Drive device

Abstract

The invention relates to a drive device with an electro-hydraulic drive (10) and a hydraulic auxiliary system (12) which generates an auxiliary torque which, if necessary, counteracts a main torque of the electro-hydraulic drive (10).

Description

[0001] drive device

[0002] The invention relates to a drive device, in particular for a mobile work machine.

[0003] EP 3 569 775 B 1 discloses a hydraulic arrangement with a variable displacement pump that can be driven by an internal combustion engine of a vehicle. A retarder valve is arranged on or in a working line of the hydraulic arrangement, via which valve pressure medium delivered by the variable displacement pump can be guided to a retarder throttle. The hydraulic arrangement has a hydraulic braking function in retarder operation, the retarder throttle having a fixed cross-section, and a pump pressure or pump volume flow can be controlled or regulated in retarder operation. The pump volume flow and the pressure drop at the fixed retarder throttle result in a controllable or regulated power loss and thus a controllable or regulated additional braking torque for the hydraulic arrangement in retarder operation.

[0004] EP 2 399 861 B1 discloses a hydrostatic drive system of a mobile work machine, in particular an industrial truck, with a working hydraulic system and a hydraulic pump for supplying the working hydraulic system, wherein the pump is driven by a drive machine, in particular an internal combustion engine, and is designed as a variable displacement pump with an adjustable delivery volume.In this case, a pressure compensator is assigned to a delivery line leading from the pump to the working hydraulics, which pressure compensator is designed as an inlet pressure compensator of the working hydraulics and is arranged in a return line branching off from the delivery line to the container and is designed as a throttling control valve in the intermediate position with a blocking position and a flow position, wherein the pressure compensator is acted upon by the delivery pressure of the pump present in the delivery line in the direction of the flow position and by a spring as well as the highest pressure of the controlled consumers of the working hydraulics in the direction of the blocking position, wherein a heat exchanger device for cooling the pressure medium of the drive system is arranged in the return line, wherein by changing the delivery volume of the variable displacement pump, the pressure medium volume flow flowing via the heat exchanger device can be adapted to the cooling power requirement of the drive system.By using a variable displacement pump, the displacement of the variable displacement pump can be changed and thus adjusted independently of the speed of the engine driving the pump. By increasing or decreasing the displacement of the variable displacement pump accordingly, a high pressure fluid flow can be provided in the return line for flow through the heat exchanger when high cooling capacity is required, or reduced when low cooling capacity is required.

[0005] Furthermore, classically designed electric motor drives are known in which the applied torque is generated 100% by the installed electric motor for the drive or, if no independent service brake is available, is intercepted or fed back into an energy storage device, preferably in the form of a battery, during braking. Braking, in particular, can then lead to situations in which more energy is returned to the system than it can absorb in a given operating state. The existing excess energy can cause damage or thermal overload of the existing drive components if the energy absorption capacity of a storage device, preferably in the form of a battery, or the heat dissipation capacity of an inverter or motor is insufficient. Current drive systems freely available on the market can only partially absorb such occurrences.Using so-called brake choppers, the excess electrical energy fed back between the electric motor, inverter, and storage medium can be limited, thus protecting the storage medium. However, thermal overload of the electric motor cannot be completely ruled out. In the event of such an overload, an electric motor typically switches to a so-called de-rating mode, in which only a portion of the torque can be applied or absorbed. This results in a drive system being insufficiently decelerated and, for safety reasons, requiring immediate switching to emergency stop mode.

[0006] Based on this prior art, the object of the invention is to provide an improved solution that helps to avoid the disadvantages described.

[0007] A drive device having the features of patent claim 1 in its entirety solves this problem.

[0008] The drive device according to the invention, equipped with an electro-hydraulic drive and a hydraulic auxiliary system, enables the generation of an auxiliary torque that, if necessary, counteracts the main torque of the electro-hydraulic drive. By means of the hydraulic auxiliary system, preferably designed as a complete hydromechanical unit, a defined torque is deliberately applied to the electro-hydraulic drive, which counteracts an undesirable, externally implied torque formed by a hydraulic and / or mechanical load, thereby reducing the mechanical and thermal load on the drive and preventing component overloading and de-rating of the electric motor. This creates a drive that is always available, and unwanted interruptions to the work process, which can occur with current solutions, are eliminated.

[0009] Preferably, the auxiliary torque of the auxiliary system is provided by adjusting a hydraulic pressure via a preferably controllable hydraulic resistance. If a certain external torque of a hydraulic or mechanical nature is exerted on the main drive in the form of the electro-hydraulic drive during braking of the work function, this can be counteracted by adjusting the resistance of the device. Possible adjustment variants are: fixed, discrete digital, proportional, open-loop, or closed-loop.

[0010] In a further preferred embodiment of the drive device according to the invention, the auxiliary torque is used to control the temperature of the electric motor, preferably with the involvement of an associated inverter and / or a battery supplying the electric motor. This is achieved by adapting the hydraulic pressure via a fixed or adjustable resistor, which can optionally be controlled via an electronic control unit.

[0011] The temperature control for the electric motor and inverter can be achieved using inverter and motor performance data as input variables (temperature, speed, current, torque,...) and / or machine performance data as input variables (speed, direction, up / down, load,...) and / or

[0012] Control signals, for example from a joystick, can be used as input variables.

[0013] In another particularly preferred embodiment of the drive device according to the invention, the electro-hydraulic drive comprises a hydraulic pressure supply device, for example in the form of a fixed-displacement hydraulic pump, which is coupled via one drive train to an output side of the electric motor and via another drive train to the drive side of the auxiliary system generating the auxiliary torque. In this way, temperature control for the electric motor and inverter can be achieved by reducing the torque on a main drive shaft between the electric motor and the hydraulic drive of a mechanical-hydraulic component by means of discrete interconnection or proportional adjustment. Alternatively, a transmission-mechanical component with a ratio can also be used.

[0014] In a further preferred embodiment of the drive device according to the invention, the auxiliary system that generates the auxiliary torque has a further pressure supply device, preferably in the form of a further fixed-displacement hydraulic pump, which, driven via the further drive train of the one pressure supply device, generates a delivery volume flow that is at least partially guided via a hydraulic resistance. In this way, a universally usable device for minimizing the thermal load on an electro-hydraulic drive and reliably protecting an energy storage device, preferably in the form of a battery, by reducing the resulting engine torque is created in a particularly cost-effective manner. This has no equivalent in the prior art.

[0015] Further embodiments of the drive device according to the invention are the subject of the further subclaims and the subject of the invention is also the use of a drive device as stated above.

[0016] The drive device according to the invention and its use are explained in more detail below using an exemplary embodiment shown in the drawing. The single figure shows the essential mechanical, hydraulic, and electrical components of the drive device in a schematic representation, not to scale, in the form of a circuit diagram.

[0017] The drive device shown in the figure with its essential components has an electro-hydraulic drive 10 that interacts with a hydraulic auxiliary system 12. The auxiliary system 12 is designed to generate an auxiliary torque that, if necessary, counteracts a main torque of the electro-hydraulic drive 10, as will be explained in more detail below. Furthermore, the drive device has an electric motor 14 as part of the drive 10, which interacts with an inverter 16, which in turn is connected via paths A1, A2 to an energy storage device in the form of a battery 18. Furthermore, the inverter 16 is coupled to the electric motor 14 via suitable paths B1, B2. The electric motor 14 drives a drive shaft 22 in the usual way via an output shaft 20 for the purpose of driving a main drive 23 as part of the electro-hydraulic drive 10.For this purpose, the output shaft 20 is connected to the drive shaft 22 via a coupling point 24. Furthermore, the main drive 23 drives another output shaft 26, which is connected via another coupling point 28 to another drive shaft 30, which serves to drive the auxiliary system 12 or an associated auxiliary drive 31. As the arrow shows, all shafts 20, 22, 26, and 30 rotate in the same direction.

[0018] The main drive 23, controlled by the drive power of the electric motor 14, delivers fluid, such as a hydraulic medium, in a closed or open hydraulic circuit 32, which is only partially shown in the figure. The main delivery direction of the main drive 23 is derived from the arrows D3 and D4, and the delivery direction within the circuit 32 is again indicated by an arrow. In this respect, the main drive 23 is designed as a feed pump device and is exposed on the inlet side to an East, which is symbolically represented in the figure by an arrow 34. A corresponding East with an arrow representation 34 is assumed for the output side of the auxiliary drive 31 as part of the hydraulic auxiliary system 12, which is therefore supplied with this East on its output side E3.

[0019] Furthermore, the drive device as a whole comprises a control unit 36, which is also technically referred to as an ECU (Electronic Control Unit). The control unit 36 ​​is connected to the inverter 16 via control lines G5 and G6 and to the storage device in the form of the battery 18 via further control lines G7 and G8. Furthermore, a temperature monitoring device 38 is connected to the input side of the control unit 36 ​​via a measurement data line G4, which transmits the current operating temperature of the electric motor 14, which is detected by the temperature monitoring device, to the control unit 36. An additional control line G3 is used to control the electric motor from the control unit 36.The auxiliary drive 31 in the form of a hydraulic pump is driven by the main drive 23 via the shafts 26 and 30 and the coupling point 28 and is connected with its inlet side E2 to a supply line c, which draws fluid from a storage tank 40. The auxiliary drive 31 in the form of the feed pump then delivers fluid with a predeterminable volume and with a predeterminable pressure to a supply circuit f, which can be part of the overall hydraulic circuit 32. At a predeterminable branch point 42 in the supply circuit f, preferably immediately after the outlet side E3 of the auxiliary drive 31, a hydraulic resistor, designated as a whole by 44, is connected to a bypass line d, which, as shown in the figure, is flowed through by fluid from the bypass line d between the connections F1 and F2 on the inlet side and on the outlet side of the resistor 44.A discharge line e is connected to the output side of the resistor 44 and thus to the connection F2, via which fluid can be returned, for example, to the storage tank 40 (not shown).

[0020] In the exemplary embodiment shown, the hydraulic resistance 44 is formed from an electrically proportionally actuated adjustable throttle 46, wherein an actuating magnet 48 is used to control the adjustable throttle 46, which can be actuated by the control unit (ECU) 36 via a control line G1. Instead of the adjustable throttle 46, another resistance can be used (not shown), for example in the form of a nozzle, a fixed throttle, a mechanically adjustable throttle, a pressure relief valve, an electrically digitally actuated fixed throttle, an electrically digitally actuated pressure relief valve, an electrically proportionally actuated pressure relief valve, etc. In addition to the use of valves of any type, it is also possible to generate a hydraulic resistance 44 via a hydraulic storage device, such as a hydraulic accumulator (not shown).

[0021] Finally, it should be mentioned that so-called machine performance data such as speed, direction up / down, load, etc. are passed on to the control unit 36 ​​by means of a suitable recording device 50.

[0022] The drive device according to the invention provides a universally usable device for minimizing the thermal load on the electric motor drive in the form of the electric motor 14. Furthermore, the storage device, here in the form of the electric battery 18, is simultaneously protected by reducing the engine torque generated at the main drive 23 by means of the auxiliary drive 12 with its associated auxiliary drive 31 and the hydraulic resistance 44. Thus, a device for adjusting the temperature balance of an electric motor drive 10 is created, preferably for use in electrically powered mobile or quasi-mobile work machines. As already explained, the aforementioned hydraulic auxiliary system 12 is coupled to the main drive 23 via a connecting or coupling element 28.By means of the fixed or adjustable hydraulic resistance 44, a certain pressure drop can be generated at the output side E3 of the auxiliary drive 31 within a hydraulic circuit, here in the form of the supply circuit f. This pressure drop, in turn, generates a certain auxiliary torque in the additional drive shaft 30, which serves as the so-called auxiliary drive shaft of the device, via a mechanical-hydraulic component in the form of the auxiliary system 12. The auxiliary torque required to support the main drive 23 is then transmitted to the main drive shaft, i.e., to the additional output shaft 26, via the additional coupling point 28 as a connecting element. The additional main drive shaft, or drive shaft 22, is mechanically coupled to the motor output shaft 20 via the connection point 24.If the resistance changes via the hydraulic resistance device 44 on the output side E3 of the auxiliary drive 31, the auxiliary torque T on the further drive shaft 30 changes to support the electric motor 14. The torque T on the output shaft 20 of the electric motor 14 is equal to the torque on the further output shaft 26 minus the torque on the further drive shaft 30. Accordingly, the relationship also applies that the torque on the further output shaft 26 is equal to the torque on the drive shaft 22 for the main drive 32.

[0023] If a certain external torque of a hydraulic or mechanical nature is applied to the main drive 23 during braking of the work function, this can be counteracted by adjusting the hydraulic resistance 44 of the drive device, as already explained above. Accordingly, it is possible to regulate the temperature of the electric motor 14 and the inverter 16 by adjusting the auxiliary torque on the additional drive shaft 30 for the auxiliary drive 31, by adapting a hydraulic pressure on the output side E3 of the auxiliary drive 31 via the aforementioned fixed or adjustable resistance 44, which is preferably controlled via the electronic control unit in the form of the control device 36.Furthermore, it is possible to regulate the temperature of the electric motor 14 and its associated inverter 16 by reducing the torque in the respective main drive shaft 22, 26 of a mechanical-hydraulic component in the form of the main drive 23 by means of discrete wiring or proportional adjustment. Alternatively, a torque reduction could also be achieved by a gear-mechanical component using a transmission ratio, which is not shown.

[0024] In addition to the possibility of an adaptive torque delay for the electric motor 14, the drive device according to the invention can also be used to control the charging capacity of the storage device, preferably in the form of the battery 18, based on so-called performance data of the storage medium such as charge state, temperature, load.

[0025] In summary, the drive device according to the invention creates a type of retarder solution that is particularly suitable for use with electric machines. In the event of any type of failure on the electric drive side (electric motor 14 overheating, inverter 16 collapsing, lines A1, A2, B1, B2, etc. overloaded, battery 18 full), machines without a separate service brake can still be safely braked to a defined maximum speed or even brought to a standstill using the hydraulic auxiliary system 12 presented.

[0026] In particular, machines with closed-loop hydrostatic drive systems often do not have a separate service brake; braking is more or less achieved by adjusting the feed pump, which then regulates the machine. This is usually not a problem when using a diesel engine; however, it is with an electric motor. This can lead to the problems already described, which cannot be addressed with the classic hydraulic drivetrain setup.

[0027] In a specific solution, the auxiliary drive 31 of the auxiliary system 12 is used on the mechanically connected drive train to the main drive 23 in order to be able to generate a defined braking torque when needed or in the event of a fault. For this purpose, the hydraulic resistance 44, preferably in the form of a proportional pressure relief valve, is inserted into the working connection on the output side E3 of the auxiliary drive 31.

[0028] By applying a defined current to the electric motor side, the pressure and thus the braking torque follow the input signal. Preferably, an inverse pressure relief valve is used as the hydraulic resistance 44 to ensure maximum braking performance in the event of a power failure.

[0029] The "health status" of the main drive 23 is continuously monitored via a performance management system, which is preferably implemented in the control unit 36. If it is determined that battery 18, electric motor 14, etc. require a certain amount of relief, the retarder function (7-50 Nm) is proportionally activated and braking is applied.

[0030] Due to the modular design of the drive device according to the invention, it is possible to retrofit it into existing components on the respective work machine.

Claims

Patent claims Drive device with an electro-hydraulic drive (10) and with a hydraulic auxiliary system (12) which generates an auxiliary torque which, if necessary, counteracts a main torque of the electro-hydraulic drive (10). Drive device according to claim 1, characterized in that the auxiliary torque of the auxiliary system (12) is achieved by adjusting a hydraulic pressure via a preferably controllable hydraulic resistor (44). Drive device according to claim 1 or 2, characterized in that the temperature of the electric motor (14) is regulated by means of the auxiliary torque, preferably with the inclusion of an associated inverter (16) and / or a battery (18) supplying the electric motor (14).Drive device according to one of the preceding claims, characterized in that the electro-hydraulic drive (10) has a hydraulic pressure supply device (23), preferably in the form of a constant hydraulic pump, which is coupled via a drive train (22) to an output side (20) of the electric motor (14) and via a further drive train (26) to the drive side (30) of the auxiliary system (12) generating the auxiliary torque. Drive device according to one of the preceding claims, characterized in that the auxiliary system (12) which generates the auxiliary torque has a further pressure supply device (31), preferably in the form of a further constant-displacement hydraulic pump which, via the further drive train (26) of the one pressure supply device (23), generates a delivery volume flow which is guided at least partially via the hydraulic resistance (44). Drive device according to one of the preceding claims, characterized in that the hydraulic resistance (44) on the fluid output side (E3) of the further pressure supply device (31) generates a pressure gradient which, via the further drive train (26) of the one pressure supply device (23), imparts the respective auxiliary torque to the latter.Drive device according to one of the preceding claims, characterized in that the hydraulic resistance (44) is adjustable by means of a control device that can be controlled by an engine control unit (ECU) (36) and that receives sensor data from the electric motor (14) via a sensor device (38), which can preferably be controlled by the engine control unit (36). Drive device according to one of the preceding claims, characterized in that the electric motor (14) is supplied by at least one battery (18), which preferably delivers its current to the inverter (16) of the electric motor (14). Drive device according to one of the preceding claims, characterized in that the respective battery (18) is connected to the engine control unit (36) for charge capacity control. Use of a drive device, preferably according to one of the preceding claims, characterized in that by means of a hydromechanical overall system (10, 12) a defined torque is impressed on a drive (23) as required, which counteracts an undesirable, externally implied torque in a retarding manner.

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