Drive unit

Abstract

A drive unit having an electrohydraulic drive (10) and a hydraulic auxiliary system (12), the auxiliary system generating an auxiliary torque that opposes the main torque of the electrohydraulic drive (10) when necessary.

Description

[Technical Field]

[0001] The present invention relates to a drive arrangement, in particular for a portable work machine. [Background technology]

[0002] Patent Document 1 discloses a hydraulic system with a variable displacement pump that can be driven by the internal combustion engine of a vehicle, in which a retarder valve is arranged in or in the working line of the hydraulic system, via which the pressure medium delivered from the variable displacement pump can be guided to a retarder orifice, the hydraulic system having a hydraulic braking function when the retarder is activated, the retarder orifice having a fixed cross-sectional area, and the pump pressure or pump volume flow being open-loop or closed-loop controllable when the retarder is activated. The pump volume flow and the pressure drop across the fixed retarder orifice result in an open-loop or closed-loop controllable power loss, which results in an open-loop or closed-loop controllable additional braking torque for the hydraulic system when the retarder is activated.

[0003] Patent Document 2 discloses a hydrostatic drive system for a portable work machine, in particular an industrial truck, which includes a working hydraulic system and a hydraulic pump for supplying the working hydraulic pressure, the pump being driven by a drive machine, in particular an internal combustion engine, and configured as a variable displacement pump with an adjustable transfer volume. A pressure balancer is associated with the transfer line leading from the pump to the working hydraulic system, configured as an input pressure balancer for the working hydraulic system, and is arranged in a return line branching from the transfer line to a tank, configured as a control valve with a shut-off position and a through-flow position, with a throttle in an intermediate position. The pressure balancer is supplied with pressure in the through-flow position by the transfer pressure of the pump occurring in the transfer line and in the blocking position by a spring and the maximum load pressure of the driven load of the working hydraulic system. A heat exchanger is arranged in the return line for cooling the pressure medium of the drive system, and by varying the transfer volume of the variable displacement pump, the volumetric flow of the pressure medium flowing through the heat exchanger can be adapted to the cooling power requirements of the drive system. The use of a variable displacement pump allows the pump volume to be varied and adapted accordingly, regardless of the speed of the drive machine that drives the pump, so that by appropriately increasing or decreasing the pump volume, a larger flow of pressure medium can be provided in the return line for flowing through the heat exchanger when a higher cooling power is required, or reduced when a lower cooling power is required.

[0004] Furthermore, conventionally designed electric drives are known in which 100% of the applied torque is generated for the drive via an installed electric motor or, unless an independent drive brake is present, absorbed during the braking process or recovered in an energy storage device, preferably in the form of a battery. Braking, in particular, can lead to situations in which more energy is returned to the system than can be accommodated in a given driving situation. The excess energy can lead to damage or thermal overload of existing drive components if the energy storage capacity of the storage device, preferably in the form of a battery, or the heat dissipation capacity of the inverter or motor is insufficient. Currently available drive systems on the market can only respond to this type of event to a limited extent. So-called braking choppers can limit the electrical excess energy returned between the electric motor, inverter, and storage medium, thereby protecting the storage medium, but cannot reliably prevent overload of the electric motor. In such an overload situation, the electric motor usually enters a so-called derating mode, in which it can use or absorb only a portion of the torque within its range. As a result, the drive system cannot be sufficiently braked and must go directly into emergency stop mode for safety reasons. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent No. 3569775 [Patent Document 2] European Patent No. 2399861 Summary of the Invention [Problem to be solved by the invention]

[0006] Based on this prior art, the object of the present invention is to provide an improved solution which contributes to avoiding the above-mentioned drawbacks. [Means for solving the problem]

[0007] This problem is solved by a drive device that has the overall features of patent claim 1.

[0008] The drive according to the present invention comprises an electrohydraulic drive and a hydraulic auxiliary system, which can generate an auxiliary torque and, if necessary, counteract the main torque of the electrohydraulic drive. The hydraulic auxiliary system, preferably in the form of an entire hydraulic installation, applies a predetermined torque to the electrohydraulic drive, which counteracts undesired torques generated by external hydraulic and / or mechanical loads, thereby reducing the mechanical and thermal loads of the drive and avoiding overloading of components and derating of the electric motor. In this way, a drive that is always available is created, and unintended interruptions of the work process, which can occur with current solutions, are eliminated.

[0009] Preferably, the auxiliary torque of the auxiliary system is generated by adapting the hydraulic force via a preferably controllable hydraulic resistance. If, when braking a work function, a predetermined external torque of a hydraulic or mechanical nature acts on the main drive in the form of an electrohydraulic drive, this can be countered by adjusting the resistance of the device. Possible adjustment variations in this case are fixed setting, discontinuous digital adjustment, proportional adjustment, open-loop control or closed-loop control.

[0010] In another preferred embodiment of the drive according to the invention, the electric motor is thermoregulated using an auxiliary torque, preferably incorporating an associated inverter and / or a battery powering the electric motor, by adapting the hydraulic force via a fixed or adjustable resistance, which resistance is optionally controlled via an electronic control unit.

[0011] Temperature regulation of electric motors and inverters Inverter and motor performance data as input quantities (temperature, speed, current, torque, etc.), and / or Machine performance data as input quantities (speed, direction, up / down, load, etc.) and / or Control signals as input quantities, e.g. by a joystick This can be done using

[0012] In another particularly preferred embodiment of the drive device according to the invention, the electrohydraulic drive has a hydraulic power supply, for example in the form of a constant displacement hydraulic pump, which is connected via a drive train to the driven side of the electric motor and via another drive train to the drive side of an auxiliary system that generates an auxiliary torque. In this way, thermal regulation of the electric motor and inverter is achieved by reducing the torque at the main drive shaft between the electric motor and the hydraulic drive of the mechanical-hydraulic component by discontinuous coupling or proportional regulation. Alternatively, mechanical gear components with variable speed mechanisms can also be used.

[0013] In another preferred embodiment of the drive device according to the invention, the auxiliary system for generating the auxiliary torque has a further pressure supply device, preferably in the form of a further fixed displacement hydraulic pump, which can be driven via another drive train of the first pressure supply device and generates a transfer volume flow that is guided at least partially via a hydraulic resistance. In this way, a universally usable device that minimizes the thermal load of the electrohydraulic drive by reducing the generated motor torque and a reliable protection of the energy store, preferably in the form of a battery, are obtained in a particularly cost-effective manner, which therefore has no counterpart in the prior art.

[0014] Further embodiments of the drive device according to the invention are the subject of other subclaims, and the subject of the invention is also the use of a drive device as described above.

[0015] The drive device according to the invention and its use will now be explained in more detail using an embodiment shown in the drawings, in which the only figure shows the main mechanical, hydraulic and electrical components of the drive device in the form of a circuit diagram, in principle and not to scale. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 shows the main mechanical, hydraulic and electrical components of the drive in the form of a circuit diagram, in principle and not to scale. DETAILED DESCRIPTION OF THE INVENTION

[0017] The drive, whose main components are shown in the figure, comprises an electro-hydraulic drive 10 cooperating with a hydraulic auxiliary system 12. This auxiliary system 12 can generate an auxiliary torque that, if necessary, counteracts the main torque of the electro-hydraulic drive 10, as will be described in more detail below. The drive also comprises an electric motor 14 as part of the drive 10, which cooperates with an inverter 16, which is connected via paths A1 and A2 to an energy store in the form of a battery 18. The inverter 16 is further coupled to the electric motor 14 via appropriate paths B1 and B2. The electric motor 14 drives a drive shaft 22 via a driven shaft 20 in the usual manner, which in turn drives a main drive 23 as part of the electro-hydraulic drive 10. For this purpose, the driven shaft 20 is coupled to the drive shaft 22 via a coupling 24. Furthermore, the main drive 23 drives another driven shaft 26, which is connected via another connection point 28 to another drive shaft 30, which is used to drive the auxiliary system 12 or an associated auxiliary drive 31. As indicated by the arrows, all shafts 20, 22, 26, 30 rotate in the same direction.

[0018] The main drive 23 is controlled by the drive power of the electric motor 14 and transfers a fluid, such as a hydraulic medium, in a closed or open hydraulic circuit 32, which is only partially shown in the figure. The main transfer directions of the main drive 23 are evident from the arrows D3 and D4, which also indicate the transfer direction within the circuit 32. In this respect, the main drive 23 is configured in the form of a transfer pumping device and receives a load on its input side, which is symbolically indicated by an arrow 34. This load, indicated by the arrow 34, is received on the output side of an auxiliary drive 31 as part of the hydraulic auxiliary system 12, insofar as it acts on the output side E3 of this auxiliary system.

[0019] The entire drive system further comprises a controller 36, also referred to in technical terms as an ECU (Electronic Control Unit). This controller 36 is connected to the inverter 16 via control lines G5 and G6 and to a storage device in the form of a battery 18 via further control lines G7 and G8. A temperature monitoring device 38 is further connected to the input of the controller 36 via a measurement data line G4, which data line transmits the actual operating temperature of the electric motor 14 detected by the temperature monitoring device to the controller 36. An additional control line G3 originating from the controller 36 is used to control the electric motor.

[0020] The auxiliary drive 31 in the form of a hydraulic pump is driven by the main drive 23 via the shafts 26, 30 and the coupling point 28 and is connected at its input side E2 to a supply line c, which draws fluid from a storage tank 40. The auxiliary drive 31 in the form of a transfer pump then discharges fluid with a determinable volume and a determinable pressure into a supply circuit f, which may be part of the overall hydraulic circuit 32. In the supply circuit f, preferably immediately after the output side E3 of the auxiliary drive 31, at a determinable branch point 42, a hydraulic resistance, generally designated 44, is connected in a bypass line d, through which the fluid flows from the bypass line d between connection ends F1 and F2 on the input or output side of the resistance 44, as shown in the diagrammatic representation. A discharge line e is connected to the output side of the resistance 44, and thus to connection end F2, via which the fluid can be returned, for example, to the storage tank 40 (not shown).

[0021] In the illustrated embodiment, the hydraulic resistance 44 is formed by an electrically proportionally controlled adjustable throttle 46, for which an actuating magnet 48 is used, which is controllable by the controller (ECU) 36 via a control line G1. Instead of the adjustable throttle 46, other resistances (not shown) can be used, for example in the form of a nozzle, a fixed throttle, a mechanically adjustable throttle, a pressure limiting valve, an electrically digitally controlled fixed throttle, an electrically digitally controlled pressure limiting valve, an electrically proportionally controlled pressure limiting valve, etc. In addition to the use of various types of valves, there is also the possibility of generating the hydraulic resistance 44 via a hydraulic storage device, for example a hydrostatic accumulator (not shown).

[0022] And it is further noted that so-called machine performance data, such as speed, up / down direction, load, etc., can be communicated to the controller 36 using suitable sensing devices 50 .

[0023] The drive device according to the present invention provides a universally applicable device for reducing the thermal load of an electric drive in the form of an electric motor 14, while simultaneously protecting a reservoir in the form of an electric battery 18, in particular by reducing the motor torque occurring in the main drive 23 via the associated auxiliary drive 31 and hydraulic resistance 44 of the auxiliary drive 12. In this way, a device for adapting the thermal balance of the electric drive 10 is provided for effective use in preferably electrically driven portable or semi-portable work machines. The above-mentioned hydraulic auxiliary system 12 is, as already explained, connected to the main drive 23 via a connecting or coupling element 28. Using a fixedly adjusted or adjustable hydraulic resistance 44, a predetermined pressure gradient can be generated in the hydraulic circuit at the output side E3 of the auxiliary drive 31, here in the form of a supply circuit f. This pressure gradient then generates a predetermined auxiliary torque via a mechanical-hydraulic component in the form of the auxiliary system 12 on the other drive shaft 30, which is used as the so-called auxiliary drive shaft of the machine. In this case, the auxiliary torque required to assist the main drive 23 is transmitted to the main drive shaft, i.e., to the further driven shaft 26, via the further connection point 28 as a connecting element. The further main drive shaft or drive shaft 22 is here mechanically coupled to the motor driven shaft 20 via the connection point 24. If the resistance on the output side E3 of the auxiliary drive 31 changes via the hydraulic resistance device 44, the auxiliary torque T on the further drive shaft 30 assisting the electric motor 14 changes. In this case, it can be said that the torque T on the driven shaft 20 of the electric motor 14 is equal to the torque on the further driven shaft 26 minus the torque on the further drive shaft 30. It therefore also follows that the torque on the further driven shaft 26 is equal to the torque on the drive shaft 22 of the main drive 32.

[0024] If a predetermined external torque of a hydraulic or mechanical nature acts on the main drive 23 when braking a work function, this can be countered by adjusting the hydraulic resistance 44 of the drive, as already explained above. Thus, there is the possibility of adjusting the temperature of the electric motor 14 and the inverter 16 by adapting the auxiliary torque at the other drive shaft 30 for the auxiliary drive 31 by adapting the fluid pressure at the output side E3 of the auxiliary drive 31 via the aforementioned fixed or adjustable resistance 44 (which is preferably controlled via an electronic control unit in the form of a controller 36). Furthermore, there is the possibility of adjusting the temperature of the electric motor 14 and the associated inverter 16 by reducing the torque at the main drive shafts 22, 26, respectively, in a mechanical-hydraulic component in the form of the main drive 23, using a discontinuous connection or proportional adjustment. Alternatively, torque reduction can also be achieved by means of a gear-mechanical component, but this is not shown.

[0025] In addition to the possibility of adaptively retarding the torque for the electric motor 14, the drive device according to the invention also allows for charge capacity regulation for a storage medium, preferably in the form of a battery 18, using so-called performance data of the storage medium, such as the state of charge, temperature, load, etc.

[0026] In summary, the drive according to the invention provides a retarder-type solution that is particularly suitable for use in electric machines: in the event of various faults on the electric drive side (overheating of the electric motor 14, failure of the inverter 16, overloading of the conductors A1, A2, B1, B2, etc., full charge of the battery 18), in the case of machines that do not have a separate drive brake, these machines can nevertheless be reliably braked to a defined maximum speed or brought to a standstill using the hydraulic auxiliary system 12 described above.

[0027] In particular, machines with hydrostatic travel drives in closed circuits often dispense with a separate drive brake; braking is more or less achieved via adjustment of the transfer pump, which brakes the machine. This is largely not a problem when using diesel machines, but is a problem with electric machines. The aforementioned problems can arise here, which cannot be addressed by the conventional design of the hydrostatic drive train.

[0028] In a specific solution, the auxiliary drive 31 of the auxiliary system 12 is used to the main drive 23 in order to be able to build up a defined braking moment on the mechanically coupled drive train on demand or in the event of a failure. For this purpose, a hydraulic resistor 44, preferably in the form of a proportional pressure limiting valve, is inserted in the working connection of the output side E3 of the auxiliary drive 31.

[0029] By supplying a defined current to the electric motor, the pressure and therefore the braking torque follow the input signal. Preferably, a back pressure limiting valve is used as hydraulic resistor 44 to ensure maximum braking power in the event of a current loss.

[0030] The "health" of the main drive 23 is continuously monitored via a performance management system, preferably implemented in the controller 36. If it is detected that the battery 18, electric motor 14, etc., requires a predetermined load removal, a proportional retarder function (7-50 Nm) is applied to delay braking.

[0031] Due to the modular design of the drive according to the invention, it is also possible to retrofit it into components already present in the respective working machine.

Claims

1. A drive unit having an electrohydraulic drive (10) and a hydraulic auxiliary system (12), the hydraulic auxiliary system (12) generating an auxiliary torque that opposes a main torque of the electrohydraulic drive (10) when necessary.

2. 2. The drive arrangement according to claim 1, characterized in that the auxiliary torque of the auxiliary system (12) is formed by adapting a hydraulic force via a hydraulic resistance (44), which is preferably controllable.

3. 3. The drive device according to claim 1, wherein the auxiliary torque is used to regulate the temperature of the electric motor (14), preferably by incorporating an associated inverter (16) and / or a battery (18), the battery (18) supplying the electric motor (14).

4. 4. The drive arrangement according to claim 1, wherein the electrohydraulic drive (10) comprises a hydraulic power supply (23), preferably in the form of a fixed displacement hydraulic pump, which is coupled via a drive train (22) to the driven side (20) of the electric motor (14) and via another drive train (26) to the drive side (30) of the auxiliary system (12) which generates the auxiliary torque.

5. 5. The drive device according to claim 1, wherein the auxiliary system (12) for generating the auxiliary torque comprises a further pressure supply device (31), preferably in the form of a further fixed displacement hydraulic pump, which is drivable via the further drive train (26) of one of the pressure supply devices (23) and generates a transferred volume flow that is guided at least partially via the hydraulic resistance (44).

6. 6. The drive device according to claim 1, wherein the hydraulic resistance (44) generates a pressure gradient on the fluid output side (E3) of the other pressure supply device (31), and the pressure gradient provides the corresponding auxiliary torque to one of the pressure supply devices (23) via the other drive train (26).

7. 7. The drive device according to claim 1, wherein the hydraulic resistance (44) is adjustable by a control device controllable by a motor controller (ECU) (36), the motor controller (ECU) (36) receiving sensor data from the electric motor (14) via a sensor device (38), the electric motor (14) being preferably controllable by the motor controller (36).

8. 8. The drive arrangement according to claim 1, wherein the electric motor (14) is powered by at least one battery (18), the battery (18) preferably providing its power to the inverter (16) of the electric motor (14).

9. 9. A drive arrangement according to any one of claims 1 to 8, characterized in that each battery (18) is connected to the motor controller (36) for charge capacity regulation.

10. Use of a drive device, preferably a drive device according to any one of claims 1 to 9, characterized in that the entire hydro-mechanical system (10, 12) applies a torque to the drive (23) as required, said torque counteracting in a retarding manner any undesired torque coming from outside.

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