Self regulating pressure compensated hydraulic system for differential pressure control

Abstract

A hydraulic system (1) is provided, comprising: a valve assembly (10), wherein the valve assembly (10) comprises a main spool (11) configured to be in fluid connection to a hydraulic circuit (101) of an actuator (100), wherein a supply pressure (P) is provided to an inlet port (12a) of a proportional flow control valve (12) and a control port (13a, 13c) for a pressure regulating valve (13), wherein an outlet port (12b) of the proportional flow control valve (12) is in fluid connection to either of a first and second hydraulic valve activator (11a, 11b) of the main spool (11) for activation of either of the first and second hydraulic valve activator (11a, 11b), respectively, wherein the pressure regulating valve (13) further is in fluid connection to the other of the first and second valve activator (11a, 11b) of the main spool (11) for activation of the other of the first and second hydraulic valve activator (11a, 11b), respectively, and providing a regulating pressure (RP) which is at a set offset from the supply pressure (P), to the other of the first and second hydraulic valve activator (11a, 11b) of the main spool (11), wherein the main spool (11) comprises a centering spring device (11c) biased for centering the main spool (11) in a neutral, closed position of the inlet port (11d) of the main spool (11), wherein the outlet port (12b) of the proportional flow control valve (12) further is in fluid connection to an inlet port (11d) of the main spool (11), wherein the pressure regulating valve (13) further is in fluid connection to a tank port (T), wherein, upon fluid connection of the main spool (11) to the hydraulic circuit (101) of the actuator (100), the hydraulic system (1) is configured to self-regulate a pressure (OP) at the outlet port (12b) of the proportional flow control valve (12) by the aid of the main spool (11), to correspond to the sum of the opposite acting regulating pressure (RP) and work pressure of the centering spring device (11c), forming a threshold pressure for the main spool (11) to leave the neutral, closed position and move to an open position of the inlet port (11d) of the main spool (11), wherein the hydraulic system (1) is configured for a differential pressure regulation of the differential pressure across the proportional flow control valve (12). A hydraulic arrangement (200) comprising a plurality of hydraulic systems is also provided, as well as a working machine comprising a hydraulic system.

Description

SELF REGULATING PRESSURE COMPENSATED HYDRAULIC SYSTEM FOR DIFFERENTIAL PRESSURE CONTROLTechnical field

[0001] The present invention relates generally to a pressure compensated hydraulic system, a hydraulic arrangement comprising hydraulic systems, and a method performed by a hydraulic system.

[0002] In general, it is desirable for hydraulically controlled actuators or hydraulic functions that as much of the pressure and hydraulic energy is consumed over the actuators themselves and not over the valve assembly and fluid connections used for regulating the actuators as the latter will lead to a high energy consumption, low efficiency and generation of heat loss in the system instead of the intended driving of the actuators. As the field of e.g. construction equipment and vehicles is undergoing a shift towards electrification, there is an increased focus on increasing energy efficiency and reducing energy consumption. Furthermore, hydraulic systems connected to several hydraulic actuators to be run simultaneously require many components in order to provide for individual controlling, wherein each actuator or function is provided with the correct amount of hydraulic oil, and thus to remain unaffected by the controlling of the other actuators in a reliable manner. One example within the field of construction equipment, is the tilt rotator which tilt and rotation function need to be individually controlled in a reliable and precise manner. Attempts to overcome low reliability and preciseness in such systems, involves costly and complex control systems and settings, often with restrictions on the speed at which certain functions and actuators can be driven or operated. This above, increases cost, system weight, space consumption, which are parameters of critical importance to reduce.

[0003] It is known to use conventional proportional flow control valves with a variable flow area using a restrictor for the purpose of controlling the flow rate in hydraulic systems and circuits. The flow through proportional flow control valve ise.g. dependent on the differential pressure across the valve for a given opening and flow area. This makes them challenging to regulate in situations with common and large variations in inlet pressure or actuator pressure, i.e. where the differential pressure is likely to vary. Generally, high sudden increases in differential pressures over the valves, either due to variations in the hydraulic system or because some actuators fluidly connected to the system require a pressure increase while others don’t, may cause high flow rates and undesired heat losses in some valves, especially actuators that don’t require a fast increase in hydraulic flow. High differential pressures may cause high flow rates and undesired heat losses, however for some applications this may be required to achieve a quick response of the function or to control certain actuators. Hence an ability to strike a balance between energy consumption and high performance is valuable in the field. Known solutions of seeking to control a differential pressure across a proportional flow control valve includes bypass compensation, where the excess flow is directed away from the proportional flow control valve to achieve the desired differential pressure. Another known solution is pre compensation, where the flow entering the proportional flow control valve is restricted by an upstream pressure compensator to achieve the desired differential pressure. A further known solution is post compensation, where the flow exiting the proportional flow control valve is restricted by a downstream pressure compensator to achieve the desired differential pressure.

[0004] It is further known to use a pressure compensator and proportional pressure reducers for controlling the differential pressure across, and the direction of, respectively, a main spool in a hydraulic system, e.g. for controlling a hydraulic circuit of a consumer or actuator. A drawback of such pressure compensated systems with a pilot controlled main spool is the large number of components needed which increases cost and adds complexity which makes the system less robust. Proportional pressure reducers are further sensitive to high pressures in the return lines, which both reflects a lack of robustness and limits the allowed pressure scope and usability.

[0005] It is further known to use a pressure compensator and direct controlled main spool for controlling the differential pressure across, and the direction of, respectively, a main spool in a hydraulic system, e.g. for controlling a hydraulic circuit of a consumer or actuator. A drawback of such pressure compensated systems with a direct controlled main spool is the limitations of the magnetic coils that provides the direct control, which only works up to a certain flow rate of hydraulic oil due to limitations of the magnetic force of the coils. Thus, main spools of this kind are sensitive to high flow rates. Furthermore, the magnetic coils have to be arranged axially aligned with the main spool, which limits the possibilities for an optimized design.Summary of invention

[0006] An object of the present invention is to alleviate some of the disadvantages of the prior art and to provide a hydraulic system which requires fewer components and is cheaper to manufacture. A further object of the present invention is to provide a hydraulic system that is more robust. A further object of the present invention is to provide a hydraulic system that is easy and reliable to regulate. A further object of the present invention is to provide a hydraulic system that is less space consuming and easier to implement in small and limited spaces. A further object of the present invention is to use conventional components that are cheap and reliable.

[0007] According to one embodiment, a hydraulic system is provided, comprising: a valve assembly, wherein the valve assembly comprises a main spool configured to be in fluid connection to a hydraulic circuit of an actuator, wherein a supply pressure P is provided to an inlet port of a proportional flow control valve and a control port for a pressure regulating valve, wherein an outlet port of the proportional flow control valve is in fluid connection to either of a first and second hydraulic valve activator of the main spool for activation of either of the first and second hydraulic valve activator, respectively,wherein the pressure regulating valve further is in fluid connection to the other of the first and second valve activator of the main spool for activation of the other of the first and second hydraulic valve activator, respectively, and providing a regulating pressure (RP) which is at a set offset from the supply pressure (P), to the other of the first and second hydraulic valve activator of the main spool, wherein the main spool comprises a centering spring device biased for centering the main spool in a neutral, closed position of the inlet port of the main spool, wherein the outlet port of the proportional flow control valve further is in fluid connection to an inlet port of the main spool, wherein the pressure regulating valve further is in fluid connection to a tank port, wherein, upon fluid connection of the main spool to the hydraulic circuit of the actuator, the hydraulic system is configured to self-regulate a pressure (OP) at the outlet port of the proportional flow control valve by the aid of the main spool, to correspond to the sum of the opposite acting regulating pressure (RP) and work pressure of the centering spring device, forming a threshold pressure for the main spool to leave the neutral, closed position and move to an open position of the inlet port of the main spool, wherein the hydraulic system is configured for a differential pressure regulation of the differential pressure across the proportional flow control valve.

[0008] According to one embodiment, the differential pressure across the proportional flow control valve is the differential pressure between the inlet port and the outlet port of the proportional flow control valve.

[0009] According to one embodiment, the hydraulic system is configured for a differential pressure control, for setting a differential pressure across the proportional flow control valve, comprising the differential pressure regulation and a setting of the regulating pressure (RP) offset.

[0010] According to one embodiment, a mean differential pressure across the proportional flow control valve, over a time period of 1s, is kept within a range of + / -25% from a set differential pressure.

[0011] According to one embodiment, the main spool is arranged upstream of the actuator.

[0012] According to one embodiment, the main spool is arranged downstream of the actuator.

[0013] According to one embodiment, the main spool is arranged upstream and downstream of the actuator.

[0014] According to one embodiment, the outlet port of the proportional flow control valve is selectively in fluid connection to either of a first and second hydraulic valve activator of the main spool, and the pressure regulating valve is in fluid connection to the other of the first and second valve activator of the main spool, via a directional valve.

[0015] According to one embodiment, an orifice connects the outlet port of the proportional flow control valve and the inlet port of the pressure regulating valve.

[0016] According to one embodiment, the orifice connects the outlet port of the proportional flow control valve and the inlet port of the pressure regulating valve between the directional valve and the main spool.

[0017] According to one embodiment, the main spool is a 4 / 3 way, 4 / 2 way or a 2 / 2 way directional valve.

[0018] According to one embodiment, the directional valve is a 4 / 3 way or a 4 / 2 way directional valve.

[0019] According to one embodiment, the valve assembly further comprises a check valve (18) arranged between the outlet port of the proportional valve and the main spool.

[0020] According to one embodiment, the pressure regulating valve comprises an electrohydraulic pressure setting for setting the regulating pressure (RP) offset.

[0021] According to one embodiment, a further main spool is arranged in parallel to the main spool.

[0022] According to one embodiment, the hydraulic system is a pressure compensated hydraulic system.

[0023] According to one embodiment, the centering spring device comprises a first and second centering spring.

[0024] According to one embodiment, a hydraulic arrangement comprising a plurality of hydraulic systems according to any of the embodiments herein, e.g. the embodiments of paragraphs

[0007] -

[0023] is provided, wherein the supply pressure (P) is fluidly connected in parallel, wherein the tank port is fluidly connected in parallel.

[0025] According to one embodiment, the hydraulic arrangement comprises only one single shared pressure regulating valve.

[0026] According to one embodiment, a method performed by a hydraulic system according to any of the embodiments herein, e.g. the embodiments of paragraphs

[0007] -

[0025] , the method comprising:- receiving or determining a regulating pressure (RP) offset setting,- setting a regulating pressure (RP) offset to form the threshold pressure for the main spool to leave the neutral, closed position of the inlet port of the main spool and move to an open position of the inlet port of the main spool, as a sum of the regulating pressure RP and the work pressure of the centering spring device.

[0027] According to one embodiment, the method further comprising:- sensing a pressure (P),- setting an electrohydraulic pressure of the pressure regulating valve for setting the regulating pressure (RP) offset, based on the sensed pressure (P).

[0028] According to one embodiment, the method further comprising:- sensing actuator type.

[0029] According to one embodiment, the method further comprising:- sensing an opening degree of the opening area of the flow control valve.

[0030] According to one embodiment, the method further comprising:- receiving a plurality of pressure signals (PA) indicative of the pressures used by a plurality of actuators in fluid connection to a corresponding plurality of hydraulic systems, respectively in a hydraulic arrangement,- determining the highest pressure (PLS) among the plurality of pressure signals (PA),- receiving a signal indicative of the highest set differential pressure (DPset) across a proportional flow control valve among the plurality of hydraulic systems,- receiving a pressure signal indicative of the supply pressure (P),- transmitting a signal for controlling the pressure relief valve so that it opens if the supply pressure (P) exceeds (PLs)+(DPset).

[0031] According to one embodiment, a method performed by a hydraulic arrangement comprising a plurality of hydraulic systems is provided, wherein each of the plurality of hydraulic systems comprises a valve assembly, wherein the valve assembly is configured to be in fluid connection to a hydraulic circuit of anactuator, wherein a supply pressure P is provided to an inlet port of a proportional flow control valve, wherein an outlet port of the proportional flow control valve further is in fluid connection to an inlet port of the hydraulic circuit, further comprising a pressure sensing device, the method comprising:- receiving a plurality of pressure signals (PA) indicative of the pressures used by a plurality of actuators in fluid connection to the plurality of hydraulic systems, respectively),- determining the highest pressure (PLS) among the plurality of pressure signals (PA),- receiving a signal indicative of the highest set differential pressure (DPset) across a proportional flow control valve among the plurality of hydraulic systems,- receiving a pressure signal indicative of the supply pressure (P),- transmitting a signal for controlling the pressure relief valve so that it opens if the supply pressure (P) exceeds (PLs)+(DPset).

[0032] According to one embodiment, the method further comprising:- receiving a maximum allowed supply pressure (Pmax) indication signal,- transmitting a signal for controlling the pressure relief valve so that it opens if (P)>(PLs)+(DPset ) Or (Pmax)-

[0033] According to one embodiment, a hydraulic system according to any of the embodiments herein, e.g. the embodiments of paragraphs

[0007] -

[0025] is provided, further comprising: processing circuitry; and a memory, said memory containing instructions executable by said processing circuitry, whereby said system is operative for:- receiving or determining a regulating pressure (RP) offset setting,- setting a regulating pressure (RP) offset to form the threshold pressure for the main spool to leave the neutral, closed position of the inlet port of the main spool, and move to an open position of the inlet port of the main spool, as a sum of the regulating pressure RP and the work pressure of the centering spring device.

[0034] According to one embodiment, hydraulic system is further operative for:- sensing a pressure (P),- setting an electrohydraulic pressure of the pressure regulating valve for setting the regulating pressure (RP) offset, based on the sensed pressure (P).

[0035] According to one embodiment, hydraulic system is further operative for:- sensing actuator type.

[0036] According to one embodiment, hydraulic system is further operative for:- sensing an opening degree of the opening area of the flow control valve.

[0037] According to one embodiment, hydraulic system is further operative for:- receiving a plurality of pressure signals (PA) indicative of the pressures used by a plurality of actuators in fluid connection to a plurality of hydraulic systems, respectively of a hydraulic arrangement,- determining the highest pressure (PLS) among the plurality of pressure signals (PA), receiving a signal indicative of the highest set differential pressure (DPset) across a proportional flow control valve among the plurality of hydraulic systems,- receiving a pressure signal indicative of the supply pressure (P),- transmitting a signal for controlling the pressure relief valve so that it opens if the supply pressure (P) exceeds (Pi_s)+(DPSet).

[0038] According to one embodiment, a hydraulic arrangement comprising a plurality of hydraulic systems is provided, wherein each of the plurality of hydraulic system comprises a valve assembly, wherein the valve assembly is configured to be in fluid connection to a hydraulic circuit of an actuator, wherein a supply pressure P is provided to an inlet port of a proportional flow control valve, wherein an outlet port of the proportional flow control valve further is in fluid connection to an inlet port of the hydraulic circuit, further comprising a pressure sensing device, the hydraulic arrangement further comprising: processing circuitry; and a memory, said memory containing instructions executable by said processing circuitry, whereby said hydraulic arrangement is operative for:- receiving a plurality of pressure signals (PA) indicative of the pressures used by a plurality of actuators in fluid connection to the plurality of hydraulic systems of the hydraulic arrangement,- determining the highest pressure (PLS) among the plurality of pressure signals (PA),- receiving a signal indicative of the highest set differential pressure (DPset) across a proportional flow control valve among the plurality of hydraulic systems,- receiving a pressure signal indicative of the supply pressure (P),- transmitting a signal for controlling the pressure relief valve so that it opens if the supply pressure (P) exceeds (PLs)+(DPset).

[0039] According to one embodiment, the hydraulic arrangement further operative for:- receiving a maximum allowed supply pressure (Pmax) indication signal,- transmitting a signal for controlling the pressure relief valve so that it opens if (P)>(P|_s)+(DP set) Or (P max).

[0040] According to one embodiment, a computer program is provided comprising computer readable code means to be run in a hydraulic system, which computer readable code means when run in the hydraulic system causes the hydraulic system to carry out the method according to any of the embodiments herein, e.g the embodiments of paragraphs

[0026] -

[0032] , According to one embodiment, a computer program (605) is provided, comprising computer readable code means to be run in a hydraulic system (1 ) according to any of the embodiments herein, e.g. the embodiments of paragraphs

[0007] -

[0023] ,

[0033] -

[0037] which computer readable code means when run in the hydraulic system (1 ) causes the hydraulic system (1 ) to carry out the method according to any of the embodiments herein, e.g the embodiments of paragraphs

[0026] -

[0032] ,

[0041] According to one embodiment, a carrier containing the computer program according to paragraph

[0040] is provided, wherein the carrier is one of an electronic signal, optical signal, radio signal or computer readable storage medium.

[0042] According to one embodiment, a working machine comprising a hydraulic system according to any of the embodiments herein, e.g. the embodiments of paragraphs

[0007] -

[0025] ,

[0033] -

[0039] is provided.

[0043] According to one embodiment, a working machine comprising a hydraulic arrangement comprising a plurality of hydraulic systems according to any of the embodiments herein, e.g. the embodiments of paragraphs

[0007] -

[0025] ,

[0033] -

[0039] is provided.Brief description of drawings

[0044] The invention will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:

[0045] FIG. 1 A shows a hydraulic system comprising a valve assembly according to an embodiment in fluid connection to a hydraulic circuit of an actuator.

[0046] FIG. 1 B shows a hydraulic system according to one embodiment.

[0047] FIG. 1 C shows a hydraulic system according to one embodiment.

[0048] FIG. 1 D shows a hydraulic system according to one embodiment.

[0049] FIG. 2 shows a hydraulic system comprising a valve assembly according to an embodiment in fluid connection to a hydraulic circuit of an actuator.

[0050] FIG. 3A shows a hydraulic system comprising a valve assembly according to an embodiment in fluid connection to a hydraulic circuit of an actuator.

[0051] FIG. 3B shows hydraulic system according to one embodiment.

[0052] FIG. 4A shows a hydraulic system comprising a valve assembly according to an embodiment in fluid connection to an hydraulic circuit of an actuator, further comprising a main spool which can regulate flow of hydraulic fluid in both directions through the actuator and a directional valve.

[0053] FIG. 4B shows the hydraulic system of FIG. 4A, further comprising a valve, e.g. a check valve.

[0054] FIG. 5A shows a hydraulic arrangement comprising a plurality of hydraulic systems.

[0055] FIG. 5B shows a hydraulic arrangement comprising a plurality of hydraulic systems 1 according to Fig. 4A with the exception that the arrangement only comprises one single pressure regulating valve.

[0056] FIG. 5C shows a hydraulic arrangement comprising a plurality of hydraulic systems 1 according to Fig. 4B with the exception that one of the hydraulic systems comprises a further main spool arranged in parallel to the main spool.

[0057] FIG. 5D shows a hydraulic arrangement with a pressure sensing device.

[0058] FIG. 5E shows a flow chart schematically showing method steps of an embodiment of a method performed by a hydraulic system or arrangement.

[0059] FIG. 6A shows a working machine comprising a hydraulic system 1.

[0060] FIG. 6B shows a working machine comprising a hydraulic arrangement comprising a plurality of hydraulic systems.

[0061] FIG. 7A shows a flow chart schematically showing method steps of an embodiment of a method performed by a hydraulic system.

[0062] FIG. 7B shows a flow chart schematically showing method steps of an embodiment of a method performed by a hydraulic system.

[0063] FIG. 7C shows a flow chart schematically showing method steps of an embodiment of a method performed by a hydraulic system.

[0064] FIG. 7D shows a flow chart schematically showing method steps of an embodiment of a method performed by a hydraulic system.

[0065] FIG. 8 shows a block schematic of a hydraulic system according to an embodiment of the invention.Detailed description

[0066] In the following, a detailed description of the invention will be given. In the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. It will be appreciated that these figures are for illustration only and are not in any way restricting the scope of the invention.

[0067] FIG. 1 A shows a hydraulic system 1 comprising a valve assembly 10 being in fluid connection to a hydraulic circuit 101 of an actuator 100. According to one embodiment, the hydraulic system 1 is a pressure compensated hydraulic system 1 . According to one embodiment, pressure compensated indicates that the output or function of the system 1 s output, such as e.g providing a hydraulic system 1 with a differential pressure control is independent, i.e. that it compensates for variations of the supply pressure P. According to one embodiment, the actuator 100 is also defined as a consumer, a load, tool, machine, motor or implement 100. According to one embodiment, a valve assembly 10 is herein understood as comprising several valves and components, which may or may not be in a common block, manifold or in a single body configuration. As such, according to one embodiment, a valve assembly 10 may comprise several blocks or parts that are physically separated or divided.According to one embodiment, the valve assembly 10 comprises a main spool 11 configured to be in fluid connection to the hydraulic circuit 101 of the actuator 100. According to one embodiment, the main spool 11 is a main spool valve 11 . According to one embodiment, the main spool is a 2 / 2 valve or a 2-way, 2 position valve, wherein the main spool 11 comprises 2 holes or ports (inlet and outlet) and 2 positions (open or closed). The main spool 11 moves towards and eventually to an open position when a first or second valve activator 11 a, 11 b is activated. The main spool 11 of Fig. 1 moves towards and eventually to an open position when the second valve activator 11 b is activated. It is biased to resume to its initial closed position by the force of a centering spring device 11 c. According to one embodiment, the valve assembly 10 further comprises a proportional flow control valve 12 comprising an inlet port 12a and an outlet port 12b. According to oneembodiment, the proportional flow control valve 12 is a proportional valve 12. According to one embodiment, proportional flow control valve 12 is configured to control the flow through the proportional flow control valve depending on a differential pressure across the proportional flow control valve 12. The proportional flow control valve 12 is configured for enabling controlling the opening or restriction, i.e. the opening area for the flow through the proportional flow control valve 12, to a consumer line 24a, further to the main spool 11 . A given differential pressure across the proportional control valve 12, at a given opening area, provides a given flow rate. Hence, controlling the differential pressure provides for a more exact controlling of the flow rate through the same. The proportional flow control valve 12 as such is a standard component, however a technical effect of the herein described embodiments provides for controlling the differential pressure across the same enabling the controlling of the flow rate in an improved manner. According to one embodiment, the proportional flow control valve 12 is a pilot valve for the main spool 11 . According to one embodiment, the proportional flow control valve 12 is a pilot-operated, normally closed, electro-proportional throttle with reverse free-flow check. Energizing the coil generates an opening force on the pilot stage which vents the main stage poppet to open proportionally.According to one embodiment, the valve 12 is a normally closed, electroproportional throttle that is spring-biased closed. Energizing the coil generates an opening force on the spool proportional to the command current, and this force is countered by the spring and flow forces. This force balance creates a metering orifice whose effective size is proportional to the current. According to one embodiment, a supply pressure P is in fluid connection, supplied or provided to the inlet port 12a of the proportional flow control valve 12 and a control port 13a, 13c for a pressure regulating valve 13. According to one embodiment, the control port 13a, 13c is arranged as a control port 13a on a pressure regulating valve 13 and hydraulically acted upon by the supply pressure P. According to one embodiment, an outlet port 12b of the proportional flow control valve 12 is in fluid connection to either of a first and second hydraulic valve activator 11a, 11 b of the main spool 11. According to one embodiment, an outlet port 12b of the proportional flow controlvalve 12 is in fluid connection to either of a first and second hydraulic valve activator 11a, 11 b of the main spool 11 for activation of either of the first and second hydraulic valve activator 11a, 11 b, respectively. According to one embodiment, being in fluid connection herein comprises an ability to activate the first and second hydraulic valve activator 11a, 11 b. This could e.g. be due to sufficient fluid pressure. According to one embodiment, the fluid connection between the outlet port 12b and either of the first and second hydraulic valve activator 11a, 11 b is provided by a fluid line 24b in fluid connection to fluid line 24a, also defined herein as a consumer line 24a between the outlet port 12b and the main spool 11 . Fluid line 24b, and, as defined below, regulating line 26, are indicated with dashed lines in the figures in accordance with common practice for hydraulic circuit diagrams, as they are so called pilot lines or control lines as opposed to main flow lines. They may be indicated with solid lines. In the embodiment of Fig. 1 , the hydraulic valve activator 11a, 11 b to which the outlet port 12b is in fluid connection may not change or is not changeable or is not selectable during operation, for instance by the aid of a directional valve 14 as e.g. described in FIGs 4-5, however, it is clear that either of may be selected for fluid connection upon installation. According to one embodiment, the pressure regulating valve 13 further is in fluid connection to the other of the first and second valve activator 11a, 11 b of the main spool 11 . According to one embodiment, the pressure regulating valve 13 further is in fluid connection to the other of the first and second valve activator 11a, 11 b of the main spool 11 for activation of the other of the first and second hydraulic valve activator 11a, 11 b, respectively. According to one embodiment, being in fluid connection herein comprises an ability to activate the first and second hydraulic valve activator 11a, 11 b. This could e.g. be due to sufficient fluid pressure. In other words, this is the other of the first and second valve activator 11a, 11 b, being in fluid connection to the proportional flow control valve 12. Thus, by “the other”, is meant the hydraulic valve activator 11a, 11 b not being in fluid connection to the outlet port 12b of the proportional flow control valve 12. In the embodiment of FIG. 1A, the hydraulic valve activator 11a, 11 b to which the pressure regulating valve 13 is in fluid connection may notchange or is not changeable or is not selectable, for instance by the aid of a directional valve 14 as e.g. described in FIGs 4-5 during operation, however, it is clear the other of the hydraulic valve activator 11a, 11 b is selected for fluid connection upon installation. According to one embodiment, the outlet port 12b is in fluid connection to the valve activator 11a, 11 b acting towards the open position, i.e. to force the main spool 11 towards the open position against the force of the centering spring device 11c. According to one embodiment, the pressure regulating valve 13 providing a regulating pressure RP which is at a set or pre-set offset from the supply pressure P, to the other of the first and second hydraulic valve activator 11a, 11 b of the main spool 11 . According to one embodiment, the offset from the supply pressure P is also referred to as a regulating pressure RP offset. Again, the other of the first and second hydraulic valve activator 11a, 11 b is the hydraulic valve activator 11a, 11 b not being in fluid connection to the outlet port 12b of the proportional flow control valve 12. According to one embodiment, the pressure regulating valve 13 is a pressure reducing valve 13. According to one embodiment, the regulating pressure RP is a function of the supply pressure P and a loading element, such as e.g. a spring in the pressure regulating valve 13 acting against the supply pressure P to restrict the flow between a regulating line 26 and tank T. According to one embodiment, the spring in the pressure regulating valve 13 is settable for setting the regulating pressure RP offset. Thus, according to one embodiment, the flow direction in regulating line 26 is towards tank T. According to one embodiment, setting the regulating pressure RP comprises setting the offset from the supply pressure P. According to one embodiment, the pressure regulating valve 13 comprises an electrohydraulic pressure setting for setting the regulating pressure RP offset. According to one embodiment, controlling the regulating pressure RP offset comprises controlling the regulating pressure RP. According to one embodiment, the supply pressure P is monitored for controlling the electrohydraulic pressure setting. According to one embodiment, the electrohydraulic setting is provided according to the principle described for the pressure regulating valve 13 in connection with FIG. 1 C, or the pressure relief valve 28 on connection with FIG. 5D. According to one embodiment, theregulating pressure RP is lower than the supply pressure P. According to one embodiment, an orifice 17 connects the outlet port 12b of the proportional flow control valve 12 and the inlet port of the pressure regulating valve 13, in order to provide a sufficient flow, by withdrawing or draining the flow from a main flow line 24a or a consumer line 24a via fluid line 24b, to a regulating line 26, in order to maintain a sufficient regulating pressure RP. Notably, the purpose of orifice 17 is to provide and be a source of hydraulic fluid to the regulating line 26. The flow direction is from the outlet port 12b via orifice 17 and towards the pressure regulating valve 13 and inlet port 13a’. Thus, hydraulic fluid passing through the orifice 17 is neither in a fluid connection to the hydraulic valve activator 11a, 11 b nor is it in fluid connection to the hydraulic valve activator 11a, 11b for activation of the hydraulic valve activator 11 , 11 b, respectively. Thus, the flow through the orifice 17 itself is not able or sufficient to activate the hydraulic valve activator 11 , 11 b, respectively. According to one embodiment, the main spool 11 comprises a centering spring device 11c biased for centering the main spool in a neutral position. According to one embodiment, the neutral position is a closed position of the main spool 11 . According to one embodiment, the neutral position comprises a closed position of the inlet port 11 d of the main spool 11 . According to one embodiment, all ports are blocked in the neutral position, so no fluid will flow through the main spool 11 . According to one embodiment, the neutral position comprises a closed position of the inlet port 11d of the main spool 11 means that at least the inlet port 11 d of the main spool 11 is in a closed position, however other ports could be open for instance in some cases where the ports may be connected to the tank port T. In some embodiments, these ports could also be closed. According to embodiments, the centering spring device 11c may be either extended or compressed when acting against its biasing force. According to one embodiment, the outlet port 12b of the proportional flow control valve 12 further is in fluid connection to an inlet port 11d of the main spool 11 . According to one embodiment, the outlet port 12b is in fluid connection to an inlet port 11 d of the main spool 11 via a consumer line 24a. According to one embodiment, the proportional flow control valve 12 is an internally pilot controlled valve. Accordingto one embodiment, the proportional flow control valve 12 is controlled using a solenoid for adjusting the flow area through the valve, i.e. an opening area, and thus an opening degree of the opening area. A proportional flow control valve 12 is generally configured to handle larger forces from the hydraulic oil, i.e. larger flow rates, compared to e.g. main spools with direct control capability using solenoids. Such main spools using solenoids are often limited to handle only up to a certain flow rate, e.g. around 80L / min yet, are bulky and space consuming with axially arranged solenoids. Thus, an effect is that in the hydraulic systems 1 of the present invention, the flow rate is instead controlled by the more able and robust, yet simple proportional flow control valve 12 which increases the ability to handle larger flow rates through the main spool 11 and thus provides for using a wider range of actuators 100 requiring higher flow rates, in a reliable manner.

[0068] According to one embodiment, the pressure regulating valve 13 is in fluid connection to a tank port T. According to one embodiment, the tank port T is further in fluid connection to a tank or reservoir for the hydraulic fluid. According to one embodiment, the outlet port 13b of the pressure regulating valve 13 is in fluid connection to the tank port T. According to one embodiment, the outlet port 13b of the pressure regulating valve 13 is in fluid connection to the tank port T via fluid line 19. According to one embodiment, fluid line 19 is further connected to fluid line 16 to which the tank port T is connected. According to one embodiment, the hydraulic system 1 is in fluid connection to the hydraulic circuit 101 of the actuator 100 via the main spool 11 . According to one embodiment, as seen in FIG. 1 , the hydraulic system 1 is in fluid connection to the hydraulic circuit 101 of the actuator 100 via the main spool 11 , wherein the main spool 11 is arranged upstream of the hydraulic circuit 101. Thus, according to one embodiment, an outlet port 11e of the main spool 11 is in fluid connection to an inlet port 101 a of the hydraulic circuit 101 . This is sometimes referred to as a meter-in regulation of the actuator 100. According to one embodiment, an outlet port 101 b of the hydraulic circuit 101 is in fluid connection to a tank port T via fluid line 20. According to one embodiment, the tank port T is the same tank port T being in fluid connection to the outlet port 13b of the pressure regulating valve 13. According to one embodiment, the mainspool 11 is configured to self-regulate upon fluid connection to the actuator 100. According to one embodiment, the main spool 11 is configured to self-regulate upon fluid connection to the actuator 100 and upon providing a supply pressure P. According to one embodiment, self-regulating means that no further external regulation is required for the movement of the valve and / or for controlling the pressure OP that it or the system regulates. According to one embodiment, a pressure OP at the outlet port 12b of the proportional flow control valve 12 is regulated or self-regulated to correspond to the sum of the opposite acting regulating pressure RP and work pressure of the centering spring device 11c forming a threshold pressure for the main spool 11 to leave the neutral position and move towards and / or to an open position According to one embodiment, wherein, upon fluid connection of the main spool 11 to the hydraulic circuit 101 of the actuator 100, the hydraulic system 1 is configured to provide a pressure OP at the outlet port 12b of the proportional flow control valve 12 that is self-regulated by the aid of the main spool 11 , to correspond to the sum of the opposite acting regulating pressure RP and work pressure of the centering spring device 11c, forming a threshold pressure for the main spool 11 to leave the neutral position, and move to an open position. Thus, the main spool 11 provides for a selfregulating of pressure OP together with other described features of the hydraulic system 1 . According to one embodiment, wherein, upon fluid connection of the main spool 11 to the hydraulic circuit 101 of the actuator 100, the hydraulic system 1 is configured to self-regulate a pressure OP at the outlet port 12b of the proportional flow control valve 12 by the aid of the main spool 11 , to correspond to the sum of the opposite acting regulating pressure (RP) and work pressure of the centering spring device 11c, forming a threshold pressure for the main spool 11 to leave the neutral position and move to an open position, Thus, the hydraulic system 1 is configured for a differential pressure regulation over the proportional flow control valve 12. According to one embodiment, the hydraulic system 1 is configured for a differential pressure regulation of the differential pressure across the proportional flow control valve 12. According to one embodiment, the hydraulic system 1 is configured for a differential pressure regulation of the differentialpressure between the inlet port 12a and the outlet port 112b of the proportional flow control valve 12. According to one embodiment, the hydraulic system 1 is configured for a differential pressure control of the differential pressure between the inlet port 12a and the outlet port 112b of the proportional flow control valve 12 comprising the differential pressure regulation and a setting of the regulating pressure RP. According to one embodiment, the hydraulic system 1 is configured for a differential pressure control of the differential pressure between the inlet port 12a and the outlet port 112b of the proportional flow control valve 12 comprising the differential pressure regulation and a setting of the regulating pressure RP offset. According to one embodiment, the system 1 takes into account the work pressure of the centering spring device 11c for the differential pressure control. According to one embodiment the differential pressure control or setting is manually operated by an operator in the cabin 301 of a vehicle 300 to which the actuator 100 is coupled or connected. According to one embodiment a set differential pressure comprises a desired differential pressure, which is comprises setting a regulating pressure RP offset e.g. by the operator or by the built-in preset characteristics of the pressure regulating valve 13. According to one embodiment, a mean differential pressure across the proportional flow control valve 12, between the inlet port 12a and the outlet port 112b of the proportional flow control valve (12), over a time period of 1s, is kept within a range of + / -25% from a set differential pressure.

[0069] The work pressure of the centering spring device 11 c is provided by the work force of the centering spring device 11 c and the cross-sectional area of the hydraulic valve activators 11a, 11b acting against the centering spring device pressure. According to one embodiment, a pressure OP at the outlet port 12b of the proportional flow control valve 12 is then self-regulated to correspond to the sum of the opposite acting regulating pressure RP and work pressure of the centering spring device 11c forming a threshold pressure for the main spool 11 to leave the neutral position. Thus, according to one embodiment, upon supplying pressure P, self-balancing of the main spool 11 is carried out in that the main spool 11 leave the neutral position at a sufficient build up of pressure at the outletport 12b of the proportional flow control valve 12 to the point where the threshold pressure has been met and just overcome. Then, a consumer line 24a over the main spool 11 to the hydraulic circuit 101 of the actuator 100 is open as the main spool 11 has moved from a neutral, to an open position by the pressure OP at the outlet port 12b acting on the hydraulic valve activator 11a, 11 b against the work pressure of the centering spring device 11c, and further pressure build up at the outlet port 12b as well as a differential pressure change over the proportional flow control valve 12, stop or at least change very little. According to what has been described, the hydraulic system 1 is configured to provide a pressure OP at the outlet port 12b of the proportional flow control valve 12 that is self-regulated to correspond to the sum of the opposite acting regulating pressure RP and work pressure of the centering spring device 11c forming a threshold pressure for the main spool 11 to leave the neutral position, and move towards and / or to an open position. According to one embodiment, the open position comprises an open position of the inlet port 11 d of the main spool 11 . According to one embodiment, the open position comprises an open position of the inlet port 11d of the main spool 11 but could comprise that other ports are open or closed as later described in e.g. FIG. 3B.

[0070] According to one embodiment, the differential pressure across the proportional flow control valve 12 is the differential pressure between the pressure OP at the outlet port 12b and the inlet port 12a of the proportional flow control valve 12. According to one embodiment, the pressure at the inlet port 12a of the proportional flow control valve 12a is the supply pressure P. Naturally, an increase of the supply pressure P, i.e. a new supply pressure P, allows for a further build up of pressure OP at outlet port 12b since this means that a new threshold pressure has been defined. However, since the threshold is defined by the sum of the regulating pressure RP, which is at an essentially constant level (offset) in relation to the supply pressure P, and the work pressure of the centering spring device 11c, the differential pressure essentially will not change. According to one embodiment, the differential pressure across the flow control valve 12 is kept essentially constant. According to one embodiment, the differential pressureacross the flow control valve 12 is kept essentially constant at least when pressure at the outlet port 12b has reached the threshold pressure and the main spool 11 has moved to the open position from the neutral position. According to one embodiment, a mean differential pressure across the proportional flow control valve 12, over a time period of 1s, is kept within a range of + / -25% from a set differential pressure. According to one embodiment, a mean differential pressure across the proportional flow control valve 12, over a time period of 1s, is within a range of + / -25% from a set differential pressure. According to one embodiment, the differential pressure regulation provides that a mean differential pressure across the proportional flow control valve 12 over a time period of 1s, is within a range of + / -25% from a set differential pressure. According to one embodiment, the differential pressure regulation provides that a mean differential pressure across the proportional flow control valve 12 over a time period of 1s, is controlled to be within a range of + / -25% from a set differential pressure. According to one embodiment, a differential pressure or a mean differential pressure across the proportional flow control valve 12 is measured between the inlet port 12a and the outlet port (112b) of the proportional flow control valve (12). According to one embodiment, a mean differential pressure across the proportional flow control valve 12, over a time period of 1s is kept within a range of + / -15% from a set differential pressure. According to one embodiment, a mean differential pressure across the proportional flow control valve 12, over a time period of 1s, is kept within a range of + / -25% from a set differential pressure, at least when pressure at the outlet port 12b has reached the threshold pressure and the main spool 11 has moved to the open position from the neutral position. According to one embodiment, a mean differential pressure across the proportional flow control valve 12, over a time period of 1s, is kept within a range of + / -15% from a set differential pressure, at least when pressure at the outlet port 12b has reached the threshold pressure and the main spool 11 has moved to the open position from the neutral position. As outlined here, a positive effect of the invention lies in the ability to adjust the proportional flow control valve 12 based on an essentially constant and known differential pressure across the same for a given setting of certainparameters, comprising regulating pressure RP offset and work pressure of the centering spring device 11c. In use, various factors like adjustments, pressure increases etc., will momentarily and at very short intervals which has no implication to the overall effect, change the differential pressure until the system 1 has again reached the set or desired differential pressure, which is reflected by defining the mean differential pressure as above. According to one embodiment, the pressure regulating valve 13 is set at a regulating pressure of 75 bar when the supply pressure is 100 bar. According to one embodiment, the regulating pressure RP is set to be 25 bar below the supply pressure P, thus the offset equals 25 bar. According to one embodiment, the work pressure of the centering spring device 11c is set at a working interval of 15-20 bar, more preferably 15 bar. According to one embodiment, the work pressure of the centering spring device 11c is at least 2 bar. According to one embodiment, the centering spring device 11c is at least 5 bar. The work pressure should at least overcome the internal friction of the main spool 11 in order to enable a precise regulation. According to one embodiment, the differential pressure across the proportional flow control valve 12 is set to be 10 bar. Thus, by setting the regulation pressure RP offset, the differential pressure across the proportional flow control valve 12 is adjustable for optimizing the performance based on different operating cases or actuators 100. According to one embodiment, the regulating pressure RP offset is preset. According to one embodiment the regulating pressure RP offset is preset by the manufacturer or by the installer. According to one embodiment, the set regulating comprises a settable regulating pressure RP offset. According to one embodiment, setting the regulating pressure RP offset is carried out manually by the operator. According to one embodiment, setting the regulating pressure RP offset is carried out automatically when connecting the actuator 100 to the working machine 300. This could e.g. be carried out by sensing the type of actuator 100 via an identification step. The identification could e.g. be carried out using NFC methods and technologies. According to one embodiment, sensing the type of actuator 100, i.e. sensing actuator type, is carried out via a radio transmitter or radio transponder or radio transceiver in the actuator 100 or tool. According to one embodiment, acorresponding device is arranged on the working machine 300 for communication with the radio transmitter or radio transponder or radio transceiver in the actuator 100 or tool. According to one embodiment, a radio transceiver is arranged on the working machine 300. According to one embodiment, sensing the type of actuator 100, i.e. sensing actuator type, is carried out via electrical transmission, or an electronic data transmission, upon connecting the actuator 100 to the working machine 300. According to one embodiment, sensing the type of actuator 100, i.e. sensing actuator type, is carried out by optical image recognition, i.e. wherein an image capturing device, such as a camera, for instance arranged to the working machine 300, captures image data comprising the actuator 100, and a subsequent image recognition step is carried out in a control unit connected to the image capturing device. According to one embodiment, the regulating pressure RP offset is controlled to change continuously and dependent on the opening degree of the opening area of the flow control valve 12. A larger opening degree provides a higher set regulating pressure RP offset, and thus an increasing differential pressure across the flow control valve 12. According to one embodiment, the regulating pressure RP offset setting may be controlled to increase further as the maximum opening degree of the flow control valve 12 has been reached. According to one embodiment, the regulating pressure RP offset setting is controlled to be kept as low as possible until the maximum opening degree of the flow control valve 12 has been reached, after which the regulating pressure RP offset is allowed to increase further. As a result, the energy loss may be kept as low as possible as the differential pressure is kept as low as possible until the degree of the opening area, and thus the opening area, is as large as possible, i.e. eventually entirely open. According to one embodiment, the work pressure of the centering spring device 11c is lower than the difference between the supply pressure P and the adjustment pressure RP. Thus, according to one embodiment, the work pressure of the centering spring device 11c is lower than the pre-set offset from the supply pressure P. Thus, the hydraulic system 1 allows for adjusting the differential pressure across the proportional flow control valve 12 to find an optimal balance between low energy consumption and high performance. Thehydraulic system 1 , using fewer standard components, provides a simple, less complex solution that enables a reliable and precise drive of one or several actuators 100.

[0071] What is described in Fig. 1 A is an embodiment, wherein the actuator 100 is operated or run in one direction and no direct regulation of the flow from the actuator is carried out as for instance no directional valve is used in the system 1 . If such system 1 would be used for actuators 100 or consumers with a pulling load, i.e. if a construction vehicle is driven downhill, no braking of the actuator 100 would be possible. Therefore, the embodiment of FIG. 1 is especially suitable for driving a conveyor belt. According to one embodiment, the actuator 100 is a conveyor belt.

[0072] FIG. 1 B shows a similar hydraulic system 1 as in FIG. 1 A, however the source of hydraulic fluid to the regulating line 26 is not provided from fluid line 24b via an orifice 17. According to this embodiment, the source of hydraulic fluid to the regulating line 26 is an external source 29 of hydraulic fluid. According to one embodiment, as seen in FIG. 1 C, the control port 13c is connected to a pressure transducer 13d which senses the supply pressure P and is configured to transmit a control signal to an electrically controlled pressure regulating valve 13 which regulates an opening between the inlet port 13a’ and outlet port 13b of the pressure regulating valve 13 to correspond to that of spring for a given RP pressure offset at a given supply pressure P. According to one embodiment, as seen in FIG. 1 C, the control port 13c is connected to a pressure transducer 13d which senses the supply pressure P and is configured to transmit a control signal to an electrically controlled pressure regulating valve 13 which regulates an opening between the inlet port 13a’ and outlet port 13b of the pressure regulating valve 13 to achieve a given RP pressure offset at a given supply pressure P. Thus, the opening is regulated to provide a regulating pressure RP that corresponds to a pressure P - (minus) a set or desired regulating pressure RP offset. Thus, the control port 13c may be located at a distance from the pressure regulating valve 13. According to one embodiment, the pressure regulating valve 13 is controlledby sending an electric current through a magnetic coil, which generates a movement and a force of a cone against a seat, all comprised in the pressure regulating valve 13, with a force proportional to the electric current. When the cone is lifted from, and thereby not in contact with the seat, an opening of the pressure regulating valve 13 is created providing a flow and relief of hydraulic fluid / oil to the tank port T. According to one embodiment, the pressure regulating valve 13 may be proportionally controlled for providing different pressures or positions. The pressure to be relieved or reduced is acting against the force of the cone and thus the pressure by the same given its design, as generated by the magnetic coil. When the force from the hydraulic fluid / oil pressure exceeds the force by the magnetic coil, the cone is lifted from the seat and releases hydraulic fluid / oil to the tank port T. According to one embodiment, a relationship between the pressure of the cone and the electric current through the magnetic coil is defined by the design of the valve, e.g. in one example, 1000mA may provide a 200 bar opening pressure, i.e. a threshold for opening the pressure regulating valve 13 by lifting the cone from the seat. Thus, by sensing the supply pressure P, a control signal is sent to provide a threshold pressure RP that is P-RP offset.

[0073] According to one embodiment, as seen in FIG. 1 D, the control port 13a is configured for providing a hydraulic reference signal for the supply pressure P and an electrically controlled pressure regulating valve 13 is further configured to transmit a control signal for controlling the pressure regulating valve 13, which regulates an opening between the inlet port 13a’ and outlet port 13b of the pressure regulating valve 13 to correspond to that of spring for a given RP pressure offset at a given supply pressure P. Thus, the opening is regulated to provide a regulating pressure RP that corresponds to a pressure P - (minus) a set or desired regulating pressure RP offset in a similar manner to that described in connection with Fig. 1 C.

[0074] According to another embodiment, as seen in FIG. 2, the hydraulic system 1 is in fluid connection to the hydraulic circuit 101 of the actuator 100 via the main spool 11 , wherein the main spool is arranged downstream of thehydraulic circuit. This is sometimes referred to as a meter-out regulation of the actuator 100.

[0075] FIG. 2 shows a hydraulic system 1 comprising a valve assembly 10 being in fluid connection to a hydraulic circuit 101 of an actuator 100. The embodiment as seen in FIG. 2 comprises the features of FIG. 1 , however, the hydraulic system 1 is in fluid connection to the hydraulic circuit 101 of the actuator 100 via the main spool 11 , wherein the main spool is arranged downstream of the hydraulic circuit 101 . Thus, according to one embodiment, the outlet port 101 b of the hydraulic circuit 101 is in fluid connection to an inlet port 11 d of the main spool 11 .According to this embodiment, the outlet port 11 e of the main spool 11 is in fluid connection to a tank port T via fluid line 21 . According to one embodiment, the tank port T is the same tank port T being in fluid connection to the outlet port 13b of the pressure regulating valve 13. Therefore, the main spool 11 is configured to control the flow of hydraulic fluid out from the actuator 100, and can be used for braking the actuator 100. Such embodiment of the hydraulic system 1 could be used for braking a construction vehicle being driven downhill. The embodiment, would for instance be useful for driving or controlling a fan with a large swing mass, or other actuators 100 with large mechanical inertia. The speed of the fan or speed of such actuators 100 may be controlled, as it enables braking or slowing down of the fan speed or speed of the actuator 100.

[0076] FIG. 3A shows a hydraulic system 1 comprising a valve assembly 10 being in fluid connection to a hydraulic circuit 101 of an actuator 100, according to an embodiment. According to the embodiment, the hydraulic system 1 is in fluid connection to the hydraulic circuit 101 of the actuator 100 via the main spool 11 , wherein the main spool 11 is arranged upstream as well as downstream of the hydraulic circuit 101. In other words, the hydraulic system 1 via the main spool 11 provides a so called meter-in as well as a meter-out regulation of the actuator 100. This is sometimes referred to as a meter-in / meter-out regulation of the actuator 100. Thus, according to the embodiment, an outlet port 11 e of the main valve 11 is in fluid connection to an inlet port 101a of the hydraulic circuit 101. According tothe embodiment, an outlet port 101 b of the hydraulic circuit 101 is in fluid connection to a further inlet port 11 d’ of the main spool 11 . A further outlet port 11e’ of the main spool 11 is in fluid connection to a tank port T. According to this embodiment, the outlet port 11 e of the main spool 11 is in fluid connection to a tank port T via fluid line 22. The embodiment of FIG. 3 is a combination of FIG. 1 and FIG. 2 in that the main spool 11 is configured to control the flow of hydraulic fluid both to and from the actuator 100. This is an advantage compared to e.g. the embodiment in FIG. 2 as the flow path is considerable shorter between the proportional flow control valve 12 and the main spool 11 . As a result, there is a reduced risk of oscillations in pressure and / or flow of hydraulic fluid for instance resulting from flow line flexibility. At the same time, the hydraulic system 1 of FIG. 3 maintains the capacity of braking the actuator 100.

[0077] FIG. 3B shows a hydraulic system 1 similar to that of FIG. 3A, wherein the main spool 11 is configured so that the inlet port 11d is in neutral, closed position, however, the inlet port 11 d’ in fluid connection to the outlet port 101b of the hydraulic circuit 101 and the outlet port 11e’ in fluid connection to tank port T is simultaneously in an open position. One purpose with such embodiment, is to achieve a free wheel function. When the inlet port 11d has moved to an open position, the ports 11d’, 11 e’ remain in an open position.

[0078] FIG. 4A shows a hydraulic system 1 comprising a valve assembly 10 being in fluid connection to a hydraulic circuit 101 of an actuator 100, according to an embodiment. According to the embodiment, the hydraulic system 1 is in fluid connection to the hydraulic circuit 101 of the actuator 100 via the main spool 11 , wherein the main spool 11 is arranged upstream as well as downstream of the hydraulic circuit 101 of the hydraulic circuit 101 . The embodiment of FIG. 4A is similar to the embodiment of FIG. 3A, however further comprises a main spool 11 which can regulate flow of hydraulic fluid in both directions through the actuator 100. According to one embodiment, the main spool 11 is a 4 / 3 way directional valve. According to one embodiment, the main spool 11 is a 4 / 2 way directional valve. According to one embodiment, the main spool 11 is a 2 / 2 way directionalvalve. Thus, the main spool 11 has four holes or ports and three positions. Thus, according to the embodiment, an inlet and outlet port 11 e of the main spool 11 is in fluid connection to an inlet and outlet port 101 a of the hydraulic circuit 101 . According to the embodiment, an inlet and outlet port 101 b of the hydraulic circuit 101 is in fluid connection to a further inlet and outlet port 11 d’ of the main spool 11 . Such inlet and outlet ports are also known as a and b ports of a 4 / 3 valve, or consumer connection ports. A further outlet port 11 e’ of the main spool 11 is in fluid connection to a tank port T. According to this embodiment, the outlet port 11 e’ of the main spool 11 is in fluid connection to a tank port T via fluid line 23. According to one embodiment, the tank port T is the same tank port T being in fluid connection to the outlet port 13b of the pressure regulating valve 13. Thus, the embodiment according to FIG. 4A enables driving the actuator 100 in both directions. The embodiment would for instance be useful for driving a conveyor belt that can be reversed, i.e. driven in an opposite direction, or a construction machine that can be driven in both directions, i.e. forward and backward. Thus, an outlet port 12b of the proportional flow control valve 12 may be in fluid connection to either of a first and second hydraulic valve activator 11 a, 11 b of the main spool 11 . According to the embodiment of FIG 4A, “either of’ comprises that the outlet port 12b may either be in fluid connection to the first hydraulic valve activator 11 a or be in fluid connection to the second hydraulic valve activator 11 b, and which may change during operation based on which direction the actuator 100 is to be driven, i.e. “either of” here comprises that the outlet port 12b is selectively in fluid connection to either of the first and second hydraulic valve activator 11 a, 11 b via a directional valve 14 . As described below, a controllable directional valve 14 controls which of the first and second hydraulic valve activator 11a, 11 b the outlet port 12b is in fluid connection to, and consequently, the direction of flow through the actuator 100. At the same time, the controllable directional valve 14 consequently controls which of the first and second hydraulic valve activator 11 , 11 b, the inlet port of the pressure regulating valve 13 is in fluid connection to.

[0079] According to one embodiment, the pressure regulating valve 13 is in fluid connection to the other of the first and second valve activator 11 a, 11 b of the mainspool 11 , via a directional valve 14. Hence, by “the other of” is meant the hydraulic valve activator 11a, 11 b not being in fluid connection to the outlet port 12b of the proportional flow control valve. The controlling of directional valve 14 control the direction of flow through the actuator 100 and hence the driving direction through the actuator 100. According to one embodiment, the centering spring device 11c comprises a first spring 11c’. According to one embodiment the centering spring device 11c comprises a first spring 11c’ and a second spring 11c”. According to one embodiment, the first and second spring 11c’, 11c” are arranged on the side of the first and second hydraulic valve actuator 11a, 11 b, respectively. In FIG. 4A, the outlet port 12b of the proportional flow control valve 12 is currently in fluid connection to the first hydraulic valve activator 11 a of the main spool 11 via the directional valve 14. At the same time, the pressure regulating valve 13 is in fluid connection to the second valve activator 11 b of the main spool 11 flow control valve providing a regulating pressure RP which is at a pre-set offset from the supply pressure P to the second hydraulic valve activator 11 b of the main spool 11 . The outlet port 12b of the proportional flow control valve 12 is further being in fluid connection to an inlet port 11d of the main spool 11 . The current position of the directional valve 14 provides for a counterclockwise flow through the actuator 100 when a pressure OP at the outlet port 12b of the proportional flow control valve 12 corresponds to the sum of the opposite acting regulating pressure RP and work pressure of the centering spring device 11c, 11c” and overcomes a threshold pressure for the main spool 11 to leave the neutral position. According to one embodiment, leaving the neutral position is moving towards an open position. Thus, the pressure OP at the outlet port 12b of the proportional flow control valve 12 is regulated or self-regulated to correspond to the sum of the opposite acting regulating pressure RP and work pressure of the centering spring device 11c, 11c” and overcomes a threshold pressure for the main spool 11 to leave the neutral position. According to one embodiment, upon activation of the directional valve 14, the outlet port 12b of the proportional flow control valve 12 is changed to be in fluid connection to the second hydraulic valve activator 11b of the main spool 11 via the directional valve 14. At the same time, the pressure regulating valve 13 is changedto be in fluid connection to the first valve activator 11a of the main spool 11 providing a regulating pressure RP which is at a set or pre-set offset from the supply pressure P to the second hydraulic valve activator 11 b of the main spool 11 . Such position of the directional valve 14 provides for a clockwise flow through the actuator 100 when a pressure OP at the outlet port 12b of the proportional flow control valve 12 is regulated to correspond to the sum of the opposite acting regulating pressure RP and work pressure of the centering spring device 11c, 11c’ and overcomes a threshold pressure for the main spool 11 to leave the neutral position.

[0080] According to one embodiment, an orifice 17 connects the outlet port 12b of the proportional flow control valve 12 and the inlet port of the pressure regulating valve 13, between the directional valve 14 and the main spool 11 , in order to provide a sufficient flow, by withdrawing or draining the flow from a main flow line 24a or a consumer line 24a to a regulating line 26, in order to maintain a sufficient regulating pressure RP. An advantage of arranging the orifice at this position, the flow direction will vary through the orifice 17 depending on which direction the actuator 100 is driven. As a result, a risk of unwanted particles in the system 1 getting stuck in the orifice is reduced and the valve assembly 10 and system 1 is self-cleaning. According to one embodiment, the orifice 17 is arranged on the other side of the directional valve 14. According to one embodiment, the directional valve 14 is a 4 / 3 way valve. An advantage of using a 4 / 3 valve for the directional valve 14 is that a such valve is closed in the neutral position, which provides an increased safety and reliability in that two valves need to be controlled or actuated in for actuating the actuator 100. According to one embodiment, the directional valve 14 is a 4 / 2 way valve. According to one embodiment, the directional valve 14 is a 2 / 2 way valve.

[0081] Fig. 4B shows the hydraulic system comprising a valve assembly 10 being in fluid connection to a hydraulic circuit 101 of an actuator 100, according to FIG. 4A, wherein a further valve 18 is introduced in the line between the outlet port 12b of the flow control valve 12 and main spool 11 . According to one embodiment,the line is also known as the feeding line. According to one embodiment, the line is the consumer line 24a. According to one embodiment, the valve 18 is a check valve 18. According to one embodiment, the check valve 18 is a spring loaded check valve 18. According to one embodiment, the flow direction is between the flow control valve 12 and the main spool 11 . By providing a check valve 18 in the feeding line or consumer line 24a provides for driving an actuator 100 which load could act hydraulically against the valve assembly 10, in a safe and reliable manner. For instance, after driving and stopping uphill with a vehicle having a hydraulic motor, such that the vehicle wants to roll backwards, this will start driving the actuator 100 in the form of the hydraulic motor in a backward direction, i.e. an opposite direction for driving uphill. As a result, a pressure is created that goes backwards through the main spool 11 , and into the valve assembly 10. A check valve 18 prevents flow and pressure further into the valve assembly 10 and the regulating circuit 10, which would increase the pressure OP at the outlet port 12b of the flow control valve 12 and thus the pressure against either of the first and second hydraulic valve activator 11a, 11b. This will prevent the main spool 11 to return to its neutral position. For other applications as opposed to the hydraulic motor like the above, i.e. where the actuator 100 may not provide a pressure back to the hydraulic circuit or system 1 , such as e.g. a cylinder, fan drive or other actuator which do not rely on the valve assembly 10 to prevent the actuator 100 from moving backwards when stopping, , a check valve 18 may not be necessary in the system 1 .

[0082] FIG. 5A shows a hydraulic arrangement 200 comprising a plurality of hydraulic systems 1 according to FIG. 4B, however, any of the hydraulic systems 1 and embodiments thereof, as e.g. described herein and e.g. in FIG. 1-3 could be comprised in a hydraulic arrangement 200 in an analogous manner. Furthermore, Fig. 5A discloses a hydraulic arrangement 200 comprising two hydraulic systems 1 , however the hydraulic arrangement 200 may comprise any number of hydraulic systems 1 , i.e. any plurality of hydraulic systems 1 that is suitable for the specific application or use. Furthermore, any suitable combination of the hydraulic systems 1 of the embodiments as described in FIG. 1-4 may be used in such hydraulicarrangement 200 that is suitable for the specific application or use. According to one embodiment the supply pressure P is fluidly connected in parallel. According to one embodiment, the hydraulic systems 1 are connected to a common tank port T. According to the embodiment, each hydraulic systems 1 connected in parallel, comprises a pressure regulating valve 13. This enables an individual controlling of the flow to and individual optimization of the balance between energy efficiency and performance for each actuator 100 in fluid connection to the respective hydraulic system 1 . For instance, if a large variation of actuators 100 and tools with individual requirements may be connected to a vehicle 300, and which may be hard to predict it may be beneficial to be able to individually control the differential pressure, for instance for trimming up a specific actuator 100 without increasing energy losses on other actuators with lower requirements. Each main spool 11 may also have centering spring devices 11c with individually set spring forces, and work pressures, to further enhance the capacity of the hydraulic system 1 for individual controlling of actuators 100 by setting individual differential pressures according to the present need of flow from the actuator 100. Furthermore, the proportional flow control valves 12 of each hydraulic system 1 are individually controlled which provides for the individual controlling of each actuator 100 and assuring that the correct amount of hydraulic fluid if provided to each actuators 100. According to one embodiment, the hydraulic arrangement 200 comprises a plurality of hydraulic systems 1 that are individually pressure compensated. According to one embodiment, the hydraulic arrangement 200 according to FIG. 5A may be provided without check valves 18. According to one embodiment, at least one of the plurality of hydraulic systems 1 comprised in the hydraulic arrangement 200 is provided with a check valve 18. According to one embodiment, any number of the plurality of hydraulic systems 1 comprised in the hydraulic arrangement 200 is provided with a check valve 18. For instance, certain hydraulic systems 1 may be dedicated for actuators 100 which may not provide a pressure back to the hydraulic circuit or system 1 .

[0083] FIG. 5B shows a hydraulic arrangement 200 comprising a plurality of hydraulic systems 1 according to FIG. 5A with the exception that the arrangement200 only comprises one single pressure regulating valve 13. According to one embodiment, the one single pressure regulating valve 13 is shared between the hydraulic systems 1 . This enables a reduction in cost, space consumption and complexity compared to using a pressure regulating valve 13 for each hydraulic system 1 . According to one embodiment, the hydraulic arrangement 200 comprises a plurality of pressure regulating valves 13 which each are dedicated to a group of hydraulic systems 1 , i.e. the number of hydraulic systems 1 exceeds the number of pressure regulating valves 13. Each group of hydraulic systems 1 may relate to a certain function, in order to vary the regulating pressure or flow or flow rate individually between the groups / functions. Furthermore, in order to provide a relative optimization between energy efficiency and performance for such embodiment, the size of the proportional flow control valve 12 in the respective hydraulic system 1 of the hydraulic arrangement 200 may be individually selected or configured, to provide sufficient and just right flow to each respective actuator 100, wherein the same supply pressure P may be provided for all functions and actuators 100 and a single and common pressure regulating valve 13. According to one embodiment, an opening degree of the opening area of the proportional flow control valves 12 in the respective hydraulic system 1 may be controlled to provide a similar effect as the described size configuration of the valve 12 with a single and common pressure regulating valve 13. This embodiment may be beneficial for a hydraulic arrangement 200 using the same set up of actuators 100 with known specific requirements. Similar to the hydraulic arrangement 200 of FIG. 5A, although the hydraulic arrangement comprises two hydraulic systems 1 , the hydraulic arrangement 200 may comprise any plurality of hydraulic systems 1 that is suitable for the specific application or use. According to one embodiment, the hydraulic arrangement 200 according to FIG. 5B may be provided without check valves 18. According to one embodiment, at least one of the plurality of hydraulic systems 1 comprised in the hydraulic arrangement 200 is provided with a check valve 18. According to one embodiment, any number of the plurality of hydraulic systems 1 comprised in the hydraulic arrangement 200 is provided with a check valve 18.

[0084] FIG. 5C shows a hydraulic arrangement 200 comprising a plurality of hydraulic systems 1 according to Fig. 5B with the exception that one of the hydraulic systems 1 comprises a further main spool 11 arranged in parallel to the main spool 11 . According to one embodiment, each of the plurality of hydraulic systems 1 comprises a valve assembly 10, wherein the valve assembly is configured to be in fluid connection to a hydraulic circuit of an actuator 100. According to one embodiment, each of the plurality of hydraulic systems 1 comprises a valve assembly 10, wherein each of the valve assemblies 10 is configured to be in fluid connection to a hydraulic circuit of an actuator 100. According to one embodiment, each of the plurality of hydraulic systems 1 comprises a valve assembly 10, wherein the valve assemblies 10 are configured to be in fluid connection to a hydraulic circuit of an actuator 100. According to one embodiment, a hydraulic arrangement 200 is provided comprising at least one hydraulic system 1 comprising a further main spool 11 arranged in parallel to the main spool 11 . According to one embodiment, a hydraulic arrangement 200 is provided comprising a plurality of hydraulic systems 1 comprising a further main spool 11 arranged in parallel to the main spool 11 . According to one embodiment, a hydraulic system 1 is provided comprising a further main spool 11 arranged in parallel to the main spool 11 . By providing a further main spool 11 arranged in parallel to the main spool a higher flow rate capacity is provided for enabling driving or operating specific actuators 100 requiring a higher flow rate. According to one embodiment, the hydraulic arrangement 200 according to FIG. 5C may be provided without check valves 18. According to one embodiment, at least one of the plurality of hydraulic systems 1 comprised in the hydraulic arrangement is provided with a check valve 18. According to one embodiment, any number of the plurality of hydraulic systems 1 comprised in the hydraulic arrangement is provided with a check valve 18.

[0085] FIG. 5D shows a hydraulic arrangement 200 according to FIG. 5B or FIG. 5C, wherein a pressure sensing device 27 e.g. comprising a pressure transducer 27 is arranged for sensing the pressure used by a plurality of actuators 100, respectively. According to one embodiment, as seen in FIG. 5D, the pressuresensing device 27 comprises one pressure transducer 27, which is configured for sensing the pressure, arranged at each of the actuator 100 connections, respectively. According to one embodiment, a pressure transducer 27 may the arranged at any suitable position that provides measuring the pressure required by each of the actuators 100, e.g. including inside the main spool 11 , at or between the inlet port 11 d and outlet port 11 e, or between the inlet port 11 d’ and 11 e’ of the main spool 11 . According to one embodiment, one single and common pressure transducer 27 is arranged for sensing the highest pressure among a plurality, or among each of the actuator 100 connections, via hydraulic check valves and the common pressure transducer 27. According to one embodiment, the hydraulic check valves are arranged at the positions corresponding to the pressure transducers 27 of FIG. 5D, and further in fluid connection to a single and common pressure transducer 27. According to one embodiment, a pressure relief valve 28 is arranged between the supply pressure P and the tank port T. According to one embodiment, the pressure relief valve 28 is arranged in parallel to the hydraulic systems 1 . According to one embodiment, the plurality of actuators 100 comprises the actuators having the pressure relief valve 28 and / or the pressure transducer 27 arranged in parallel. The load or pressures used by the plurality of actuators 100 measured by at least one pressure transducer 27 may be transmitted to a control unit of the hydraulic system 1 or arrangement 200. The hydraulic system 1 or arrangement 200 determines the highest sensed pressure, herein also referred to as Load Sense, PLS. According to one embodiment PLS corresponds to the highest pressure required by any of the actuators 100. The hydraulic system 1 or arrangement 200 determines or receives a signal indicative of the set differential pressure (DPset) across the proportional flow control valve 12 related to the particular hydraulic system 1 at which PLS has been determined. According to one embodiment, the hydraulic system 1 or arrangement 200 determines or receives a signal indicative of the highest set differential pressure (DPset) across a proportional flow control valve 12 of a hydraulic system 1 in fluid connection to any of the plurality of actuators 100. According to one embodiment, DPset is set to be sufficiently high to provide a stable regulation which in some cases are around 2-3% of the working pressure of the system, and for providing a desired flow through the proportional flow control valve 12 at full opening. According to one embodiment, the hydraulic system 1 or arrangement 200 receives a maximum allowed supply pressure Pmax indication signal. According to one embodiment, the hydraulic system 1 or arrangement 200 determines Pis+DPset. According to one embodiment, the hydraulic system 1 or arrangement 200 determines if the supply pressure P exceeds Pi_s+DPset, e.g. via the pressure relief valve 28. According to one embodiment, the hydraulic system 1 or arrangement 200 determines the lowest of Pis+DPset or Pmax. According to one embodiment, the hydraulic system 1 or arrangement 200 determines if the supply pressure P exceeds the lowest of Pis+DPsetor Pmax. According to one embodiment, this is the same thing as determining if the supply pressure P exceeds any of Pis+DPset or Pmax. According to one embodiment, the hydraulic system 1 or arrangement 200 transmits a signal for controlling the pressure relief valve 28 so that it opens if the supply pressure P exceeds Pi_s+DPSet. According to one embodiment, the hydraulic system 1 or arrangement 200 transmits a signal for controlling the pressure relief valve 28 so that it opens if the supply pressure P exceeds the lowest of the values Pis+DPset or Pmax. According to one embodiment, the pressure relief valve 28 is controlled by sending an electric current through a magnetic coil, which generates a movement and a force of a cone against a seat, all comprised in the pressure relief valve 28, with a force proportional to the electric current. When the cone is lifted from, and thereby not in contact with, the seat, an opening of the pressure relief valve 28 is created providing a flow and relief of hydraulic flu id / oil to the tank port T. According to one embodiment, the pressure relief valve 28 may be proportionally controlled for providing different pressures or positions. The pressure to be relieved or reduced is acting against the force of the cone and thus the pressure by the same given its design, as generated by the magnetic coil. When the force from the hydraulic flu id / oil pressure exceeds the force by the magnetic coil, the cone is lifted from the seat and releases hydraulic flu id / oil to the tank port T. According to one embodiment, a relationship between the pressure of the cone and the electric current through the magnetic coil is defined by the design of thevalve, e.g. in one example, 1000 mA may provide a 200 bar opening pressure, i.e. a threshold for opening the pressure relief valve 28 by lifting the cone from the seat. According to one embodiment the pressure relief valve 28 comprises an electrohydraulic pressure setting. According to one embodiment, a pressure transducer 27b is arranged for sensing the supply pressure P. According to one embodiment, the pressure transducer 27b and pressure transducer 13d are a single pressure transducer.

[0086] FIG. 5E shows a flow chart schematically showing method steps of an embodiment of a method performed by a hydraulic system 1 or hydraulic arrangement 200. A procedure or a method in a hydraulic system 1 will now be described with reference to FIG. 5E. The method comprises receiving 350 a plurality of pressure signals PA indicative of the pressures used by a plurality of actuators 100 in fluid connection to a corresponding plurality of hydraulic systems 1 , respectively, of a hydraulic arrangement 200. The method further comprises determining 352 the highest pressure PLS among the plurality of pressure signals PA. The method further comprises receiving 354 a signal indicative of the set differential pressure DPset across the proportional flow control valve 12 related to the particular hydraulic system 1 at which PLS has been determined. According to one embodiment, the hydraulic system 1 or arrangement 200 determines or receives a signal indicative of the highest set differential pressure (DPset) across a proportional flow control valve 12 among the plurality of hydraulic systems 1 . Such signal may e.g. be a signal directly from a cabin 301 of the vehicle 300 comprising the hydraulic system 1 or arrangement 200, or may be based on a set differential pressure, and / or regulating pressure RP offset and known and stored work pressures of the centering spring devices 11c. According to one embodiment, the method further comprises receiving 355 a maximum allowed supply pressure Pmax indication signal. According to one embodiment, the method further comprises receiving 356 a pressure signal indicative of the supply pressure P. According to one embodiment, method further comprises determining 358 if P> PLs+DPset, , i.e. if the supply pressre P exceeds PLs+DPset. According to one embodiment, the method further comprises transmitting 360 a signal for controllingthe pressure relief valve 28 so that it opens if the supply pressure P exceeds Pis+DPset. According to one embodiment, the method further comprises determining 361 if P> P max, i.6. if the supply pressure P exceeds Pmax. According to one embodiment, the method further comprises transmitting 362 a signal for controlling the pressure relief valve 28 so that it opens if P> Pis+DPset or Pmax , i.e. if the supply pressure P exceeds Pis+DPset or Pmax. According to one embodiment, opening of the pressure relief valve 28 comprises releasing the excess flow back to the tank T should too much oil and consequently supply pressure P have been provided from the excavator 300 connected to the actuator 100 and / or the hydraulic system 1 .

[0087] One purpose of the herein described method is to limit the supply pressure P to the sum of the highest pressure required by any of the actuators 100 and the highest set differential pressure (DPset) across a proportional flow control valve 12 of a hydraulic system 1 in fluid connection to any of the plurality of actuators 100 , such that unnecessary pressure build-up and thereby energy consumption, can be avoided. According to one embodiment, the method can also limit the Pmax of the arrangement 200 to prevent overload in that the control signal for the supply pressure P is limited to a value that corresponds to the maximum allowed system pressure or the supply pressure P.

[0088] According to one embodiment, the hydraulic systems 1 described herein are pressure compensated hydraulic systems 1 .

[0089] FIG. 6A shows a perspective view of a working machine 300 comprising a hydraulic system 1 , according to an embodiment. Fig. 6B shows a perspective view of a working machine 300 comprising a hydraulic arrangement 200, according to an embodiment. According to one embodiment, the working machine 300 is a construction machine 300. According to one embodiment, the working machine 300 is an earth moving machine 300. According to one embodiment, the actuator 100 is a tilt rotator. According to one embodiment, the actuator 100 comprises the hydraulic system 1 . According to one embodiment, the actuator 100 comprises the hydraulic arrangement 200. According to one embodiment, thehydraulic system 1 is integrated with the actuator 100. According to one embodiment, the hydraulic arrangement 200 is integrated with the actuator 100. According to one embodiment, the tilt rotator is further connected to an actuator 100. According to one embodiment, the tilt rotator comprises the hydraulic system 1 . According to one embodiment, the tilt rotator comprises a hydraulic arrangement 200.

[0090] FIG. 7A shows a flow chart schematically showing method steps of an embodiment of a method performed by a hydraulic system 1 . According to one embodiment, the hydraulic system 1 is comprised in a hydraulic arrangement 200. A procedure or a method in a hydraulic system 1 will now be described with reference to FIG. 7A. The method comprises receiving or determining 402 a regulating pressure RP offset setting. According to one embodiment, receiving a regulating pressure RP offset setting comprises receiving a regulating pressure RP offset setting signal. The method further comprising setting 405 a regulating pressure RP offset. According to one embodiment, the regulating pressure RP offset is set to form the threshold pressure for the main spool 11 to leave the neutral position as a sum of the regulating pressure RP and the work pressure of the centering spring device 11c. According to one embodiment, setting the regulating pressure RP offset is carried out by an operator of a vehicle 300. According to one embodiment, setting the regulating pressure RP offset is carried out by selecting an actuator 100 and / or intended use of the actuator 100 type.

[0091] FIG. 7B shows a flow chart schematically showing method steps of an embodiment of a method performed by a hydraulic system 1 . A procedure or a method in a hydraulic system 1 will now be described with reference to FIG. 7B. According to one embodiment, the method further comprises sensing 402 a pressure P. The method further comprising setting an electrohydraulic pressure of the pressure regulating valve 13 depending or based on the sensed pressure P for setting the regulating pressure RP offset. According to one embodiment, setting an electrohydraulic pressure of the pressure regulating valve 13 comprises transmitting an electrohydraulic control signal to the pressure regulating valve 13.According to one embodiment, setting the regulating pressure RP offset based on the sensed pressure P comprises setting the regulating pressure RP.

[0092] FIG. 7C. shows a flow chart schematically showing method steps of an embodiment of a method performed by a hydraulic system 1 . A procedure or a method in a hydraulic system 1 will now be described with reference to FIG. 7C. According to one embodiment, the method further comprises sensing 400 actuator 100 type connected to or being in the proximity of the vehicle 300 such that it is about to be connected to the vehicle 300. According to one embodiment, depending on the actuator 100 type the step 401 of determining a regulating pressure RP offset is carried out.

[0093] FIG. 7D shows a flow chart schematically showing method steps of an embodiment of a method performed by a hydraulic system 1 . A procedure or a method in a hydraulic system 1 will now be described with reference to FIG. 7D. According to one embodiment, the method further comprises sensing 401 an opening degree of flow control valve 12. According to one embodiment, regulating pressure RP offset is set to be determined continuously and dependent on the opening degree of the flow control valve 12. Reference is made to

[0068] where this is described further.

[0094] According to one embodiment, the method of FIG. 7A-7D are performed by a hydraulic arrangement 200.

[0095] According to one embodiment, the method of FIG. 7A-7D is carried out in connection with the method of FIG. 5E, before or after the method steps of FIG. 5E.

[0096] FIG. 8 shows a block schematic of a hydraulic system 1 or hydraulic arrangement 200 according to an embodiment of the invention. FIG. 8, e.g. in conjunction with the embodiments of hydraulic systems 1 in the figures, shows a hydraulic system 1 . The hydraulic system 1 or hydraulic arrangement 200 comprises processing circuitry 603 and a memory 604. The processing circuitry603 may comprise one or more programmable processor, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The memory contains instructions executable by said processing circuitry, whereby the hydraulic system 1 is operative for receiving 402 a regulating pressure I RP offset setting signal. The hydraulic system 1 is further operative for setting 404 a regulating pressure RP offset. According to one embodiment, the regulating pressure RP offset is set to form the threshold pressure for the main spool 11 to leave the neutral, position as a sum of the regulating pressure RP and the work pressure of the centering spring device 11c. According to one embodiment, the hydraulic system 1 comprises a control system for setting the regulating pressure RP offset.

[0097] According to one embodiment, the hydraulic system 1 is further operative for sensing 403 a supply pressure P. The hydraulic system 1 is further operative for setting 404 an electrohydraulic pressure of the pressure regulating valve 13 depending or based on the sensed supply pressure P for setting the regulating pressure RP.

[0098] According to one embodiment, the hydraulic system 1 is further operative for sensing actuator type 400.

[0099] According to one embodiment, the hydraulic system 1 is further operative for sensing an opening degree of the flow control valve 12.

[0100] According to one embodiment, the memory contains instructions executable by said processing circuitry, whereby the hydraulic system 1 is operative for receiving 350 a plurality of pressure signals PA indicative of the pressures used by a plurality of actuators 100 in fluid connection to a corresponding plurality of hydraulic systems 1 , respectively of a hydraulic or arrangement 200. According to one embodiment, the hydraulic system 1 is further operative for determining 352 the highest pressure PLS among the plurality of pressure signals PA. According to one embodiment, the hydraulic system 1 or arrangement 200 is further operative for receiving 354 a signal indicative of the setdifferential pressure DPset across the proportional flow control valve 12 related to the particular hydraulic system 1 at which PLS has been determined. According to one embodiment, the hydraulic system 1 or arrangement 200 is further operative for receiving 354 a signal indicative of the highest set differential pressure DPset across a proportional flow control valve 12 among the plurality of hydraulic systems 1 . Such signal may e.g. be a signal directly from a cabin 301 of the vehicle 300 comprising the hydraulic system 1 or arrangement 200, or may be based on a set differential pressure RP offset and known and stored work pressures of the centering spring devices 11 c. According to one embodiment, the hydraulic system 1 is further operative for receiving 355 a maximum allowed supply pressure Pmax indication signal. According to one embodiment, the hydraulic system 1 is further operative for receiving 356 a pressure signal indicative of the supply pressure P. According to one embodiment, the hydraulic system 1 is further operative for determining 358 if P> Pis+DPset, , i.e. if the supply pressre P exceeds Pis+DPset. According to one embodiment, the hydraulic system 1 is further operative for transmitting 360 a signal for controlling the pressure relief valve 28 so that it opens if the supply pressure P exceeds Pis+DPset. According to one embodiment, the hydraulic system 1 is further operative for determining 361 if P> P max, I-©. if the supply pressure P exceeds Pmax. According to one embodiment, the hydraulic system 1 is further operative for transmitting 362 a signal for controlling the pressure relief valve 28 so that it opens if P> Pis+DPset or Pmax , i.e. if the supply pressure P exceeds Pis+DPset or Pmax.

[0101] According to one embodiment, what is described in and in relation to FIG. 8 may be a hydraulic arrangement 200. According to one embodiment, a hydraulic arrangement 200 may comprise at least one hydraulic system 1 as described in connection with FIGS. 7-8. According to embodiment, a hydraulic arrangement 200 may comprise a plurality of hydraulic systems 1 as described in FIG. 7-8. According to one embodiment, a hydraulic arrangement 200 may comprise any suitable share of hydraulic systems as described in connection with FIG. 7-8.

[0102] In some embodiments, the feature(s) of the system 1 , or arrangement 200, e.g. the processing circuitry and the memory, which perform the method steps may be a group of network nodes, wherein functionality for performing the method are spread out over different physical, or virtual, nodes of the network. In other words, the feature(s) of the system 1 or arrangement 200 which perform the method steps may be a cloud-solution, i.e. the feature(s) of the arrangement 100 which perform the method steps may be deployed as cloud computing resources that may be distributed in the network. According to one embodiment the different nodes of the network comprises entities within one or several systems 1 and arrangements 200 in radio frequency communication.

[0103] According to other embodiments, the system 1 or arrangement 200 may further comprise a communication unit 602, which may be considered to comprise conventional means for communicating with relevant entities, such as other computers or devices or control units, to which it is operatively connected, including such computers, devices or control units located in the operator’s cabin 301 . Such entities may comprise other similar systems 1 or arrangements 200. In an embodiment the communication unit 602 may comprise chip set adopted for communication via CAN bus (Controller Area Network) or communication adopted to ISO 11898. Other examples of standards which may be supported by the communication interface 265are: ZigBee, Bluetooth, Bluetooth low energy (BLE), RFID (Radio frequency identification), USB (Universal serial bus), or IEEE 802.11 (Institute of Electrical and Electronics Engineers), including but not limited to 802.11a / b / n or other similar forthcoming standards. The communication unit 602 may comprise an antenna. The communication unit 602 may be connectable to an external antenna. The instructions executable by said processing circuitry 603 may be arranged as a computer program 605 stored e.g. in the memory 604. The processing circuitry 603 and the memory 604 may be arranged in a subarrangement 601 . The sub-arrangement 601 may be a micro-processor and adequate software and storage therefore, a Programmable Logic Device, PLD, or other electronic component(s) / processing circuit(s) configured to perform the methods mentioned above. According to one embodiment, the processing circuitry603 may comprise a single Central Processing Unit (CPU), or could comprise two or more processing units. For example, the processing circuitry 603 may include general purpose microprocessors, instruction set processors and / or related chips sets and / or special purpose microprocessors such as Application Specific Integrated Circuits (ASICs). The processing circuitry 603 may also comprise a storage for caching purposes. According to some embodiments, the system 1 or arrangement 200 comprises further functionality useful for the system 1 or arrangement 200 to serve its purpose, such as power supply, internal communications bus, internal cooling, database engine, operating system, not limiting to other functionalities.

[0104] The computer program 605 may comprise computer readable code means, which when run in a system 1 or arrangement 200 causes the system 1 or arrangement 200 to perform the steps described in any of the described embodiments of the system 1 or arrangement 200. What is referred to as a computer readable code means herein may be referred to as a computer readable code. The computer program 605 may be carried by a computer program product connectable to the processing circuitry 603. The computer program product may be the memory 604. The memory 604 may be realized as for example a RAM (Random-access memory), ROM (Read-Only Memory) or an EEPROM (Electrical Erasable Programmable ROM). Further, the computer program may be carried by a separate computer-readable medium, such as a CD, DVD or flash memory, from which the program could be downloaded into the memory 604. Alternatively, the computer program may be stored on a server or any other entity connected to the system 1 or arrangement 200, to which the system 1 or arrangement 200 has access via the communication unit 602. The computer program may then be downloaded from the server into the memory 604.

[0105] Although the description above contains a plurality of specificities, these should not be construed as limiting the scope of the concept described herein but as merely providing illustrations of some exemplifying embodiments of the described concept. It will be appreciated that the scope of the presently describedconcept fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the presently described concept is accordingly not to be limited. Reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more". All structural and functional equivalents to the elements of the abovedescribed embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed hereby. Moreover, it is not necessary for an apparatus or method to address each and every problem sought to be solved by the presently described concept, for it to be encompassed hereby.

[0106] A preferred embodiment of a system, arrangement, method, computer program, carrier, according to the invention has been described. However, the person skilled in the art realizes that this can be varied within the scope of the appended claims without departing from the inventive idea.

[0107] All the described alternative embodiments above or parts of an embodiment can be freely combined without departing from the inventive idea as long as the combination is not contradictory.

Claims

CLAIMS1 . A hydraulic system (1 ), comprising: a valve assembly (10), wherein the valve assembly (10) comprises a main spool (11 ) configured to be in fluid connection to a hydraulic circuit (101 ) of an actuator (100), wherein a supply pressure (P) is provided to an inlet port (12a) of a proportional flow control valve (12) and a control port (13a, 13c) for a pressure regulating valve (13), wherein an outlet port (12b) of the proportional flow control valve (12) is in fluid connection to either of a first and second hydraulic valve activator (11a, 11 b) of the main spool (11 ) for activation of either of the first and second hydraulic valve activator (11a, 11b), respectively, wherein the pressure regulating valve (13) further is in fluid connection to the other of the first and second valve activator (11a, 11b) of the main spool (11 ) for activation of the other of the first and second hydraulic valve activator (11a, 11 b), respectively, and providing a regulating pressure (RP) which is at a set offset from the supply pressure (P), to the other of the first and second hydraulic valve activator (11a, 11 b) of the main spool (11 ), wherein the main spool (11 ) comprises a centering spring device (11 c) biased for centering the main spool (11 ) in a neutral, closed position of the inlet port (11 d) of the main spool (11 ), wherein the outlet port (12b) of the proportional flow control valve (12) further is in fluid connection to an inlet port (11 d) of the main spool (11 ), wherein the pressure regulating valve (13) further is in fluid connection to a tank port (T), wherein, upon fluid connection of the main spool (11 ) to the hydraulic circuit (101 ) of the actuator (100), the hydraulic system (1 ) is configured to self-regulate a pressure (OP) at the outlet port (12b) of the proportional flow control valve (12) by the aid of the main spool (11 ), to correspond to the sum of the opposite acting regulating pressure (RP) and work pressure of the centering spring device (11c),forming a threshold pressure for the main spool (11 ) to leave the neutral, closed position and move to an open position of the inlet port (11 d) of the main spool (11 ), wherein the hydraulic system (1 ) is configured for a differential pressure regulation of the differential pressure across the proportional flow control valve (12).

2. The hydraulic system (1 ) according to claim 1 , wherein the differential pressure across the proportional flow control valve (12) is the differential pressure between the inlet port (12a) and the outlet port (12b) of the proportional flow control valve (12).

3. The hydraulic system (1 ) according to any of the preceding claims, wherein the hydraulic system (1 ) is configured for a differential pressure control, for setting a differential pressure across the proportional flow control valve (12), comprising the differential pressure regulation and a setting of the regulating pressure (RP) offset.

4. The hydraulic system (1 ) according to any of the preceding claims, wherein a mean differential pressure across the proportional flow control valve (12), over a time period of 1 s, is kept within a range of + / -25% from a set differential pressure.

5. The hydraulic system (1 ) according to any of the preceding claims, wherein the main spool (11 ) is arranged upstream of the actuator (100).

6. The hydraulic system (1 ) according to any of the preceding claims, wherein the main spool (11 ) is arranged downstream of the actuator (100).

7. The hydraulic system (1 ) according to any of the preceding claims, wherein the main spool (11 ) is arranged upstream and downstream of the actuator (100).

8. The hydraulic system (1 ) according to any of the preceding claims, wherein the outlet port (12b) of the proportional flow control valve (12) is selectively in fluid connection to either of a first and second hydraulic valve activator (11 a, 11 b) of the main spool (11 ), and the pressure regulating valve (13) is in fluid connection tothe other of the first and second valve activator (11a, 11 b) of the main spool (11 ), via a directional valve (14).

9. The hydraulic system (1) according to any of the preceding claims, wherein an orifice (17) connects the outlet port (12b) of the proportional flow control valve (12) and the inlet port 13a’ of the pressure regulating valve (13).

10. The hydraulic system (1 ) according to claim 9 and claim 8, wherein the orifice (17) connects the outlet port (12b) of the proportional flow control valve (12) and the inlet port 13a’ of the pressure regulating valve (13) between the directional valve (14) and the main spool (11 ).11 . The hydraulic system (1 ) according to any preceding claims, and claim 8, wherein the main spool (11 ) is a 4 / 3 way, 4 / 2 way or a 2 / 2 way directional valve.

12. The hydraulic system (1 ) according to any preceding claims, wherein the directional valve (14) is a 4 / 3 way or a 4 / 2 way directional valve.

13. The hydraulic system (1 ) according to any of the preceding claims, wherein the valve assembly (10) further comprises a check valve (18) arranged between the outlet port (12b) of the proportional valve (12) and the main spool (11 ).

14. The hydraulic system (1 ) according to any of the preceding claims, wherein the pressure regulating valve (13) comprises an electrohydraulic pressure setting for setting the regulating pressure (RP) offset.

15. The hydraulic system (1 ) according to any of the preceding claims, wherein a further main spool (11 ’) is arranged in parallel to the main spool (11 ).

16. The hydraulic system (1 ) according to any of the preceding claims, wherein the hydraulic system (1 ) is a pressure compensated hydraulic system (1 ).

17. The hydraulic system (1 ) according to any of the preceding claims, wherein the centering spring device (11c) comprises a first and second centering spring (11c’, 11c”).

18. A hydraulic arrangement (200) comprising a plurality of hydraulic systems (1) according to any of the preceding claims, wherein the supply pressure (P) is fluidly connected in parallel, wherein the tank port (T) is fluidly connected in parallel.

19. The hydraulic arrangement (200) according to claim 18, wherein the hydraulic arrangement (200) comprises only one single shared pressure regulating valve (13).

20. A method performed by a hydraulic system (1 ) according to any of the preceding claims 1-17, the method comprising:- receiving or determining (402) a regulating pressure (RP) offset setting,- setting (405) a regulating pressure (RP) offset to form the threshold pressure for the main spool (11) to leave the neutral, closed position of the inlet port (11 d) of the main spool (11 ) and move to an open position of the inlet port (11 d) of the main spool (11 ), as a sum of the regulating pressure (RP) and the work pressure of the centering spring device (11c).21 . The method according to claim 20, wherein the method further comprising:- sensing (403) a pressure (P),- setting (404) an electrohydraulic pressure of the pressure regulating valve (13) for setting the regulating pressure (RP) offset, based on the sensed pressure (P).

22. The method according to any of the preceding claims 20 or 21 , wherein the method further comprising:- sensing (400) actuator (100) type.

23. The method according to any of the preceding claims 20-22, wherein the method further comprising:- sensing (401 ) an opening degree of the opening area of the flow control valve (12).

24. The method according to any of the preceding claims 20-23, and claim 18 or 19, wherein the method further comprising:- receiving (350) a plurality of pressure signals (PA) indicative of the pressures used by a plurality of actuators (100) in fluid connection to a corresponding plurality of hydraulic systems (1 ), respectively in a hydraulic arrangement (200),- determining (352) the highest pressure (PLS) among the plurality of pressure signals (PA),- receiving (354) a signal indicative of the highest set differential pressure (DPset) across a proportional flow control valve (12) among the plurality of hydraulic systems (1),- receiving (356) a pressure signal indicative of the supply pressure (P),- transmitting (360) a signal for controlling the pressure relief valve (28) so that it opens if the supply pressure (P) exceeds (PLs)+(DPset).

25. A method performed by a hydraulic arrangement (200) comprising a plurality of hydraulic systems (1 ), wherein each of the plurality of hydraulic systems (1 ) comprises a valve assembly (10), wherein the valve assembly (10) is configured to be in fluid connection to a hydraulic circuit (101 ) of an actuator (100), wherein a supply pressure P is provided to an inlet port (12a) of a proportional flow control valve (12), wherein an outlet port (12b) of the proportional flow control valve (12) further is in fluid connection to an inlet port (101a) of the hydraulic circuit (101 ), further comprising a pressure sensing device (27), the method comprising:- receiving (350) a plurality of pressure signals (PA) indicative of the pressures used by a plurality of actuators (100) in fluid connection to the plurality of hydraulic systems (1 ), respectively,- determining (352) the highest pressure (PLS) among the plurality of pressure signals (PA),- receiving (354) a signal indicative of the highest set differential pressure (DPset) across a proportional flow control valve (12) among the plurality of hydraulic systems (1 ),- receiving (356) a pressure signal indicative of the supply pressure (P),- transmitting (360) a signal for controlling the pressure relief valve (28) so that it opens if the supply pressure (P) exceeds (PLs)+(DPset).

26. The method according to any of the preceding claims 24 or 25, wherein the method further comprising:- receiving (355) a maximum allowed supply pressure (Pmax) indication signal,- transmitting (362) a signal for controlling the pressure relief valve (28) so that it opens if (P)> (PLs)+(DPset) or (Pmax).

27. A hydraulic system (1 ) according to any of the preceding claims 1 -17, further comprising: processing circuitry (603); and a memory (604), said memory (604) containing instructions executable by said processing circuitry (603), whereby said system (1) is operative for:- receiving or determining (402) a regulating pressure (RP) offset setting, setting 405 a regulating pressure (RP) offset to form the threshold pressure for the main spool (11 ) to leave the neutral, closed position of the inlet port(11 d) of the main spool (11 ), and move to an open position of the inlet port (11 d) of the main spool (11 ), as a sum of the regulating pressure RP and the work pressure of the centering spring device (11c).

28. The hydraulic system (1) according to claim 27, further operative for:- sensing (403) a pressure (P),- setting (404) an electrohydraulic pressure of the pressure regulating valve (13) for setting the regulating pressure (RP) offset, based on the sensed pressure (P).

29. The hydraulic system (1 ) according to any of the preceding claims 27-28, further operative for:- sensing (400) actuator (100) type.

30. The hydraulic system (1 ) according to any of the preceding claims 27-29, further operative for:- sensing (401 ) an opening degree of the opening area of the flow control valve (12).31 . The hydraulic system (200) according to any of the preceding claims 27-30 and 18 or 19, further operative for:- receiving (350) a plurality of pressure signals (PA) indicative of the pressures used by a plurality of actuators (100) in fluid connection to a plurality of hydraulic systems (1 ), respectively of a hydraulic arrangement (200),- determining (352) the highest pressure (PLS) among the plurality of pressure signals (PA),- receiving (354) a signal indicative of the highest set differential pressure (DPset) across a proportional flow control valve (12) among the plurality of hydraulic systems (1 ),- receiving (356) a pressure signal indicative of the supply pressure (P),- transmitting (360) a signal for controlling the pressure relief valve (28) so that it opens if the supply pressure (P) exceeds (Pi_s)+(DPSet).

32. A hydraulic arrangement (200) comprising a plurality of hydraulic systems (1 ), wherein each of the plurality of hydraulic system (1 ) comprises a valve assembly (10), wherein the valve assembly (10) is configured to be in fluid connection to a hydraulic circuit (101 ) of an actuator (100), wherein a supply pressure P is provided to an inlet port (12a) of a proportional flow control valve, wherein an outlet port (12b) of the proportional flow control valve (12) further is in fluid connection to an inlet port (101a) of the hydraulic circuit (101), further comprising a pressure sensing device (27), the hydraulic arrangement (200) further comprising: processing circuitry (603); and a memory (604), said memory (604) containing instructions executable by said processing circuitry (603), whereby said hydraulic arrangement (200) is operative for:- receiving (350) a plurality of pressure signals (PA) indicative of the pressures used by a plurality of actuators (100) in fluid connection to the plurality of hydraulic systems (1) of the hydraulic arrangement (200),- determining (352) the highest pressure (PLS) among the plurality of pressure signals (PA),- receiving (354) a signal indicative of the highest set differential pressure (DPset) across a proportional flow control valve (12) among the plurality of hydraulic systems (1 ),- receiving (356) a pressure signal indicative of the supply pressure (P),- transmitting (360) a signal for controlling the pressure relief valve (28) so that it opens if the supply pressure (P) exceeds (Pi_s)+(DPset).

33. The hydraulic arrangement (200) according to claim 32, further operative for:- receiving (355) a maximum allowed supply pressure (Pmax) indication signal,- transmitting (362) a signal for controlling the pressure relief valve (28) so that it opens if (P)> (Pi_s)+(DPset) or (Pmax).

34. A computer program (605) comprising computer readable code means to be run in a hydraulic system (1), which computer readable code means when run in the hydraulic system (1) causes the hydraulic system (1) to carry out the method according to any of the preceding claims 20-26.

35. A carrier containing the computer program (605) according to claim 34, wherein the carrier is one of an electronic signal, an optical signal, a radio signal or a computer readable storage medium.

36. A working machine (300) comprising a hydraulic system (1 ) according to any of the preceding claims 1-19, 27-33.

37. A working machine (300) comprising a hydraulic arrangement (200) comprising a plurality of hydraulic systems (1 ) according to any of the preceding claims 1-19, 27-33.

Images