Patent Application
20140373519
The present invention relates generally to hydraulic systems, and more particularly to an electro-hydraulic system utilizing a directional control valve and a discharge valve configured to provide a float function for a hydraulic cylinder.
In the case of performing work using an excavator or similar vehicle, the primary purpose of a float valve is to return hydraulic fluid to a hydraulic tank by making flow paths of the bore chamber side and rod chamber side of boom cylinders communicate with each other during a boom-down operation. In the prior art, the float function is usually achieved by a directional control valve with a special spool which has a “4th position” in which the pump supply is blocked and both cylinder ports are connected to the reservoir.
Described herein is a solution for achieving a float function for a hydraulic actuator taking advantage of advantages associated with electric displacement controlled pumps (use of such pumps in hydraulic systems gives advantages inn response, stability, efficiency, and productivity). Thus, both sides of a hydraulic cylinder may be connected to tank (cylinder function is “floating”), while the limited amount of flow delivered by the pump is discharged to tank through a separate discharge valve. Therefore, use of a four-position valve, which is more complicated than is necessary, may be avoided. The introduction of an electronically-controlled variable-capacity pump allows for a simpler valve assembly and more efficient pump operation during a float function.
According to one aspect of the invention, a method of controlling a float function of a cylinder having a first side and a second side includes connecting a second side of the cylinder to a reservoir; connecting the first side of the cylinder to an output of a pump and to the reservoir; and supplying an amount of flow from a pump less than an amount supplied by the pump under loaded conditions.
Optionally, connecting the first side of the cylinder to the reservoir includes opening a discharge valve between the first side of the cylinder and the reservoir.
Optionally, connecting the second side of the cylinder to the reservoir and connecting the first side of the cylinder to the output of the pump includes actuating a directional control valve connected to the first side of the cylinder, to the second side of the cylinder, to the reservoir, and to the output of the pump.
Optionally, supplying an amount of flow from the pump less than an amount supplied by the pump under loaded conditions includes reducing the capacity of a variable capacity pump.
Optionally, the variable capacity pump is an electric displacement control pump.
According to another aspect of the invention, a hydraulic valve assembly includes a directional control valve having a pump port, a reservoir port, a first cylinder port, and a second cylinder port; and a discharge valve having a first position defining a closed fluid path and a second position defining an open fluid path between a first cylinder port of the discharge valve and a reservoir port of the discharge valve. The directional control valve has a first position defining an open fluid path between the pump port and the second cylinder port, and an open fluid path between the first cylinder port and the reservoir port. The directional control valve has a second position defining an open fluid path between the pump port and the first cylinder port and an open fluid path between the second cylinder port and the reservoir port.
Optionally, the hydraulic valve assembly includes a ride control valve with a first position defining a closed fluid path and a second position defining an open fluid path from a cylinder port of the ride control valve to an accumulator port of the ride control valve.
Optionally, the hydraulic valve assembly includes an electric displacement control pump fluidly coupled to the pump port.
Optionally, the hydraulic valve assembly includes an electronic control unit configured to control the directional control valve to move into the second position and to control the discharge valve to move into the second position to enable a float function of the hydraulic valve assembly.
Optionally, the electronic control unit, when enabling the float function of the hydraulic valve assembly, is configured to control a variable capacity pump to supply an amount of flow less than an amount supplied by the pump under loaded conditions.
Optionally, the directional control valve is a three-position valve.
According to another aspect of the invention, a system includes a reservoir; a pressure cylinder; a variable capacity pump; a directional control valve having: a first position connecting the pump to a first side of the pressure cylinder and connecting a second side of the pressure cylinder to the reservoir, a second position connecting the pump to a second side of the pressure cylinder and connecting a first side of the pressure cylinder to the reservoir, and a third position blocking fluid flow to and from the pressure cylinder; a discharge valve that when opened, when the directional control valve is in the second position, connects the pump and the second side of the pressure cylinder to the reservoir; and an electronic control unit configured to control the position of the directional control valve, the activation of the discharge valve, and the displacement of the pump.
Optionally, the system includes an accumulator connected to the first side of the pressure cylinder and a ride control valve positioned between the accumulator and the first side of the pressure cylinder, wherein the electronic control unit is configured to open the ride control valve when the directional control valve is in the third position.
Optionally, the directional control valve is limited to three operating positions.
Optionally, the variable capacity pump includes electric displacement control.
Optionally, the position of the directional control valve, the activation of the discharge valve, and the displacement of the pump are controlled by a plurality of solenoids that are electrically activated by the electronic control unit.
The foregoing and other features of the invention are hereinafter described in greater detail with reference to the accompanying drawings.
Referring to
The pump 20 may be a variable-capacity hydraulic pump in which the displacement is electrically controlled (e.g., using solenoids) by the electric displacement control 45.
The directional control valve 30 may be, for example, proportional and solenoid operated (the position of the valve spool is proportional to an input current or voltage). The directional control valve 30 may be connected to the outlet of the pump 20, the reservoir 15, and first and second ports (bore-side and rod-side) of the hydraulic cylinder 25. The directional control valve 30 may have a pump port for connecting to the pump 20, a reservoir port for connecting to the reservoir 15, a first (for example, a rod-side) cylinder port for connecting to the first (for example, rod) side 25B of the cylinder 25, and a second (for example, bore-side) cylinder port for connecting to a second (for example, bore) side 25A of the cylinder 25. (The sides of the cylinder may be switched depending on the specific configuration of the exemplary system.) The exemplary directional control valve 30 is a three position valve.
The directional control valve 30 may have a first position defining an open fluid path between the pump port and the bore-side cylinder port, and an open fluid path between the rod-side cylinder port and the reservoir port.
The directional control valve 30 may also have a second position defining an open fluid path between the pump port and the rod-side cylinder port and an open fluid path between the bore-side cylinder port and the reservoir port.
Further, the directional control valve may also have a third position (for example, the neutral position) that defines a closed fluid path, preventing fluid from flowing to or from any of the ports of the directional control valve.
The discharge valve 35 may be solenoid controlled and is shown as a two position valve (open/close) arranged between the rod side of the hydraulic cylinder 25 and the reservoir 15. The first position defines a closed fluid path and the second position defines an open fluid path between a rod-side cylinder port of the discharge valve and a reservoir port of the discharge valve.
The ECU 40 may receive input signals from, for example, user controls, such as one or more joysticks. Alternatively or additionally, the ECU 40 may include autonomous programming which generates command signals without user input. The ECU 40 may, based on the input and/or generated command signals, provide output signals to control solenoids of the discharge valve 35, directional control valve 30, electric displacement control 45, and any other connected devices.
Referring now to
System 100 includes an additional feature beyond the float function (as explained above): a ride control function. The system 100 further includes a hydraulic accumulator 150 connected to the bore side 125A of the cylinder 125, a ride control valve 155 positioned between the bore side 125A of the cylinder and the accumulator 150. The ride control valve 155 has a first position defining a closed fluid path and a second position defining an open fluid path from a bore-side cylinder port of the ride control valve 155 to an accumulator port of the ride control valve 155. The discharge valve 135, as described above, is positioned between the rod side 125B of the cylinder 125 and the reservoir 115. The ride control function is engaged by leaving the directional valve 130 in the neutral (closed) position and opening the ride control valve 155 and the discharge valve 135.
At block 210, the bore side 25A, 125A of the cylinder is connected to a reservoir 15, 115. Block 210 may specifically include actuating a directional control valve connected between the bore side of the cylinder and the reservoir.
At block 220, the rod side of the cylinder is connected to an output of a pump and to the reservoir. Block 220 may specifically include opening a discharge valve between the rod side of the cylinder and the reservoir, and opening a directional control valve between the rod side of the cylinder and the pump.
At block 230, an amount of flow from a pump less than an amount supplied by the pump under loaded conditions is supplied. Block 230 may specifically include reducing the capacity of a variable capacity pump. The variable capacity pump may be an electric displacement control pump.
Although the illustrated method illustrates a specific order of executing functional logic blocks, the order of execution of the blocks may be changed relative to the order shown and/or may be implemented in a state-driven or an object-oriented manner. Also, two or more blocks shown in succession may be executed concurrently or with partial concurrence. Certain blocks also may be omitted. Further, although certain blocks have been described as being executed or performed by specific functional components of the system, these blocks need not be performed by these components or may be performed by one or more other components. It is understood that all such variations are within the scope of the present invention.
Any of the blocks of the method 200 may be embodied as a set of executable instructions (e.g., referred to in the art as code, programs, or software) that are respectively resident in and executed by the ECU 40, 140 and/or the Electric Displacement Control 45, 145. The method 200 may be one or more programs that are stored on respective non-transitory computer readable mediums, such as one or more memory devices (e.g., an electronic memory, a magnetic memory, or an optical memory).
The exemplary embodiments described herein enable the float function (as illustrated in
Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.
This application claims the benefit of U.S. Provisional Application No. 61/583,356 filed Jan. 5, 2012, which is hereby incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2013/020513 | 1/7/2013 | WO | 00 | 7/3/2014 |
| Number | Date | Country | |
|---|---|---|---|
| 61583356 | Jan 2012 | US |
