WORK MACHINE

Description

[0001] The present invention relates to a working machine such as a crane or an excavator, e.g. a cable excavator, which is equipped with a device for emergency lowering.

[0002] For many types of machinery or vehicles, it is essential to be able to return to a safe state in certain situations. For example, with a crane or excavator, it is crucial to be able to safely lower a lifted load to the ground if the machine becomes unstable or if another situation poses a danger to bystanders. According to current best practices, such emergency lowering is achieved by providing a backup power supply or a sufficiently sized battery in the DC electrical system (also known as the intermediate circuit).

[0003] If a fully electric machine has an energy storage device arranged in the DC intermediate circuit, e.g. a battery, the energy stored in it is used to provide the energy required when performing the emergency lowering or to absorb the energy generated in the process.

[0004] Problems arise when the energy storage device in the DC link malfunctions and is no longer able to supply or absorb energy for emergency lowering. In such a case, damage to structural components is accepted to ensure safety. For example, the electrical energy generated during emergency lowering, which would have been absorbed by a functioning energy storage device, is fed into the DC link regardless of losses, even though it is known that this causes overvoltage damage, typically leading to the complete destruction of the components connected to the DC link. Thus, damage to the machine is knowingly accepted to achieve a safe state during emergency lowering.To prevent such damage, some prior art designs also include braking resistors or brake choppers that convert electrical energy generated by an emergency lowering into thermal energy, thus preventing damage.

[0005] Additionally or alternatively, a holding brake, whose function is to lock or fix a component of the machine, can also be used for braking, although this inevitably leads to severe damage to the holding brake, which is designed solely for securing or releasing the component's position. The machine components that interact with the holding brake during braking also suffer significant damage. However, all of this is accepted in order to perform an emergency lowering and thus achieve a safe state for the machine.

[0006] DE 10 2010 063 911 A1 discloses a working machine which has the features from the preamble of claim 1.

[0007] As described above, it is therefore disadvantageous if an emergency lowering of a component of a machine is to be carried out and the energy storage device located on the DC intermediate circuit is unavailable during the emergency lowering process. According to the current state of the art, either additional components, namely braking resistors or brake choppers, must be provided, or damage to the holding brake must be expected.

[0008] The aim of the present invention is to enable an emergency lowering of a section of a working machine without the disadvantages listed above, even when the energy storage device arranged on the DC intermediate circuit is not available for this purpose.

[0009] The stated objectives are achieved with a device that has all the features of claim 1. Advantageous embodiments of the device are listed in the dependent claims.

[0010] A working machine according to the invention, in particular a crane or excavator, comprises a primary energy source for feeding electrical energy into an intermediate circuit, a unit for performing an operation of the working machine, at least one electric drive connected to the intermediate circuit to operate the unit of the working machine, a holding brake for locking or releasing the unit, and an energy storage device connected to the intermediate circuit to provide electrical energy requested from the intermediate circuit when a unit is actuated and / or to absorb electrical energy fed into the intermediate circuit, wherein in the event of an emergency lowering of the unit, the at least one electric drive is designed to convert the kinetic energy generated thereby into electrical energy and feed it into the intermediate circuit.The invention is characterized in that, in the event of a simultaneous failure of the energy storage device during emergency lowering, the primary energy source is designed to absorb the energy fed into the intermediate circuit by the electric drive.

[0011] The machine has at least one electric drive system (and may also include other loads) which is supplied from a common intermediate circuit, preferably a DC intermediate circuit. This at least one electric drive system includes, for example, a hoist drive. Each hoist drive has a holding brake, which is actuated electrically or electro-hydraulically. To release the holding brake, it must be supplied with energy. An energy storage device, also called a cycle energy storage device, is connected to the DC intermediate circuit and is implemented, for example, in the form of a battery. This energy storage device reduces the load peaks caused by the electric drives and other loads and is capable of absorbing power.

[0012] The energy for the machine's operation comes from the primary energy source, which can be, for example, one or more chargers or a diesel generator set with an HVDC connection (a high-voltage direct current connection). Under normal operating conditions, the power flow from the primary energy source, through the energy storage system, to the drive system and any connected loads is delayed.

[0013] When loads are lowered via hoists using electric motors and inverters during an emergency lowering operation, these devices require electrical power to function. The holding brake also requires electrical energy to release. In both cases, the electrical power is supplied by the primary power source. To lower the load on a structure, the holding brake must be released. The load is then lowered. During this lowering process, power is fed back into the DC link. Without a functioning energy storage device, the voltage in the DC link rises until the components connected to the DC link are destroyed. According to the invention, it is therefore advantageous to use the primary power source as a power sink to prevent damage to components connected to the DC link.

[0014] Furthermore, the difference from the state of the art lies in the fact that additional components for load reduction are not required. After the fault in the energy storage system has been rectified, the machine can continue operating without further servicing.

[0015] According to an advantageous modification of the present invention, the electric drive can comprise an inverter connected to the intermediate circuit and an electric motor, preferably wherein a shaft of the electric motor is coupled to an associated component, in particular rigidly coupled.

[0016] This means that when a load is lowered by the system, the electric motor operates as a generator, and the inverter transfers the resulting energy to the DC link. Conversely, when the electric motor is driven as a motor, for example when lifting a load, the inverter must draw the necessary energy from the DC link and supply it to the electric motor.

[0017] Advantageously, it can also be provided that the inverter connected to the intermediate circuit is designed to convert a direct current in the intermediate circuit into an alternating current in order to supply the electric motor with alternating current and / or to convert an alternating current generated by the electric motor into direct current and feed it into the intermediate circuit.

[0018] In particular, the inverter may be a DC-AC inverter capable of converting direct current to alternating current and vice versa. Alternating current is required to operate an electric motor, whereas the intermediate circuit is often operated with direct current, as the resulting losses are significantly lower.

[0019] According to an optional modification of the present invention, it can further be provided that in the event of a failure of the energy storage device occurring simultaneously with emergency lowering, the primary energy source is designed to supply the intermediate circuit with energy in order to provide the inverter of the at least one electric drive with a supply voltage.

[0020] This is advantageous because a minimum voltage must be present at the DC input of the associated inverter to operate at least one electric drive.

[0021] In the absence of a functioning energy storage system, the energy required for this is provided directly by the primary energy source.

[0022] According to an advantageous embodiment of the present invention, it can be provided that, in the event of a simultaneous failure of the energy storage device during emergency lowering, the primary energy source is designed to supply the intermediate circuit with sufficient energy so that the holding brake, supplied with energy from the intermediate circuit, is able to release the component. To move a component fixed by the holding brake into a safe position during emergency lowering, a certain amount of energy is initially required to move the holding brake into an open state to release the component. If the energy storage device, from which the energy normally required for this is drawn, is defective, the primary energy source also takes over in this case and supplies the holding brake with sufficient energy to release the component.

[0023] According to the present invention, it is provided that in the event of a failure of the energy storage device occurring simultaneously with emergency lowering, the primary energy source is designed to absorb energy fed into the intermediate circuit by the at least one unit via the electric drive, which was generated during lowering into a safe state.

[0024] Since the energy storage system is no longer able to absorb the energy generated when the structure is lowered, the primary energy source is used as a power sink to prevent damage to the components connected to the DC link. If, however, the primary energy source were not able to absorb the energy fed into the DC link by the electric drive when the structure is lowered, the unabsorbed energy would lead to damage to the components connected to the DC link.

[0025] According to a further advantageous embodiment of the present invention, the primary energy source can be at least one charger and / or a fuel-powered generator set, e.g., powered by diesel, hydrogen, or the like. Both the charger and the generator set have sufficient capacity to absorb the energy generated during an emergency lowering or to provide the energy required for the emergency lowering.

[0026] According to the present invention, it is provided that in the event of a simultaneous failure of the energy storage device during emergency lowering, the electric drive is designed to limit the rotational speed in the electric motor caused by lowering a structure in order not to exceed a maximum power consumption of the primary energy source.

[0027] Since the primary energy source is not primarily designed to absorb the energy generated when lowering a structure, its power consumption may be limited. To account for this, the invention provides that, in the event of an emergency lowering operation with a simultaneously defective energy storage device, the lowering of a structure proceeds significantly more slowly to avoid exceeding the maximum power consumption of the primary energy source. Because the power fed into the DC intermediate circuit is directly proportional to the speed of a lowering process, reducing the lowering speed also reduces the maximum power consumption.

[0028] According to a further optional development of the present invention, it can be provided that in the event of a simultaneous failure of the energy storage device during emergency lowering, the primary energy source is designed to supply the intermediate circuit with energy, so that the holding brake supplied with energy from the intermediate circuit is able to lock the assembly in order to secure the assembly in a safe position.

[0029] If the lowering process was successful, it is still necessary to secure the lowered component in its current position. This is done using the holding brake, the energy for which is supplied by the primary energy source. However, the defective energy storage device cannot provide the energy required for locking the component in this position, so the primary energy source is used again.

[0030] Furthermore, according to the present invention, it can be provided that in the event of a simultaneous failure of the energy storage device during emergency lowering, the primary energy source is designed to reduce the voltage remaining in the intermediate circuit after lowering the at least one component into a safe position by operating the primary energy source as an energy sink.

[0031] Finally, it is necessary to reduce the voltage level in the DC link to a level where it no longer poses a danger. To achieve this, the remaining voltage in the DC link is fed to the primary power source, which acts as an energy sink.

[0032] According to the invention, it can further be provided that the at least one working element is a lifting mechanism or a rotary mechanism of a working machine.

[0033] Furthermore, according to the invention, the working machine can be a fully electric working machine in which each component is preferably operated via an electric drive.

[0034] Furthermore, a method for controlling a working machine according to one of the variants listed above is presented.

[0035] The procedure may provide that, in the event of a defective energy storage system and a request for emergency lowering, the energy required for the emergency lowering is supplied by the primary energy source.

[0036] It can therefore be advantageous to provide the necessary supply voltage for operating an inverter from the primary energy source. This is the only way to ensure that the conversion via the inverter can continue to take place.

[0037] Furthermore, it may be provided that the primary energy source provides the energy to open a holding brake if the energy storage system fails in the event of an emergency lowering.

[0038] Furthermore, the primary energy source can also act as an energy sink in this case, absorbing the energy fed into the DC intermediate circuit when a component is lowered. Advantageously, the rotational speed can be reduced when the component is lowered to avoid exceeding the maximum power consumption of the primary energy source.

[0039] Once the component is in a safe position, the holding brake is closed, whereby, according to a further development of the procedure, it may be provided that the energy for closing the holding brake comes from the primary energy source.

[0040] Finally, in the event of an emergency voltage reduction due to a defective energy storage device, it may be further provided that the primary energy source is used as an energy sink to reduce the DC link voltage.

[0041] Further features, details, and advantages will become apparent from the following character description. This will show: Fig. 1: a schematic basic structure of the machine according to the invention, and Fig. 2: a flowchart to illustrate the different steps of a control unit of the machine or of a method used to control the machine.

[0042] Fig. 1 shows a schematic basic structure of a working machine according to the invention 1.

[0043] The diagram shows a fully electric machine 1 in which the components 4, which perform the work of the machine 1, are driven by electric drives 5. The machine 1 comprises several electric drives 5, each of which has an inverter 7 and an electric motor 8. The electric drives 5 are mechanically coupled to their respective components 4 via the shaft of the electric motor 8. Each component 4 has a holding brake (not shown). Fig. 1 (shown), which holds a load lifted or operated by the device 4. The respective inverters 7 of the electric drives 5 are electrically connected to the intermediate circuit 3, preferably the DC intermediate circuit.

[0044] Optionally, 3 additional high-voltage consumers 9, such as high-voltage heaters, DC / DC converters, compressors or the like, are located on the DC intermediate circuit.

[0045] The working machine 1 also includes an energy storage device 6, which can also be referred to as a cycle energy storage device, and which is likewise connected to the DC intermediate circuit 3. The energy storage device 6 is both a source and a sink for electrical energy during the working process of the working machine 1. In addition, the working machine 1 also has a primary energy source 2, which is, for example, a generator set (also: genset) or a charger. The primary energy source 2 supplies the working machine 1 with electrical energy.

[0046] The electric drives 5 are designed to feed electrical energy back into the system during braking. This occurs, for example, when lowering a load on a lifting mechanism 4, where the kinetic energy of the lowering action is converted into electrical energy via the regenerative operation of the electric motor 8. The inverter 7 connected to the electric motor 8 then ensures that the recuperated electrical energy is fed into the DC link 3. During normal operation, the electrical energy fed back into the DC link 3 is absorbed by the energy storage device 6, which acts as an energy sink. This ensures that the DC link 3 is not overloaded with energy, which could damage the components connected to it.Furthermore, it should be noted that in order to operate the electric drives 5, it is necessary to apply a minimum voltage to the DC input of a respective inverter 7 in order to be able to convert the energy from direct current to alternating current and vice versa.

[0047] Fig. 2 Figure 1 shows a sequence of steps S 1 to S 5 that are carried out by a control unit of a working machine 1 or a method of the present invention when an emergency lowering of a structure 4 is required and at the same time the energy storage unit 6 fails.

[0048] In the event of a failure of the energy storage device 6, the sink for electrical energy typically used in an emergency lowering procedure is missing. Furthermore, the energy storage device 6 can no longer provide the minimum voltage required for a respective inverter 7. Consequently, none of the components 4 of the machine 1 can be operated, making it impossible to bring the machine 1 to a safe state using the emergency lowering procedure.

[0049] In the first step of the in Fig. 2 The diagram shown ensures that a voltage is present in the DC intermediate circuit 3 so that the inverters 7 are ready for operation (S 1). The primary energy source 2 is used as the electrical energy source to provide the voltage to the DC intermediate circuit 3.

[0050] Subsequently, in step S 2, the holding brake of the component 4 is released. Electrical energy from the DC intermediate circuit 3, which is also supplied by the primary energy source 2, is used for this release.

[0051] Particularly in the case of components 4 with vertical loads, e.g., a hoist or similar device, the component 4 rotates after the holding brake is released due to the load (S 3) dropping under its own weight. This feeds energy back into the DC intermediate circuit 3, which is generated by the electric motor 8 and converted accordingly by the inverter 7. The energy fed back into the DC intermediate circuit 3 is then drawn by the primary energy source 2. It can be advantageous to limit the rotational speed of component 4 so that the maximum power consumption of the primary energy source 2 is not exceeded.

[0052] If, in the subsequent step S4, the component 4 is in a safe position, the holding brake is closed. The energy required to close the holding brake comes from the primary energy source 2, which now acts as a source again.

[0053] In the final step S 5, the intermediate circuit voltage is reduced so that the DC intermediate circuit 3 no longer poses a risk during maintenance or similar procedures. The primary energy source 2 is used as an energy sink in this process.

[0054] In contrast to prior art implementations, additional components for load reduction, which would normally be necessary in the event of an emergency lowering and a simultaneously defective energy storage device, can be dispensed with. Thus, in the invention, after the faults in the energy storage device 6 have been rectified, the machine 1 can be returned to regular operation without the need for further service measures.

Claims

1. Work machine (1), in particular a crane or an excavator, comprising: a primary energy source (2) for injecting electrical energy into an intermediate circuit (3), a mechanism (4) for performing an activity of the work machine (1), at least one electric drive (5) connected to the intermediate circuit (3) to operate the mechanism (4) of the work machine (1), a holding brake for blocking or releasing the mechanism (4), and an energy store (6) connected to the intermediate circuit (3) to, upon actuation of the mechanism (4), provide the electrical energy demanded from the intermediate circuit (3) and / or to absorb the electrical energy injected into the intermediate circuit (3), wherein, during an emergency lowering of the mechanism (4), the at least one electric drive (5) is configured to convert the kinetic energy thereby produced into electrical energy and to inject it into the intermediate circuit (3), characterized in that, in the event of a failure of the energy store (6) occurring simultaneously with the emergency lowering, the primary energy source (2) is configured to absorb the energy injected into the intermediate circuit (3) by the electric drive (5), in that, in the event of a failure of the energy store (6) occurring simultaneously with the emergency lowering, the primary energy source (2) is configured to absorb the energy injected into the intermediate circuit (3) by the at least one mechanism (4) via the electric drive (5), which energy was produced during a lowering into a safe state, and in that, in the event of a failure of the energy store (6) occurring simultaneously with the emergency lowering, the electric drive (5) is configured to limit a rotational speed of the electric motor (8) caused by a lowering of a mechanism (4) so as not to exceed a maximum power that can be absorbed by the primary energy source (2).

2. Work machine (1) according to claim 1, wherein the electric drive (5) comprises an inverter (7) connected to the intermediate circuit (3) and an electric motor (8), preferably wherein a shaft of the electric motor (8) is coupled, in particular rigidly coupled, to an associated mechanism (4).

3. Work machine (1) according to claim 2, wherein the inverter (7) connected to the intermediate circuit (3) is configured to convert a direct current in the intermediate circuit (3) into an alternating current in order to supply the electric motor (8) with alternating current and / or to convert an alternating current generated by the electric motor (8) into direct current and inject it into the intermediate circuit (3).

4. Work machine (1) according to either of the preceding claims 2 or 3, wherein, in the event of a failure of the energy store (6) occurring simultaneously with the emergency lowering, the primary energy source (2) is configured to supply the intermediate circuit (3) with energy so as to provide a supply voltage to the inverter (7) of the at least one electric drive (5).

5. Work machine (1) according to any one of the preceding claims, wherein, in the event of a failure of the energy store (6) occurring simultaneously with the emergency lowering, the primary energy source (2) is configured to supply the intermediate circuit (3) with energy such that the holding brake supplied with energy from the intermediate circuit (3) is able to release the mechanism (4).

6. Work machine (1) according to any one of the preceding claims, wherein, in the event of a failure of the energy store (6) occurring simultaneously with the emergency lowering, the primary energy source (2) is configured to supply the intermediate circuit (3) with energy such that the holding brake supplied with energy from the intermediate circuit (3) is able to block the mechanism (4) in order to secure the mechanism (4) in a safe position.

7. Work machine (1) according to any one of the preceding claims, wherein, in the event of a failure of the energy store (6) occurring simultaneously with the emergency lowering, the primary energy source (2) is configured to lower the voltage remaining in the intermediate circuit (3) after a lowering of the at least one mechanism (4) into a safe position, by the primary energy source (2) operating as an energy sink.

8. Work machine (1) according to any one of the preceding claims, wherein the at least one mechanism (4) is a hoisting mechanism or a slewing mechanism.