposite side of the of the power machine  100 , although neither is shown in  FIG. 1 . Other lift arm structures, with different geometries, components, and arrangements can be coupled to the power machine  100  or other power machines upon which the embodiments discussed herein can be practiced without departing from the scope of the present discussion. 
     An implement carrier  130  is pivotally attached to the lift arm  116  at attachment point  132 . One or more actuators such as hydraulic cylinder  136  are pivotally attached to the implement carrier and the lift arm structure  114  to cause the implement carrier to rotate under power about an axis that extends through the attachment point  132  in an arc approximated by arrow  128  in response to operator input. In some embodiments, the one or more actuators pivotally attached to the implement carrier and the lift arm assembly are hydraulic cylinders capable of receiving pressurized hydraulic fluid from the power conversion system  106 . In these embodiments, the one or more hydraulic cylinders  136 , which are sometimes referred to as tilt cylinders, and are further representative examples of actuators  208  shown in  FIG. 2 . Although no implements are shown as being attached to the power machine  100  in  FIG. 1 , the implement carrier  130  is configured to accept and secure any one of a number of different implements (e.g., implement  212  shown in  FIG. 2 ) to the power machine  100  as may be desired to accomplish a particular work task. 
     In some applications, a simple bucket can be attached to the implement carrier  130  to accomplish a variety of tasks. However, many other attachments that include various actuators such as cylinders and motors, to name two examples, can also be attached to the implement carrier  130  to accomplish a variety of tasks. A partial list of the types of implements that can be attached to the implement carrier  130  includes augers, planers, graders, combination buckets, wheel saws, and the like. These are only a few examples of the many different types of implements that can be attached to power machine  100 . The power machine  100  provides a source, accessible at connection point  134 , of power and control signals that can be coupled to an implement to control various functions on such an implement, in response to operator inputs. In one embodiment, connection point  134  includes hydraulic couplers that are connectable to the implement  212  for providing power signals in the form of pressurized fluid provided by the power conversion system  106  for use by an implement that is operably coupled to the power machine  100 . Alternatively or in addition, connection point  134  includes electrical connectors that can provide power signals and control signals to an implement to control and enable actuators of the type described above to control operation of functional components on an implement. Actuation devices  210  located on an implement are controllable using control valve assembly  204  of power system  106 . 
     Power machine  100  also illustratively includes a cab  140  that is supported by the frame  102  and defines, at least in part, an operator compartment  142 . Operator compartment  142  typically includes an operator seat (not shown in  FIG. 1 ) and operator input devices  202  (shown schematically in  FIG. 2 ) and display devices accessible and viewable from a sitting position in the seat. When an operator is seated properly within the operator compartment  142 , the operator can manipulate operator input devices  202  to control such functions as driving the power machine  100 , raising and lowering the lift arm structure  114 , rotating the implement carrier  130  about the lift arm structure  114  and make power and control signals available to implement  212  via the sources available at connection point  134 . 
     In some embodiments, an electronic controller  150  (shown in  FIGS. 1 and 2 ) is configured to receive input signals from at least some of the operator input devices  202  and provide control signals to the power conversion system  106  and to implements via connection point  134 . It should be appreciated that electronic controller  150  can be a single electronic control device with instructions stored in a memory device and a processor that reads and executes the instructions to receive input signals and provide output signals all contained within a single enclosure. Alternatively, the electronic controller  150  can be implemented as a plurality of electronic devices coupled on a network. The disclosed embodiments are not limited to any single implementation of an electronic control device or devices. The electronic device or devices such as electronic controller  150  are programmed and configured by the stored instructions to function and operate as described. 
     Referring now more particularly to  FIG. 2 , further features of power machine  100  are shown in block diagram form in accordance with exemplary embodiments. As shown, the one or more operator input devices  202  are operatively coupled to electronic controller  150  via a network  205  or other hard wired or wireless connection. The operator input devices  202  are manipulable by an operator to provide control signals to the electronic controller  150  via network  205  to communicate control intentions of the operator. The operator input devices  202  are to provide control signals for controlling some or all of the functions on the machine such as the speed and direction of travel, raising and lowering the lift arm structure  114 , rotating the implement carrier  130  relative to the lift arm structure, and providing power and control signals to an implement to name a few examples. Operator input devices  202  can take the form of joystick controllers, levers, foot pedals, switches, actuable devices on a hand grip, pressure sensitive electronic display panels, and the like. 
     In response to control signals generated by operator input devices  202 , electronic controller  150  controls operation of control valve assembly  204  and actuators  208 . In addition, electronic controller  150  can control actuators  210  on implement  212  or alternatively provide signals to an implement controller  214  that can, in turn, directly control one or more actuators  210  or provide control signals back to the electronic controller  150  to signal that control valve assembly  204  be actuated to provide hydraulic fluid to one or more of the actuators  210 . Control of actuators  208  and  210  is, in at least some respects, performed using electrical signals on control lines or network  207  to control spool valves of control valve assembly  204  to selectively direct the flow of hydraulic fluid from pump  206  to those actuators. Flow of hydraulic fluid to actuators  210  on implement  212  is through hydraulic lines connected to the implement at connection point  134 . Disclosed embodiments are described with reference to control of a control valve assembly  204  for selectively providing pressurized hydraulic fluid to actuators  208  on power machine  100 , which can include lift cylinders  120  and tilt cylinders  136 , and actuators  210  on implement  212  attached to implement carrier  130 . 
       FIG. 3  illustrates a simple block diagram of one embodiment of a series control valve assembly  300  of the type that might be employed as control valve assembly  204  in the power machine  100  discussed above. Embodiments discussed in more detail below show and describe an open center series control valve assembly, but some of the concepts discussed herein can be applied to other types of control valves and need not be limited to an open center series control valve. Generally, the series control valve assembly  300  receives pressurized hydraulic fluid from pump  206 , which draws fluid from a reservoir  304 , which may or may not be pressurized. The series control valve assembly  300  includes a plurality of valve elements  306 ,  308 , and  310  in a priority arrangement, i.e. valve element  306  receives pressurized fluid from the pump  206  first, and then fluid is provided next to valve element  308 , and then to valve element  310 . While three valve elements are shown, in alternative embodiments, an series control valve assembly can include a different number of valve elements. As shown, each of the valve elements  306 ,  308 , and  310  is connected to and controls an actuator  312 ,  314 , and  316  in a corresponding circuit. For the purposes of discussing the embodiments below, valve element  308  will be referred to as a first valve element, valve element  310  will be referred to as a second valve element, and valve element  306  will be referred to as a third valve element. As shown, the third valve element  306  has priority over both the first and second valve elements  308  and  310 . First valve element  308  likewise has priority over the second valve element  310 . After the pressurized fluid has passed through the control valve assembly  300 , it is returned from the control valve assembly  300  to the reservoir  304 . How oil passes through the control valve assembly  300  will be discussed in more detail below. 
     Referring now to  FIGS. 4-7 , series control valve assembly  300  is shown in more detail. Series control valve assembly  300  includes features that allow an upstream circuit that controls a machine function, such as the tilt function, to be controlled in either direction regardless of whether a high load exists on a downstream circuit, such as the implement circuit, that might otherwise prevent the upstream function from being actuated. The series control valve assembly  300  is described below with respect to the control of specific functions of a power machine, but it should be appreciated that concepts discussed below need not be incorporated only on the functions with which they are shown. More particularly, a bypass feature described below associated with a valve element that controls a tilt function can be incorporated on any spool or other applicable valve element to realize the advantages provided by such a feature. Series control valve assembly  300  is illustratively a spool valve assembly with three spools (although any number can be used). As illustrated, the third valve element  306  selectively provides hydraulic fluid to one or more lift arm actuators  312 , the first valve element  308  selectively provides hydraulic fluid to one or more tilt actuators  314  and the second valve element  310  selectively provides hydraulic fluid to an auxiliary hydraulic port  316 . Although other types of actuators may be employed, in the illustrated embodiment, the lift arm actuators  312  and tilt actuators  314  are hydraulic cylinders and will be described as such. In some embodiments, at least the first valve element  310  is a proportional spool that allows for metered flow as the spool moves from an unactuated position to a fully actuated position. By metering flow, partial actuation of a spool valve, in response to an operator input, for example, allows the operator to advantageously control the rate at which an actuator controlled by a proportional spool is operated. Thus, the rate at which a lift arm is raised or lowered or an implement carrier is rotated can be controlled. Any of the other valve elements in the series control valve assembly  300  can also be proportional spools. 
     In this example, third valve element  306  is a four-position lift spool, with position  322  being a float position in which each of a base end  330  and a rod end  332  of the one or more lift cylinders  312  ported to the reservoir  304  so that the lift arm is allowed to float while the power machine is traveling over terrain. Position  324  of the third valve element  306  is a commanded lowering position in which hydraulic fluid is ported to the rod ends  332  of the lift arm actuators  312  to lower the lift arm. Position  326  is a centered or unactuated position in which no command is provided to the lift cylinders  312 , which causes the lift cylinders to remain in their current position. Position  328  is a raising position in which hydraulic fluid is ported to the base end  330  of actuator  312  to raise the lift arm. 
     The first valve element  308  is illustratively a three-position tilt spool. A first position  342  is illustratively a roll back position in which hydraulic fluid is ported to the rod ends  352  of tilt actuators  314  to cause the implement carrier  130  and any attached implement to pivot, or roll back, toward the lift arm structure  114 . Position  344  is an centered or unactuated position in which no command is provided to the tilt cylinders  314 , which causes the lift cylinders to remain in their current position. Position  346  being a roll out position in which hydraulic fluid is ported to base end  354  of actuator  314 , which causes the implement carrier and any attached implement to pivot, or roll out, away from the lift arm structure  114 . The second valve element  310  is also a three-position spool, with position  362  being a first actuated position configured to providing hydraulic fluid to a first line of the auxiliary port  134 , position  364  being an unactuated centered position, and position  366  being a second actuated position for providing hydraulic fluid to a second line of auxiliary port  134 . Check valves  311 ,  331  and  361  precede inlets to third, second, and third valve elements  306 ,  308  and  310 , respectively, to prevent the flow of hydraulic fluid back through the spools when each of the spools is being actuated. 
       FIG. 4  illustrates each of the first  308 , second  310 , and third  306  valve elements in a centered or unactuated position. Hydraulic fluid is allowed to flow through each of the first, second, and third valve elements and back to reservoir  304 . Referring now for the moment more specifically to  FIG. 5 , shown is control valve assembly  300  with lift spool  306  shifted to the raising position  328  to provide hydraulic fluid to the lift arm actuators  312  to raise the lift arm. In this position, hydraulic fluid from pump  206  passes through check valve  311  and into base end  330  of actuators  312 , thus extending the actuator. The fluid path is illustrated with arrows in  FIG. 5 . As discussed above, at least the first element is a proportional spool. In an open center valve assembly, shifting the spools in either direction toward an actuated position may allow some fluid to continue to flow through the unactuated position toward downstream circuits unless and until the spool is fully shifted to the actuated position.  FIG. 5 , as well as  FIGS. 6 and 7  illustrate the spools being shifted into a fully actuated position and arrows showing fluid flow do not indicate that any fluid flow is provided downstream via the unactuated positions, even though when the spools are not fully actuated, some fluid flow can be provided through the unactuated positions downstream. Hydraulic fluid forced from rod end  332  of actuator  312  is routed back through third valve element  306  and directed toward first valve element  308 . This fluid path is also illustrated with arrows. When the lift arm actuators  312  are fully extended, porting fluid to the base end  330  of the cylinder will not force any more fluid out of the lift cylinders and into the downstream circuit. Furthermore, continuing to provide fluid to the base end of the lift cylinders could result in an extremely high pressure buildup on the base end. A relief valve  380  coupling the outlet of the relief valve to reservoir relieves high pressure port fluid away from the base end of the lift cylinder in this instance out of the control valve assembly  300  and eventually to the inlet of the reservoir  304 . 
     In exemplary embodiments, each of valve elements  306 ,  308  and  310  of control valve assembly  300  has a port relief/anti-cavitation valve for relieving pressures across the corresponding actuator when the spool is in a centered position and/or the corresponding actuator is subject to cavitation. As such, relief valve  390  is shown coupled between base ends  330  of lift actuators  312  and reservoir  304 . Relief valve  400  is shown coupled between base ends  354  of tilt actuators  314  and reservoir  304 . Relief valve  420  is shown coupled between rod ends  352  of tilt actuators  314  and reservoir  304 . Finally, relief valve  410  is shown coupled between a first auxiliary port and reservoir  304 . 
     As mentioned, relief valve  380  acts to relieve pressure in the system when an actuator is deadheaded by dumping hydraulic fluid to reservoir  304  when a relief pressure of the valve  380  is reached or exceeded. In conventional designs, the use of downstream functions is severely compromised or effectively eliminated when fluid is run over the relief valve  380 . Also, under conventional designs, when downstream pressures are high (such as near relief), functionality of upstream circuits are limited or compromised. Due to cylinder differential areas in upstream circuits, upstream circuits can be activated in one direction with high downstream pressure. That is, the lower cylinder area end (i.e. the rod end) can be relieved to reservoir over port relief valves so that a cylinder can be extended. However, it is not the case that an upstream cylinder can be retracted in such a situation in conventional designs. In fact, in many conventional open center valve configurations, the pressure conditions present when a downstream circuit is at high or even at relief pressure is that any attempt to retract an upstream cylinder will result in no retraction or even slight extension. In certain implement operating conditions, the ability to retract the tilt cylinder  314  (i.e., roll back the implement carrier) is desirable. While this is not possible under some conventional control valve designs, disclosed embodiments include features which allow the tilt cylinder to be retracted under a broader range of conditions. 
     Features of control valve assembly  300  that overcome the above-described limitations of some conventional control valve designs are now discussed with reference to  FIGS. 6 and 7 .  FIG. 6  illustrates first valve element  308  in the form of a tilt spool moved to the second actuated position  342  in which hydraulic fluid is ported to the rod end  352  of actuator  314  through a path illustrated with arrows, to roll back the implement carrier  130  and any attached implement  212 .  FIG. 7  illustrates first valve element  308  in a first actuated position  346  in which hydraulic fluid is ported to base end  354  of actuator  314  to roll out the implement carrier and any attached implement. 
     As compared to conventional designs, the tilt circuit is modified such that when the first valve element  308  is shifted to the second actuated position  342  as shown in  FIG. 6 , the base ends  354  of the tilt cylinders  314  are ported (drained) to reservoir  304  through a fluid path  370  within the first valve element  308  and a drain line  372 , as opposed to being connected to the inlet of the second valve element  310  as would be conventionally done. This fluid path  370  and drain line  372  can be considered to be parallel with the downstream function, from a perspective of the inlet to first valve element  308 , in that both the second valve element  310  and the drain line  372  are connected to the outlet side of the first valve element  308 . The drain line  372  is not actually in parallel with the downstream function from a perspective of the outlet of first valve element  308 , though, as they do not share a common node at the outlet side of the first valve element  308 . Rather, the drain line  372  is an alternative path such that the implement circuit is bypassed with no hydraulic fluid being provided to the inlet of the second valve element  310  via the second actuated position  342 , although if the spool is not fully actuated into the second actuated position  342 , some fluid may be provided to the inlet of the second valve element  310  via the unactuated position of the first valve element  308 . When the first valve element  308  is in the first actuated position  346  to port hydraulic fluid to the base ends  354  of the tilt cylinders  314  so as to extend the cylinder, hydraulic fluid is provided to the inlet of the second valve element  310  and not to the drain  372  as shown in  FIG. 7 . This arrangement allows the first work function, in this embodiment, the tilt function, to be controlled in either direction whether or not a high load exists on the downstream circuit, in this embodiment, the implement circuit. This also allows the implement circuit to be controlled, except when the tilt cylinder is being retracted at full spool stroke. This arrangement advantageously allows for control of the actuator coupled to the first valve element in either direction, regardless of whether there is a high pressure load downstream of the first valve element. In addition, in embodiments where proportional valves are employed, any actuator in communication with the second valve element can still be controlled if the first valve element is not in one of the fully actuated positions. In the embodiment described above, if a tilt cylinder is slowly retracted from a position when an implement is operating a cutting function, such as a planer, the implement is still actuated when the tilt cylinder is retracted. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. For example, in various embodiments, different types of power machines can be configured to implement the control valve assembly and power conversion systems and methods. Further, while particular control valve assembly configurations and work functions are illustrated, other valve configurations and types of work functions can also be used. Other examples of modifications of the disclosed concepts are also possible, without departing from the scope of the disclosed concepts.