Truck mixer

Abstract

The invention relates to a truck mixer having a mixing device (10). The mixing device (10) has a rotatable mixing drum (12), an electric drive unit (14) designed to control the rotational speed of the mixing drum (12), and a brake device (20). The braking device (20) can be adjusted between a release state, in which rotation of the mixing drum (12) is released, and a stop state, in which the mixing drum (12) is locked. The truck mixer is designed to automatically lock the mixing drum (12) by means of the braking device (20) in the event of a failure of the electric drive unit (14).

Description

Technical Field

[0001] The invention relates to a truck mixer. Background Art

[0002] Truck mixers are designed, for example, as mobile concrete mixers, which can transport fresh concrete to a construction site. To this end, truck mixers have a rotatable mixing drum, for example, arranged at the rear end of the truck mixer. The mixing drum rotates during transport in order to thoroughly mix the concrete and to avoid or reduce curing or quality degradation during transport. Usually, in this case, the mixing drum is hydraulically driven. However, hydraulic drive systems for the mixing drum are heavy, expensive and maintenance-intensive.

[0003] Moreover, in the case of truck mixers, it is desirable to provide an electric traction drive instead of an internal combustion engine, as is the case in other trucks. Likewise, it may be desirable to replace the hydraulic drive system for the mixer drum with an electric drive system. However, in this case, there may be problems with operational reliability. For example, in the event of a failure of the control electronics, the mixer drum may rotate at too high a rotational speed or may not stop at the correct time, with the result that potentially undesirable drive situations or other operational situations may occur. Summary of the invention

[0004] A first aspect relates to a truck mixer with a mixing device. The truck mixer can be designed, for example, as a mobile concrete mixer. The truck mixer can be based, for example, on a truck with a mixing device at its rear end. The truck mixer can be designed, for example, for transporting fresh concrete to a construction site. However, the truck mixer can also be designed for transporting other substances, such as other building materials that must be mixed during transportation. The truck mixer can have a traction drive. The traction drive can, for example, have a traction motor for providing traction for the truck mixer. The traction drive can have a transmission, by which the traction can be transmitted to the output of the truck mixer, such as a corresponding driven shaft. The truck mixer can, for example, be designed as a three-axle or four-axle truck. The truck mixer can also be designed as a semi-trailer. The truck mixer can in this case not have, for example, its own traction drive. The truck mixer can, for example, have a coupling device designed to connect the truck mixer to a tractor unit. The tractor unit can provide electrical energy for operating the truck mixer via the coupling device. The truck mixer can also be designed as a tractor unit combination, wherein the truck mixer has a tractor unit and a trailer with a mixing device.

[0005] The mixing device may have a rotatable mixing drum. The mixing drum may be rotatably mounted, for example, by corresponding bearings on the frame of the truck mixer. The mixing device may, for example, have an upper feed hopper, through which fresh concrete can be poured into the mixing drum. During transportation, the mixing drum may, for example, rotate in one direction so as to thoroughly mix the transported goods, such as fresh concrete, during transportation. A propeller may be arranged in the mixing drum, which additionally thoroughly mixes the fresh concrete during the rotation of the mixing drum. By reversing the direction of rotation, the fresh concrete can be conveyed out of the mixing drum, for example, by the propeller in the manner of a screw conveyor. The mixing device may, for example, have a chute, through which the transported goods can be discharged at the destination. However, different elements may also be provided to output the new concrete, such as plastic pipes. During output, the concrete may additionally be made more fluid using a superplasticizer. Alternatively, the output may also be carried out by a truck mixing pump instead of by the mixing device.

[0006] The stirring device has an electric drive unit, which is designed to control the rotation speed of the stirring drum. The drive unit can, for example, specify the stopping of the stirring drum, the start of rotation, and the rotation speed of the stirring drum during the rotation of the stirring drum. To this end, the electric drive unit has, for example, an electric drive motor, the rotation speed of which can be set by predetermined power-on. The electric drive motor can, for example, be designed as a synchronous motor or an asynchronous motor. The shaft of the drive motor can be connected to the stirring drum by the transmission of the electric drive unit. The stirring device can, for example, have a power supply for the electric drive unit. The supply of electricity can, for example, be carried out by a high-voltage battery, which also supplies electrical energy to the electric traction drive of the truck mixer. However, the supply of electricity can also be carried out by a generator driven by a conventional internal combustion engine of the truck mixer. The electric drive motor can, for example, also be used for braking and alternatively or additionally locking the stirring drum. However, in the event of failure of the electronic device or the power supply, the safe stop of the stirring drum may no longer be guaranteed.

[0007] The mixing device has a brake device. The brake device can be adjusted between a release state, in which the rotation of the mixing drum is released, and a stop state, in which the mixing drum is locked. For this purpose, the brake device can, for example, have a multi-disc clutch, by means of which the mixing drum can be connected to the chassis of the truck mixer in a rotationally fixed manner. For this purpose, the brake device can be designed to end the rotation of the mixing drum, for example, in the event of a failure or malfunction of the electric drive unit.

[0008] The truck mixer is designed to automatically lock the mixing drum by means of a brake device in the event of a failure of the electric drive unit. A failure of the drive unit may, for example, be a failure in the control of the rotational speed of the mixing drum. However, a failure of the drive unit may also be, for example, a failure in the supply of electrical energy for driving the electric drive motor and thus the mixing drum. The hydraulic drive unit brakes the mixing drum in the event of a failure due to its operating principle and holds the mixing drum in place. If the hydraulic drive unit for the mixing drum is replaced by an electric drive unit, this characteristic of the drive unit no longer exists inherently compared to a hydraulic drive unit. Therefore, a brake device is provided in order to be able to ensure safe operation of the truck mixer.

[0009] In one embodiment of the truck mixer, an electric drive unit is provided, which has an electric drive motor and a power supply device. The power supply device may have an electrical energy storage device, such as a battery. The power supply device may also have a generator, by which mechanical energy can be converted into electrical energy. The power supply device may, for example, be provided exclusively to the electric drive unit. The power supply device may also optionally supply electricity to the traction drive of the truck mixer. The power supply device may be designed to additionally supply power for its activation to the brake device. The brake device may be designed as an electric brake device, which automatically changes to its stop state in a de-energized state. Thus, the brake device may be preloaded in its stop state by, for example, a spring or a magnet. For example, the electric brake device may be activated by applying a voltage or by supplying electricity. In order to set the brake device to its release state, the brake device must, for example, be energized. Therefore, the multi-disc clutch may, for example, be adjusted to an open state by an electromagnet in opposition to the spring force of the spring. By supplying electricity, the brake device may, for example, be kept in its release state and then automatically return to the stop state if the power supply is lost.

[0010] The power supply device can be designed to supply power to the drive motor for rotating the mixing drum and to supply power to the braking device for keeping the braking device in its released state. Thus, in the event of a power failure, the braking device can be automatically adjusted to its stopped state. Thus, for example, if the power supply to the braking device by the power supply device is interrupted, the mixing drum is automatically braked to a stop and then held in place. As a result, automatic fixing of the mixing drum in place can be provided. In addition, if the energy storage device of the power supply device is completely empty, locking of the mixing drum can be ensured. Moreover, locking of the mixing drum can be automatically achieved when the truck mixer or at least the power supply device is turned off.

[0011] In one embodiment of the truck mixer, it is provided that the electric drive unit has an inverter. The inverter can be designed as a power electronic device of the electric drive unit. The inverter can be designed to detect a fault situation in the electric drive unit and, in the case of a detected fault situation, to set the brake device to a stopped state. Thus, by means of the inverter, for example, the adjustment of the brake device between its two states can be actively controlled. The inverter can monitor the electric drive unit and adjust the brake device according to its state. For example, if it is desired to start rotating the mixing drum, the inverter can also automatically adjust the brake device to its released state. The inverter can have corresponding sensors or be connected to corresponding sensors, by which state variables of the electric drive unit or even the mixing device as a whole can be detected. The inverter can evaluate the corresponding sensor signals and thus detect a fault situation. For example, the corresponding fault situation can be specified at the factory. For example, individual thresholds can be defined for the individual state variables, and the mixing device must not exceed these thresholds. If these thresholds are exceeded, the mixing drum can be automatically locked.

[0012] In one embodiment of the truck mixer, it is provided that the inverter is designed to monitor at least one state variable of the electric drive unit and compare it with the desired state in order to detect a fault condition. The desired state may, for example, correspond to a predetermined state variable. For example, the desired state may have a predetermined instantaneous rotational speed of the mixing drum. Alternatively or additionally, the desired state may have a predetermined threshold value for the state variable. For example, the desired state may have a maximum instantaneous rotational speed of the mixing drum. The desired state may, for example, be predetermined by the current operating mode and, alternatively or additionally, by the instantaneous desired rotational speed of the mixing drum.

[0013] The state variable may be, for example, an operating temperature. The operating temperature may be the instantaneous temperature of an element of the truck mixer. For example, the operating temperature may be the temperature of the windings of the electric drive motor of the electric drive unit. As a result, overheating may be avoided, or in the event of overheating, the mixing drum may be locked to avoid damage. The state variable may be, for example, a rotational speed. The rotational speed may be, for example, the instantaneous rotational speed of the mixing drum, and alternatively or additionally the instantaneous rotational speed of the shaft of the electric drive motor of the electric drive unit. As a result, in the event of a rotational speed control failure, damage may be avoided by locking the mixing drum. The state variable may be, for example, a rotational direction. The rotational direction may be, for example, the current rotational direction of the mixing drum, and alternatively or additionally the current rotational direction of the shaft of the electric drive motor of the electric drive unit. As a result, for example, an undesired emptying of the mixing drum may be reliably prevented. A plurality or all of these state variables may also be monitored by the inverter and compared with a desired state in order to detect a fault condition. The desired state may be stored, for example, in a table in a data memory of the inverter. The desired state may also be determined by the inverter according to the current operating state of the truck mixer and the desired behavior of the mixing device. The inverter may, for example, have a microprocessor for this purpose.The desired state may have a corresponding desired value and, alternatively or additionally, threshold values ​​for some or all monitored state variables.

[0014] The inverter can also be designed to switch off the electric drive unit in the event of a detected fault condition. For this purpose, a fuse can be disconnected, for example, in order to interrupt the power supply to the electric drive motor. For example, in the event of a detected fault condition, a zero rotation speed can be predetermined for the mixing drum by the inverter. For this purpose, a corresponding control signal can be output, for example, to the mixing device, for example to its electric drive unit.

[0015] In one embodiment of the truck mixer, an electric drive unit is provided, which has a first electric energy source and a second electric energy source, wherein the first electric energy source is designed to supply power to the brake device and the second electric energy source is designed to supply power to the inverter to detect a fault condition. Therefore, the electric drive unit can have a separate energy source for monitoring the brake device and the inverter. Therefore, the inverter can further operate in the event of failure of the first energy source, for example in order to control the electric drive motor of the electric drive unit of the stirring device, for example in order to turn off the electric drive motor. Therefore, if the first electric energy source fails, the inverter is further supplied with energy. Therefore, the brake device can also be optionally further controlled by the inverter. In addition, energy sources with different voltages, different capacitances and alternatively or additionally different powers can therefore be provided. The first electric energy source can be designed, for example, as a high-voltage battery. The first electric energy source can be designed, for example, as a traction battery for a traction drive of a truck mixer. The second electric energy source can be designed, for example, as a low-voltage battery. The second electric energy source can, for example, represent an electric energy source for a vehicle electrical system. The first electric energy source and alternatively or additionally the second electric energy source can be designed to supply power to the drive motor of the electric drive unit.

[0016] In one embodiment of the truck mixer, it is provided that the truck mixer has an electric traction drive. For example, the truck mixer may not have an internal combustion engine. The traction force of the truck mixer may, for example, be provided purely electrically. The electric traction drive may, for example, have an electric traction motor that converts electrical energy into mechanical energy. Optionally, the electric traction motor may also be designed for recovery. Due to the provision of the electric traction drive, the truck mixer can be fully powered. In addition, the corresponding electrical energy source can therefore be used together to supply the mixing device and the traction drive. Therefore, the truck mixer can be particularly cheap and environmentally friendly. In addition, the hydraulic system in the truck mixer can therefore be completely omitted. Therefore, the individual components of the truck mixer can be arranged in its installation space in a particularly simple and flexible manner. Optionally, the truck mixer also has electric steering. For example, the truck mixer can have a corresponding electric motor, with which the steerable shaft of the truck mixer is rotated or by which this rotation is supported.

[0017] In one embodiment of the truck mixer, it is provided that the first electrical energy source is also designed to supply power to the electric traction drive. If the traction drive fails due to a failure of the first electrical energy source, the mixer drum can also be locked in a simple manner. For example, in this case, the first electrical energy source is designed as a traction battery.

[0018] In one embodiment of the truck mixer, provision is made for the first electrical energy source to be connected to the brake device via a DC-DC voltage converter. Thus, a relatively low voltage can easily be provided for operating the brake device and in particular for keeping the brake device in its released state. Thus, for example, a separate energy source can be dispensed with from the traction drive. Thus, the power consumption of the brake device can be kept low. At the same time, the first electrical energy source can therefore also provide a high current and, alternatively or additionally, also a high voltage for supplying electrical energy to the traction drive.

[0019] In one embodiment of the truck mixer, provision is made for the inverter to be designed to monitor the state of the brake device and to switch off the electric drive motor if the brake device has changed to the stationary state. Thus, for example, it can be avoided that the electric drive motor continues to operate against the brake device in the stationary state. For example, a fault situation may also occur at the brake device, which can thus be detected, wherein further damage can then be avoided by switching off the drive unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The mixing device of a truck mixer is schematically shown. DETAILED DESCRIPTION

[0021] Figure 1 A mixing device 10 of a truck mixer is schematically shown. The mixing device 10 has a mixing drum 12 driven by an electric drive unit 14. To this end, the electric drive unit 14 has an inverter 16 and an electric drive motor 18. The inverter 16 controls the power supply of the electric drive motor 18, with which the rotation speed of the mixing drum 12 can be controlled.

[0022] The electric drive motor 18 is mechanically connected to a transmission 22 of the electric drive unit 14 via a brake device 20. The transmission 22 provides a transmission ratio between the electric drive motor 18 and the mixing drum 12. The brake device 20 can be adjusted between a release state that releases the rotation of the mixing drum 12 and a stop state that locks the mixing drum 12. The brake device 20 is designed as an electric brake device 20, which automatically changes to its stop state in a power-off state. Therefore, in the embodiment shown, the spring preloads the brake device 20 in its stop state. As long as the rotation of the mixing drum 12 is requested and it is assumed that the brake device 20 is powered and is therefore in its release state, the inverter 16 controls the brake device 20 to adjust to the release state.

[0023] The truck mixer is designed to automatically lock the mixing drum 12 by means of a brake device 20 in the event of a failure of the drive unit 14. There are several possibilities for this. The electric drive unit 14 has a power supply device 24. The power supply device 24 is designed to supply power to the drive motor 18 for rotating the mixing drum 12 and to supply power to the brake device 20 for keeping the brake device in its released state. To this end, the power supply device 24 has a first electrical energy source 26 and a second electrical energy source 28, which are connected to each other via a DC-DC voltage converter 30. The first electrical energy source 26 is designed as a traction battery with a high-voltage battery, through which an electric traction drive (not shown) of the truck mixer can be supplied with power for its operation. In addition, the first electrical energy source 26 supplies power to the brake device 20. This power supply can be carried out directly or, in an alternative shown in dashed lines, in different embodiments, via a further DC-DC voltage converter 32 that connects the brake device 20 to the first energy source 26. The second electrical energy source 28 is designed as a low-voltage battery that provides an onboard voltage of 24 volts. The inverter 16 is electrically connected to the first energy source 26 and the second energy source 28. Thus, the inverter 16 as a power electronic device can control the output of electrical power via the first energy source 26 and also for operating the electric drive motor 18 of the stirring device 10 in the illustrated embodiment.

[0024] In the case of a first fault, for example due to a defect in the traction drive of the truck mixer, the power supply of the first energy source 26 to the brake device 20 fails. As a result, the brake device 20 can no longer be held in the released state, and the spring presses the brake device 20 into its stopped state. The mixer drum 12 is thus braked and eventually locked.

[0025] Furthermore, the inverter 16 is designed to detect a fault situation in the electric drive unit 14 and, in the event of a fault situation being detected, to set the brake device 20 to a stopped state. Thus, the inverter 16 is designed to monitor the operating temperature of the electric drive motor 18, the rotation speed of the electric drive motor 18 and the rotation direction of the electric drive motor 18 as state variables of the electric drive unit 14. These monitored state variables are compared with a desired state, which, for example, has a corresponding limit of the deviation from the current desired state variable. Thus, a fault situation can be detected and, as a reaction to the fault situation, the mixing drum 12 can be locked by controlling the brake device 20 using the inverter 16 and thereby setting the brake device 20 to a stopped state.

[0026] In addition, the inverter 16 is also designed to monitor the state of the brake device 20. If the inverter 16 detects that the brake device 20 is in an undesirable state, the inverter 16 can shut down the electric drive motor 18 for the mixing drum 12. In the embodiment shown, if the brake device 20 becomes stationary, for example due to a failure of its power supply, the inverter 16 shuts down the electric drive motor 18.

[0027] Reference numerals: 10 stirring device 12 stirring drum 14 electric drive unit 16 inverter 18 electric drive motor 20 braking device 22 transmission device 24 power supply device 26 first electrical energy source 28 second electrical energy source 30 DC-DC voltage converter 32 further DC-DC voltage converter

Claims

1. A truck mixer having a mixing device (10), wherein: The stirring device (10) comprises a rotatable stirring drum (12), an electric drive unit (14) designed to control the rotation speed of the stirring drum (12), and a braking device (20). The braking device (20) is adjustable between a released state and a stopped state, wherein in the released state, the rotation of the mixing drum (12) is released, and in the stopped state, the mixing drum (12) is locked. The truck mixer is designed to automatically lock the mixing drum (12) through the braking device (20) in the event of a failure of the electric drive unit (14).

2. The truck mixer according to claim 1, wherein: The electric drive unit (14) comprises an electric drive motor (18) and a power supply device. The braking device (20) is designed as an electric braking device (20), and the electric braking device (20) automatically changes to its stopped state in a power-off state. The power supply device (24) is designed to supply power to the drive motor (18) to rotate the mixing drum (12) and to supply power to the brake device (20) to keep the brake device in its released state.

3. The truck mixer according to claim 1 or 2, wherein: The electric drive unit (14) has an inverter (16) which is designed to detect a fault situation in the electric drive unit (14) and, in the event of a detected fault situation, to set the braking device (20) to the stopped state.

4. The truck mixer according to claim 3, wherein: The inverter (16) is designed to monitor at least one of the following state variables of the electric drive unit (14) and compare it with an expected state in order to detect the fault condition: - operating temperature; - rotation speed; and - Direction of rotation.

5. The truck mixer according to claim 3 or 4, wherein: The electric drive unit (14) has a first electrical energy source (26) designed to supply power to the brake device (20) and a second electrical energy source (28) designed to supply power to the inverter (16) for detecting a fault condition.

6. Truck mixer according to one of the preceding claims, wherein The truck mixer has an electric traction drive.

7. The truck mixer according to claim 6 referring back to claim 5, wherein: The first electrical energy source (26) is also designed to supply electrical power to the electric traction drive.

8. Truck mixer according to one of claims 5 to 7, wherein: The first electrical energy source (26) is connected to the braking device (20) via a DC-DC voltage converter (30).

9. The truck mixer according to one of claims 3 to 8, wherein: The inverter (16) is designed to monitor the state of the braking device (20) and to switch off the electric drive motor (18) if the braking device (20) has become the stationary state.

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