Hydraulic system
By controlling the valve configuration of the hydraulic system, the problem of rapid movement and return of large-cylinder volume actuators has been solved, resulting in faster operating cycles and lower power consumption, making it suitable for work tools such as shearing machines.
Patent Information
- Application Number
- CN202480032311.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-05-26
- Filing Date
- 2024-05-21
- Publication Date
- 2025-12-09
AI Technical Summary
Existing hydraulic systems, with actuators having relatively large cylinder volumes, struggle to rapidly move large amounts of hydraulic fluid in a short time, leading to increased back pressure, delayed actuator movement, and increased power consumption of the hydraulic pump. Simultaneously, the operating cycle of the working tool is prolonged when it returns to its initial position.
By configuring the controller, the first and second directional control valves of the hydraulic system are opened, and hydraulic fluid is pumped to the actuator while the pressure reducing valve is closed to move to the second position; upon return, the pressure reducing valve and control valve are opened to allow hydraulic fluid to return to the reservoir, increasing the flow rate of the return path.
It effectively reduces back pressure in the hydraulic system, allowing the actuator to return to its initial position more quickly, shortening the operating cycle and improving fuel efficiency.
Smart Images
Figure CN121100232A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a hydraulic system. In particular, the present disclosure relates to a hydraulic system for a work machine. BACKGROUND
[0002] A work machine can be used to operate one or more work tools. A work tool can be operated by means of one or more actuators, such as hydraulic actuators.
[0003] A hydraulic actuator is a device that provides mechanical movement in response to a flow of hydraulic fluid into / out of the hydraulic actuator. A hydraulic fluid pump can be provided so as to pump hydraulic fluid into and out of the hydraulic actuator.
[0004] Against this background, it is an object of the present disclosure to provide an improved or at least commercially useful alternative controller for a hydraulic system, a hydraulic system and a method for controlling a hydraulic system. SUMMARY
[0005] According to a first aspect of the present disclosure, there is provided a controller configured to control a hydraulic system for a work tool. The controller is configured to cause an actuator of the hydraulic system to move from a first position to a second position, wherein:
[0006] the controller causes a first directional control valve and a second directional control valve of the hydraulic system to open, such that hydraulic fluid is pumped from a hydraulic fluid pump to the actuator to cause the actuator to move to the second position, and
[0007] the controller causes a pressure relief valve of the hydraulic system to close, such that hydraulic fluid does not flow through the pressure relief valve; and
[0008] the controller is configured to cause the actuator to move from the second position to the first position, wherein:
[0009] the controller causes the first directional control valve and the second directional control valve to open, such that hydraulic fluid is pumped from the hydraulic fluid pump to the actuator to cause the actuator to move to the first position; and
[0010] the controller causes the pressure relief valve to open to allow hydraulic fluid to return from the actuator to a hydraulic fluid reservoir.
[0011] According to a first aspect of the present disclosure, there is provided a controller for a hydraulic system. The controller can be configured to control an actuator for a work tool in order to operate the work tool. In some embodiments, the work tool can be a shear (i.e. a hydraulic shear). The actuator can move the shear, for example, from a first position (e.g. an open position) to a second position (e.g. a closed position), and vice versa. Advantageously, the controller can cause the hydraulic system to open an additional valve when moving the actuator from the second position (closed position) to the first position (open position) to allow hydraulic fluid to return to the hydraulic fluid reservoir. Such a configuration allows a relatively high flow rate of hydraulic fluid to be provided on the return path of the hydraulic system when moving from the second position (closed position) to the first position (open position). As such, the work tool can be able to move from the second position to the first position at a relatively fast rate. Therefore, the work tool can return to the first position at a faster rate, thereby reducing the duration of the operating cycle of the work tool.
[0012] Embodiments of the present disclosure can be particularly suitable for work tools having actuators with relatively large cylinder volumes. For example, in some embodiments, the actuator can have a cylinder volume of at least 60 litres, 80 litres, 100 litres, 120 litres or 140 litres. Where the actuator has a relatively large cylinder volume, attempting to move a relatively large volume of hydraulic fluid in a short duration can create significant back pressure in the hydraulic system. The back pressure can effectively delay movement of the actuator, thereby increasing the cycle time of the actuator. It will also be appreciated that the back pressure caused by the flow of hydraulic fluid causes the hydraulic pump to work harder than would otherwise be necessary. By opening an additional flow path for the hydraulic fluid, the controller of the first aspect effectively reduces the back pressure in the hydraulic system, thereby allowing the actuator to return to the first position more quickly and with lower power consumption. Therefore, the controller of the first aspect can improve the operating cycle of the work tool and can also improve the fuel efficiency associated with the work tool.
[0013] In some embodiments, the work tool to be controlled can be a shear or other work tool in which the majority of the mechanical work performed by the work tool in an operating cycle is due to movement of the actuator from the first position to the second position. As such, when moving from the second position to the first position, the work tool performs very little (if any) effective work. Therefore, in some embodiments, the flow rate of hydraulic fluid through the hydraulic system can limit the rate at which the work tool can return to the first position in a new operating cycle. According to the first aspect, the controller can cause the hydraulic system to effectively increase the flow rate of hydraulic fluid on the return path to allow the actuator to return to the first position relatively quickly.
[0014] Importantly, the pressure relief valve can be closed during the primary work operation of the hydraulic system (first position to second position) as it is undesirable to allow high flow rates on the return path while the actuator is performing mechanical work.
[0015] According to a second aspect of the disclosure, there is provided a hydraulic system for a work tool. The hydraulic system comprises: an actuator for the work tool; a first directional control valve configured to control hydraulic fluid flow to and from the actuator; a second directional control valve configured to control hydraulic fluid flow to and from the actuator; a hydraulic pump configured to pump hydraulic fluid to the actuator via the first directional control valve and the second directional control valve; a hydraulic fluid reservoir connected to the first directional control valve and the second directional control valve and configured to receive hydraulic fluid flowing from the actuator via the first directional control valve and the second directional control valve; a pressure relief valve configured to control hydraulic fluid flow from the actuator to the hydraulic fluid reservoir, the pressure relief valve being connected to the hydraulic fluid reservoir and configured to receive hydraulic fluid from the work tool; and the controller of the first aspect of the disclosure.
[0016] According to a third aspect of the disclosure, there is provided a method of controlling a hydraulic system for a work tool. The method comprises:
[0017] moving an actuator of the work tool from a first position to a second position, wherein:
[0018] a first directional control valve and a second directional control valve of the hydraulic system are opened such that hydraulic fluid is pumped from a hydraulic fluid pump to the actuator to move the actuator to the second position, and
[0019] a pressure relief valve of the hydraulic system is closed such that hydraulic fluid does not flow through the pressure relief valve; and
[0020] moving the actuator from the second position to the first position, wherein:
[0021] the first directional control valve and the second directional control valve are opened such that hydraulic fluid is pumped to the actuator to move the actuator to the first position; and
[0022] the pressure relief valve is opened to allow hydraulic fluid to return from the actuator to a hydraulic fluid reservoir.
[0023] It will be appreciated that the second and third aspects can include any of the optional features and associated advantages of the first aspect of the disclosure. In particular, the controller of the first aspect and / or the hydraulic system of the second aspect can be used to perform the method of the third aspect. BRIEF DESCRIPTION OF DRAWINGS
[0024] Embodiments of the disclosure will now be described with reference to the following non-limiting drawings, in which:
[0025] - Figure 1 is a schematic diagram of a hydraulic system according to an embodiment of the disclosure;
[0026] - Figure 2 is a schematic diagram of the hydraulic system of Figure 1 as it moves from a first position to a second position;
[0027] - Figure 3 is a schematic diagram of the hydraulic system of Figure 1 as it moves from the second position to the first position;
[0028] - Figure 4 is a graph showing the change in hydraulic area of some valves of the hydraulic system in response to a joystick command to move the actuator from the second position to the first position;
[0029] - Figure 5 is a schematic diagram of a hydraulic system of another embodiment of the disclosure as it moves from a first position to a second position;
[0030] - Figure 6 is a schematic diagram of a hydraulic system of another embodiment of the disclosure as it moves from the second position to the first position;
[0031] - Figure 7 is a graph showing the change in hydraulic area of some valves of the hydraulic system in response to a joystick command to move the actuator from the second position to the first position;
[0032] - Figure 8 is a schematic diagram of a hydraulic system according to another embodiment of the disclosure, in which the actuator is moving from a first position to a second position;
[0033] - Figure 9 is a schematic diagram of a hydraulic system according to another embodiment of the disclosure, in which the actuator is moving from a second position to a first position;
[0034] - Figure 10 is a block diagram of a controller and hydraulic system according to an embodiment of the disclosure; and
[0035] - Figure 11 is a block diagram of a method according to an embodiment of the disclosure. DETAILED DESCRIPTION
[0036] According to an embodiment of the disclosure, there is provided a hydraulic system 1. A schematic diagram of the hydraulic system 1 is shown in Figure 1. As shown in Figure 1, the hydraulic system 1 comprises a first hydraulic fluid pump 3, a second hydraulic fluid pump 5, a first directional control valve 10, a second directional control valve 20, an actuator 30, a pressure relief valve 40 and a hydraulic reservoir 50.
[0037] The first hydraulic fluid pump 3 can be configured to pump hydraulic fluid from a hydraulic fluid reservoir (not shown in FIG. 1) through the hydraulic system 1. In the embodiment of FIG. 1, the first hydraulic fluid pump 3 is configured to pump hydraulic fluid to the first directional control valve 10 (Aux 1). In other embodiments, the first hydraulic fluid pump 3 can be configured to pump hydraulic fluid to multiple valves and / or actuators 30. The first hydraulic fluid pump 3 can be any pump suitable for pumping hydraulic fluid.
[0038] In some embodiments, the hydraulic system 1 can include multiple hydraulic fluid pumps. For example, in the embodiment of FIG. 1, a second hydraulic fluid pump 5 is provided. The second hydraulic fluid pump 5 can be provided in a similar manner to the first hydraulic fluid pump 5. In the embodiment of FIG. 1, the second hydraulic fluid pump 5 is configured to pump hydraulic fluid to the second directional control valve 20 (Aux 2). By providing two hydraulic fluid pumps 3, 5, the hydraulic system can pump relatively high flow rates of hydraulic fluid to the actuators 30.
[0039] The first directional control valve 10 is configured to control the flow of hydraulic fluid to and from the actuators 30. As such, the first directional control valve can be configured to allow hydraulic fluid flow to the actuators 30 and also to allow hydraulic fluid to return from the actuators 30, or the first directional control valve 10 can be configured to block hydraulic fluid flow to / from the actuators 30. In the embodiment of FIG. 1, the first directional control valve 10 can be a 4-port, 3-position directional control valve.
[0040] A 4-port, 3-position directional control valve can include an inlet port 11, 21 configured to receive hydraulic fluid from a hydraulic fluid pump; a return port (not shown in FIG. 1) configured to output hydraulic fluid to a hydraulic fluid reservoir; a first actuator outlet 13, 23; and a second actuator outlet 14, 24. The first and second actuator outlets 13, 23, 14, 24 can be connected to either side of a cylinder of an actuator 30, for example, to drive the actuator 30. The 3 positions of the directional control valve 10, 20 can include a closed position in which all ports are blocked. A first operating position can allow hydraulic fluid to flow between the inlet port 11 and the first actuator outlet, and allow hydraulic fluid to flow between the second actuator outlet and the return port. A second operating position can allow hydraulic fluid to flow between the inlet port and the second actuator outlet, and allow hydraulic fluid to flow between the first actuator outlet and the return port. Schematic diagrams of such directional control valves are shown in FIGS. 8 and 9 of the present disclosure, discussed in more detail below.
[0041] The directional control valves 10, 20 of the present disclosure can be controlled by pilot pressure, or directly by, for example, solenoids or any other suitable form of electromechanical interface known to those skilled in the art between a controller and the directional control valves 10, 20.
[0042] In some embodiments, each directional control valve 10, 20, 30 can be controlled by a pair of solenoids in combination with a biasing spring. The biasing spring is configured to hold each directional control valve in a closed position when each solenoid is inactive. A first solenoid (HE) can be configured to move the directional control valve such that the inlet port 11, 21 is connected to the first actuator outlet 13, 23. A second solenoid can be configured to move the directional control valve such that the inlet port is connected to the second actuator outlet 14, 24. Each solenoid can be controlled by a suitable signal from a controller 80 (see Figure 10 described further below).
[0043] Although the embodiment of Figure 1 utilises a 4-port, 3-position directional control valve, it will be appreciated that other forms of directional control valve suitable for controlling the flow of hydraulic fluid to and / or from the actuator 30 can be utilised in embodiments of the present disclosure.
[0044] The second directional control valve 20 shown in Figure 1 can be provided in a similar manner to the first directional control valve 10. Thus, the actuator 30 can be supplied with hydraulic fluid from both the first directional control valve 10 and the second directional control valve 20.
[0045] The pressure relief valve 40 is configured to control the flow of hydraulic fluid from the actuator 30 to a hydraulic fluid reservoir. The pressure relief valve 40 can be connected to the hydraulic fluid reservoir and configured to receive hydraulic fluid from the actuator 30. In the embodiment of Figure 1, the pressure relief valve 40 is connected between the hydraulic fluid reservoir and the first port 33 of the actuator. Thus, when the actuator is moving from the first position to the second position (see, for example, Figure 2), the pressure relief valve 40 is connected to the high pressure side of the actuator 30, where the pressure relief valve 40 is configured to close. When the actuator is moving from the second position to the first position, the pressure relief valve 40 is connected to the lower pressure, return side of the actuator (see, for example, Figure 3).
[0046] In some embodiments, the pressure relief valve 40 can be configured to provide a pressure relief function. In some embodiments, the pressure relief function can be controlled by the controller. Thus, the pressure relief valve 40 can be controlled by the controller to provide a pressure relief above a pressure threshold. In some embodiments, the pressure relief threshold can be set by the controller. For example, the pressure threshold can be a value no greater than 40 MPa. In some embodiments, the pressure relief valve 40 can operate in a pressure relief mode (i.e. where the pressure relief threshold is active) or an open mode (where the pressure relief valve 40 is open (i.e. the pressure relief threshold is effectively 0 MPa)).
[0047] The actuator 30 can be any actuator 30 suitable for use with the hydraulic system 1. The actuator 30 shown in FIG. 1 can be a hydraulic linear actuator. The actuator 30 can be provided as part of a work machine. In particular, the actuator 30 can be configured to provide mechanical power to a work tool of the work machine. In particular, the work tool can be a shear (not shown in FIG. 1) or other work tool in which a majority of the mechanical work performed by the work tool during an operating cycle is due to the actuator moving from a first position to a second position. Thus, when moving from the second position to the first position, the work tool performs very little, if any, effective work. Accordingly, it can be desirable for the actuator to move relatively quickly from the second position to the first position in order to reduce the operating cycle time of the actuator / work tool. By way of example, the following description will refer to a work tool such as a shear, in which the shear is in an open position when the actuator 30 is in the first position. The shear is in a closed position when the actuator 30 is in the second position. It will be appreciated that embodiments of the present disclosure are applicable to work tools, including work tools having an open position and a closed position.
[0048] In the embodiment of FIG. 1, a cylinder 31 of the actuator 30 is shown schematically. A piston 32 is located in the cylinder 31. The cylinder 31 includes a first port (HE port) 33 and a second port (RE port) 34 on opposite sides of the piston 32. The first port 33 and the second port 34 can be connected to first and second actuator outlets, respectively. Accordingly, the piston 32 (and thus the actuator 30) can be driven between the first position (i.e., the open position of the shear) and the second position (i.e., the closed position of the shear) by controlling the flow of hydraulic fluid to the first and second ports 33, 34 of the actuator 30.
[0049] For example, FIG. 2 shows the hydraulic system 1 in a configuration in which the actuator 30 is moving from the first position (open position of the shear) to the second position (closed position of the work tool). As shown in FIG. 2, the first directional control valve 10 and the second directional control valve 20 are each configured to allow hydraulic fluid to flow from the first hydraulic fluid pump 3 and the second hydraulic fluid pump 5 to the first port 33 of the actuator, thereby causing the piston 32 of the actuator to move toward the second position. Hydraulic fluid also flows from the second port 34 of the cylinder 31 out to the second outlets 14, 24 of the first and second directional control valves 10, 20 and on to the hydraulic fluid reservoir.
[0050] As shown in FIG. 2, the pressure relief valve 40 is disposed on the high pressure side of the hydraulic system when the actuator is moved from the first position to the second position. Thus, in the case of the pressure relief valve 40, during normal operation of the hydraulic system, no hydraulic fluid can flow through the pressure relief valve 40. In the case where the pressure relief valve 40 is configured to provide a pressure relief function, the pressure relief valve 40 can prevent over-pressurization from occurring in the hydraulic system 1 (i.e., the pressure relief valve 40 will prevent the pressure on the high pressure side of the hydraulic circuit from exceeding a pressure threshold). Thus, for the configuration of the hydraulic system 1 shown in FIG. 2, it should be appreciated that, in normal use (i.e., without over-pressurization), the return path for hydraulic fluid to the hydraulic fluid reservoir is provided solely by the first directional control valve 10 and the second directional control valve 20.
[0051] FIG. 3 shows the hydraulic system 1 in a configuration where the actuator 30 is being moved from the first position (open position of the work tool) to the second position (closed position of the work tool).
[0052] As shown in FIG. 3, the first directional control valve 10 and the second directional control valve 20 are each configured to allow hydraulic fluid to flow from the first hydraulic fluid pump 3 and the second hydraulic fluid pump 5 to the second port 34 of the actuator 30, thereby causing the piston 32 of the actuator 30 to move toward the first position. Hydraulic fluid also flows out of the first port 33 of the cylinder 31 to the first outlets 13, 23 of the first directional control valve 10 and the second directional control valve 20, and continues to the hydraulic fluid reservoir. When the controller directs the pressure relief valve 40 to allow hydraulic fluid flow to the hydraulic fluid reservoir, hydraulic fluid also flows out of the first port 33 and to the hydraulic fluid reservoir via the pressure relief valve 40. For example, the controller can set the pressure threshold to about 0 MPa to allow hydraulic fluid to flow through the pressure relief valve 40 without any intentional impediment. Thus, by opening the pressure relief valve 40, the hydraulic system 1 (relative to the configuration of FIG. 2) increases the ability of hydraulic fluid flow on the low pressure, return side of the actuator 30. In embodiments where the actuator does not perform a significant amount of work when moving from the second position to the first position, such as in the case of the actuator opening a shear or similar work tool, the speed of movement is typically limited by the flow rate of hydraulic fluid out of the cylinder 31. Thus, by increasing the available path on the return side of the hydraulic system when moving from the second position to the first position, the rate of hydraulic fluid flow can be increased, thereby allowing for faster movement.
[0053] For example, in some embodiments, the controller is configured to control the hydraulic system such that the actuator moves from the second position to the first position in a duration of no more than 30 seconds, 25 seconds, 20 seconds, 15 seconds, or 10 seconds. In the embodiment of FIG. 1, where the actuator 30 drives a shear, the controller can control the hydraulic system such that the actuator 30 for the shear moves from the first position (open) to the second position (closed) in about 12-14 seconds. With the pressure relief valve 40 open, it can take about 8-9 seconds to move from the second position (closed) to the first position (open). Thus, in some embodiments, the use of the pressure relief valve 40 to increase the flow capacity on the return circuit can reduce the time to move the actuator from the second position to the first position relative to the time taken to move from the first position to the second position by about 30% to 40%.
[0054] In some embodiments, the controller can be configured to move the first directional control valve 10 and the second directional control valve 20, as well as the pressure relief valve 40, at different rates in order to control the movement of the actuator 30. For example, in some embodiments where the controller receives a command (e.g., a joystick command) to move the actuator from the second position to the first position, the controller can gradually open the first directional control valve 10 and the second directional control valve 20 as the actuator moves from the first position to the second position. For example, the controller can control the first directional control valve 10 and the second directional control valve 20 such that the open area of each of the directional control valves 10, 20 increases as the actuator 30 moves. Such control of the actuator 30 is well known to those skilled in the art. In contrast, the controller can be configured to control the pressure relief valve to be fully open at the start of the movement from the second position to the first position. By way of example, FIG. 4 shows a plot of the open valve area of each of the first control valve and the second control valve (Aux 1, Aux 2) in response to a change in a joystick command to move the actuator from point A (the second position) to point B (the first position). FIG. 4 also shows a plot of the open valve area of the pressure relief valve in response to the joystick command as the actuator 30 moves from the second position to the first position.
[0055] In some embodiments of the present disclosure, it can be desirable to further increase the flow capacity on the return circuit. In such embodiments, one or more additional directional control valves can be utilized to provide additional capacity on the return circuit. Thus, in some embodiments, the hydraulic system 1 can further include a third directional control valve 50 configured to control the flow of hydraulic fluid to and from the actuator 30. The third directional control valve can be a 4-port, 3-position directional control valve similar to the first directional control valve 10 and the second directional control valve 20. FIGS. 5 and 6 show a schematic of a hydraulic system including the third directional control valve 50.
[0056] In the embodiments of FIGS. 5 and 6, the third directional control valve 50 can be provided by another directional control valve 50 that is not currently in use on the work machine for a given work tool. For example, in the embodiments of FIGS. 5 and 6, the bucket directional control valve B1 can not be used to operate the shear.
[0057] As shown in FIG. 5, the hydraulic fluid pump is not connected to the inlet port 51 of the third directional control valve 50 (i.e., the inlet port 51 is blocked). The second actuator outlet 54 is also not connected to (i.e., blocked from) the hydraulic system. Similar to the first outlet ports 13, 23 of the other directional control valves 10, 20, the first outlet port 53 is connected to the first outlet 33 of the actuator. A return port (not shown) can be connected to a hydraulic fluid reservoir. Thus, the third directional control valve 50 can be controlled in a similar manner as the first and second directional control valves 10, 20.
[0058] For example, as shown in FIG. 5, when the actuator 30 is moved from the first position to the second position, no hydraulic fluid flows through the third directional control valve 50 (similar to the pressure relief valve 40). When the actuator 30 is moved from the second position to the first position, as shown in FIG. 6, hydraulic fluid flows through the third directional control valve 50 to the hydraulic fluid reservoir. Thus, the third directional control valve 50 provides an additional flow path for hydraulic fluid on the return path when the actuator 30 is moved from the second position to the first position. Accordingly, the hydraulic system can also reduce cycle times of the work tool by providing an additional return path that is sometimes open when the actuator 30 is not performing a significant amount of work.
[0059] FIG. 7 shows a plot of the opening valve area of each of the first and second control valves (Aux 1, Aux 2) in response to a change in joystick command to move the actuator from point A (second position) to point B (first position), similar to the plot of FIG. 4. FIG. 7 also shows a plot of the change in opening valve area of the third directional control valve 50 (bucket CTHE). From the description of FIG. 4, it will be appreciated that the third directional control valve 50 is controlled in a similar manner as the pressure relief valve 40, with the valve fully open at the beginning of movement from the second position to the first position.
[0060] FIGS. 8 and 9 show a diagram of the hydraulic circuit shown in the schematic diagrams of FIGS. 5 and 6. FIGS. 8 and 9 show the return paths from the return ports 12, 24 of the first and second directional control valves 10, 20 to the hydraulic fluid reservoir 90.
[0061] As discussed above, the hydraulic system 1 of the present disclosure can be controlled by a controller 80. FIG. 10 shows a block diagram of the controller 80 according to the present disclosure. The controller 80 of FIG. 10 can be configured to receive a first signal from a user input terminal 90 to cause the controller 80 to move an actuator 30 of the hydraulic system 1 from a first position to a second position. In some embodiments, the controller 80 can also receive a second signal from the user input terminal 90 to cause the controller 80 to move the actuator 30 of the hydraulic system 1 from the second position to the first position. As shown in FIG. 10, the controller 80 can be configured to output control signals to the first directional control valve 10, the second directional control valve 20, and the third directional control valve 30 (AUX1, AUX2, BKT) first and second solenoids (HE, RE). The controller 80 can also be configured to output signals to a solenoid configured to control the pressure relief valve 40 (RV). Thus, the controller 80 can be configured to control the hydraulic system 1 described above.
[0062] According to another embodiment, a method 100 of controlling a hydraulic system 1 for a work tool is provided. FIG. 11 shows a block diagram of the method 100. The method 100 can be performed by the controller 80 discussed above when configured to control the hydraulic system 1 of FIG. 1.
[0063] In a first step 101 of the method, an actuator of a work tool is moved from a first position to a second position. To provide the movement, the first directional control valve 10 and the second directional control valve 20 of the hydraulic system 1 are opened such that hydraulic fluid is pumped from the hydraulic fluid pumps 3, 5 to the actuator 30 to move the actuator 30 to the second position. Additionally, the pressure relief valve 40 of the hydraulic system 1 is closed such that hydraulic fluid does not flow through the pressure relief valve 40.
[0064] In a second step 102, the actuator 30 is moved from the second position to the first position. To provide the movement, the first directional control valve 10 and the second directional control valve 20 are opened such that hydraulic fluid is pumped to the actuator 30 to move the actuator to the first position. Additionally, the pressure relief valve 40 is opened to allow hydraulic fluid to return from the actuator 30 to the hydraulic fluid reservoir.
[0065] Industrial applicability
[0066] According to the present disclosure, a controller, a hydraulic system, and a method of controlling a hydraulic system are provided. The hydraulic system can be configured to provide mechanical power to an actuator of a work tool. In particular, the work tool can be a shear. In some embodiments, the hydraulic system and the work tool can be provided as part of a work machine, such as an excavator. Thus, the shear can be mounted on a boom of the excavator. Accordingly, embodiments of the present disclosure can be implemented on a hydraulic system of an excavator.
[0067] Embodiments of the present disclosure can be particularly suitable for work tools having actuators with relatively large cylinder volumes. For example, in some embodiments, the actuators can have cylinder volumes of at least 60 liters, 80 liters, 100 liters, 120 liters, or 140 liters. With relatively large cylinder volumes for the actuators, attempting to move a relatively large volume of hydraulic fluid in a short duration can create significant back pressure in the hydraulic system. The back pressure can effectively delay movement of the actuators, thereby increasing cycle times for the actuators. It should also be appreciated that the back pressure caused by the flow of hydraulic fluid causes the hydraulic pump to work harder than it otherwise would need to. For example, a typical back pressure for a hydraulic system of an excavator operating a shear can be about 14 MPa with the pressure relief valve not open. By opening the pressure relief valve according to embodiments of the present disclosure (e.g., FIGS. 2-3), the back pressure can be reduced to about 7 MPa. By also opening an additional directional control valve (e.g., FIGS. 5-6), the back pressure can be reduced to about 3 MPa. Thus, embodiments of the present disclosure can reduce back pressure in the hydraulic system by at least about 50% or 75%.
[0068] By opening an additional flow path for the hydraulic fluid, the controller of the first aspect effectively reduces back pressure in the hydraulic system, thereby allowing the actuators to return to the first position more quickly and with less power consumption. Thus, the controller of the first aspect can improve operating cycles for the work tool, and can also improve fuel efficiency associated with the work tool.
[0069] In some embodiments, the work tool to be controlled can be a shear or other work tool in which a majority of the mechanical work performed by the work tool in an operating cycle is due to movement of the actuators from the first position to the second position. Thus, when moving from the second position to the first position, the work tool performs very little, if any, effective work. Accordingly, in some embodiments, the flow rate of the hydraulic fluid through the hydraulic system can limit the rate at which the work tool can return to the first position in a new operating cycle. According to the first aspect, the controller can effectively increase the flow rate of the hydraulic fluid on the return path to allow the actuators to return to the first position relatively quickly.
Claims
1. A controller configured to control an actuator of a hydraulic system for a work tool, wherein the controller is configured to move the actuator of the hydraulic system from a first position to a second position, wherein: the controller causes a first directional control valve and a second directional control valve of the hydraulic system to open, such that hydraulic fluid is pumped from a hydraulic fluid pump to the actuator to move the actuator to the second position, and the controller causes a pressure relief valve of the hydraulic system to close, such that hydraulic fluid does not flow through the pressure relief valve; and the controller is configured to move the actuator from the second position to the first position, wherein: the controller causes the first directional control valve and the second directional control valve to open, such that hydraulic fluid is pumped from the hydraulic fluid pump to the actuator to move the actuator to the first position; and the controller causes the pressure relief valve to open to allow hydraulic fluid to return from the actuator to a hydraulic fluid reservoir.
2. The controller of claim 1, wherein the controller is configured to control the hydraulic system such that the actuator is moved from the second position to the first position in a duration of no more than 10 seconds.
3. The controller of any one of claims 1 to 2, wherein the controller is configured to receive a first signal from a user input terminal to cause the controller to move the actuator of the hydraulic system from the first position to the second position; and / or the controller is configured to receive a second signal from a user input terminal to cause the controller to move the actuator of the hydraulic system from the second position to the first position.
4. The controller of any preceding claim, wherein when the controller moves the actuator of the hydraulic system from the first position to the second position, the controller causes the pressure relief valve to operate in a pressure relief mode, wherein the pressure relief valve is open to release pressure above a pressure threshold defined by the controller.
5. The controller of any claim 4, wherein the pressure threshold is a pressure of at least 30 MPa or at least 40 MPa.
6. The controller of any one of claims 1 to 5, wherein the controller is configured to cause a third directional control valve of the hydraulic system to close when the actuator is moved from the first position to the second position, such that hydraulic fluid does not flow through the third directional control valve; and the controller is configured to cause a third directional control valve of the hydraulic system to open when the actuator is moved from the second position to the first position to allow hydraulic fluid to return from the actuator to the hydraulic fluid reservoir.
7. A hydraulic system for a work tool, the hydraulic system comprising: an actuator for the work tool; a first directional control valve configured to control hydraulic fluid flow to and from the actuator; a second directional control valve configured to control hydraulic fluid flow to and from the actuator; a hydraulic pump configured to pump hydraulic fluid to the actuator via the first directional control valve and the second directional control valve; a hydraulic fluid reservoir connected to the first directional control valve and the second directional control valve and configured to receive hydraulic fluid flowing from the actuator via the first directional control valve and the second directional control valve; a pressure relief valve configured to control hydraulic fluid flow from the actuator to the hydraulic fluid reservoir, the pressure relief valve connected to the hydraulic fluid reservoir and configured to receive hydraulic fluid from the work tool; and a controller according to any one of claims 1 to 5.
8. A hydraulic system for a work tool, the hydraulic system comprising: an actuator for the work tool; a first directional control valve configured to control hydraulic fluid flow to and from the actuator; a second directional control valve configured to control hydraulic fluid flow to and from the actuator; a third directional control valve configured to control hydraulic fluid flow to and from the actuator; a hydraulic pump configured to pump hydraulic fluid to the actuator via the first directional control valve and the second directional control valve; a hydraulic fluid reservoir connected to the first directional control valve, the second directional control valve, and the third directional control valve and configured to receive hydraulic fluid flowing from the actuator via the first directional control valve, the second directional control valve, and the third directional control valve; a pressure relief valve configured to control hydraulic fluid flow from the actuator to the hydraulic fluid reservoir, the pressure relief valve connected to the hydraulic fluid reservoir and configured to receive hydraulic fluid from the work tool; and a controller according to claim 6.
9. The hydraulic system of claim 7 or 8, wherein one or more of the first directional control valve, the second directional control valve, and the third directional control valve is a 4-port, 3-position directional control valve.
10. The hydraulic system of any one of claims 7 to 9, wherein the work tool is a shear, wherein in the first position the shear is open and in the second position the shear is closed.
11. The hydraulic system of any one of claims 7 to 10, wherein the actuator comprises a cylinder configured to receive hydraulic fluid, wherein the cylinder has a volume of at least 60 liters.
12. The hydraulic system of any one of claims 7 to 11, further comprising: an additional hydraulic fluid pump, wherein the hydraulic fluid pump is configured to pump hydraulic fluid to the actuator via the first directional control valve and the additional hydraulic fluid pump is configured to pump hydraulic fluid to the actuator via the second directional control valve.
13. The hydraulic system of any one of claims 7 to 12, wherein when the controller moves an actuator of the hydraulic system from the first position to the second position, the pressure relief valve is configured to operate in a pressure relief mode in which the pressure relief valve opens to release pressure above a pressure threshold defined by the controller.
14. The hydraulic system of claim 13, wherein the pressure threshold is a pressure of at least 30 MPa or at least 40 MPa.
15. A method of controlling a hydraulic system for a work tool, comprising moving an actuator of the work tool from a first position to a second position, wherein: a first directional control valve and a second directional control valve of the hydraulic system open such that hydraulic fluid is pumped from a hydraulic fluid pump to the actuator to move the actuator to the second position, and a pressure relief valve of the hydraulic system closes such that hydraulic fluid does not flow through the pressure relief valve; and moving the actuator from the second position to the first position, wherein: the first directional control valve and the second directional control valve open such that hydraulic fluid is pumped to the actuator to move the actuator to the first position; and the pressure relief valve opens to allow hydraulic fluid to return from the actuator to a hydraulic fluid reservoir.
16. The method of claim 15, wherein the actuator is moved from the second position to the first position in a duration of no more than 10 seconds.
17. The method of claim 15 or claim 16, wherein a third directional control valve of the hydraulic system closes such that hydraulic fluid does not flow through the third directional control valve when the actuator is moved from the first position to the second position; and a third directional control valve of the hydraulic system opens to allow hydraulic fluid to return from the actuator to the hydraulic fluid reservoir when the actuator is moved from the second position to the first position.
18. The method of any one of claims 15 to 17, wherein the pressure relief valve operates in a pressure relief mode when an actuator of the hydraulic system is moved from the first position to the second position, wherein the pressure relief valve opens to release pressure above a pressure threshold defined by the controller.
19. The method of claim 18, wherein the pressure threshold is a pressure of at least 30 MPa or at least 40 MPa.