Modular hydraulic pump system

Abstract

A hydraulic pump system comprises a high-pressure line (10), a low-pressure line (12), and at least two pump units (200a, 200b, 200c). Each pump unit comprises a cylinder space (14a, 14b, 14c), a piston (16a, 16b, 16c) arranged in the cylinder space, and a chamber (18a, 18b, 18c) contained within the cylinder space and having a volume limited by the piston. Further, the piston can be brought to recurring reciprocating motion with respect to the cylinder space so that the volume of the chamber simultaneously decreases for producing volume flow, and increases for receiving volume flow, respectively. The valve arrangement (22a, 22b, 22c) controls the fluid communications so that in a first state, the chamber is, in turn, in fluid communication with the high-pressure line (10) when the volume of the respective chamber is simultaneously decreasing, and in a second state, the chamber is in fluid communication with the low-pressure line (12) when the volume of the respective chamber is simultaneously increasing. This system enables efficient control of the flow and pressure of hydraulic fluid in various applications.

Description

[0001] MODULAR HYDRAULIC PUMP SYSTEM

[0002] Field of the invention

[0003] The invention relates to a hydraulic pump system.

[0004] Background of the invention

[0005] In non-road mobile machinery, the future means that fuel tanks and diesel engines will gradually become secondary in the implementation of power transmission of the machines, or cease to exist, and electrical transmission will be used in addition to or instead of them, to guarantee that the machines are emission free, whereby electric motors and electric motor drives, various battery and charging solutions, as well as energy control systems will be introduced.

[0006] This also involves changes in the solutions of oil hydraulics of machines, which were previously based on a diesel engine and hydraulic pumps driven by it for producing pressurized medium to be used in machine functions, such as a swivelled boom or a crane or drive transmission. The pressurized medium is utilized in linearly moving or rotating actuators for implementing the various functions of the machine. The pressurized medium is typically hydraulic fluid, for example hydraulic oil.

[0007] With respect to hydraulic control systems, there is thus a clear need for new solutions which are suitable for future machines and elsewhere.

[0008] Brief summary of the invention

[0009] The hydraulic pump system according to the invention will be presented in claim 1.

[0010] The method for controlling the hydraulic pump system according to the invention will be presented in claim 31 . Claim 36 relates to a hydraulic pump system comprising a memory in which a computer program code is stored, wherein at least one memory and computer program code are configured so that at least one processor of the hydraulic pump system implements the method according to the invention.

[0011] Claim 37 relates to a computer program code comprising a computer program code which, when run by processors, makes the hydraulic pump system implement the method according to the invention.

[0012] Other claims disclose some more specific examples of the invention.

[0013] The hydraulic pump system comprises a high-pressure line, a low-pressure line, and at least two pump units.

[0014] Each pump unit includes a cylinder space, a piston placed in the cylinder space, and a chamber contained in the cylinder space and having a volume limited by the piston. The piston can be brought to a recurring reciprocating motion with respect to the cylinder space so that the volume of the chamber simultaneously decreases accordingly, for producing a volume flow. Further, the piston can be brought to a recurring reciprocating motion with respect to the cylinder space so that the volume of the chamber simultaneously increases accordingly, for receiving a volume flow.

[0015] Each pump unit also comprises a valve arrangement whose first operating state is used to bring the chamber, in turn, into fluid communication with the high-pressure line when the volume of said chamber is simultaneously decreasing. In the second operating state of the valve arrangement, the chamber is in fluid communication with the low-pressure line when the volume of said chamber is simultaneously increasing.

[0016] In an example, the hydraulic pump system also comprises one or more power units arranged to maintain said recurring reciprocating motion. The speed of said reciprocating motion is varied in proportion to a control signal given by an electronic control unit and received by said electric motor arrangement for controlling or changing the volume flow of hydraulic fluid supplied by the pump unit. In some examples, the hydraulic pump system is implemented by utilizing modules having a number of components or elements. The hydraulic pump system can be expanded by connecting a module to another similar module or to a different module. Other components or elements needed may also be connected to a module. The module may comprise ports for hydraulic fluid, for connecting components or elements, ports of other modules, or hydraulic fluid lines.

[0017] In some examples, the hydraulic pump system is capable of compensating for fluctuations of hydraulic fluid and volume flow in the high-pressure line and / or the low-pressure line, or between them.

[0018] For enabling the methods to be implemented in the hydraulic pump system, the hydraulic pump system may also comprise an electronic control unit adapted to control the functions of the hydraulic pump system by means of control signals. It is thus possible, for example, to maintain said recurring reciprocating motion and also to vary the speed of the motion, whereby the volume flow of hydraulic fluid produced can be controlled and varied as desired. Controlling the speed is implemented by means of, for example, an electric motor arrangement.

[0019] Description of the drawings

[0020] In the following, the invention will be described in more detail with reference to the appended drawings, in which

[0021] Fig. 1 shows a reduced schematic view of a hydraulic pump system according to an example of the invention;

[0022] Figs. 2a, 2b and 2c each show a reduced schematic view of a hydraulic pump system according to an example of the invention, and a valve arrangement thereof; Figs. 3a, 3b, 3c, and 3d each show a reduced schematic view of an additional unit or an additional module for a hydraulic pump system according to an example of the invention, and a valve arrangement thereof;

[0023] Fig. 4a shows a reduced schematic view of a line unit or a line module for a hydraulic pump system according to an example of the invention, with a linear actuator connected to the same;

[0024] Fig. 4b shows a reduced schematic view of a line unit or a line module for a hydraulic pump system according to an example of the invention, with a rotating actuator connected to the same;

[0025] Fig. 4c shows a reduced schematic view of a hydraulic pump system according to an example of the invention, with a pump unit of an open circuit connected to the same;

[0026] Fig. 4d shows a reduced schematic view of a hydraulic pump system according to an example of the invention, with a pump unit of a closed circuit connected to the same;

[0027] Fig. 4e shows a reduced schematic view of a hydraulic pump system according to some examples of the invention;

[0028] Fig. 5 shows a reduced schematic view of the control of a hydraulic pump system according to an example of the invention;

[0029] Fig. 6 shows a reduced schematic view of a method for controlling a hydraulic pump system according to an example of the invention;

[0030] Figs. 7a and 7b show examples of applications of a hydraulic pump system for recovering energy;

[0031] Fig. 8 shows a reduced schematic view of a hydraulic pump system according to some examples of the invention;

[0032] Figs. 9a, 9b and 9c show reduced schematic views of a valve arrangement and a transmission arrangement for a hydraulic pump system according to some examples of the invention, as well as the operation of the transmission system;

[0033] Figs. 10a and 10b show reduced schematic views of bearing wobblers according to some examples of the invention;

[0034] Fig. 11 shows a reduced schematic view of a hydraulic pump system according to some examples of the invention.

[0035] Detailed description of the invention

[0036] In the following, the hydraulic pump system and its parts and operation will be described with reference to the appended figures which are illustrative / sche- matic and not intended to limit the scope of the invention. There may be differences between the figures and the described examples, which differences are appreciated and applicable by a person skilled in the art without deviating from the core idea of the invention.

[0037] Figures 1 , 2a and 2b show a set of components or elements according to an example of a hydraulic pump system, wherein the components or elements may also constitute a unit or a module in which the presented invention can be applied.

[0038] In this description, a unit or a module refers to the above-mentioned set according to an example. Alternatively, a module refers to an entity which can be expanded by connecting it to another similar module or a different module. Other components or elements needed may also be connected to a module. The module may comprise ports for hydraulic fluid, for connecting components or elements, ports of other modules, or hydraulic fluid lines.

[0039] The unit and the module can be implemented, in whole or in part, as a structure, for example as one or more hydraulic manifolds, in which lines for hydraulic fluid are implemented, for example, by means of drill holes, and to which e.g. valves of valve arrangements are connected. The hydraulic manifold is formed of, for example, a piece of metal by machining.

[0040] Alternatively, the hydraulic pump system may be implemented, either in whole or in part, by utilizing components or elements, such as valves of valve arrangements, wherein lines and fluid communications between them are provided by means of hydraulic lines implemented with, for example, hoses or pipes.

[0041] As shown in the examples of Figs. 1 , 2a, 2b, and 2c, the hydraulic pump system comprises a high-pressure line 10, a low-pressure line 12, at least two pump units 200a, 200b, 200c, and a valve arrangement 22a, 22b, 22c, which in one example may constitute a module 24.

[0042] The pressure of hydraulic fluid is lower in the low-pressure line 12 than in the high-pressure line 10, wherein the pressure difference can be used to carry out work in e.g. an actuator. The lines 10, 12 are implemented by means of, for example, drill holes, hoses, or pipes.

[0043] In an example, the line 10, 12 may consist of two or more branches 10a, 10b, 10c, 12a, 12b, 12c, as shown in Fig. 1. One of the branches 10a, 10b, 10c of the line 10 and one of the branches 12a, 12b, 12c of the line 12 may be provided for each pump unit 200a, 200b, 200c. Said branches of the line 10, on one hand, and said branches of the line 12, on the other hand, may be connectible to a common line, for example within or outside the module 24. Each line 10, 12 may consist of two or more sections which are in communication with each other and are located within and / or outside one module or more modules.

[0044] Each pump unit 200a, 200b, 200c comprises a cylinder space 14a, 14b, 14c, a piston 16a, 16b, 16c arranged in the cylinder space 14a, 14b, 14c, and a chamber 18a, 18b, 18c contained within the cylinder space 14a, 14b, 14c and having a volume limited by the piston 16a, 16b, 16c. In an example, the cylinder space 14a, 14b, 14c is implemented by means of a drill hole in the hydraulic manifold.

[0045] The piston 16a, 16b, 16c can be brought into a recurring reciprocating motion with respect to the cylinder space 14a, 14b, 14c so that the volume of the chamber 18a, 18b, 18c simultaneously decreases for producing volume flow and increases for receiving volume flow, respectively. In the operation of the valve arrangement 22a, 22b, 22c, first states and second states are provided. By means of the first states, each chamber 18a, 18b, 18c is, in turn, in fluid communication with the high-pressure line 12 when the volume of said chamber 18a, 18b, 18c simultaneously decreases. By means of the second states, each chamber 18a, 18b, 18c is in fluid communication with the low-pressure line 10 when the volume of said chamber 18a, 18b, 18c simultaneously increases.

[0046] According to the examples of Figs. 2a, 2b and 2c, the number of pump units 200a, 200b, 200c in the module 24 is two or more, preferably three or more, including at least a first pump unit 200a and a second pump unit 200b.

[0047] In an example shown in Fig. 2a, the valve arrangement 22a, 22b, 22c of each pump unit 200a, 200b, 200c comprises two non-return valves 22a1 , 22a2, 22b1 , 22b2, 22c1 , 22c2 which may also be spring loaded. For implementing said first state, the first one of these is arranged to be opened and the second one to be closed when the volume of the chamber 18a, 18b, 18c of the respective pump unit 200a, 200b, 200c is decreasing. Thus, the pressure of hydraulic fluid increases and causes said opening and closing. Further, for implementing said second state, the first one of these is arranged to be closed and the second one to be opened when the volume of the chamber 18a, 18b, 18c of the respective pump unit 200a, 200b, 200c is increasing. Thus, the pressure of hydraulic fluid decreases and causes the opening of the closed valve and the closing of the opened valve.

[0048] In another example, shown in Fig. 2b, the valve arrangement 22a, 22b of each pump unit 200a, 200b comprises a valve which is a hydraulically piloted directional valve. Said directional valve has a first hydraulic pilot line 24a adapted to gauge the pressure in the chamber 18a of the first pump unit, and a second hydraulic pilot line 24b adapted to gauge the pressure in the chamber 18b of the second pump unit. Said directional valve also comprises a shaft 24c reciprocating in the drill hole.

[0049] For implementing said first state, the pressure in the first hydraulic pilot line 24a is adapted to move the shaft 24c in a first direction. It is thus typical that the volume and the pressure of the chamber 18a of the first pump unit 200a are increasing, and the volume and the pressure of the chamber 18a of the second pump unit 200b are decreasing, or the pressure difference causes the movement.

[0050] For implementing said second state, the pressure in the second hydraulic pilot line 24b is adapted to move the shaft 24c in an opposite second direction. It is thus typical that the volume and the pressure of the chamber 18a of the first pump unit 200a are decreasing, and the volume and the pressure of the chamber 18a of the second pump unit 200b are increasing, or the pressure difference causes the movement.

[0051] In a third example, shown in Fig. 2c, the valve arrangement 22a, 22b, 22c of each pump unit 200a, 200b, 200c comprises one or more dividing discs which are so-called valve discs, wherein at least one of them is rotating or rotatable and can be brought into different rotary positions. For the chamber 18a, 18b, 18c of the pump unit 200a, 200b, 200c, the rotating valve disc is provided with a channel, for example a curved channel for said first state when the rotating valve disc is in its first rotary position, and a second channel, for example a curved channel, for said second state when the rotating valve disc is in its second rotary position. By means of said channels, hydraulic fluid is led through the rotating valve disc. Hydraulic fluid can also be led by other valve discs and channels therein.

[0052] In a fourth example, shown in Fig. 2c, the valve arrangement 22a, 22b, 22c of two or more pump units 200a, 200b, 200c is common to them or is combined as a valve arrangement comprising one or more dividing discs, so-called valve discs, wherein at least one of them is rotating or rotatable, and can be brought into different rotary positions. For the chambers 18a, 18b, 18c of said two or more pump units 200a, 200b, 200c, the rotating valve disc is provided with at least two channels, e.g. curved channels, for said first state when the rotating valve disc is in its first rotary position, and at least two second channels, e.g. curved channels, for said second state when the rotating valve disc is in its second rotary position. By means of said channels, hydraulic fluid is led through the rotating valve disc. Hydraulic fluid can also be led by other valve discs and channels therein. The valve arrangement 22a, 22b, 22c may comprise a transmission element 78a, 78b for rotating the valve disc described above. In an example, one or more transmission elements 78a, 78b may comprise a power unit adapted to move the valve disc and being, for example, an electric motor arrangement. In another example, one or more transmission elements 78a, 78b are connected to a transmission element 20 which will be described below. The operation of the valve disc rotated by the transmission element 20 can be synchronized with the change in the volume of the chambers 18a, 18b, 18c of the pump unit 200a, 200b, 200c. Said synchronization is implemented, for example, mechanically, or it is controlled by means of control signals from an electronic control unit 70 which will be described below.

[0053] In the examples described above, it may also be possible that two or more transmission elements 78a, 78b are connected to each other so that their operation can be synchronized with each other, or one power unit can be used to actuate all these rotating valve discs. Thus, it may also be possible that two or more rotating valve discs are actuated by means of a coupling between one transmission element 78a, 78b and the transmission element 20. The coupling between the transmission element 78a, 78b and the transmission element 20 can be implemented with, for example, mechanical or electromechanical components. Examples of the components include one or more of the following: gearwheels; or gear systems. The components may be electrically controllable, whereby the control of the components can be implemented with, for example, an electronic control unit which generates control signals for controlling the component / s.

[0054] According to the example of Fig. 1 , the hydraulic pump system further comprises one or more transmission elements 20, to which the pistons 16a, 16b, 16c of at least two pump units 200a, 200b, 200c are connected. The function of the transmission element 20 is to bring said pistons 16a, 16b, 16c into the above described recurring reciprocating motion in relation to the respective cylinder spaces 14a, 14b, 14c of these pump units 200a, 200b, 200c so that the volumes of the respective chambers 18a, 18b, 18c of these pump units 200a, 200b, 200c decrease and increase accordingly. In an example, the transmission element 20 constitutes or comprises a rotatable transmission means adapted to convert the rotary motion of the transmission means to a reciprocating linear motion of the pistons 16a, 16b, 16c of each pump unit 200a, 200b, 200c connected to it.

[0055] In an example, the transmission element 20 constitutes or comprises a linear screw, a camshaft, an eccentric shaft, or a crankshaft, which may be of a type known as such. Several connecting rods may be connected to the crankshaft, for example two or three articulated rods, which may be of a type known as such. The crankshaft is connected by two or more connecting rods to the pistons 16a, 16b, 16c of at least two pump units 200a, 200b, 200c. In an example, said camshaft, eccentric shaft or crankshaft constitutes or comprises a rotatable transmission means. In an example, a linear screw actuates the piston 16a, 16b, 16c which slides within the cylinder space 14a, 14b, 14c.

[0056] In an example, each transmission element 20 further comprises one or more power units which are adapted to rotate the transmission element 20 at variable speeds and which may constitute or comprise an electric motor arrangement 30 whose rotational speed is adjustable, for example by means of a frequency converter.

[0057] In an example, each transmission element 20 further comprises one or more electric motor arrangements 30 adapted to rotate the transmission element 20 at variable speeds.

[0058] The speed of the transmission element 20 is dependent on or proportional to the control signal received. The purpose of controlling the speed is to change the volume flow supplied by the pump units 200a, 200b, 200c. This is based on the fact that the speed of the transmission element 20 affects the frequency of the reciprocating motion of the piston 16a, 16b, 16c of each pump unit 200a, 200b, 200c, on which frequency the volume flow exiting or entering the respective chamber 18a, 18b, 18c in a given unit of time is dependent.

[0059] In an example, the transmission element 20 is adapted to bring the motions of the pistons 16a, 16b, 16c of two or more pump units 200a, 200b, 200c to different phases so that said pump units 200a, 200b, 200c will provide a combined or total volume flow which is, in some way, optimal or, for example, as even as possible in a situation where the above described frequency of the reciprocating motion is not changing.

[0060] In an example, particularly in the case of two pump units 200a, 200b, 200c, as shown in Fig. 2, the magnitude of the phase difference between said phases is 180 degrees. This means that the respective pistons 16a, 16b, 16c always move in opposite directions.

[0061] In an example, particularly in the case of three pump units 200a, 200b, 200c, as shown in Fig. 1 , the magnitude of the phase difference between said phases is 120 degrees. This means that the respective pistons 16a, 16b, 16c move, at times, in opposite directions and, at times, in the same direction.

[0062] In an example, the hydraulic pump system comprises two or more transmission elements 20 of the above described type. Two or more of these transmission elements 20 may be engaged to each other by one or more coupling elements 62. Thus, two or more transmission elements 20 can be driven by just one power unit, for example an electric motor arrangement 42, whose rotational speed is adjustable by e.g. a frequency converter.

[0063] The coupling element 62 may comprise a mechanical coupler which may be of a type known as such.

[0064] In an example, the coupling element 62 can be switched in a controllable manner to a first state in which the two transmission elements 20 connected to the respective coupling element 62 are forced to rotate together in synchronization. It can also be switched to a second state in which said two transmission elements 20 can rotate separately and asynchronously. In said second state, one transmission element 20 may be rotatable and the other transmission element 20 may be stopped, but a third state may also be provided for this. Thus, the coupling element 62 can disengage transmission elements from each other so that they can operate independently.

[0065] In an example, the speed of the pistons 16a, 16b, 16c of one or more pump units 200a, 200b, 200c deviates from the speed of the pistons 16a, 16b, 16c of one or more other pump units 200a, 200b, 200c in such a way that a combined or total volume flow is supplied in said one or more pump units 200a, 200b, 200c, deviating from the combined or total volume flow supplied by said other pump units 200a, 200b, 200c. For implementing this, the hydraulic pump system may comprise a number of separate, independently operating power units, such as electric motor arrangements 30.

[0066] In an example, the pump units 200a, 200b, 200c implementing the same speed are arranged in one unit / module 24, and the pump units 200a, 200b, 200c implementing another speed are arranged in another unit / module 24. Said units / modules 24 may be connected to each other.

[0067] In another example, the maximum volumes of the chambers 18a, 18b, 18c of one or more pump units 200a, 200b, 200c deviate from the volume of the chambers 18a, 18b, 18c of one or more other pump units 200a, 200b, 200c in such a way that a combined or total volume flow is produced in said one or more pump units 200a, 200b, 200c which deviates from the combined or total volume flow produced by said other pump units 200a, 200b, 200c. The maximum volume in each pump unit 200a, 200b, 200c is determined by either the maximum volume of the chamber 18a, 18b, 18c or the combination of the maximum distance travelled by the piston 16a, 16b, 16c and the diameter of the cylinder space 14a, 14b, 14c. For implementing this, the dimensions of said chambers 18a, 18b, 18c deviate from the dimensions of the chambers 18a, 18b, 18c of the other pump units 200a, 200b, 200c in such a way that different combined or total volume flows are achieved while the speeds of the respective pistons 16a, 16b, 16c remain the same.

[0068] In an example, the maximum distances travelled by the pistons 16a, 16b, 16c of one or more pump units 200a, 200b, 200c deviate from the maximum distance travelled by the pistons 16a, 16b, 16c of one or more other pump units 200a, 200b, 200c in such a way that a combined or total volume flow is achieved in said one or more pump units 200a, 200b, 200c which deviates from the combined or total volume flow produced by said other pump units 200a, 200b, 200c. For implementing this, the maximum distance travelled by the pistons 16a, 16b, 16c, caused by two or more transmission elements 20, deviates from the maximum distance travelled by the pistons 16a, 16b, 16c of the other pump units 200a, 200b, 200c in such a way that different combined or total volume flows are achieved even where the speeds of the respective pistons 16a, 16b, 16c remain the same. Variation in the maximum distance is achieved by varying, for example, the dimensions of the crankshaft and the connecting rod.

[0069] Next, other sets of components or elements will be discussed, which are possibly included in the hydraulic pump system and which may also constitute a unit or a module, for example an auxiliary unit or auxiliary module 68.

[0070] Further, as shown in the examples of Figs. 3a, 3b, 3c, and 3d, the hydraulic pump system may comprise a first line 28a for conveying hydraulic fluid, a cylinder space 32, a piston 34 arranged in the cylinder space 32, and a chamber 36 contained in the cylinder space 32 and having a volume limited by the piston 34. According to an example, these may constitute an auxiliary unit or auxiliary module 68. In another example, the hydraulic pump system or auxiliary unit / auxiliary module 68 may also comprise a second line 28b for conveying hydraulic fluid. In a third example, the hydraulic pump system or auxiliary unit / auxiliary module 68 may also comprise a valve arrangement 40.

[0071] In an example, the hydraulic pump system comprises an auxiliary unit / auxiliary module 68 which comprises at least one pump unit 300a, 300b, 300c, 300d. At least one pump unit is connected to the low-pressure line 12 directly via the first line, or is connected to the low-pressure line 12 and / or the high-pressure line 10 via the valve arrangement 40, wherein the auxiliary unit / auxiliary module can be used to compensate for fluctuations of hydraulic fluid and volume flow occurring in the high-pressure line 10 and / or the low-pressure line 12 or between them when the hydraulic pump system is used to operate one or more actuators.

[0072] The piston 34 can be brought to a recurring reciprocating motion in relation to the cylinder space 32 so that the volume of the chamber 36 simultaneously decreases, to produce volume flow or to increase hydraulic fluid in the first or second line 28a, 28b, and increases, to receive volume flow or to decrease hydraulic fluid in the first or second line 28a, 28b, respectively. The purpose may also be to transfer hydraulic fluid between the first and second lines 28a, 28b. With these functions, it is possible, where needed, to compensate for fluctuations of hydraulic fluid and volume flow occurring in the high-pressure line 10 and / or the low-pressure line 12, or between them, when the hydraulic pump system is in operation.

[0073] According to the example of Fig. 3a, the chamber 36 may be in continuous fluid communication with the first line 28a.

[0074] According to the examples of Figs. 3b and 3c, a valve arrangement 40 is coupled to the first line 28a and adapted to move to a state in which fluid communication between the chamber 36 and the first line 28a is allowed, and to a state in which fluid communication between the chamber 36 and the first line 28a is prevented.

[0075] As shown in the examples of Figs. 3c and 3d, a valve arrangement 40 is connected to the first and second lines 28a, 28b, and adapted to move into a state in which fluid communication between the chamber 36 and the first line 28a is allowed when fluid communication between the chamber 36 and the second line 28b is prevented, and into a state in which fluid communication between the chamber 36 and the first line 28a is prevented when fluid communication between the chamber 36 and the second line 28b is allowed. According to the example of Fig. 3d, the valve arrangement 40 may also be adapted to move into a state in which fluid communication between the chamber 36 and both the first line 28a and the second line 28b is prevented simultaneously.

[0076] In an example, the valve arrangement 40 comprises an electrically controlled directional valve for closing and opening the first line 28a and / or the second line 28b, for example a 2 / 2 valve, a 3 / 2 valve or a 4 / 2 valve. According to some examples, the valve arrangement 40 may prevent fluid communication between the first and second lines 28a, 28b.

[0077] As shown in the examples of Figs. 3a, 3b, 3c, and 3d, the hydraulic pump system further comprises an auxiliary transmission element 38 to which the piston 34 is connected and whose function is to bring said piston 34 to a recurring reciprocating motion in relation to the cylinder space 32 so that the volume of the chamber 36 simultaneously decreases and increases, respectively.

[0078] In an example, the auxiliary transmission element 38 constitutes or comprises a rotatable transmission means which is adapted to convert the rotary motion of the transmission means to a reciprocating linear motion of the piston 34 connected to it.

[0079] In an example, the auxiliary transmission element 38 constitutes or comprises a linear screw, a camshaft, an eccentric shaft, or a crankshaft, which may be of a type known as such. One or more connecting rods may be connected to the crankshaft, and these may be of a type known as such. The crankshaft is connected by a connecting rod to the piston 34. In an example, said camshaft, eccentric shaft or crankshaft constitutes or comprises a rotatable transmission means. In an example, a linear screw actuates the piston 34 sliding within the chamber 36.

[0080] In an example, the auxiliary transmission element 38 further comprises one or more power units which are adapted to rotate the auxiliary transmission element 38 at variable speeds and which may constitute or comprise an electric motor arrangement 42.

[0081] In an example, the auxiliary transmission element 38 further comprises one or more electric motor arrangements 42 adapted to rotate the auxiliary transmission element 38 at variable speeds.

[0082] The speed of the auxiliary transmission element 38 is dependent on or proportional to a control signal received. The purpose of controlling the speed is to change the volume flow produced by means of the chamber 36. This is based on the fact that the speed of the auxiliary transmission element 38 affects the frequency of the reciprocating motion of each piston 34, on which frequency, the volume flow exiting or entering the respective chamber 36 in a given unit of time is dependent.

[0083] In an example, the hydraulic pump system comprises two or more auxiliary transmission elements 38 described above. Two or more of these auxiliary transmission elements 38 may be connected to each other by means of one or more coupling elements 62. Thus, two or more auxiliary transmission elements 38 can be driven by just one power unit, for example an electric motor arrangement 42. The auxiliary transmission element 38 may be connected to the transmission element 20 by means of one or more coupling elements 62.

[0084] The hydraulic pump system may comprise two or more auxiliary units / auxiliary modules 68. An auxiliary unit / module 68 may be connected to a unit / module 24, a different unit / module, or another auxiliary unit / auxiliary module 68.

[0085] Next, other sets of components or elements will be discussed, which are possibly included in the hydraulic pump system and which may also constitute a unit or a module, for example a line unit or line module 44.

[0086] As shown in the examples of Figs. 3a, 3b, 3c, 3d, 4a, 4b, 4c, 4d, and 4e, the hydraulic pump system may also comprise a set of hydraulic lines which may constitute a line unit or line module 44. Said lines include the high-pressure line 10 with at least a first main branch 100 and a second main branch 102, and the low-pressure line 12 with at least a first main branch 120 and a second main branch 122.

[0087] As shown in Figs. 4A, 4b, 4c, 4d, and 4e, the high-pressure line 10 may further comprise a third main branch 104, and the low-pressure line 12 may further comprise a third main branch 124.

[0088] In an example, the first line 28a, which may be included in an auxiliary unit / auxiliary module 68, is in continuous fluid communication with the first main branch 120 of the low-pressure line 12, or an electrically controllable shut-off valve element 46 is connected between them for separating the first line 28a and the first main branch 120 of the low-pressure line 12 from each other and for bringing them into fluid communication with each other.

[0089] In an example, the second line 28b, which may be included in the auxiliary unit / auxiliary module 68, is in continuous fluid communication with the first main branch 102 of the high-pressure line 10, or an electrically controlled shutoff valve element 46 or separate electrically controllable shut-off valve element 26 is connected between them for separating the second line 28a and the first main branch 102 of the high-pressure line 10 from each and for bringing them into fluid communication with each other. Said shut-off valve element 26, 46 can control the fluid communications of the first and second lines 28a, 28b simultaneously.

[0090] The shut-off valve element 26, 46 is, for example, a 2 / 2 valve or a 4 / 2 valve. The shut-off valve element 26, 46 may be included in the line unit / line module 44.

[0091] In an example, the chambers 18a, 18b, 18c of the pump units 200a, 200b, 200c in at least one unit / module 24 can be brought into fluid communication with the first main branch 100 of the high-pressure line 10 when the pump unit 200a, 200b, 200c is supplying volume flow, and with the first main branch 120 of the low-pressure line 12 when the pump unit 200a, 200b, 200c is receiving volume flow.

[0092] According to the examples of Figs. 4A and 4b, the hydraulic pump system further comprises at least one electrically controllable shut-off valve element 64 for separating the first and second main branches 100, 102 of the high-pressure line 10 from each other and for bringing them into fluid communication with each other. Furthermore, the hydraulic pump system may also comprise at least one electrically controllable shut-off valve element for separating the first and third main branches 100, 104 and / or the second and third main branches 102, 104 of the high-pressure line 10 from each other and for bringing them into fluid communication with each other.

[0093] In addition to this, the hydraulic pump system may comprise at least one electrically controllable shut-off valve element 66 for separating the first and second main branches 120, 122 of the low-pressure line 12 from each other and for bringing them into fluid communication with each other. Moreover, the hydraulic pump system may comprise at least one electrically controllable shutoff valve element for separating the first and third main branches 120, 124 and / or the second and third main branches 122, 124 of the low-pressure line 12 from each other and for bringing them into fluid communication with each other. The above mentioned shut-off valve element, for example shut-off valve element 64, 66, is, for example, a 2 / 2 valve.

[0094] By means of this arrangement, the main branches 100, 102, 104, 120, 122, 124 may have pressure levels deviating from each other, for example, in a situation where several pump units 200a, 200b, 200c or units / modules 24 are connected to these main branches. By means of this arrangement, it is also possible to connect main branches 100, 102, 104 of the high-pressure line 10 and / or to connect main branches 120, 122, 124 of the low-pressure line 12 when volume flows are to be combined or the same pressure level is to be maintained in them.

[0095] Next, the connecting of an actuator to the hydraulic pump system will be discussed, with reference to Figs. 4a and 4b, for example.

[0096] In an example, the hydraulic pump system comprises a linearly moving or rotating actuator 50 and a valve arrangement 52.

[0097] The actuator 50 is adapted to receive volume flow via the valve arrangement 52 for carrying out work by means of pressurized hydraulic fluid, and for returning said volume flow.

[0098] In an example, a closed circuit can be created in the hydraulic pump system, where the hydraulic fluid is returned from the actuator to the pump units 200a, 200b, 200c or the unit / module 24 in which they are arranged.

[0099] According to the example of Fig. 4a, for implementing a closed circuit, the hydraulic pump system comprises a supply line 48a and a return line 48b in addition to the actuator 50 and the valve arrangement 52. The actuator 50 is, for example, a linear actuator, such as a hydraulic cylinder.

[0100] By means of the supply line 48a, the high-pressure line 10 or one of its main branches is in fluid communication with the actuator 50, for receiving volume flow in said actuator 50. By means of the return line 48b, the low-pressure line 12 or one of its main branches is in fluid communication with the actuator 50, for receiving volume flow returned from the actuator 50 in the low-pressure line 12 or one of its main branches.

[0101] In an example, hydraulic fluid is returned from the actuator to a tank for hydraulic fluid in the hydraulic pump system. In an example, hydraulic fluid is drawn from the tank for hydraulic fluid into the low-pressure line 12 or one of its branches.

[0102] According to the examples of Figs. 4b and 4c, the hydraulic pump system comprises an actuator 50, a valve arrangement 52, a supply line 48d, and a return line 48e. The actuator 50 is, for example, a rotating actuator, such as a hydraulic motor. In this way, the actuator is connected by means of the valve arrangement to the supply line and the return line, to be driven by the pressure difference between these. The speed of the actuator, such as the rotational speed, and the direction of operation, are adjustable by means of the valve arrangement.

[0103] The high-pressure line 10 or a main branch thereof is in fluid communication with the actuator via the supply line 48d, for receiving fluid flow in said actuator 50. By means of the return line 48e, the actuator 50 is in fluid communication with the low-pressure line 12, for receiving volume flow returned from the actuator 50 in the low-pressure line 12. In this way, hydraulic fluid returning from the actuator is returned to the low-pressure line and the pump units 200a, 200b, 200c or the unit / module 24, to be used further for operating the actuator.

[0104] According to the example of Figs. 4b and 4d, the hydraulic pump system may comprise a pump 76 adapted to return hydraulic fluid from the tank 48c to the low-pressure line 12, or a main branch thereof, utilizing the supply line 48a with which the pump 76 and the line 12 are in fluid communication. The supply line 48f may comprise a valve arrangement, for example a non-return-valve, for preventing volume flow from the line 12 back to the pump 76 and the fluid tank 48c.

[0105] The low-pressure line 12 or a main branch thereof may be adapted to deliver hydraulic fluid to the tank 48c by utilizing the return line 48f. An electrically controllable adjustable valve element 74 may be connected to the return line 48f, for closing and opening the return line 48f to control the volume flow in the return line 48f.

[0106] Preferably, the pump 76 and the fluid tank 48c, which are connected to the line 12 as described above, make it possible to draw hydraulic fluid out of the line 12, for example for cooling, and to replace hydraulic fluid removed from the line 12 with hydraulic fluid which has been cooled. In this way, drawing hydraulic fluid out of the line 12 can be varied as needed, for example depending on warming up of hydraulic fluid caused by the operation of actuators 50 connected to the low-pressure line 12 and the high-pressure line 10. Consequently, it should be noted that it is also possible to replace the pump 76 and the fluid tank 48c, and their connections to the line 12, with a separate cooling system, particularly if the filling of hydraulic fluid and replacement of possible losses of hydraulic fluid are also arranged in a different way.

[0107] For enabling the methods to be implemented in the hydraulic pump system, the hydraulic pump system may also comprise an electronic control unit 70 adapted to control the functions of the hydraulic pump system by means of control signals. Control signals are received by, for example, the above described transmission element 20, 78a, 78b, 79c, the auxiliary transmission element 38, the electric motor arrangement 30, 42, the valve arrangement 40, 52, forming e.g. an electrically controlled directional valve, or an electrically controllable shut-off valve element, such as the shut-off valve element 46, 64, 66, 74.

[0108] The hydraulic pump system and its electronic control unit 70 make it possible to maintain the recurring reciprocating motion of the pistons 16a, 16b, 16c of the pump units 200a, 200b, 200c and, in an example, also to vary their speed, whereby the volume flow produced can be varied or controlled as desired. The control of the speed is implemented by means of, for example, the electric motor arrangement 30 described above.

[0109] According to an example shown in Fig. 4c, a pump unit 500 of an open circuit is connected to the high-pressure line 10 and the low-pressure line 12. The pump unit of the open circuit comprises an adjustable-displacement pump 77 connected via a supply line 48g to the high-pressure line 12. The supply line is preferably provided with a non-return valve, whereby flow of hydraulic fluid from the low-pressure line 12 to the pump can be prevented. In this way, the direction of operation of the pump is set to be suitable to supply volume flow into the high-pressure line 10. The pump unit of the open circuit further comprises a tank 48c for storing hydraulic fluid, and a return line 48f connected via an adjustment valve to the low-pressure line 10. The adjustable-displacement pump 77 can be driven by a power source which is separate from the transmission element 20 driving the pump units 200a, 200b, 200c and from the electric motor arrangement 30, and is connected to the adjustable-displacement pump by a transmission element of its own. Examples of power sources include, for example, diesel engines and electric motors. The pump unit of the open circuit can be used together with the pump units 200a, 200b, 200c to provide volume flow for operating one or more actuators 50 connected to the high-pressure line 10 and the low-pressure line.

[0110] According to an example shown in Fig. 4c, the pump unit 500 of the open circuit is directly connected to the first main branch 100 of the high-pressure line 10 and the first main branch 120 of the low-pressure line 12. The first main branch 100 of the high-pressure line and the second main branch 120 of the low-pressure line are directly connected to the pump units 200a, 200b, 200c of the modules, whereby the volume flow of hydraulic fluid supplied by the pump unit of the open circuit can thus be combined with the volume flow produced by the pump units. The combined volume flow thus formed can be led further to selected main branches downstream, such as the second main branch 102 of the high-pressure line, the third main branch 104 of the high- pressure line, the second main branch 122 of the low-pressure line, and the third main branch 124 of the low-pressure line, by shut-off valve elements 64, 66 between the main branches. On the other hand, shut-off valve elements 64, 66 can be used to block the combined volume flow to some of the following: the first main branch 100 of the high-pressure line 10 and the first main branch 120 of the low-pressure line; the first main branch 100 and the second main branch 102 of the high-pressure line 10, as well as the first main branch 120 and the second main branch 122 of the low-pressure line. It should be noted that the volume flow combined with the shut-off valve elements 64, 66 can also be divided into all the main branches by opening the shut-off valve elements. In an example shown in Fig. 4d, a pump unit 400 of a closed circuit is connected to the high-pressure line 10 and the low-pressure line 12. The pump unit of the closed circuit comprises an adjustable-displacement pump 77 connected to the high-pressure line 12 via a supply line 48g. The pump unit of the closed circuit further comprises a return line 48f connected to the low-pressure line 10 via an adjustment valve. The adjustable-displacement pump 77 can be driven by a power source which is separate from the transmission element 20 driving the pump units 200a, 200b, 200c and from the electric motor arrangement 30 and is connected to the adjustable-displacement pump by a transmission element of its own. The adjustable-displacement pump can be used to supply volume flow to the high-pressure line 10 or the low-pressure line 12. Examples of power sources include, for example, diesel engines and electric motors. The pump unit of the closed circuit can be used, together with or instead of the pump units 200a, 200b, 200c, to supply volume flow for driving one or more actuators 50 connected to the high-pressure line 10 and the low- pressure line. It should be noted that in the example of Fig. 4d, actuators can be connected to the high-pressure line 10 or its main branch, and to the low- pressure line or its main branch, as described in connection with Figs. 4b and 4c. It should be noted that compensation for fluctuations in hydraulic fluid and volume flow is provided by volume flow supplied by the auxiliary unit / auxiliary module 68.

[0111] According to the example of Fig. 4e, the first main branch 100 of the high- pressure line of the hydraulic pump system is connected by a shut-off valve element 65 to the third main branch 104 of the high-pressure line, and the first main branch 120 of the low-pressure line 12 is connected by a shut-off valve element 67 to the third main branch 124 of the low-pressure line 12. In this way, the first main branch 120 of the high-pressure line and the third main branch 104 of the high-pressure line as well as the first main branch 124 of the low-pressure line 12 and the third main branch of the low-pressure line 12 can be connected directly to each other. Furthermore, in an example, the first main branch 100 of the high-pressure line of the hydraulic pump system is connected by a shut-off valve element 64 to the second main branch 102 of the high-pressure line, and the first main branch 120 of the low-pressure line 12 is connected by a shut-off valve element 66 to the second main branch 122 of the low-pressure line 12. Moreover, in an example, the second main branch 102 of the high-pressure line of the hydraulic pump system is connected by a shut-off valve element 64 to the third main branch 104 of the high-pressure line, and the second main branch 122 of the low-pressure line 12 is connected by a shut-off valve element 66 to the third main branch 124 of the low-pressure line 12. In this way, the volume flow between the main branches can be controlled in a flexible way.

[0112] According to the example of Fig. 4e, the pump units 200a, 200b, 200c (200c not shown in Fig. 4e) of the module 24 may comprise a valve arrangement 22a, 22b, 22c (22c not shown in Fig. 4e) having electrically controlled shut-off valve elements. Thus, the valve arrangement can be controlled with control signals from the control unit 70 so that the valve arrangement has a first state and a second state, whereby using the first state, the chamber is, in turn, in fluid communication with the high-pressure line 12 while the volume of said chamber is simultaneously decreasing, and whereby using the second state of the valve arrangement, the chamber is in fluid communication with the low- pressure line 10 while the volume of said chamber is simultaneously increasing. Thus, the module can be applied to transfer energy to the high-pressure line 10 and the low-pressure line 12, to be consumed in one or more actuators 50 connected to the high-pressure line 10 or the low-pressure line 12. In an example, the valve arrangement can further be controlled with control signals so that in the first state of the valve arrangement, the chamber is, in turn, in fluid communication with the high-pressure line 12 while the volume of said chamber simultaneously increasing, and in the second state of the valve arrangement, the chamber is in fluid communication with the low-pressure line 10 while the volume of said chamber is simultaneously decreasing. Thus, the module can be used for charging energy into an energy storage connected to the hydraulic pump system.

[0113] It should be noted that in an example, the pump unit 400 of a closed circuit, shown in Fig. 4d, can also be connected to the hydraulic pump system shown in Fig. 4e, in the way shown in Fig. 4d. Thus, volume flow supplied by the pump unit 400 of the closed circuit can be used for charging an energy storage connected to the hydraulic pump system, by controlling the valve arrangement of one or more modules 24 with control signals, whereby the pressure difference between the high-pressure line 10 and the low-pressure line 12 causes the transmission element 20 connected to the module to be operated, and further, the electric motor arrangement to be used as a generator.

[0114] Figure 5 shows a reduced schematic view of the control of a hydraulic pump system according to an example of the invention. The hydraulic pump system may comprise an electronic control unit 70 which is connected to one or more modules 24, each comprising two or more pump units 200a, 200b, 200c, by which pressure is supplied to the low-pressure line 12 and the high-pressure line of the hydraulic pump system, for operating at least one actuator 50 connected to these lines. The hydraulic pump system further comprises one or more auxiliary units / auxiliary modules 68 for compensating for fluctuations in hydraulic fluid and volume flow occurring in the high-pressure line 10 and / or the low-pressure line 12 or between them when the hydraulic pump system is used to operate said one or more actuators.

[0115] In an example, the hydraulic pump system may comprise one or more electric motor arrangements 30 which are connected via at least one transmission element to the pump units 200a, 200b, 200c of the modules, for driving them and thereby supplying a pressure difference between the high-pressure line 10 and the low-pressure line, for driving one or more actuators 50.

[0116] In an example, the hydraulic pump system may comprise one or more electric motor arrangements 42 connected via at least one transmission element to the pump units 300a, 300b, 300c of an auxiliary unit / auxiliary module, for operating them and thereby compensating for fluctuations in hydraulic fluid and volume flow when one or more actuators 50 are in operation.

[0117] Next, the operation of a hydraulic pump system, equipped with one or more auxiliary units or auxiliary modules, will be discussed with reference to Fig. 5. When an actuator is connected to the high-pressure line and the low-pressure line, its operation may cause fluctuations in hydraulic fluid and volume flow between the high-pressure line 10 and the low-pressure line 12. This causes asymmetry between the high-pressure line and the low-pressure line, which may impair the stable and predictable operation of the actuator. The asymmetry may be manifested as, for example, a high difference in the pressure and / or volume flows in the high-pressure line and the low-pressure line between different travel directions of the actuators. Depending on the type of the actuator, the fluctuation in the pressure difference between the high-pressure line and the low-pressure line may affect the performance, stability and energy efficiency of the actuator.

[0118] Examples of actuators include, for example, a linear actuator and a hydraulic motor.

[0119] Structure of a linear actuator:

[0120] Cylinder:

[0121] The cylinder is a hollow pipe in which a piston reciprocates. The cylinder has two ends: one high-pressure connection and one low-pressure connection.

[0122] Piston:

[0123] The piston is a component moving within the cylinder and dividing the cylinder into two parts: a piston rod side part and an opposite part. The piston is provided with seals preventing hydraulic fluid from leaking past it.

[0124] Piston rod:

[0125] The piston rod is connected to the piston and extends outside the cylinder. It transfers the movement to an external load or mechanism. The actuator may be a part of a moving machine, whereby the actuator may cause a movement of the machine, effective on an external load or a mechanism of the machine.

[0126] Operating principle of a linear actuator:

[0127] 1. Piston movement upwards:

[0128] When hydraulic fluid is supplied from the high-pressure line 10 to the lower part of the cylinder (on the piston side), the piston of the linear actuator will move upwards.

[0129] Because the piston rod takes space in the upper part of the cylinder, the amount of displaced hydraulic fluid is smaller when the piston moves upwards than when the piston moves downwards.

[0130] This displaced smaller amount of hydraulic fluid is transferred to the low- pressure line.

[0131] 2. Piston movement downwards: When hydraulic fluid is supplied from the high-pressure line 10 to the upper part of the cylinder (on the piston rod side), the piston will move downwards.

[0132] Because the piston rod does not take space in the lower part of the cylinder, the amount of displaced hydraulic fluid is larger when the piston moves downwards than when the piston moves upwards.

[0133] This displaced larger amount of hydraulic fluid is transferred to the low- pressure line.

[0134] Development of asymmetry between the high-pressure line and the low-pressure line:

[0135] Difference in the amount of hydraulic fluid: The amount of displaced hydraulic fluid is smaller when the piston moves upwards than when it moves downwards. This is because the piston rod takes space in the upper part but not in the lower part of the cylinder.

[0136] Difference in volume flow: The difference in the amount of displaced hydraulic fluid when the piston moves in different directions causes asymmetry between the high-pressure line and the low-pressure line, which may cause fluctuations in volume flow in the system.

[0137] In the following, typical effects of fluctuation in the pressure difference between the high-pressure line and the low-pressure line on an actuator will be described.

[0138] Force of movement:

[0139] Higher pressure difference: If the pressure difference between the high- pressure line and the low-pressure line increases, the force of the movement of the actuator (e.g. hydraulic cylinder) increases. This is because the higher pressure difference produces a higher force for the movement of the actuator.

[0140] Low pressure difference: If the pressure difference decreases, the force of the movement of the actuator decreases. This may lead to slower and weaker operation.

[0141] Stability of the system: Stable pressure difference: A stable pressure difference secures steady and reliable operation. This is important for the control and security of the system.

[0142] Varying pressure differences: Large fluctuations in the pressure difference may cause instability in the operation of the actuator, which may lead to jerking movement or loss of control.

[0143] Energy efficiency:

[0144] Optimal pressure difference: A correctly adjusted pressure difference may improve the energy efficiency of the system, because the actuator operates more efficiently and loses less energy.

[0145] Non-optimal pressure difference: If the pressure difference is not on an optimal level, the system may consume more energy and produce more heat, which may impair overall efficiency.

[0146] Temperature and wear:

[0147] Higher pressure differences: A higher pressure difference may increase the temperature in the system, which may accelerate wear of components and reduce their service life.

[0148] Lower pressure differences: A lower pressure difference may reduce accumulation of heat and extend the service life of components.

[0149] In the following, typical effects of fluctuation in volume flows in the high-pressure line and the low-pressure line on an actuator will be described.

[0150] Rate of movement of the actuator:

[0151] Increasing volume flow: A higher volume flow from the high-pressure line to the actuator will lead to faster movement. For example, the piston speed in a hydraulic cylinder will increase.

[0152] Decreasing volume flow: A lower volume flow will lead to slower movement. The movement of the actuator will slow down, which may affect production efficiency.

[0153] Stability of the system:

[0154] Stable volume flow: A stable volume flow secures steady operation. This is important for the actuator to operate in a predictable and controlled manner.

[0155] Fluctuating volume flows: Fluctuations in volume flow may cause unstable operation of the actuator, such as a jerky movement or sudden changes in speed. Changes in pressure:

[0156] Increasing volume flow: When the volume flow increases, the pressure in the high-pressure line may increase as well, which may cause an increase in the pressure of the system, and possibly pressure surges. Decreasing volume flow: When the volume flow decreases, the pressure may decrease, which may affect the capacity of the actuator to perform its functions in an efficient way.

[0157] Temperature and wear:

[0158] Higher flow rates: A higher volume flow may increase the temperature in the system, because the fluid moves faster and causes more friction. This may accelerate the wear of components.

[0159] Lower flow rates: A lower volume flow reduces the accumulation of heat, which may extend the service life of the system and its parts.

[0160] Energy efficiency:

[0161] Optimal flow: A correctly adjusted volume flow improves energy efficiency, because the actuator will operate at the designed speed and power without extra loss of energy.

[0162] Non-optimal flow: Unsteady or incorrectly adjusted volume flow may impair energy efficiency and lead to increased energy consumption and production of heat.

[0163] In an example, a hydraulic pump system equipped with one or more auxiliary units / auxiliary modules 68 may comprise a line module 44 with a high-pressure line 10 and a low-pressure line 12, wherein one or more actuators 50 are connected to the high-pressure line 10 and the low-pressure line 12, to be driven by the pressure difference between the high-pressure line and the low-pressure line. Furthermore, one or more auxiliary units / auxiliary modules 68 are connected to the high-pressure line and / or the low-pressure line, to compensate for fluctuations in hydraulic fluid and volume flow occurring in the high- pressure line 10 and / or the low-pressure line 12 or between them when the hydraulic pump system is used for driving 92, 94 one or more actuators.

[0164] In an example, the hydraulic pump system comprises an electronic control unit 70 configured to generate control signals 86 which are input in one or more electric motor arrangements 30 adapted to drive pump units 200a, 200b, 200c of one or more modules. The electric control system is further configured to generate second control signals 87 and to input the generated second control signals in at least one electric motor arrangement 42 which is adapted to operate a pump unit 300a, 300b, 300c of an auxiliary unit / auxiliary module 68 in the high-pressure line 10 and / or the low-pressure line 12 or between them, to compensate for fluctuations in hydraulic fluid and volume flow when the hydraulic pump system is used to operate 92, 94 one or more actuators connected to the high-pressure line 10 and the low-pressure line 12, to be driven by the pressure difference between the high-pressure line and the low-pressure line. The asymmetry caused by the operation of these actuators can be compensated for by controlling the operation of the auxiliary unit / auxiliary module 68 with control signals.

[0165] In an example, the hydraulic pump system comprises an electronic control unit 70 configured to generate control signals 86 and to input the generated control signals to one or more of the following: transmission element 20, 78a, 78b, 79c, or electric motor arrangement 30, or valve arrangement 52. In this way, the hydraulic pump system can be used to drive 92, 94 one or more actuators 50. The control unit 70 is further configured to generate second control signals 87 and to input the generated control signals to one or more of the following: auxiliary transmission element 38 or electric motor arrangement 42, valve arrangement 40. In this way, fluctuations in hydraulic fluid and volume flow can be compensated 96 for when one or more actuators 50 are in operation.

[0166] In an example, the electronic control unit 70 may be configured to determine control signals 87 for compensating 96 for fluctuations in hydraulic fluid and volume flow on the basis of the speeds of movements, directions of movements, and cylinder spaces above and below the pistons of the actuators to be operated simultaneously. The control unit uses data on the direction of movement, the cylinder space above the piston, and the cylinder space below the piston of each actuator, to determine the asymmetry caused by the operation of each actuator. The control unit determines the combined asymmetry of the actuators to be driven simultaneously, and uses this combined asymmetry to generate the control signals for compensating for fluctuations in hydraulic fluid and volume flow. The asymmetry can be determined, for example, as an increase in the pressure difference between the high-pressure line 10 and the low-pressure line 12, or as a decrease in the pressure difference between the high-pressure line 10 and the low-pressure line 12, from a given target value. If the pressure difference between the high-pressure line 10 and the low-pressure line 12 decreases, a control signal can be generated by the control unit to activate a pump unit 300a, 300b, 300c, 300d for transferring hydraulic fluid between the pump unit 300a, 300b, 300c and the high-pressure line 10 or the low-pressure line 12, whereby the pressure difference between the high-pressure line and the low-pressure line can be brought towards the target value and a balance. Data on the cylinder volume above the piston and the cylinder volume below the piston in each actuator can be configured for the control unit. Data on the direction of movement of the actuator can be received from the actuator or determined on the basis of the function to be performed by the actuator.

[0167] In an example, asymmetry in the hydraulic pump system, for example an increase in the pressure difference between the high-pressure line 10 and the low-pressure line 12, or a decrease in the pressure difference between the high-pressure line 10 and the low-pressure line 12, from a given target value, can be determined by measuring the electric current used by the electric motor arrangement 30.

[0168] In an example, the control unit 70 may be connected to one or more interface devices 81 by which a user can give control commands 82 to be interpreted as a movement of one or more actuators 50 connected to the hydraulic pump system, and as a respective control command or control request. The control unit may receive control commands or control requests generated in this way by the user.

[0169] In an example, the control unit 70 may be connected to one or more automatic controls 83 of a machine, for controlling sequences of movements, or routines, run by one or more actuators of the machine. From the automatic control, the control unit may receive control commands 84 or control requests relating to one or more actuators 50 connected to the hydraulic pump system, and their movements.

[0170] In an example, the control unit 70 may generate control signals 86 on the basis of control commands or control requests given by the user, as well as control commands or control requests received from the automatic control of the machine. The control signals determine the actuators 50 to be operated simultaneously, and their directions of movement, whereby the combined asymmetry of the actuators to be operated simultaneously can be determined. On the basis of the combined asymmetry, it is possible to determine second control signals for compensating for fluctuations in hydraulic fluid and volume flow.

[0171] In an example of the method, the recurring reciprocating movement of the pistons 16a, 16b, 16c of two or more pump units 200a, 200b, 200c is maintained in, for example, one or more units / modules, so that volume flow can be received in the chambers 18a, 18b, 18c of the respective pump units 200a, 200b, 200c by drawing hydraulic fluid from the low-pressure line 12. After this, volume flow can be produced in these chambers 18a, 18b, 18c by removing pressurized hydraulic fluid to the high-pressure line 10.

[0172] In an example of the method, the speed of the reciprocating movement is also varied in proportion to the control signal received from the electronic control unit 70 into the respective electric motor arrangement 30, for controlling the volume flow supplied.

[0173] The above described hydraulic pump system may be supplemented with or it comprises elements, devices and functionalities which are necessary for implementing the basic functions of its hydraulic circuit. These include, for example, implementing pressure limits by means of valve arrangements, enabling and controlling fluid communications, as well as controlling the direction of flow of hydraulic fluid, e.g. with non-return valves, filtering hydraulic fluid, and storing pressurized hydraulic fluid in a pressure accumulator.

[0174] The above described hydraulic pump system can be implemented, either in whole or in part, as one or more hydraulic blocks in which lines for hydraulic fluid are provided by means of e.g. drill holes and to which e.g. valves of valve arrangements are fastened. Alternatively, said hydraulic system can be implemented, either in whole or in part, by utilizing elements, such as valves of valve arrangements, between which the lines and fluid communications are implemented with e.g. lines of hoses or pipes. Each valve arrangement implements the above-described functionality. The components needed for implementing the valve arrangement are known as such and may comprise one or more valves of various types. The valve arrangement and its components may be based on various operating principles, e.g. proportional valves, servo valves, slide valves, or cartridge valves. The symbols shown in the figures and depicting the valve arrangement and / or its components do not limit the implementation of the valve arrangement but illustrate one example for implementing the functionality of the respective valve arrangement.

[0175] Figure 6 shows a simplified method for controlling a hydraulic pump system according to an example of the invention. The method can be performed by a hydraulic pump system according to an example, comprising a high-pressure line 10, a low-pressure line 12, and at least two first pump units 200a, 200b, 200c for operating at least one actuator 50 connected to the high-pressure line and the low-pressure line by means of the pressure difference between the high-pressure line and the low-pressure line. The hydraulic pump system further comprises an electric motor arrangement 30 adapted to drive at least two first pump units 200a, 200b, 200c, and at least one second pump unit 300a, 300b, 300c to compensate for fluctuations in hydraulic fluid and volume flow in the high-pressure line 10 and / or the low-pressure line 12, and a second electric motor arrangement 42 adapted to drive said at least one second pump unit 300a, 300b, 300c, and an electronic control unit 70 connected to the first and second electric motor arrangements. In step 602 of the method, first control signals 86 are generated by the electronic control unit 70 of the hydraulic pump system, and the generated control signals are input in one or more first electric motor arrangements 30, for driving at least one actuator 50 with two first pump units 200a, 200b, 200c. In step 604 of the method, second control signals 87 are generated by the electronic control unit 70 of the hydraulic pump system, and the generated second control signals are input in at least one second electric motor arrangement 42 to compensate for fluctuations in hydraulic fluid and volume flow in the high-pressure line 10 and / or the low-pressure line 12, or between them, by driving said at least one second pump unit 300a, 300b, 300c when the hydraulic pump system is applied to operate one or more actuators 50 connected to the high-pressure line 10 and the low-pressure line 12, to be powered by the pressure difference between the high-pressure line and the low-pressure line.

[0176] It should be noted that steps 602 and 604 of the method can be carried out simultaneously so that when the supply of volume flow is controlled with control signals for driving an actuator / actuators 50, second control signals are simultaneously used for supplying volume flow to compensate for the asymmetry caused by the operation of the actuator / actuators.

[0177] In an example, the method comprises, in step 602, determining the actuators to be driven simultaneously, on the basis of control commands or control requests generated by the user, and control commands or control requests received from the automatic control of the machine. For example, the control unit 70 may be connected to one or more automatic controls 83 of the machine for controlling sequences of movements, or routines, run by one or more actuators of the machine. From the automatic control, the control unit may receive control commands or control requests relating to one or more actuators 50 connected to the hydraulic pump system, and their movement. For example, the control unit may be connected to user controls, or a control unit for them, and in this way receive control commands or control requests generated by the user, or data derived from a user’s control command or control request and indicating a request to apply an actuator. The actuators 50 to be used simultaneously, and the directions of their movement, can thus be determined in the control unit on the basis of data received from the user and / or the automatic control. Thus, the combined asymmetry of the actuators to be applied simultaneously can be determined in step 604 on the basis of the speeds of movements, directions of movement, and cylinder spaces above and below the piston, of the actuators to be operated simultaneously.

[0178] In an example, the control signals 86 of the control unit 70 for applying actuators, and the control signals 87 for compensating for fluctuations in hydraulic fluid and volume flow comprise, or indicate, the speed of the electric motor arrangement. The control signals can thus set the rotational speed of the electric motor arrangement 30, 42 and have an effect on the pressure difference between the high-pressure line and the low-pressure line, as well as fluctuations in hydraulic fluid and volume flow. In an example, the volume flow supplied by the pump units 300a, 300b, 300c of the auxiliary module / auxiliary unit 68 is proportional to the speeds of movements of the actuators to be applied simultaneously as well as the combined cylinder volumes above the pistons of the actuators and the cylinder volumes below the pistons of actuators.

[0179] In an example, the volume flow produced by each module 24 is proportional to the volume flow required by the actuators to be applied simultaneously.

[0180] In an example, the electronic control unit 70 may be arranged to define the control signals 86 for applying the actuators on the basis of the volume flow required by the actuators. The volume flow required by the actuators is an actuator-specific value.

[0181] Figures 7a and 7b show examples of applications of the hydraulic pump system for recovering energy. Figures 7a and 7b illustrate a hydraulic pump system to which an electric energy storage 1 is connected, and which hydraulic pump system is arranged to convert the pressure difference between the high- pressure line 10 and the low-pressure line 12 by a valve arrangement 22a, 22b, 22c into electric energy and to use it for charging the electric energy storage 1. The electric energy storage may be a battery system. In an example according to Figs. 7a and 7b, the hydraulic pump system comprises one or more modules 724a, 724b and a line module 44, wherein one or more actuators 50 can be connected to the line module 44, to be operated by means of the pressure difference between the high-pressure line and the low-pressure line. The modules 724a, 724b may be the above-described modules 24 whose electric motor arrangements 30 are connected to the electric energy storage 1 . Each module may be connected to receive electric energy from the electric energy storage and to charge the electric energy storage with electric energy. In this way, the electric motor arrangements of the modules can be driven by energy contained in the electric energy storage, and the electric motor arrangements can supply the electric energy storage with electric energy. Each module can thus have two operating modes, whereby in one mode it consumes energy received from the electric energy storage, and in the other mode it charges the electric energy storage with energy. In the mode in which the module 724a, 724b consumes energy received from the electric energy storage, the electric motor arrangement of the module receives electric energy from the electric energy storage, and the electric energy is converted to a movement of the transmission element 20 and, by means of the pump units 200a, 200b, 200c, further to a volume flow of hydraulic fluid in the high-pressure line 10 and the low-pressure line 12. Thus, the pump units produce a pressure difference between the high-pressure line and the low- pressure line in the line module, for applying one or more actuators 50. In this mode, the valve arrangement 22a, 22b, 22c of each pump unit in the module is controlled so that in the first state of the valve arrangement, the chamber is, in turn, in fluid communication with the high-pressure line 12 when the volume of the respective chamber is simultaneously decreasing, and in the second state of the valve arrangement, the chamber is in fluid communication with the low-pressure line 10 when the volume of the respective chamber is simultaneously increasing.

[0182] In the mode of the module 724a, 724b in which it charges the electric energy storage with electric energy, the electric motor arrangement 30 of the module is used as a generator for converting the pressure difference between the high- pressure line 10 and the low-pressure line 12 of the line module into electric energy. Thus, the pump units convert the pressure difference between the high-pressure line and the low-pressure line of the line module into a movement of a transmission element 20 connected to the electric motor arrangement. In this mode, the valve arrangement 22a, 22b, 22c of each pump unit is controlled so that in the first state of the valve arrangement, the chamber is, in turn, in fluid communication with the high-pressure line 12 when the volume of the respective chamber is simultaneously increasing, and in the second state of the valve arrangement, the chamber is in fluid communication with the low- pressure line 10 when the volume of the respective chamber is simultaneously decreasing. Thus, in the mode of the module where it consumes energy received from the electric energy storage, the control of the valve arrangement 22a, 22b, 22c is substantially reverse to that in the mode of the module 724 where it charges the electric energy storage with electric energy. In an example, the modules 724a, 724b have a first mode in which electric energy is converted by pump units 200a, 200b, 200c further to a volume flow of hydraulic fluid in the high-pressure line 10 and the low-pressure line 12, and a second mode in which the pressure difference between the high-pressure line and the low-pressure line 12 is converted to electric energy, controlled by control signals of the electronic control unit. Electric control signals can be used to select the mode of each module by controlling the valve arrangements 22a, 22b, 22c, for example electric shut-off valve elements, of the pump units of the module. For example, in the first mode of the module, the valve arrangement 22a, 22b, 22c of each pump unit of the module is controlled so that in the first state of the valve arrangement, the chamber is, in turn, in fluid communication with the high-pressure line 12 when the volume of the respective chamber is simultaneously decreasing, and in the second state of the valve arrangement, the chamber is in fluid communication with the low-pressure line 10 when the volume of the respective chamber is simultaneously increasing. In the second mode of the module, the valve arrangement 22a, 22b, 22c of each pump unit of the module is controlled so that in the first state of the valve arrangement, the chamber is, in turn, in fluid communication with the high-pressure line 12 when the volume of the respective chamber is simultaneously increasing, and in the second state of the valve arrangement, the chamber is in fluid communication with the low-pressure line 10 when the volume of the respective chamber is simultaneously decreasing. Thus, in the mode of the module where it consumes energy received from the electric energy storage, the control of the valve arrangement 22a, 22b, 22c is substantially reverse to that in the mode of the module 724 where it charges the electric energy storage with electric energy.

[0183] According to an example, the hydraulic pump system may comprise several modules 724, some of which operate in the mode in which electric energy is consume by converting electric energy by driving actuators 50 connected to the hydraulic pump system, and some of which operate in the mode in which the electric energy storage 1 is charged with electric energy.

[0184] In Figs. 7a and 7b, energy recovery and consumption are illustrated with arrows indicating the directions of energy. In both figures, the module 724a is operating in the mode in which it consumes electric energy from the electric energy storage 1 , whereby the arrow indicates the direction of electric energy away from the electric energy storage towards the module 724a. In both figures, the module 724b is operating in the mode in which it charges the electric energy storage 1 with electric energy, whereby the arrow indicates the direction of electric energy from the module 724b towards the electric energy storage. In the module 724a, electric energy is converted by the pump units 200a, 200b, 200c to a pressure difference between the high-pressure line 10 and the low-pressure line 12, whereby energy is transferred to the line module 44. In the module 724b, the pressure difference between the high-pressure line 10 and the low-pressure line 12 is converted by the pump units 200a, 200b, 200c to electric energy which is used to charge the electric energy storage 1 , whereby energy is transferred from the line module to the module 724b.

[0185] According to an example, a pump unit 500 of an open circuit it connected to the hydraulic pump system. The pump unit of the open circuit can be driven by a power source whose energy is converted by the pump unit of the open circuit to a pressure difference between the high-pressure line 10 and the low-pressure line 12 of the line module. Thus, energy is transferred from the pump unit of the open circuit to the line module 44, in which it can be utilized for operating actuators 50 and / or transferred further via the pump units 200a, 200b, 200c to the electric energy storage 1 .

[0186] In an example, a pump unit 400 of a closed circuit is connected to the hydraulic pump system. The pump unit of the closed circuit can be driven by a power source whose energy is converted by the pump unit of the closed circuit to a pressure difference between the high-pressure line 10 and the low-pressure line 12 of the line module. Thus, energy is transferred from the pump unit of the closed circuit to the line module 44 in which it can be utilized for driving the actuators 50 and / or transferred further via the pump units 200a, 200b, 200c to the electric energy storage 1 .

[0187] In an example, asymmetry caused by fluctuations in hydraulic fluid and volume flow can be compensated for by a volume flow produced by an auxiliary module of the hydraulic pump system. In an example, the hydraulic pump system of Figs. 7a and 7b comprises a high-pressure line 10; a low-pressure line 12; and at least two first pump units 200a, 200b, 200c for operating at least one actuator 50 connected to the high- pressure line and the low-pressure line by the pressure difference between the high-pressure line and the low-pressure line; an electric motor arrangement 30 adapted to drive at least two first pump units 200a, 200b, 200c; and at least one second pump unit 300a, 300b, 300c for compensating for fluctuations in hydraulic fluid and volume flow in the high-pressure line 10 and / or the low- pressure line 12; and a second electric motor arrangement 42 adapted to drive said at least one second pump unit 300a, 300b, 300c; and an electronic control unit 70 connected to the first and second electric motor arrangements. A method for controlling a hydraulic pump system comprises a method comprising: generating first control signals 86 by an electronic control unit 70 of the hydraulic pump system and inputting the generated control signals in one or more first electric motor arrangements 30 for operating at least one actuator 50 with two first pump units 200a, 200b, 200c; and generating second control signals 87 by the electronic control unit 70 of the hydraulic pump system and inputting the generated second control signals in at least one second electric motor arrangement 42, for compensating for fluctuations of hydraulic fluid and volume flow in a high-pressure line 10 and / or a low-pressure line 12, or between them, by driving said at least one second pump unit 300a, 300b, 300c when the hydraulic pump system is used to operate one or more actuators 50 connected to the high-pressure line 10 and the low-pressure line 12, to be operated by the pressure difference between the high-pressure line and the low-pressure line.

[0188] In an example of the method for controlling a hydraulic pump system, the hydraulic pump system comprises at least two third pump units 200a, 200b, 200c, and a second electric motor arrangement 30 adapted to drive at least two third pump units 200a, 200b, 200c, an electric energy storage 1 being connected to the hydraulic pump system; and the method comprises: controlling said at least two third pump units 200a, 200b, 200c to convert the pressure difference between the high-pressure line 10 and the low-pressure line 12 into electric energy by applying the third pump units 200a, 200b, 200c to drive a transmission element 20 connected to the second electric motor arrangement which is arranged to charge the energy storage 1 . For example, the first pump units may be arranged in a module 724a, and the third pump units may be arranged in a module 724b, and the second pump unit may be arranged in a module 68. For example, the control of the first and third pump units comprises controlling the valve arrangement of each pump unit with control signals from an electronic control unit 70, wherein the first pump units can be used to produce a pressure difference between the high-pressure line 10 and the low-pressure line 12 for operating one or more actuators 50, and wherein third pump units can be applied to convert the pressure difference between the high-pressure line 10 and the low-pressure line 12 to a movement of the transmission element 20 connected to the electric motor arrangement, for charging the electric energy storage 1 connected to the electric motor arrangement. It should be noted that the functional state of the valve arrangements can be changed with control signals, whereby each of the first and third pump units can be controlled to produce a pressure difference between the high-pressure line 10 and the low-pressure line 12, for operating one or more actuators 50, or to apply the electric motor arrangement for charging the electric energy storage.

[0189] In an example, the method for controlling a hydraulic pump system comprises: using control signals to determine the asymmetry between the high-pressure line 10 and the low-pressure line 12 caused by the actuators to be operated simultaneously; determining second control signals 87 on the basis of the asymmetry determined. For example, the second control signals are applied to control the electric motor arrangement of the module 68.

[0190] In an example, the hydraulic pump system comprises at least one processor and at least one memory for storing a computer program containing instructions which, when executed by the processor, run one or more functionalities according to the example described herein. The control unit of the hydraulic pump system may comprise at least one processor and at least one memory. In a pump system, the control unit may further comprise one or more connections for data transmission. Examples of connections include data buses, Ethernet buses and buses of automation systems, which may comply with some of the following technologies: Profibus, Ethernet / IP, Modbus, CANopen, PCI (Peripheral Component Interconnect), SATA (Serial ATA). The memory may be a volatile memory or a non-volatile memory, such as a non-transitory or permanent memory. Figure 8 shows a reduced schematic view of a hydraulic pump system according to some examples of the invention. The hydraulic pump system is illustrated with reference to the pump units and valve arrangements described in connection with e.g. Figs. 2a, 2b, and 2c, whereby in the example of Fig. 8, a rotating or rotatable shaft is used instead of the dividing disc shown in the example of e.g. Fig. 2c. The pump units and valve arrangements of Fig. 8 are presented with reference to the objects discussed above in connection with Figs. 3a, 3b, 3c, 3d, 4a, 4b, 4c, 4d, 4e. In the example illustrated in Fig. 8, the valve arrangement 22a, 22b, 22c of each pump unit 200a, 200b, 200c comprises one or more rotating shafts, each of which can be brought into a rotating motion and into different rotary positions. The rotational shaft is provided with a channel for the chamber 18a, 18b, 18c of the pump unit 200a, 200b, 200c, for said first state when the shaft is in its first rotary position, and a channel for the second state when the rotating shaft is in its second rotary position. Via these channels, hydraulic fluid is conveyed through the rotating shaft from the low-pressure line 12 to the chamber and out of the chamber to the high-pressure line 10, whereby the chamber can be in fluid communication with the high- pressure line and the low-pressure line in an alternating manner. Hydraulic fluid can also be conveyed via other shafts and channels therein. In the hydraulic pump system, the transmission element 20 of each pump unit 200a, 200b, 200c may be connected to the transmission element 20 of another pump unit via a coupling element 62, wherein the electric motor arrangement 30 can be used to drive the pump units connected to each other at a time.

[0191] According to another example, in the hydraulic pump system of Fig. 8, the valve arrangement 22a, 22b, 22c of two or more pump units 200a, 200b, 200c is shared by them or is combined to form a valve arrangement comprising one or more rotating or rotatable shafts which can be brought to a rotating motion and into different rotary positions. For chambers 18a, 18b, 18c of said two or more pump units 200a, 200b, 200c, the rotating shaft comprises at least two channels for said first state when the rotating shaft is in its first rotary position, and at least two channels for said second state when the rotating shaft is in its second rotary position. Via said channels, hydraulic fluid is led through the rotating shaft. Hydraulic fluid can also be conveyed via other shafts and channels therein. The hydraulic pump system of Fig. 8 may also comprise two or more transmission elements 78a, 78b connected to each other in such a way that their operation can be synchronized, or a single power unit may be applied to actuate all these rotating shafts. Thus, it may also be possible to move two or more rotating shafts by means of a coupling between one transmission element 78a, 78b and the transmission element 20. The coupling between the transmission element 78a, 78b and the transmission element 20 can be implemented with, for example, mechanical or electromechanical components. Examples of the components include one or more of the following: gearwheels; or gear systems. The components may be electrically controllable, whereby the control of the components can be implemented with, for example, an electronic control unit which generates control signals for controlling the component / s.

[0192] It should be noted that in the hydraulic pump system of Fig. 8, the valve arrangement 22a, 22b, 22c may comprise a transmission element 78a, 78b for actuating said rotatable shaft. In an example, one or more transmission elements 78a, 78b may comprise a power unit which is adapted to actuate the rotatable shaft and is, for example, an electric motor arrangement. In another example, one or more transmission elements 78a, 78b are connected to a transmission element 20 which will be described below. By means of the transmission element 20, the operation of the rotating shaft can be synchronized with the change in the volume of the chambers 18a, 18b, 18c of the pump unit 200a, 200b, 200c. Said synchronization is implemented, for example, mechanically, or it is controlled by means of control signals from an electronic control unit 70 which will be described below.

[0193] For enabling the methods to be implemented in the hydraulic pump system of Fig. 8, the hydraulic pump system may also comprise an electronic control unit 70 adapted to control the functions of the hydraulic pump system by means of control signals. Control signals are received by, for example, the above described transmission element 20, 78a, 78b, 79c, the auxiliary transmission element 38, the electric motor arrangement 30, 42, the valve arrangement 22a, 22b, 22c, the valve arrangement 40, 52 constituting e.g. an electrically controlled directional valve, or the electrically controlled shut-off valve element, such as the shut-off valve element 46, 64, 66, 74. In an example, the electronic control unit 70 applies the transmission element 20 to enable synchronization of the operation of the rotating shaft with the change in the volume of the chambers 18a, 18b, 18c of the pump unit 200a, 200b, 200c. In an example, the electronic control unit determines the rotational speed, Roti , of the rotating shaft and the rotational speed, Rot2, of the transmission element. The rotational speeds Roti and Rot2 are in such a relation to each other that when the volume of the chamber is decreasing, the chamber 18a, 18b, 18c is in fluid communication with the high-pressure line 10 via the channel extending through the rotating shaft to the high-pressure line, and when the volume of the chamber is increasing, the chamber 18a, 18b, 18c is in fluid communication with the low-pressure line 12 via the channel extending through the rotating shaft to the low-pressure line.

[0194] The hydraulic pump system and its electronic control unit 70 make it possible to maintain the recurring reciprocating motion of one or more pistons 16a, 16b, 16c of the pump units 200a, 200b, 200c and, in an example, also to vary their speed, whereby the produced volume flow can be varied or controlled as desired. The control of the speed is implemented by means of, for example, the electric motor arrangement 30 described above. Further, the pump system and its electronic control unit 70 make it possible to synchronize the change in the volume of the respective chamber, caused by the recurring reciprocating motion of each piston 16a, 16b, 16c, with the operation of the valve arrangement, for example the rotating shaft, whereby the chamber can be brought to fluid communication with the high-pressure line and separated from the low-pressure line when the volume of the chamber is decreasing, and the chamber can be brought to fluid communication with the low-pressure line and separated from the high-pressure line when the volume of the chamber is increasing.

[0195] The operation of the rotating shaft in synchronization with the change in the volume of the chamber 18a, 18b, 18c of the pump unit 200a, 200b, 200c of the hydraulic pump system described in Fig. 8 will be described with reference to Figs. 9a, 9b, 9c, 10a, and 10b. The changes in the rotating shaft and the volume of the chamber are synchronized by setting the rotational speed, Rot2, of a bearing wobbler and the rotational speed of the rotating shaft in such a way that hydraulic fluid can be conveyed through the rotating shaft in the first states and the second states, wherein in the first states, each chamber 18a, 18b, 18c is, in turn, in fluid communication with the high-pressure line 12 when the volume of the respective chamber 18a, 18b, 18c is simultaneously decreasing, and in the second states, each chamber 18a, 18b, 18c is in fluid communication with the low-pressure line 10 when the volume of the respective chamber 18a, 18b, 18c is simultaneously increasing.

[0196] Figures 9a, 9b and 9c show reduced schematic views of a valve arrangement and a transmission arrangement for a pump unit of the hydraulic pump system according to some examples of the invention, as well as the operation of the transmission arrangement. Figure 9a illustrates the transmission arrangement for rotating a rotating or rotatable shaft for at least one pump system 200a, 200b, 200c, and for actuating a piston 16b, 16c reciprocating in relation to a cylinder space 14a, 14b, 14c. Figure 9b illustrates a transmission arrangement for actuating rotating shafts for three pump units 200a, 200b, 200c, and for actuating pistons 16b, 16c reciprocating in relation to a cylinder space 14a, 14b, 14c. The transmission arrangement comprises a transmission element 78a, 78b arranged to rotate the rotating shaft. The transmission element 78a, 78b is connected, by e.g. a gear system, to the transmission element 20 described above, for example in connection with Fig. 1. By means of the transmission element 20, the operation of the rotating shaft can be synchronized with the change in the volume of the chamber of the pump unit 200a, 200b, 200c. Said synchronization is implemented e.g. mechanically or by control signals from the electronic control unit 70 described above. In an example, the transmission element 20 is arranged to rotate at a speed Rot2, and the transmission element 78a, 78b is connected to be rotated at a speed Roti which is in relation to the rotational speed of the transmission element 20, whereby the positions of the rotating shaft can be synchronized with the change in the volume of the chamber of the pump unit 200a, 200b, 200c. In an example, the rotating shaft comprises at least two channels, via which fluid can be conveyed into and out of the cylinder space 18a, 18b, 18c. In the operation of the rotating shaft, the positions of the rotating shaft can be synchronized with the change in the volume of the chamber of the pump unit 200a, 200b, 200c by setting the transmission element 20 to rotate at the speed Rot2, wherein the transmission element 78a, 78b is connected to be rotated at the speed Roti which is in relation to the rotational speed of the transmission element 20. It should be noted that the rotating shaft may comprise at least two channels, wherein the positions of the rotating shaft can be determined on the basis of the rotary position of the channels. For example, in a first position of the rotating shaft, the first channel is arranged to convey fluid through the rotating shaft, and in the second position of the rotating shaft, the second channel is arranged to convey fluid through the rotating shaft.

[0197] In Figs. 9a and 9b, the rotating shafts are brought by the transmission arrangement to a position in which fluid (In) can be transferred via the rotating shaft into the chamber of the pump unit when the volume of the chamber of the pump unit is increasing. In an example, the transmission element 20 comprises one or more bearing wobblers, each being connected to a piston 16a, 16b, 16c for reciprocating the piston in the cylinder space 14a, 14b, 14c. The bearing wobbler is a mechanical component converting the rotational motion of the transmission element 20 to a wobbler action which causes the reciprocating motion of the piston 14a, 14b, 14c. In the wobbler action, the piece to be rotated, such as the bearing wobbler, can reach a peak amplitude at certain points of the movement, at which the piston actuated by the piece to be rotated is at the highest possible position within the cylinder space, the volume of the cylinder being at its minimum. Correspondingly, the piece to be rotated, such as the bearing wobbler, can reach an amplitude dip at a certain point in the movement, at which the piston actuated by the piece to be rotated is at the lowest possible position within the cylinder space, the volume of the cylinder being at its maximum. The bearing wobbler comprises a bearing 23a, 23b, 23c arranged to be movable in a direction transverse to the rotation axis 31 of the transmission element. The bearing is connected to the piston, whereby the rotary motion of the transmission element causes a reciprocating motion of the bearing which is converted into a movement of the piston. Preferably, the rotary motion of the transmission element comprises or causes a wobbler action. The movement of the piston can then be utilized in the operation of, for example, pumps or compressors. In an example, the movement of the bearing in the radial direction of the rotation axis of the transmission element, or in a direction transverse to the longitudinal axis of the rotation axis of the transmission element, is effected by a bearing wobbler comprising a bearing 23a, 23b, 23c and a wobbler element 21a, 21 b, 21 c. The bearing wobbler may be, for example, a part or a section of a transmission element, such as a crankshaft. The bearing wobbler may have one or more amplitude peaks on each rotation of the transmission shaft around its rotation axis.

[0198] Figures 9a, 9b and 9c show a bearing wobbler having one amplitude peak on each rotation of the transmission element 20 around its rotation axis 31 . When such a bearing wobbler is used for moving the piston, one piston stroke is achieved on each rotation of the transmission element. In an example, the bearing wobbler may comprise a wobbler element 21 a, 21 b, 21c which is a cylindrical piece, whereby its cross section in the radial direction of the rotation axis of the transmission element, or in a direction transverse to the longitudinal direction of the rotation axis of the transmission element, may be, for example, circular. The cylindrical wobbler element can be arranged in the transmission element in such a way that the longitudinal axis of the cylindrical wobbler element is parallel to the rotation axis of the transmission element and offset from the rotation axis of the transmission element. In this way, upon rotation of the transmission element, a wobbler action is caused whereby the position of the wobbler element changes back and forth in the radial direction of the rotation axis. The wobbler action of the wobbler element causes a reciprocating motion of the bearing connected to the wobbler element, which motion is further converted into a movement of the piston 16a, 16b, 16c.

[0199] Figure 9c illustrates the operation of the transmission arrangement by showing the positions 92, 94, 96, 98, 100 of the bearing wobbler, and the respective piston 16a, 16b, 16c connected to it, in different stages of the piston when the piston is moved by the transmission arrangement. In the positions 92, 94, 96, the piston 16a moves in the cylinder space 14a so that the volume of the chamber 18a increases when the piston moves downwards. In the positions 98 and 100, the piston 16a moves in the cylinder space 14a so that the volume of the chamber 18a decreases when the piston moves upwards. Increasing and decreasing of the volume of the chamber is achieved by rotating c. Thus, the chamber is in fluid communication with the high-pressure line 10 and the low- pressure line 12 via a shaft rotating at a rotation speed Roti , wherein the operation of the rotating shaft is synchronized with the change in the volume of the chamber of the pump unit 200a, 200b, 200c. Thus, in the positions 98 and 100, the chamber 18a is in fluid communication with the high-pressure line 10 via the rotating shaft when the volume of the chamber is simultaneously decreasing, and in the positions 92, 94 and 96, the chamber 18a is in fluid communication with the low-pressure line 12 via the rotating shaft when the volume of the chamber is simultaneously increasing.

[0200] Figures 10a and 10b show reduced schematic views of bearing wobblers according to some examples of the invention. The bearing wobblers can be used for producing a wobbler action in the transmission arrangements shown in Figs. 9a, 9b and 9c. As opposed to the bearing wobbler shown in Figs. 9a, 9b and 9c, Figs. 10a and 10b show bearing wobblers which are capable of producing wobbler actions with two or more amplitude peaks on each rotation around the rotation axis 31 of the transmission element 20. The bearing wobbler shown in Fig. 10a has two amplitude peaks, and the bearing wobbler shown in Fig. 10b has three amplitude peaks. With the bearing wobbler according to the example of Fig. 10a, two strokes of the piston 16a can be generated on each rotation of the transmission element. With the bearing wobbler according to the example of Fig. 10b, three strokes of the piston can be generated on each rotation of the transmission element.

[0201] In the bearing wobbler shown in Fig. 10a, the two amplitude peaks of the bearing wobbler are provided by the oval shape of the wobbler element 21 e so that the wobbler element of the bearing wobbler has an oval cross-section in the radial direction of the rotation axis 31 of the transmission element, the ends 33e of the oval being arranged on opposite sides of the rotation axis, that is, at an angle of 180 degrees around the rotation axis 31 , and the flanks 35e of the oval extend between the ends. The flanks generate amplitude dips. In this way, when the bearing wobbler is rotated, a wobbler action is generated, where the ends of the oval generate amplitude peaks in which the piston actuated by the piece to be rotated is in the highest possible position in the cylinder space, wherein the volume of the cylinder is at its minimum. Correspondingly, in the wobbler action, the flanks of the oval generate amplitude dips. The bearing wobbler can be driven at a rotational speed Rot2. Thus, the shaft rotated in the hydraulic pump system may have a rotation speed Roti in such a way that Rot1 :Rot2 is 1 :1 , wherein the shaft to be rotated, having two channels arranged at an angle of 180 degrees from each other for conveying fluid between the chamber and the high-pressure line and the low-pressure line, is synchronized with the change in the volume of the chamber of the pump unit 200a, 200b, 200c. In this way, the speeds of the bearing wobbler and the rotating shaft are adapted to each other, whereby the operation of the rotating shaft is synchronized with the change in the volume of the chamber of the pump unit 200a, 200b, 200c, and hydraulic fluid can be conveyed through the rotating shaft in the first state and the second state.

[0202] In the bearing wobbler of Fig. 10b, the three amplitude peaks of the bearing wobbler are generated by a three-branched shape of the wobbler element 21 d of the bearing wobbler so that the wobbler element of the bearing wobbler has a three-lobed cross-section in the radial direction of the rotation axis 31 of the transmission element, the tips 33d of the lobes being arranged at angles of 120 degrees from each other around the rotation axis 31 , and the adjacent lobes being separated by spaces which are, respectively, arranged at angles of 120 degrees around the rotation axis 31 . In this way, when the bearing wobbler is rotated, a wobbler action is generated where the tips 33d of the lobes generate amplitude peaks in which the piston actuated by the piece to be rotated is in the highest possible position in the cylinder space, wherein the volume of the cylinder is at its minimum. Correspondingly, in the wobbler action, the spaces between the lobes generate amplitude dips. The bearing wobbler can be driven at a rotational speed Rot2. Thus, the shaft to be rotated in the hydraulic pump system has the rotation speed Roti so that Rot1 :Rot2 is 3:2, wherein the shaft to be rotated, having two channels arranged at an angle of 120 degrees from each other for conveying fluid between the chamber and the high-pressure line and the low-pressure line, is synchronized with the change in the volume of the chamber of the pump unit 200a, 200b, 200c. In this way, the speeds of the bearing wobbler and the rotating shaft are adapted to each other, whereby the operation of the rotating shaft is synchronized with the change in the volume of the chamber of the pump unit 200a, 200b, 200c, and hydraulic fluid can be conveyed through the rotating shaft in the first state and the second state.

[0203] In an example, an amplitude peak in the bearing wobbler can be implemented by means of, for example, the geometric design of the wobbler element 21 a, 21 b, 21 c, 21 d, 21 e. The geometric design of the piece to be rotated, such as the bearing wobbler, for example the wobbler element of the bearing wobbler, with respect to its rotation axis, can be arranged so that a desired number of amplitude peaks is achieved upon rotating the piece to be rotated. For example, certain features of the design, such as asymmetry of the piece to be rotated around the rotation axis, may cause a wobbler action with amplitude peaks. It should be noted that depending on the implementation of the amplitude peaks, such as the shape of the wobbler element and / or its position with respect to the rotation axis, the amplitude peaks of the piece to be rotated may be of equal or different magnitude on one rotation cycle of the bearing wobbler. Equal amplitude peaks may enable a steady range of motion, i.e. stroke length, for the piston to which the piece to be rotated is connected. Unequal amplitude peaks may enable variation in the volume flow produced by the hydraulic pump system. In an example, the geometric shape of the piece to be rotated, for example wobbler element, in relation to its rotation axis can be arranged, for example, so that the distance of the outer surface of the piece to be rotated, in radial direction, with respect to the rotation axis, varies around the rotation axis.

[0204] Figure 11 shows a reduced schematic view of a hydraulic pump system according to some examples of the invention. The hydraulic pump system may comprise several above-described pump units 200a, 200b, 200c. The hydraulic pump system comprises two or more above-described transmission elements 20. A pump unit 200a, 200b, 200c is connected to each transmission element, wherein the transmission element may bring the piston 16a, 16b, 16c of the pump unit 200a, 200b, 200c to the above-described recurring reciprocating motion in relation to the respective cylinder space 14a, 14b, 14c of the pump unit 200a, 200b, 200c so that the volume of the respective chamber 18a, 18b, 18c of the pump unit 200a, 200b, 200c simultaneously decreases and increases, respectively. Each transmission element 20 also comprises one or more power arrangements, such as an electric motor arrangement 30, adapted to rotate the transmission element 20, preferably at variable speeds. Two or more of the transmission elements 20 may be connected to each other by means of one or more coupling elements 62. In this way, two or more transmission elements 20 can be driven by a single power unit, for example an electric motor arrangement 30, whose rotational speed may be adjustable, for example by means of a frequency converter. In an example, the hydraulic pump system comprises at least two pump units 200a, 200b, 200c, which are capable of producing different volume flows. To one of the pump units, capable of producing a volume flow Q1, a transmission element 20 is connected which is coupled to the transmission arrangement either directly or via a coupling element 62. In this way, the pump unit can be used for producing volume flow. The transmission element 20 connected to the pump unit producing the volume flow Q1 can further be coupled by the coupling element 62 to a transmission element 20 connected to another pump unit which is capable of producing a volume flow Q2, wherein the power arrangement can be used to actuate both pump units to produce a combined volume flow Q1 + Q2. It should be noted that the hydraulic pump system may comprise one, two, or more coupling elements 62 for connecting transmission elements connected to the pump units, to be driven by the power arrangement. In an example, the hydraulic pump system comprises at least two pump units 200a, with a transmission element 20 connected to each and connected to the power arrangement either directly or via a coupling element. The transmission elements connected to the pump units can be combined by means of one or more coupling elements 62, wherein the pump units can be driven by a single power arrangement. Thus, one of the power arrangements may be out of service. It should be noted that the hydraulic pump system may comprise, as shown in the examples of Figs. 3a, 3b, 3c, 3d, 4a, 4b, 4c, 4d, 4e, and 8, a high-pressure line 10 with at least a first main branch 100 and a second main branch 102, and a low-pressure line 12 with at least a first main branch 120 and a second main branch 122. Thus, the chambers 18a, 18b, 18c of two or more of said pump units can be brought into fluid communication with the first main branch 100 of the high-pressure line 10 and the first main branch 120 of the low-pressure line 12; and the chambers 18a, 18b, 18c of two or more other said pump units can be brought into fluid communication with the second main branch 102 of the high-pressure line 10 and the second main branch 122 of the low-pressure line 12. The hydraulic pump system may further comprise at least one electrically controllable shutoff valve element 64 by which the first and second main branches 100, 102 of the high-pressure line 10 can be separated from each other and brought into fluid communication with each other; and at least one electrically controllable shut-off valve element 66 by which the first and second main branches 120, 122 of the low-pressure line 12 can be separated from each other and brought into fluid communication with each other. It should be noted that the hydraulic pump system may comprise several shut-off valves 64, 65 for separating main branches of the high-pressure line and for bringing them into fluid communication with each other, and the hydraulic pump system may comprise several shut-off valves 66, 67 for separating main branches of the low-pressure line and for bringing them into fluid communication with each other. Thus, the shutoff valves can be controlled so that the first main branch of the high-pressure line is brought into fluid communication with one or more other main branches 100, 102, 104 of the second high-pressure line. Similarly, the shut-off valves can be controlled so that the first main branch of the low-pressure line is brought into fluid communication with one or more other main branches 120, 122, 14 of the second low-pressure line. In this way, the volume flow produced by the pump units can be directed to an actuator or actuators connected to each main branch, for applying the actuators as needed. In an example on controlling the shut-off valves, the shut-off valves can be switched to the second state and / or the first state by means of, for example, an electronic control unit which is configured to generate electric control signals and to input the generated control signals in shut-off valve elements. In the first state of the shut-off valves, the first main branch of the high-pressure line is separated from one or more second main branches of the high-pressure line, and the first main branch of the low-pressure line is separated from one or more second main branches of the low-pressure lines. Thus, one or more pump units are connected to the transmission element of the hydraulic pump system and are capable of supplying a volume flow, for example Q1, for operating one or more actuators connected to the first main branch of the high-pressure line and to the first main branch of the low-pressure line. In the second state of the shutoff valves, the shut-off valve elements are controlled in such a way that the first main branch of the high-pressure line is brought into fluid communication with one or more second main branches of the high-pressure line, and the first main branch of the low-pressure line is brought into fluid communication with one or more second main branches of the low-pressure line. One or more actuators are connected to one or more second main branches of the high-pressure line and to one or more second main branches of the low-pressure line and can be operated by one or more pump units which are connected by a coupling element 62 to a transmission element of the hydraulic pump system and are capable of supplying a volume flow, for example Q2, for operating one or more actuators connected to one or more second main branches of the high-pressure line and to one or more second main branches of the low-pressure line. Thus, the combined volume flow supplied to the main branches may be Q1+Q2. The volume flow can be conveyed to the main branches and the actuators by controlling the shut-off valves, whereby the main branches of the high-pressure line can be separated and brought into fluid communication with each other, and the main branches of the low-pressure line can be separated and brought into fluid communication with each other. The volume flow required by the state of each shut-off valve is supplied by controlling the coupling elements to connect and disconnect the pump units to and from the respective transmission elements, whereby the volume flow supplied by the pump units can be adjusted.

[0205] In an example, the hydraulic pump system comprises an electronic control unit 70 configured to generate electrical control signals which provide synchronization of the valve arrangement with the change in the volume of the chambers 18a, 18b, 18c of the pump unit 200a, 200b, 200c. In an example, the electronic control unit generates electrical control signals for setting the rotation speed, Roti , of the rotating shaft, and the rotation speed, Rot2, of the transmission element. The rotational speeds Roti and Rot2 are in such a relation to each other that when the volume of the chamber is decreasing, the chamber 18a, 18b, 18c is in fluid communication with the high-pressure line 10 via the channel extending through the rotating shaft to the high-pressure line, and when the volume of the chamber is increasing, the chamber 18a, 18b, 18c is in fluid communication with the low-pressure line 12 via the channel extending through the rotating shaft to the low-pressure line. It should be noted that the rotation speed, Rot2, of the transmission element, and the rotation speed, Roti , of the rotating shaft can be set in such a way that the channel extending through the rotating shaft can be used for fluid communication between the chamber and the low-pressure line, and for fluid communication between the chamber and the high-pressure line, in an alternating manner. Generated electrical control signals can be input in one or more electric motor arrangements 30 adapted to drive the pump units 200a, 200b, 200c of one or more modules, for setting the rotation speed of the transmission elements of the pump units.

[0206] The hydraulic pump system according to the disclosure above is not limited to the examples presented above, but it can be implemented further within the scope of the appended claims.

Claims

Claims1 . A hydraulic pump system, comprising:- a high-pressure line (10);- a low-pressure line (12); and- at least two pump units (200a, 200b, 200c), each pump unit comprising:- a cylinder space (14a, 14b, 14c),- a piston (16a, 16b, 16c) placed in the cylinder space, and- a chamber (18a, 18b, 18c) arranged within the cylinder space and having a volume limited by the piston; wherein the piston can further be brought into recurring reciprocating motion in relation to the cylinder space so that the volume of the chamber simultaneously decreases, for supplying volume flow, and increases, for receiving volume flow; and- a valve arrangement (22a, 22b, 22c) in whose first state the chamber is, in turn, in fluid communication with the high-pressure line (10) when the volume of the respective chamber is simultaneously decreasing, and in whose second state the chamber is in fluid communication with the low-pressure line (12) when the volume of the respective chamber is simultaneously increasing, wherein the hydraulic pump system further comprises a set of hydraulic lines, including at least:- the high-pressure line (10) with at least a first main branch (100) and a second main branch (102);- the low-pressure line (12) with at least a first main branch (120) and a second main branch (122); and wherein in the hydraulic pump system:- the chambers (18a, 18b, 18c) of two or more said pump units can be brought into fluid communication with the first main branch (100) of the high- pressure line (10) and the first main branch (120) of the low-pressure line (12);- the chambers (18a, 18b, 18c) of two or more other ones of said pump units can be brought into fluid communication with the second main branch (102) of the high-pressure line (10) and the second main branch (122) of the low-pressure line (12); and wherein the hydraulic pump system comprises:- at least one electrically controllable shut-off valve element (64), by which the first and second main branches (100, 102) of the high-pressure line(10) can be separated from each other and brought into fluid communication with each other; and- at least one electrically controllable shut-off valve element (66), by which the first and second main branches (120, 122) of the low-pressure line (12) can be separated from each other and brought into fluid communication with each other.

2. The hydraulic pump system according to claims 1 , to which an electric energy storage (1 ) is connected, wherein the hydraulic pump system is arranged to use a valve arrangement (22a, 22b, 22c) to convert a pressure difference between the high-pressure line (10) and the low-pressure line (12) to electric energy and to charge the electric energy storage (1 ) with the electric energy.

3. The hydraulic pump system according to claim 1 or 2, further comprising:- one or more transmission elements (20), to which a piston (16a, 16b, 16c) of one or more pump units is connected and which is adapted to bring the respective piston to a recurring reciprocating motion in relation to the respective cylinder space (14a, 14b, 14c) of said one or more pump unit so that the volume of the respective chamber (18a, 18b, 18c) of said one or more pump units simultaneously decreases or increases, respectively.

4. The hydraulic pump system according to claim 3, wherein the transmission element (20) further comprises one or more power units adapted to rotate the transmission element (20) at variable speeds which are proportional to a received control signal, for changing the volume flow supplied by said one or more pump units.

5. The hydraulic pump system according to any of the claims 1 to 4, wherein the valve arrangement comprises: one or more rotatable shafts which can be brought into different rotary positions and have a respective first channel for each pump unit (200a, 200b, 200c), for conveying hydraulic fluid through the respective shaft to be rotated for said first state when the shaft to be rotated has reached a first rotary position; and a respective second channel for each pump unit (200a, 200b, 200c) for conveying hydraulic fluid through the respective shaft for said second state when the shaft to be rotated has reached a second rotary position.

6. The hydraulic pump system according to claim 5, wherein the valve arrangement (22a, 22b, 22c) further comprises a transmission element (78a, 78b), to which the shaft to be rotated is connected and which is adapted to continuously rotate said shaft to be rotated.

7. The hydraulic pump system according to claim 5 or 6, wherein the operation of the shaft to be rotated is synchronized with the change in the volume of the chamber of the pump unit (200a, 200b, 200c).

8. The hydraulic pump system according to any of the claims 1 to 4, wherein the valve arrangement comprises: one or more valve discs, one of more of them being rotatable valve discs which can be brought into different rotary positions and which have a respective first channel for each pump unit (200a, 200b, 200c), for conveying hydraulic fluid through the respective valve disc for said first state when the rotatable valve disc has achieved a first rotary position, and a respective second channel for each pump unit (200a, 200b, 200c), for conveying hydraulic fluid through the respective valve disc for said second state when the rotatable valve disc has achieved a second rotary position.

9. The hydraulic pump system according to claim 8, wherein the valve arrangement (22a, 22b, 22c) further comprises a transmission element (78a, 78b), to which the rotatable valve disc is connected and which is adapted to continuously rotate said rotatable valve disc.

10. The hydraulic pump system according to any of the claims 1 to 4, wherein said at least two pump units comprise at least a first pump unit (200a) and a second pump unit (200b), each having a valve arrangement (22a, 22b) comprising a valve (22a, 22b) which is a hydraulically piloted directional valve with:- a first hydraulic pilot valve (24a) adapted to sense the pressure in the chamber (18a) of the first pump unit;- a second hydraulic pilot valve (24b) adapted to sense the pressure in the chamber (18b) of the second pump unit; and- a shaft (24c) reciprocating in a drill hole, wherein the pressure of the first hydraulic pilot line (24a) is adapted to affect the shaft in such a way that the shaft will move in a first direction for implementing said first state, andwherein the pressure of the second hydraulic pilot line (24b) is adapted to affect the shaft in such a way that the shaft will move in an opposite second direction for implementing said second state.11 . The hydraulic pump system according to any of the claims 1 to 4, wherein said valve arrangement (22a, 22b, 22c) comprises:- two non-return valves (22a1 , 22a2, 22b1 , 22b2, 22c1 , 22c2), of which- the first one is, for implementing said first state, adapted to open and the second one is adapted to close when the the volume of the chamber (18a, 18b, 18c) of the respective pump unit is decreasing, and of which- the first one is, for implementing said second state, adapted to close and the second one is adapted to open when the volume of the chamber (18a, 18b, 18c) of the respective pump unit is increasing.

12. The hydraulic pump system according to any of the claims 1 to 11 , comprising a module (24) in which the same structure comprises:- two or more said pump units, including at least a first and a second pump unit (200a, 200b);- said high-pressure line (10) or at least two of its branches (10a, 10b, 10c); and- said low-pressure line (12) or at least two of its branches (12a, 12b, 12c); and wherein the module (24) is adapted to supply a volume flow of hydraulic fluid which is available in said high-pressure line (10) or its branches (10a, 10b, 10c).

13. The hydraulic pump system according to claim 12, further comprising a set of hydraulic lines, including at least:- the high-pressure line (10) with at least a first main branch (100) and a second main branch (102);- the low-pressure line (12) with at least a first main branch (120) and a second main branch (122); and wherein the hydraulic pump system comprises at least:- a first module 824) where the chambers (18a, 18b, 18c) of the pump units can be brought into fluid communication with the first main branch (100)of the high-pressure line (10) and the first main branch (120) of the low-pressure line (12);- a second module (24) where the chambers (18a, 18b, 18c) of the pump units can be brought into fluid communication with the second main branch (102) of the high-pressure line (10) and the second main branch (122) of the low-pressure line (12); and wherein the hydraulic pump system comprises:- at least one electrically controllable shut-off valve element (64), by which the first and second main branches (100, 102) of the high-pressure line (10) can be separated from each other and brought into fluid communication with each other; and- at least one electrically controllable shut-off valve element (66), by which the first and second main branches (120, 122) of the low-pressure line (12) can be separated from each other and brought into fluid communication with each other.

14. The hydraulic pump system according to claim 12 or 13, wherein each module (24) comprises not more than either two or three said pump units (200a, 200b, 200c).

15. The hydraulic pump system according to any of the preceding claims, further comprising:- an actuator (50) having a linear or rotating motion and adapted to receive volume flow via a valve arrangement (52) for carrying out work, and to return the volume flow; and wherein the pump system comprises, for implementing a closed circuit:- a supply line (48a), via which the high-pressure line (10) or its first main branch (100) is in fluid communication with said actuator, for receiving volume flow in said actuator; and- a return line (48b), via which the low-pressure line (12) or its first main branch (102) is in fluid communication with said actuator, for receiving volume flow returned from the actuator into the low-pressure line.

16. The hydraulic pump system according to any of the preceding claims, further comprising:- an actuator (50) having a linear or rotating motion and adapted to receive volume flow via a valve arrangement (52) for carrying out work, and to return the volume flow; and the pump system comprising:- a fluid tank (48c) for storing hydraulic fluid;- a supply line (48d), via which the high-pressure line (10) or its first main branch (100) is in fluid communication with said actuator, for receiving volume flow in said actuator; and- a return line (48e), via which said actuator is in fluid communication with said low-pressure line (12), for receiving volume flow returned from the actuator (50) into the low-pressure line.

17. The hydraulic pump system according to any of the claims 1 to 4, comprising a line module (44) which comprises, in the same structure:- said first main branch (100) and second main branch (102) of the high- pressure line (10);- said first main branch (120) and second main branch (122) of the low- pressure line (12); and- said at least two electrically controllable shut-off valve elements (64, 66).

18. The hydraulic pump system according to any of the claims 1 to 17, further comprising:- a first line (28a) for transfer of hydraulic fluid;- a cylinder space (32);- a piston (34) arranged in the cylinder space;- a chamber (36) arranged within the cylinder space and having a volume limited by the piston, wherein the piston can further be brought into recurring reciprocating motion in relation to the cylinder space so that the volume of the chamber simultaneously decreases, for supplying volume flow or for increasing the amount of hydraulic fluid in the first line, and increases, for receiving volume flow or for decreasing the amount of hydraulic fluid in the first line; and wherein, in the hydraulic pump system,- the chamber (36) is in fluid communication with the first line (28a), or the hydraulic pump system further comprises a valve arrangement (40)adapted to shift into a first state, in which fluid communication of the chamber with the first line (28a) is allowed, and into a second state in which fluid communication of the chamber with the first line (28a) is prevented; and- the first line (28a) is in fluid communication with the low-pressure line (12).

19. The hydraulic pump system according to claim 1 or 18, further comprising:- a second line (28b) for transfer of hydraulic fluid; and wherein, in the hydraulic pump system,- in the first state of said valve arrangement (40), fluid communication between the chamber and the second line (28b) is prevented, and in the second state, fluid communication between the chamber and the second line (28b) is allowed; and- the second line (28b) is in fluid communication with the high-pressure line (10).

20. The hydraulic pump system according to claim 18 or 19, comprising an auxiliary module (68), which comprises, in the same structure:- said first line (28a), cylinder space (32), piston (34), and chamber (36).

21. The hydraulic pump system according to claim 18, comprising an auxiliary module (68) which comprises, in the same structure:- said first line (28a), second line (28b), cylinder space (32), piston (34), and chamber (36), as well as the valve arrangement (40).

22. The hydraulic pump system according to any of the claims 18 to 21 , further comprising an auxiliary transmission element (38), to which the piston (34) is connected and which is adapted to bring said piston in recurring reciprocating motion with respect to the cylinder space (32) so that the volume of the chamber (36) simultaneously decreases and increases, respectively.

23. The hydraulic pump system according to any of the claims 18 to 22, comprising an electronic control unit (70) configured to generate control signals (86) and to input the generated control signals in one more more electric motor arrangements (30) which are adapted to drive pump units (200a, 200b, 200c) of one or more modules, and the electronic control unit (70) being furtherconfigured to generate second control signals (87) and to input the generated second control signals in at least one electric motor arrangement (42) configured to drive a pump unit (300a, 300b, 300c) of an auxiliary module (68), to compensate for fluctuations in hydraulic fluid and volume flow in the high-pressure line (10) and / or the low-pressure line (12), or between them, when said hydraulic pump system is used to operate one or more actuators (50) connected to the high-pressure line (10) and the low-pressure line (12), to be driven by the pressure difference between the high-pressure line and the low- pressure line.

24. The hydraulic pump system according to claim 23, wherein the electronic control unit (70) is configured:- to determine the combined asymmetry of the actuators to be driven simultaneously on the basis of the speeds and directions of movement of the actuators to be used simultaneously, and the cylinder space above the piston, and the cylinder space below the piston of each actuator,- to use the combined asymmetry to generate the control signals (87) for compensating for the fluctuations in hydraulic fluid and volume flow.

25. The hydraulic pump system according to any of the claims 1 to 24, comprising a pump unit (500) of an open circuit.

26. The hydraulic pump system according to any of the claims 1 to 25, comprising a pump unit (400) of a closed circuit.

27. The hydraulic pump system according to claim 3, wherein the transmission element (20) is arranged to be rotated at a rotation speed (Rot2) with respect to the rotation speed (Roti ) of a valve arrangement, for example a valve disc and / or a rotatable shaft, so that when the volume of the chamber decreases, the chamber (18a, 18b, 18c) is in fluid communication with the high-pressure line (10) via a channel extending through the rotatable shaft to the high-pressure line, and when the volume of the chamber increases, the chamber (18a, 18b, 18c) is in fluid communication with the low-pressure line (12) via a channel extending through the rotatable shaft to the low-pressure line.

28. The hydraulic pump system according to any of the preceding claims 3 to 27, wherein the transmission element (20) comprises one or more bearing wobblers, each connected to a respective piston (16a, 16b, 16c).

29. The hydraulic pump system according to claim 28, wherein each bearing wobbler has one or more amplitude peaks.

30. The hydraulic pump system according to any of the claims 5, 6, 7, or 27, wherein the rotatable shaft comprises two channels at an angle of 180 degrees from each other, for conveying fluid between the chamber (18a, 18b, 18c) and the high-pressure line (10) and the low-pressure line (12).

31. A method for controlling a hydraulic pump system, wherein the hydraulic pump system comprises:- a high-pressure line (10);- a low-pressure line (12); and- at least two pump units (200a, 200b, 200c) for operating at least one actuator (50) connected to the high-pressure line and the low-pressure line by the pressure difference between the high-pressure line and the low-pressure line;- an electric motor arrangement (30) adapted to drive at least two first pump units (200a, 200b, 200c), and- at least one second pump unit (300a, 300b, 300c) for compensating for fluctuations in hydraulic fluid and volume flow in the high-pressure line (10) and / or the low-pressure line (12); and- a second electric motor arrangement (42) adapted to drive said at least one second pump unit (300a, 300b, 300c); and- an electronic control unit (70) connected to the first and second electric motor arrangements; the method comprising:- generating first control signals (86) by the electronic control unit (70) of the hydraulic pump system, and inputting the generated control signals in one or more first electric motor arrangements (30), for operating at least one actuator (50) by means of two first first pump units (200a, 200b, 200c);- generating second control signals (87) by the electronic control unit (70) of the hydraulic pump system, and inputting the generated second control signalsin at least one second electric motor arrangement (42), for compensating for fluctuations in hydraulic fluid and volume flow occurring in the high-pressure line (10) and / or the low-pressure line (12), or between them, by applying said at least one second pump unit (300a, 300b, 300c) when the hydraulic pump system is used for operating one or more actuators (50) connected to the high- pressure line (10) and the low-pressure line (12), to be driven by the pressure difference between the high-pressure line and the low-pressure line.

32. The method according to claim 31 , wherein the hydraulic pump system comprises at least two third pump units (200a, 200b, 200c), and a second electric motor arrangement (30) adapted to drive the at least two third pump units (200a, 200b, 200c), and to which an electric energy storage (1 ) is connected, the method comprising:- controlling said at least two third pump units (200a, 200b, 200c) to convert the pressure difference between the high-pressure line (10) and the low-pressure line (12) to electric energy by applying the third pump units (200a, 200b, 200c) to actuate a transmission element (20) connected to a second electric motor arrangement arranged to charge the electric energy storage (1 ).

33. The method according to claim 31 or 32, comprising:- determining the asymmetry between the high-pressure line (10) and the low- pressure line (12), caused by the actuators operated simultaneously by the first control signals;- determining second control signals (87) on the basis of the determined asymmetry.

34. The method according to any of the preceding claims 31 to 33, wherein each pump unit (200a, 200b, 200c) comprises:- a cylinder space (14a, 14b, 14c),- a piston (16a, 16b, 16c) arranged in the cylinder space, and- a chamber (18a, 18b, 18c) contained within the cylinder space and having a volume limited by the piston, wherein the piston can further be brought to a recurring reciprocating motion with respect to the cylinder space so that the volume of the chamber decreases respectively, for producing volume flow, and increases, for receiving volume flow; and the hydraulic pump system comprises:- a valve arrangement (22a, 22b, 22c) in whose first state the chamber is, in turn, in fluid communication with the high-pressure line (10) when the volume of the respective chamber is simultaneously decreasing, and in whose second state the chamber is in fluid communication with the low-pressure line (12) when the volume of the respective chamber is simultaneously increasing; and wherein the method comprises:- synchronizing the valve arrangement (22a, 22b, 22c) with the change in the volume of the chamber (18a, 18b, 18c) of the pump unit (200a, 200b, 200c).

35. The method according to claim 34, comprising determining the rotation speed (Rot2) of the transmission element with respect to the rotation speed (Roti ) of the valve arrangement, for example a valve disc and / or a rotatable shaft, so that when the volume of the chamber decreases, the chamber (18a, 18b, 18c) is in fluid communication with the high-pressure line (10) through the rotatable shaft, via a channel extending through the rotatable shaft to the high- pressure line, and when the volume of the chamber increases, the chamber (18a, 18b, 18c) is in fluid communication with the low-pressure line (12) through the rotatable shaft, via a channel extending through the rotatable shaft to the low-pressure line.

36. A hydraulic pump system comprising a memory in which a computer program code is stored, wherein at least one memory and the computer program code are configured so that at least one processor of the hydraulic pump system implements the method according to any of the claims 31 to 35.

37. A computer program product comprising a computer program code which, when executed by processors, makes the hydraulic pump system to implement the method according to any of the claims 31 to 35.

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