Mobile work machine, method and use of the mobile work machine

Abstract

Disclosed is a hydraulic pump for directly driving a hydraulic consumer in a mobile work machine, wherein the consumer is, in particular, a delivery cylinder of a concrete pump. To avoid pressure peaks during the transition from an actuating movement to a power stroke of the consumer, the pump is operated in various control modes. These modes are switched during the working cycle. In a first cycle section, the pump is pre-controlled with a, in particular initial, pilot pressure or controlled with a pilot valve that has a specific opening cross-section in the first cycle section and is load-sensitive with regard to the load pressure at the output. In a second cycle section, the pump is operated with a swivel angle control.

Description

Field of the invention

[0001] The invention relates to a mobile work machine according to patent claim 1. Furthermore, the invention relates to a method with the mobile work machine and a use for the mobile work machine. Background of the invention

[0002] Concrete pumps are known from the prior art. These usually have two hydraulic delivery cylinders. A piston of one of the two delivery cylinders defines a working chamber through which concrete can be sucked in from a hopper. This is achieved by moving the piston in the direction of enlarging the working chamber. The second piston of the two delivery cylinders moves against the set direction of movement of the first piston, allowing the concrete to be fed from the working chamber into a concrete line or delivery pipe. The pistons of the delivery cylinders are moved via the hydraulic cylinders, with a piston rod of the hydraulic cylinder being mechanically connected to the piston. The hydraulic cylinders, in turn, are controlled by a hydraulic pump. The filling level of the working chamber of the delivery cylinder depends on the concrete to be delivered, in particular its viscosity. A filling level of up to 80 percent of the working chamber is usually achieved.This means that once the piston has completed the desired suction stroke, the working chamber will, for example, contain 80 percent concrete and 0 percent air. If the concrete is now to be pushed out of the working chamber by moving the piston in a direction that reduces the size of the working chamber, the air in the working chamber is first compressed. During this phase, the piston accelerates due to the comparatively low resistance and, after the air compression phase, hits the concrete column in the working chamber. This creates a significant increase in pressure or a pressure peak. This has the disadvantage of generating unwanted noise. Another disadvantage is that vibrations are generated, which can be felt in the delivery line, for example, and can lead to unwanted vibrations in other components. This can go so far that it poses a danger to people.

[0003] The patents EP 0 861 375 B1 and DE 10 2007 049 413 B3 are known from the prior art. Disclosure of the invention

[0004] In contrast, the invention is based on the object of creating a mobile work machine or a concrete pump that is designed to be simple and cost-effective in terms of device technology and eliminates the disadvantages mentioned in the prior art. Furthermore, the object of the invention is to create a simple and cost-effective method for a mobile work machine that eliminates the aforementioned disadvantages. Furthermore, an advantageous use for the mobile work machine is to be provided.

[0005] The object with regard to the mobile work machine is achieved according to the features of patent claim 1, with regard to the method according to the features of patent claim 14 and with regard to the use according to the features of patent claim 15.

[0006] Advantageous further developments of the invention are the subject of the subclaims.

[0007] The solution of claim 1 is extremely advantageous because, in the first control mode, a smooth or load-sensitive behavior of the hydraulic machine is achieved in a device-technically extremely simple manner. If, for example, the pressure on the output side of the hydraulic machine increases—for example, due to a potential pressure peak from the consumer—the pumping mechanism of the hydraulic machine immediately pivots back due to the hydromechanical restoring forces without additional control or regulation. The hydraulic machine essentially collapses when the pressure on the output side increases. A mechanical feedback system known from the prior art, which prevents this, is preferably not provided in the hydraulic machine. The hydraulic machine thus easily avoids pressure peaks from the consumer.If, for example, the consumer is to be moved at a constant speed in the further second cycle section, it is advantageous to operate the hydraulic machine with a swivel angle control. The mobile work machine can thus be operated cost-effectively and simply in the two described control modes, which is particularly advantageous when the work machine is designed as a concrete pump, as explained in more detail below. With the work machine according to the invention, pressure peaks during the transition from an actuating movement of the consumer to a power stroke of the consumer can thus be easily reduced and avoided.

[0008] In other words, the hydraulic machine is pilot-controlled with a control pressure in the first cycle section. The hydraulic machine is then load-sensitive with respect to a load pressure on the output side of the hydraulic machine. For this purpose, the hydraulic machine can, in particular, have a hydromechanical ET controller. This is disclosed, for example, in document RD 92004 / 2020-03-30, Rexroth Bosch Group. The ET controller preferably has no mechanical feedback between the pumping system of the hydraulic machine and the actuating cylinder.

[0009] Preferably, the work machine is designed such that the control modes can be switched during the work cycle. For example, a control device is provided to switch the control modes during the work cycle.

[0010] The at least one consumer is, for example, a hydraulic cylinder that can be driven via the hydraulic machine and that serves, in particular via a mechanically connected delivery cylinder, to deliver a liquid medium, such as concrete. During the delivery stroke of the hydraulic cylinder, for example when delivering concrete, there is usually first an adjusting movement to compress an air space, followed by a power stroke to deliver the concrete mass. The delivery stroke occurs, for example, from a bottom dead center of the piston. In the transition area between the adjusting movement and the power stroke, pressure peaks can occur in conventional concrete pumps when they hit the liquid medium. Due to the load-sensitive design in the first cycle section, this pressure peak is avoided or effectively reduced in a simple device-related manner.

[0011] Preferably, the at least one hydraulic cylinder is connected to a delivery cylinder and drives it. The delivery cylinder has, for example, a delivery piston. A piston rod of the hydraulic cylinder can then be connected to the delivery piston of the delivery cylinder in order to move it in an extension direction and a retraction direction. The delivery piston can delimit a delivery chamber. In the extension direction of the delivery piston, the delivery chamber can be made smaller and, in the opposite direction, enlarged in the retraction direction. If the delivery chamber is reduced in size, a medium, for example concrete, can be displaced from the delivery chamber. If the delivery chamber is enlarged, the medium can be introduced into it, for example, sucked in. If the delivery cylinder has sucked in concrete, for example, the delivery chamber is only partially filled with concrete, depending on the viscosity of the concrete, for example up to 80 percent. Otherwise, air is usually present.During the delivery stroke, the delivery piston essentially moves first through an air section of the delivery chamber before it hits the concrete and pushes it out of the delivery chamber.

[0012] In a further embodiment of the invention, a controller is preferably provided for adjusting or controlling the hydraulic machine. The controller has, for example, at least one valve. Its valve spool can be actuated via a magnetic actuator in order to adjust the hydraulic machine with a desired actuating pressure. It can preferably be provided that the actuator of the valve is controlled in the first cycle section with a specific valve actuation degree, i.e., for example, generates a specific magnetic force for adjusting the valve spool. The valve actuation degree can correspond, for example, to a desired deflection or pivoting of the hydraulic machine or a specific displacement volume of the hydraulic machine. Thus, a constant control of the valve preferably takes place in order to adjust the hydraulic machine with a desired actuating pressure.The hydromechanical restoring forces on the pumping station act against the control pressure based on the output load pressure of the hydraulic machine. Above a certain load pressure, the pumping station is automatically pivoted back toward a reduced displacement by hydromechanical restoring forces. The controller, for example, is an ET controller, which is thus operated simply hydromechanically in the first phase of the cycle. An example design of the ET controller is explained in the aforementioned document RD 92004.

[0013] Preferably, the controller or a controller can be used as an electronic controller in the second cycle section. This can then adjust or regulate the valve actuation level according to the control error of the hydraulic machine's swivel angle, thus implementing swivel angle control. The controller can simply be the ET controller.

[0014] In a further embodiment of the invention, the swivel angle control is implemented such that the hydraulic machine adjusts the actual swivel angle to the target swivel angle as accurately as possible, regardless of the load pressure. Preferably, a swivel angle sensor is provided, via which the actual swivel angle of the hydraulic machine can be determined. Alternatively or additionally, it is conceivable that the actual swivel angle of the hydraulic machine is estimated. This is done, for example, using a pump model and / or the measured variables load pressure and / or control pressure and / or valve actuation level and / or speed of the hydraulic machine.

[0015] The controller for adjusting the hydraulic machine preferably has an actuating cylinder. This cylinder can have an actuating piston, which is provided for pivoting the hydraulic machine and can be subjected to the actuating pressure. The actuating piston acts, for example, on a pivoting cradle of the hydraulic machine. Preferably, the displacement volume of the hydraulic machine can be continuously adjustable via the controller. The hydraulic machine can then be pivoted proportionally to the applied actuating pressure. However, the pivoting is influenced by the system pressure, which is exploited according to the invention to achieve load sensitivity in the first cycle section. Preferably, no feedback lever connected to the actuating piston is provided between the hydraulic machine and the controller. Such a feedback lever is designed, for example, in an HD controller, as disclosed, for example, in the aforementioned document RD-E 92004.The lack of a feedback lever makes load sensitivity in the first cycle section easy. A volume flow at the output of the hydraulic machine can, for example, be continuously adjustable within a range of zero to 100 percent. A pressure reducing valve, for example, is provided as the valve for the controller. Preferably, two such pressure reducing valves are designed. In this case, the actuating cylinder can have two actuating chambers separate from the actuating piston, with each actuating chamber being fluidly connected to a respective pressure reducing valve. The pressure reducing valves, in turn, are each arranged between a pressure medium source and the actuating chambers. Depending on a preselected current strength at the actuators or magnets of the pressure reducing valves, the actuating cylinder of the hydraulic machine is proportionally supplied with a actuating pressure. The two actuating pressures for the respective actuating chambers can be controlled independently of one another.The pump displacement of the hydraulic machine, which is achieved at a specific control current, depends on the hydraulic machine's speed and operating pressure. Each pressure reducing valve is preferably assigned a flow direction.

[0016] In a further embodiment of the invention, a third cycle section can be provided. In this third cycle section of the consumer's working cycle, for example, a control mode is configured in which the hydraulic machine is operated in a manner that causes pressure limitation on the output side of the hydraulic machine due to hydromechanical restoring forces on the pumping station. This control mode can, for example, be configured in a manner similar to the first cycle section and thus enable load sensitivity. This is advantageous at the end of a stroke movement of the delivery cylinder, particularly in the direction of a reduction in the delivery chamber, in order to avoid a pressure peak when the delivery piston hits a cylinder base.

[0017] In a further embodiment of the invention, at least two consumers are provided which can be driven by the hydraulic machine. These are preferably two hydraulic cylinders which are operated in opposite directions. This means that one hydraulic cylinder can be retracted while the other is extended. Each hydraulic cylinder preferably has a piston which separates a first from a second working chamber. With two hydraulic cylinders, each piston can be connected via a piston rod to a respective delivery piston of a delivery cylinder. This means that with two hydraulic cylinders, two delivery cylinders can be operated in the working machine. This means that, for example, concrete can be sucked in via one delivery cylinder and expelled via the other delivery cylinder at the same time.

[0018] The hydraulic machine is preferably pivotable, particularly when there are two consumers, and can therefore be operated in two delivery directions. It can therefore have two working ports, with a respective consumer or a respective hydraulic cylinder being connected to each working port. A hydraulic cylinder is connected with its working chamber to the respective working port. The working chambers of the hydraulic cylinders that are not connected to the hydraulic machine are preferably fluidically connected, particularly via a swing line. The hydraulic machine can thus suck pressure medium from one working chamber of one of the hydraulic cylinders and deliver it to the other working chamber of the hydraulic cylinder, and vice versa, allowing the hydraulic cylinders to move in opposite directions.

[0019] It would be conceivable for only one hydraulic cylinder to be connected to a working port of the hydraulic machine. The hydraulic machine could then have a tank connection instead of an additional working port.

[0020] In a further embodiment of the invention, in order to reduce the delivery chamber of the delivery cylinder, the first cycle section can be provided before the second cycle section. More preferably, the second cycle section can be provided before the third cycle section. Advantageously, the first cycle section can be provided in the stroke range of the delivery piston in which the delivery piston is spaced from the medium to be delivered and is moved in an extension direction. Thus, the first cycle section is preferably provided in a stroke range in which essentially air is compressed. This is the case, for example, when gas or air is provided between the delivery piston and the actual medium to be delivered, such as concrete.Alternatively or additionally, the first cycle section can be provided in the stroke range of the delivery piston in which the delivery piston encounters the medium and is moved in the extension direction. This can be the case, for example, when the delivery piston encounters the concrete during its delivery stroke.

[0021] It is conceivable that the second cycle phase is provided in the stroke range of the delivery piston in which the delivery piston is in contact with the medium to be delivered and is moving in the extension direction. For example, it would be conceivable that after the piston has impacted the concrete, the second cycle phase is provided to displace the concrete from the delivery chamber at a constant delivery speed.

[0022] It is advantageous if the third cycle section is provided in the stroke range of the delivery piston in which the delivery piston contacts a cylinder bottom.

[0023] According to the invention, a method is provided with the mobile work machine according to one or more of the preceding aspects. In the method, the work machine is operated in a control mode in a first cycle section of the consumer's work cycle, in which the hydraulic machine is operated in a manner that causes a pressure limitation on the output side of the hydraulic machine due to hydromechanical restoring forces at the pumping station. In a second cycle section of the consumer's work cycle, the work machine is operated in a control mode in which the hydraulic machine is operated in a swivel angle control mode.

[0024] According to the invention, the mobile work machine according to one or more of the preceding aspects is used as a concrete pump.

[0025] It would be conceivable to use the concrete pump in a vehicle or a trailer or in a stationary environment.

[0026] Disclosed is a hydraulic pump for directly driving a hydraulic consumer in a mobile work machine, wherein the consumer is, in particular, a delivery cylinder of a concrete pump. To avoid pressure peaks during the transition from an actuating movement to a power stroke of the consumer, the pump is operated in various control modes. These modes are switched during the work cycle. In a first cycle section, the pump is pre-controlled with a, in particular initial, pilot pressure or controlled with a pilot valve that has a specific opening cross-section in the first cycle section and is load-sensitive with regard to the load pressure at the output. In a second cycle section, the pump is operated with a swivel angle control. Short description of the drawings

[0027] Preferred embodiments of the invention are explained in more detail below with reference to schematic drawings. They show: Fig. 1 schematically shows a mobile working machine in the form of a concrete pump according to an embodiment, and Fig. 2 shows a pressure curve of the load pressure during a working stroke of a delivery cylinder of the working machine Fig. 1.

[0028] Fig. Figure 1 shows a mobile work machine in the form of a concrete pump 1 with a first and second delivery cylinder 2, 4. These are each driven by a hydraulic cylinder 6, 8. The hydraulic cylinders 6, 8 are actuated by a hydraulic machine in the form of a hydraulic pump 10.

[0029] Each delivery cylinder 2, 4 has a delivery piston 12, 14, each of which defines a delivery chamber 16. Via a hopper 18, each delivery cylinder 2, 4 can take up concrete into its delivery chamber 16. This is achieved by moving the respective delivery piston 12, 14 in the direction of increasing the delivery chamber 16. If the respective delivery piston 12, 14 is moved in the opposite direction in the direction of decreasing the delivery chamber 16, concrete is delivered from the delivery chamber into a concrete line 20 or delivery pipe. The delivery cylinders 2, 4 are driven in opposite directions. This means that while one delivery piston 12 is moved in the direction of decreasing the delivery chamber 16, the other delivery piston 14 is moved correspondingly in the direction of increasing its delivery chamber 16, and vice versa.Via a so-called swivel pipe (S-valve) – which is not shown for simplicity – a concrete connection of a respective delivery cylinder 2, 4 can be alternately connected to the hopper 18 and the concrete line 20, depending on whether it is sucking in or displacing concrete. Instead of concrete, another liquid or gaseous medium, such as water, can also be conveyed via the delivery cylinders 2, 4.

[0030] The hydraulic cylinders 6, 8 each have a piston 22, 24. These each separate a first working chamber 26 from a second working chamber 28. The second working chambers 28 are fluidly connected via a fluid line 30. The first working chamber 26 of the hydraulic cylinder 6 is connected to a working port A of the hydraulic pump 10 via a first working line 32. The first working chamber 26 of the further hydraulic cylinder 8 is connected to a further working port B of the hydraulic pump 10 via a working line 34. The hydraulic pump 10 with the hydraulic cylinders 6, 8 forms a closed hydraulic circuit. A respective piston 22, 24 of the hydraulic cylinders 6 and 8 is connected via a respective piston rod 36 to a respective piston 12, 14 of the delivery cylinders 2 and 4 in order to move them. The piston rods 36 each pass through the second working chamber 28 of the hydraulic cylinders 6, 8.A water tank 38 for separating dirt is arranged between the hydraulic cylinders 6, 8 and the delivery cylinders 2, 4. If the piston 22 of the hydraulic cylinder 6 is moved toward enlarging its first working chamber 26, the hydraulic pump 10 pumps pressure fluid from the working line 34 into the working line 32. At the same time, the piston 24 of the other hydraulic cylinder 8 is moved toward reducing its first working chamber 26, as the hydraulic pump 10 draws pressure fluid via the working line 34 and supplies it to the hydraulic cylinder 6. The second working chambers 28, which are formed from annular spaces, are simply short-circuited via the fluid line 30.

[0031] The hydraulic pump 10 is driven via a drive shaft 40, which also drives a pilot pump 42. This provides pressure medium, from which a control pressure results for adjusting the hydraulic pump 10. The hydraulic pump 10 is pivotable, whereby its delivery volume or stroke volume can be adjusted. An actuating cylinder 44 with an actuating piston 46 is provided for adjusting the hydraulic pump 10. The actuating piston 46 separates two actuating chambers 48 and 50 from one another. It is also mechanically connected to a pumping mechanism of the hydraulic pump 10 in order to adjust a delivery volume. A respective pressure reducing valve 52, 54 is connected to each actuating chamber 48, 50. These, in turn, are fluidically connected to the pilot pump 42. Thus, if necessary, pressure medium can flow from the pilot pump 42 via a respective pressure reducing valve 52, 54 into the respective actuating chamber 48, 50.The pressure reducing valves 52, 54 are each actuated by an actuator in the form of a magnet 56. A flow rate output of the hydraulic pump 10 is continuously adjustable from zero to 100 percent. Depending on the preselected current intensity I at the magnets 56 of the pressure reducing valves 52, 54, the actuating cylinder 50 is supplied with control pressure proportionally. The two control pressures can be controlled independently of each other. The pump displacement resulting from a specific control current depends on the speed and operating pressure of the hydraulic pump 10.

[0032] According to Fig. 1, the concrete pump 1 further comprises a valve 58 or a valve arrangement connected between the working lines 32, 34 and used as a flushing and feed pressure valve. Furthermore, a pressure relief valve 60 is provided, which limits the pressure on the outlet side of the pilot pump 42. Furthermore, two high-pressure relief valves 62 are generally provided, which limit the pressure on the outlet side of the main pump and additionally include a suction function.

[0033] According to Fig. 2 schematically shows part of a working cycle of one of the feed cylinders 2, 4. Depending on the working cycle, Fig. 2 shows a pressure curve p over a time t. The left figure a shows the delivery cylinder 2 after it has taken up or sucked in concrete from the hopper 18, see. Fig. 1. Due to the viscosity of the concrete, only a portion of the conveying chamber 16 is filled with concrete; the rest contains air. Thus, an air space is formed in the conveying chamber 16 between the piston 12, which is at bottom dead center, and the concrete to be conveyed. If the piston 12 is moved via the hydraulic cylinder 6, see Fig. 1, in the direction of reducing the size of the conveying chamber 16, essentially air is compressed and displaced. From a certain stroke, the piston 12 then hits the concrete in the conveying chamber 16, which is shown in Figure b in Fig. 2. If the piston 12 hits the concrete 16, a pressure peak 64 has been produced in the prior art, which Fig. 2 in the diagram. The pressure peak 64 is part of a conventional pressure curve 66 from the prior art, which is shown in Fig. 2 for comparison purposes. Subsequently, the piston 12 delivers according to the Fig. the concrete from the conveying chamber 16, whereby in the prior art the pressure is essentially constant. A further pressure peak 68 according to Fig. In the prior art, this occurs when the piston 12 hits the cylinder bottom of the hydraulic cylinder 2. In order to avoid the pressure peaks 64 and 68, the concrete pump 1 is now made of Fig. 1, it is provided that the hydraulic pump 10 is operated in different control modes in a simple manner. A first cycle section 70 is provided for this purpose, see FIG. Fig. 2. In this cycle section, the piston 12 is moved from bottom dead center toward the concrete as shown in Figures a and b and then, after displacing the air, hits the concrete. In this first cycle section, a control mode is provided for the hydraulic pump 10, in which it is operated in a manner that, due to hydromechanical restoring forces on the pumping unit, results in a pressure limitation on the output side of the hydraulic pump 10. This means that in the present exemplary embodiment, the hydraulic pump 10 is initially pivoted by appropriate actuation of the pressure reducing valves 52, 54 such that it delivers a specific delivery volume into the first working chamber 26 of the hydraulic cylinder 6. Thus, the magnets 56 of the pressure reducing valves 52, 54 are controlled with a specific valve actuation degree in order to achieve a desired deflection of the hydraulic pump 10 and thus a specific displacement volume of the hydraulic machine.The hydraulic pump 10 is thus adjusted via a desired control pressure. When the piston 12 of the delivery cylinder 2 now hits the concrete, see . Fig. in Fig. 2, the hydraulic pump 10 automatically pivots back. Due to the impact of the piston 12 on the concrete, comparatively high hydromechanical restoring forces occur at the pumping mechanism of the hydraulic pump 10, which lead to an automatic pivoting back and thus to a pressure limitation on the output side of the hydraulic machine. Thus, the hydraulic pump 10 or variable displacement pump acts as a load-sensitive pump. There is also no mechanical feedback provided to prevent the load sensitivity of the hydraulic pump 10. Since no signal chain is active or required in the first control mode, the hydraulic pump 10 pivots back immediately without any time delay. Thus, the hydraulic pump immediately avoids the pressure peak. In the first cycle section 70, a soft pump with load sensitivity is provided. This is indicated by the characteristic curve 72 of the Fig. 2. It would also be conceivable to design the course degressively (see reference numeral 74) or progressively (see reference numeral 76) in the first cycle section.

[0034] According to Fig. 2, the first cycle section 70 is followed by a second cycle section 78, in which a different control mode is provided for the hydraulic pump 10. The control mode is a swivel angle control. This results in the piston 12, see FIG. Fig. , conveys concrete from the conveying chamber 16 at a constant speed.

[0035] In a third cycle section 80 in Fig. 2, the control mode of the first cycle section 70 is then used again. If then according to Fig. the piston 12 on the cylinder bottom, the hydraulic pump 10 is swung back again due to its load capacity.

[0036] For the second cycle section 78 from Fig. 2 is a corresponding control device 82, see. Fig. 1, with appropriate software, in particular eEP software. The control mode in the second cycle section 78 thus ensures a continuous concrete flow. Depending on the accuracy requirement, it is conceivable to provide a swivel angle sensor for the adjustable hydraulic pump 10. This allows a closed control loop to be created.

[0037] According to Fig. 2, an acceleration of the delivery piston 12 is preferably provided in the first cycle section 70—preferably at least until it hits the concrete—a constant movement of the delivery piston 12 is provided in the second cycle section 78, and a deceleration of the delivery piston 12 is provided in the third cycle section 80. The control mode in the second cycle section 78 results in a stiff pump characteristic. In contrast, a soft and load-sensitive pump characteristic is possible in the first and second cycle sections 70, 80. The stiff pump characteristic can, for example, be designed according to an EP control, as exemplified in the aforementioned document RD-E 92004.

[0038] The concrete pump 1 according to the invention thus generates a combination of a mechanical adjustment device with electronic intelligence. The hydraulic pump 10 can, if required, enable load-sensitive behavior through ET control without mechanical feedback. Furthermore, a software module eEP can be provided that controls the hydraulic pump 10 in such a way that an EP characteristic, i.e., a rigid pump characteristic, is achieved. Thus, two different behaviors can be achieved with a single hydraulic pump 10, particularly in the form of a pivoting axial piston machine.

[0039] To reduce the pressure peaks 66, 68 from Fig.To avoid this, the state of the art, for example, proposes reducing the control current, which, however, disadvantageously results in a slow system. It is also conceivable to avoid the pressure peaks hydraulically, for example, by relieving the control chambers, but this also results in a slow and sluggish system.

[0040] The concrete pump 1 ensures that when the delivery cylinders 2 and 4 start up, a soft and load-sensitive behavior of the hydraulic pump 10 is achieved. This occurs up to a point where the delivery piston 12, 14 hits the concrete surface. Once this point is reached, a so-called hard pump characteristic is set. This enables a continuous delivery flow and no delivery fluctuations due to pressure changes. Once the end of the cylinder is reached, pressure peaks and pressure drops on the low-pressure side of the hydraulic pump 10 can be avoided when the delivery piston 12, 14 hits the cylinder base. The selected pumping behavior of the hydraulic pump 10 avoids this critical condition. Thus, load-sensitive behavior of the hydraulic pump 10 is also possible during this phase.

[0041] In a further embodiment of the invention, it is conceivable to connect a respective pressure sensor to a respective working line 32, 34.

Claims

[1] Mobile work machine with at least one hydraulic machine (10), the pumping station of which is adjustable, and with at least one hydraulic consumer (6, 8) which can be driven directly via the hydraulic machine (10) and which has a working cycle, wherein the work machine is set up in such a way that in a first cycle section (70) of the working cycle of the consumer (6, 8) a control mode is provided in which the hydraulic machine (10) is pressure-controlled, wherein the mobile work machine is configured such that in this control mode the hydraulic machine (10) is pressure-controlled on the output side of the hydraulic machine (10), and wherein in a second cycle section (78) of the working cycle of the consumer (6, 8) a control mode is provided in which the hydraulic machine (10) is operated in a swivel angle control. [2] Mobile work machine according to claim 1, wherein the pressure control of the hydraulic machine (10) is a pressure limitation. [3] Mobile work machine according to one of claims 1 or 2, wherein the pressure control can be carried out by hydromechanical restoring forces on the pumping station. [4] Mobile work machine according to one of claims 1 to 3, wherein the at least one consumer is a hydraulic cylinder (6, 8) which is connected to a delivery cylinder (2, 4) for delivering a liquid medium. [5] Mobile work machine according to one of the preceding claims, wherein a controller is provided for controlling the hydraulic machine (10), which controller has at least one valve (52, 54) whose valve slide can be actuated via a magnetic actuator (56) in order to adjust the hydraulic machine (10) with a predetermined actuating pressure. [6] Mobile work machine according to claim 5, wherein the actuator (56) of the valve (52, 54) is controlled with a certain valve actuation degree in the first cycle section (70). [7] Mobile work machine according to claim 5 or 6, wherein the controller in the second cycle section (78) is used as an electronic controller which adjusts the valve actuation degree of the valve (52, 54) according to the control error of the swivel angle of the hydraulic machine (10). [8] Mobile work machine according to one of the preceding claims, wherein the control modes are changed during the working cycle. [9] Mobile work machine according to one of the preceding claims, wherein a swivel angle sensor is provided, via which an actual swivel angle of the hydraulic machine (10) can be determined, and / or wherein an actual swivel angle of the hydraulic machine (10) is estimated. [10] Mobile work machine according to one of the preceding claims, wherein in a third cycle section (80) of the working cycle of the consumer (6, 8) a control mode is provided in which the hydraulic machine (10) is operated in an operation which causes a pressure limitation on the output side of the hydraulic machine (10) due to hydromechanical restoring forces on the pumping station. [11] Mobile working machine according to one of claims 4 to 10, wherein the first and second cycle sections (78) are provided in the direction of reducing the size of a conveying chamber of the conveying cylinder (2, 4). [12] Mobile work machine according to claim 11, wherein the first cycle section (70) is provided in that stroke range of a delivery piston (12, 14) of the delivery cylinder (2, 4) in which the delivery piston (12, 14) is spaced from the medium to be delivered and is moved in the direction of a reduction of the delivery chamber (16). [13] Mobile work machine according to claim 11 or 12, wherein the second cycle section (78) is provided in that stroke range of the delivery piston (12, 14) of the delivery cylinder (2, 4) in which the delivery piston (12, 14) is in contact with the medium to be delivered and is moved in the direction of a reduction of the delivery chamber (16). [14] Method with a mobile work machine according to one of the preceding claims, wherein in the first cycle section (70) the hydraulic machine (10) is pre-controlled with a control pressure, wherein the hydraulic machine (10) is load-sensitive with regard to a load pressure on the output side of the hydraulic machine (10), and wherein in a second cycle section the hydraulic machine (10) is operated in a swivel angle control. [15] Use of the mobile working machine according to one of claims 1 to 13 as a concrete pump (1) for conveying concrete and / or a liquid.

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