Method for operating a construction machine, and construction machine

Abstract

A method for operating a construction machine (1) for the delivery of thick matter, wherein the construction machine comprises a hydraulic pump (7, 10) which is driven by an electric motor (5) and feeds a hydraulic drive (8) which is drive-connected to a thick matter pump unit (9); wherein the electric motor (5) is controlled by an electric control device (6) which can be connected to the utility grid (2) via a power connector (2). The method comprises the step of controlling the electric motor (5) by means of the control device (6) in such a way that an electric power input which is input at the power connector (2) does not exceed the maximum electric power output.

Description

[0001] Method for operating a construction machine and construction machine

[0002] The invention relates to a method for operating a construction machine for conveying thick material and to such a construction machine.

[0003] Electric construction machines for conveying thick materials typically have an electrical connection for connecting to an electrical supply network. This connection is usually protected by an electrical fuse. In the event of a power overload of such a connection, said electrical fuse can be triggered, which can lead to at least a temporary interruption of the operation of the electric construction machine. Such an overload can result from a blockage in a conveyor line for transporting the conveyed thick materials. An increase in the geodetic pumping head, which must be overcome when conveying thick materials using the construction machine, can also lead to an overload. Furthermore, an overload can be caused by the adjustment of a conveyor mast of the construction machine.Additional consumption of electrical energy to operate at least one other electrical consumer connected to the supply network can also contribute to overload.

[0004] It is an object of the present invention to provide a method for operating a construction machine for conveying thick materials, as well as such a construction machine, with improved properties. In particular, the aim is to enable particularly reliable, uninterrupted operation of the construction machine while utilizing the available maximum power as fully as possible. In other words, the aim is to achieve the highest possible output despite limited input power.

[0005] This problem is solved by the subject matter of the independent patent claims. Preferred embodiments are the subject matter of the dependent patent claims.

[0006] A method according to the invention serves to operate a construction machine. The construction machine is used to convey thick material. The construction machine can be a mobile construction machine, in particular a trailer-mounted construction machine or a self-propelled construction machine. The construction machine has an electrical mains connection to which an electrical supply network can be or is connected as intended. The supply network provides a maximum electrical output at the mains connection. The construction machine has an electric motor and an electrical control device fed with electrical power from the supply network for controlling the electric motor, for example in the form of a frequency converter. In addition, the construction machine has a hydraulic pump which is driven by the electric motor and which feeds at least one hydraulic circuit of the construction machine.At least one hydraulic drive of the construction machine is supplied from the hydraulic circuit. According to the method, the electric motor is controlled by means of the control device in such a way that the electrical power absorbed at the mains connection does not exceed the available maximum electrical power. Advantageously, the available maximum electrical power can be utilized particularly well, in particular at least almost completely, by means of the method. If the output torque to be provided by the hydraulic drive increases, there would be a risk of overloading the mains connection without the electric motor being controlled according to the method. In contrast, the method can be used to ensure that the maximum electrical power is not exceeded even with fluctuating output torque, so that in particular the triggering of an electrical fuse in the mains connection can be avoided.The method can therefore enable particularly effective utilization of the maximum electrical power. In particular, the interaction of the hydraulic components and the electrical components of the construction machine according to the method allows for particularly effective utilization of the maximum power. The supply network is preferably an AC electrical network. The AC network, which provides the maximum electrical power, can be present at a construction site. The maximum electrical power can be limited by the grid connection, for example, to a power value of 22 kW. Alternatively, the supply network can be a DC network, preferably the on-board electrical system of a truck.

[0007] In this context, thick aggregate refers to a paste-like mixture of different materials. Examples of thick aggregate include mortar, cement, screed, or concrete, each in a mixable and / or conveyable state. In this mixable and / or conveyable state, the thick aggregate has not yet hardened. Specifically, thick aggregate is a building material.

[0008] In one embodiment of the invention, to limit the electrical input power to the maximum electrical power, the torque generated by the electric motor is adjusted such that the electrical input power corresponds to the maximum electrical power. Consequently, the maximum power can be fully utilized by the electrical input power.

[0009] In a further embodiment of the invention, the hydraulic pump is a variable-displacement pump with an adjustable pivot angle, wherein the variable-displacement pump has a working speed. The working speed can correspond to a speed of the variable-displacement pump at which the variable-displacement pump has a sufficiently high, in particular its optimal, efficiency. In order to limit the electrical input power to the maximum electrical power, the torque generated by the electric motor is reduced such that the electrical input power corresponds to the maximum electrical power. As a result of the reduction in the torque generated by the electric motor, the speed of the electric motor may drop briefly.To limit the electrical input power to the maximum electrical power, the delivery capacity of the variable displacement pump is also reduced by adjusting the swivel angle accordingly and increasing the variable displacement pump's speed such that the power consumed by the variable displacement pump remains constant until the variable displacement pump's working speed is reached again. This allows the variable displacement pump to operate at working speed even if the output torque increases briefly. The same applies to the electric motor. Accordingly, the speed of the variable displacement pump can recover at constant electrical input power until the variable displacement pump's working speed is reached again.The variable displacement pump is expediently drive-connected to a drive shaft of the construction machine, with additional consumers of the construction machine, in particular in the form of constant-flow pumps, being drive-connected to the same drive shaft, in particular directly or via a gear. Accordingly, what was stated above with regard to the operating speed of the variable displacement pump can also apply mutatis mutandis to such additional consumers. For example, several, in particular three, variable displacement pumps and several, in particular four, additional consumers, in particular in the form of constant-flow pumps, can be drive-connected to the drive shaft, so that the above-explained, preferably regulated, adjustment of the speed of the electric motor can also advantageously be used to adjust a volume flow that the additional consumers deliver.

[0010] According to the method, a displacement volume of the variable displacement pump and thus also a delivery rate of a thick matter pump unit of the construction machine can be expediently reduced so that the speed of the variable displacement pump can recover. The speed of the variable displacement pump can recover from a previous drop, for example when the electrical power of the electric motor remains constant. The drop in the speed of the variable displacement pump can be caused by an increase in the pressure to be overcome by the variable displacement pump. The speed of the variable displacement pump can drop as a result of a change in the electrical power available to drive it. Such a change in the electrical power available to drive the variable displacement pump can arise as a result of switching on an additional electrical load which, like the construction machine, draws electrical energy from the supply grid, in particular via the same grid connection.Power peaks at such an additional consumer connected to the power grid can also cause the speed of the variable-displacement pump to drop. This allows the pump speed or volume flow delivered by the variable-displacement pump to be dynamically reduced if insufficient electrical power is available from the power grid.

[0011] In a further embodiment of the invention, the speed of the hydraulic pump and the speed of the electric motor are interdependent, in particular without a gear ratio or via a gear ratio. "Gear-free" can be understood as a synonym for "directly geared."

[0012] In a further embodiment of the invention, the method compares the electrical input power with the maximum electrical power in order to detect an impending overload of the mains connection and to control the electric motor in such a way that the electrical input power drawn at the mains connection does not exceed the maximum electrical power. To prevent the overload, the torque generated by the electric motor can be throttled, whereby the speed of the hydraulic pump and initially also the speed of the hydraulic drive decreases. As a result, a swivel angle of the variable displacement pump can be changed such that the torque loading the variable displacement pump drops and the electric motor can rotate at a desired speed again. During this process, the maximum electrical power can be continuously drawn from the supply grid.

[0013] If the hydraulic pump is a constant flow pump, the speed can expediently remain at a reduced level until sufficient power is again available to pump a desired quantity of hydraulic fluid through the at least one hydraulic circuit.

[0014] In a further embodiment of the invention, in order to utilize the maximum electrical power available, the torque generated by the electric motor is adjusted in such a way that any deviation of the electrical input power from the maximum electrical power is reduced, in particular minimized. In this way, power control can be implemented.

[0015] A construction machine according to the invention is used to convey thick material. The construction machine can be a mobile construction machine, in particular a trailer-mounted construction machine or a self-propelled construction machine. The construction machine has a mains connection to which a supply network can be connected as intended. The supply network provides a maximum electrical output at the mains connection. The construction machine also has an electric motor and an electrical control device for controlling the electric motor, which can be fed with electrical power from the supply network. In addition, the construction machine has a hydraulic pump that is driven by the electric motor and feeds a hydraulic circuit of the construction machine. The construction machine further has a hydraulic drive that is supplied from the hydraulic circuit.The electrical control device is configured to control the electric motor according to the method according to the invention and described above. The advantages of the method according to the invention explained above also apply to the construction machine according to the invention.

[0016] In an embodiment of the invention, the construction machine has a high-density solids pump unit, by means of which high-density solids can be pumped. The high-density solids pump unit is drive-connected to the hydraulic drive. For example, if a geodetic pumping head to be overcome by the high-density solids pump unit, over which the high-density solids must be pumped by the high-density solids pump unit, changes, this can lead to an increase in the output torque that places a load on the hydraulic drive. The same can apply if a delivery line connected to the high-density solids pump unit becomes blocked. The delivery line can be used to transport the high-density solids pumped by the high-density solids pump unit.In the event of such an increase in the output torque, an overload of the electrical mains connection can be avoided by controlling the electric motor according to the method according to the invention, and in particular also the triggering of an electrical fuse protecting the mains connection.

[0017] In a further embodiment of the invention, the hydraulic pump is designed as a variable-displacement pump, particularly in the form of an axial piston pump, with a variable piston stroke. In particular, the piston stroke depends on an adjustable pivot angle of the variable-displacement pump. Advantageously, with such a variable-displacement pump, the performance of the variable-displacement pump can be influenced in particularly fine or even continuous steps by adjusting the piston stroke.

[0018] In a further embodiment of the invention, a swash plate or wobble plate acting on the piston of the variable displacement pump can be adjusted relative to the piston stroke at the pivot angle in order to adjust the piston stroke. Such a variable displacement pump impresses with its particularly reliable piston stroke adjustment. Further advantages and features of the invention emerge from the claims and the following description of a preferred embodiment of the invention, which is illustrated with reference to the drawing. Like reference numerals refer to like, similar, or functionally identical components.

[0019] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0020] The sole Fig. 1 shows schematically a structure of an embodiment of a construction machine according to the invention, which is designed to carry out a method according to the invention.

[0021] A construction machine 1 according to the invention is used to convey thick material, for example in the form of liquid concrete. The construction machine 1 has an electrical connection 2. An electrical supply network 3 can be connected to the connection 2 as intended. In this case, the supply network 3 is an alternating current network. Alternatively, the supply network 3 can be a direct current network, for example, the on-board electrical system of a truck.

[0022] The supply network 3 provides a maximum electrical output at the network connection 2, for example, 22 kW or 75 kW. The construction machine 1 also has an electric motor 5. Furthermore, the construction machine 1 has an electrical control device 6 in the form of a frequency converter, which can be fed with electrical power from the supply network 3, for controlling the electric motor 5. The construction machine 1 also has a hydraulic pump 7. The hydraulic pump 7 is driven by the electric motor 5 and feeds a hydraulic circuit of the construction machine 1. A hydraulic drive 8 of the construction machine 1 is supplied from the hydraulic circuit. The electrical control device 6 is designed to control the electric motor 5 according to a method according to the invention.

[0023] The construction machine 1 has, for example, a high-density matter pump unit 9. High-density matter can be pumped by means of the high-density matter pump unit 9. The high-density matter pump unit 9 is drive-connected to the hydraulic drive 8. For example, the high-density matter pump unit 9 is drive-connected to the electric motor 5 by means of the hydraulic drive 8, by means of the hydraulic circuit, and by means of the hydraulic pump 7. If the hydraulic pump 7 is driven by the electric motor 5, hydraulic fluid is pumped through the hydraulic circuit. The hydraulic fluid pumped through the hydraulic circuit, in turn, drives the hydraulic drive 8. The hydraulic drive 8 transmits drive power to the high-density matter pump unit 9. The hydraulic pump 7 is designed, for example, as a variable-displacement pump 10. The variable-displacement pump 10 can be in the form of an axial piston pump. The variable-displacement pump 10 is designed with a variable piston stroke.The piston stroke can depend on an adjustable pivot angle of the variable displacement pump 10. For example, a swash plate or wobble plate of the variable displacement pump 10 acting on the piston of the variable displacement pump 10 can be adjusted relative to the piston stroke at the pivot angle in order to adjust the piston stroke.

[0024] The construction machine 1 can have additional electrical consumers that can be connected to the supply network 3 in order to obtain electrical energy for its operation, in particular via the same network connection 2. Such additional consumers can be, for example, additional electric motors, each for driving different functional units of the construction machine 1. Such a functional unit can be, for example, an agitator of the construction machine, a boom pump arranged on a conveyor boom, or the like. Further additional consumers can be a heater or lighting of the construction machine 1.

[0025] The thick matter pumping unit 9 can have conveying cylinders with variable-volume conveying chambers. For changing the volumes of the conveying chambers, in particular in opposite directions, the conveying cylinders can each have an adjustable conveying piston. The thick matter pumping unit 9 can also comprise an S-shaped S-pipe, one end of which is fluidly connected to a pressure port acting as a pump outlet. The S-pipe can be arranged in a storage chamber that can be filled with thick matter from above for storing thick matter. The S-pipe can be rotatably mounted at one end on the pressure port within the storage chamber. The variable-volume conveying chambers can open into the storage chamber. The S-pipe can be pivotable in the storage chamber relative to the conveying chambers in such a way that it can be fluidly connected alternately to one of the conveying chambers.In this way, due to the counteraction of the pivoting of the S-pipe and a change in the volume of the conveying chambers, thick matter located in the storage chamber can be alternately sucked in by means of the conveying chambers and pumped out through the S-pipe via the discharge nozzle. An agitator can be arranged in the storage chamber of the thick matter pump unit 9. The S-pipe can be drive-connected to the hydraulic drive 8 for pivoting relative to the conveying chambers. The conveying pistons can be drive-connected to the hydraulic drive 8 for changing the volumes of the conveying chambers. The method according to the invention is used, for example, to operate the construction machine 1. The method comprises controlling the electric motor 5 by means of the control device 6.The control device 6 is controlled by the electric motor 5 such that the electrical input power drawn at the grid connection 2 does not exceed the maximum electrical power. For example, the electric motor 5 can be controlled such that the maximum electrical power is not exceeded with a fluctuating output torque applied as a load to the electric motor 5. Furthermore, additional consumers of the construction machine 1, which can be supplied with electrical energy from the supply network 3 via the same grid connection 2, can be taken into account when utilizing the maximum electrical power.

[0026] For example, to limit the electrical input power to the maximum electrical power, the torque generated by the electric motor 5 is adjusted so that the electrical input power corresponds to the maximum electrical power. This adjustment can be achieved, for example, by means of a control loop comprising a controller formed by the electrical control device 6.

[0027] The hydraulic pump 7, designed as a variable displacement pump 10, has a working speed. At the working speed, the variable displacement pump 10 can exhibit optimal efficiency. To limit the electrical input power to the maximum electrical power, the delivery capacity of the variable displacement pump 10 is reduced, for example, by adjusting the pivot angle accordingly. In addition, the torque generated by the electric motor 5 is reduced, for example, such that the electrical input power corresponds to the maximum electrical power. In this case, the speed of the electric motor 5 and the variable displacement pump 10 can drop briefly. The speed can then be increased until the working speed of the variable displacement pump 10 is reached again.For example, the speed of the variable displacement pump 10 can be increased until a target speed of the electric motor 5 is reached again after the electrical input power has been electronically limited. By adjusting the swivel angle, the speed of the variable displacement pump can be increased again to the operating speed of the variable displacement pump 10. The electrical input power, for example, remains constant.

[0028] For example, a speed of the hydraulic pump 7 and a speed of the electric motor 5 are interdependent. The speed of the hydraulic pump 7 and the speed of the electric motor 5 can be interdependent without a gear ratio or via a gear ratio. According to the method, for example, the electrical input power is compared with the maximum electrical power in order to detect an impending overload of the grid connection. If an impending overload of the grid connection 2 is detected, the electric motor 5 can be controlled according to the method to avert the impending overload such that the electrical input power consumed at the grid connection 2 does not exceed the maximum electrical power.In order to utilize the maximum electrical power provided, for example, the torque generated by the electric motor 5 is adjusted in such a way that a deviation of the electrical input power from the maximum electrical power is reduced, in particular minimized.

Claims

Patent claims 1. A method for operating a construction machine (1) for conveying thick material, the construction machine (1) comprising: a mains connection (2) to which an electrical supply network (3) can be connected as intended, the supply network (3) providing a maximum electrical power at the mains connection (2), an electric motor (5), an electrical control device (6) supplied with electrical power from the supply network (3) for controlling the electric motor (5), a hydraulic pump (7) driven by the electric motor (5) and feeding a hydraulic circuit, and a hydraulic drive (8) supplied from the hydraulic circuit, the method comprising the steps of: Controlling the electric motor (5) by means of the control device (6) in such a way that an electrical power input at the mains connection (2) does not exceed the maximum electrical power.

2. Method according to claim 1, characterized in that the following steps are carried out to limit the electrical power consumption to the maximum electrical power: Adjusting the torque generated by the electric motor (5) such that the electrical input power corresponds to the maximum electrical power.

3. Method according to one of the preceding claims, characterized in that the hydraulic pump (7) is a variable displacement pump (10) with an adjustable swivel angle, the variable displacement pump (10) having a working speed, the following steps being carried out to limit the electrical power consumption to the maximum electrical power: Reducing the torque generated by the electric motor (5) such that the electrical input power corresponds to the maximum electrical power, and reducing the delivery capacity of the variable displacement pump (10) by appropriately adjusting the swivel angle and increasing the speed of the variable displacement pump (10) such that the power absorbed by the variable displacement pump (10) remains constant until the working speed of the variable displacement pump (10) is reached.

4. Method according to one of the preceding claims, characterized in that a speed of the hydraulic pump (7) and a speed of the electric motor (5) depend on each other.

5. Method according to one of the preceding claims, characterized in that the method comprises the following steps: Comparing the electrical input power with the maximum electrical power in order to detect an impending overload of the mains connection (2) and to control the electric motor (5) in order to avert the overload in such a way that the electrical input power absorbed at the mains connection (2) does not exceed the maximum electrical power.

6. Method according to one of the preceding claims, characterized in that the following steps are carried out to utilize the maximum electrical power provided: Adjusting the torque generated by the electric motor (5) such that a deviation of the electrical input power from the maximum electrical power is reduced, in particular minimized.

7. Construction machine (1) for conveying thick material, comprising: a mains connection (2) to which a supply network (3) can be connected as intended, wherein the supply network (3) provides a maximum electrical power at the mains connection (2), an electric motor (5), an electrical control device (6) which can be fed with electrical power from the supply network (3) for controlling the electric motor (5), a hydraulic pump (7) which is driven by means of the electric motor (5) and which feeds a hydraulic circuit, and a hydraulic drive (8) which is supplied from the hydraulic circuit, wherein the electrical control device (6) is set up to control the electric motor (5) according to a method according to one of the preceding claims.

8. Construction machine (1) according to claim 7, characterized in that the construction machine (1) has a thick matter pumping unit (9) by means of which thick matter can be conveyed, wherein the thick matter pumping unit (9) is drive-connected to the hydraulic drive (8).

9. Construction machine (1) according to claim 7 or 8, characterized in that the hydraulic pump (5) is designed as a variable displacement pump (10), in particular in the form of an axial piston pump, with a variable piston stroke, in particular wherein the piston stroke depends on an adjustable pivot angle of the variable displacement pump (10).

10. Construction machine (1) according to claim 9, characterized in that a swash plate or wobble plate of the variable displacement pump (10) acting on the piston of the variable displacement pump (10) is adjustable relative to the piston stroke at the pivot angle in order to adjust the piston stroke.

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