DE102021208812A1 - Mobile work machine with several DC voltage networks - Google Patents

Abstract

The invention relates to a mobile working machine with a drive (20), working hydraulics and a cooling arrangement, each of which comprises at least one electric motor (51; 52; 53; 54), the mobile working machine being supplied with electrical energy exclusively from a battery. According to the invention, a high-voltage network (70) and a first and a second low-voltage network (81; 82) are provided, with the high-voltage network (70) being able to be supplied with electrical energy from a high-voltage battery (73).

Description

The invention relates to a mobile working machine according to the preamble of claim 1.

From the DE 10 2015 111 926 A1 a mobile working machine in the form of an industrial truck or a forklift is known. The mobile work machine has an electric drive and working hydraulics with an electrically driven working pump. All electrical functions are powered by a single rechargeable battery, typically 12V, 24V or 48V.

From the DE 10 2019 203 723 A1 a hydraulic system with a working pump and an electrically driven auxiliary pump is known.

From the U.S. 5,474,428 A an electrically driven lubricating oil pump for a transmission is known.

With the present invention, a mobile working machine is to be created which, like the known forklift truck, is operated entirely with energy from a rechargeable battery, the mobile working machine not carrying an internal combustion engine, as is the case, for example, with DE 10 2017 221 754 A1 the case is. The invention is aimed at mobile working machines that are heavier than a forklift truck, with the working hydraulics providing a higher hydraulic output. As an example, reference is made to a so-called telehandler or an extendable boom forklift, as is the case, for example, in U.S. 6,595,330 B1 is shown. It has hitherto been customary to supply such mobile working machines with energy by means of an internal combustion engine. The aim of the invention is therefore to move upwards the weight or power limit up to which a mobile work machine can be operated purely on battery power.

In addition to the battery capacity, the performance implemented in the system plays a very important role in mobile work machines. Hydraulic drives are characterized by the fact that very high performance can be implemented in the smallest of spaces. If you now want to provide such high performance by means of an electric motor, the waste heat caused by electrical currents becomes an ever greater problem with increasing performance. A further problem results from the fact that, for safety reasons, high-performance batteries are preferably separated from the remaining electrical system when the mobile working machine is in the standby state. At the same time, a mobile work machine has functions that should also be able to work in the standby state.

According to claim 1, it is proposed that a high-voltage battery be provided, the electrical nominal direct voltage of which is greater than 100 V, preferably greater than 300 V, and which can be electrically connected to a high-voltage network, the first and the second electric motor each having an associated first or second voltage converter can be supplied with electrical energy directly from the high-voltage network, with a first and a second low-voltage network being provided, which can each be supplied with electrical energy at least indirectly via an associated third or fourth voltage converter from the high-voltage network, with the first low-voltage network having a electrical direct voltage which is greater than an electrical direct voltage of the second low-voltage network and less than the nominal direct voltage of the high-voltage battery, the third electric motor supplying electrical energy directly from the first low-voltage network is possible, wherein at least one control device can be supplied with electrical energy directly from the second low-voltage network, wherein the at least one first, the second and the third electric motor can be controlled at least indirectly with the control device, with the second low-voltage network thus being permanently connected to an associated low-voltage battery That the control device is permanently supplied with electrical energy, as far as the relevant low-voltage battery is sufficiently charged.

The at least one actuator can be a hydraulic cylinder or a hydraulic motor. The voltage of the high-voltage battery is preferably 800 V or 400 V, the higher the voltage being selected the higher the maximum electrical power drawn from the high-voltage battery. The maximum voltage of the high-voltage battery is essentially limited by the necessary electrical insulation measures. The electrical DC voltage of the first low-voltage network is preferably 24 V. The electrical DC voltage of the second low-voltage network is preferably 12 V. The high-voltage network and/or the first low-voltage network and/or the second low-voltage network preferably each comprise an electrical positive line and an electrical negative line , at which different electrical potentials, which are most preferably essentially constant, are present. It goes without saying that, for example in the context of switching processes, significant fluctuations in the potentials mentioned can occur for a short time.

If the mobile work machine is not in operation or in standby mode, the high voltage battery preferably electrically separated from the high-voltage network, most preferably both battery poles are separated. A contactor is preferably used for this purpose. The first and/or the second electric motor are preferably each designed as a permanently excited synchronous motor, with the associated first or second voltage converter being designed as a DC/AC converter. The third electric motor is preferably designed as a DC motor with a commutator, it being possible for the commutator to be designed with brushes or electronically.

The components of the working hydraulics mentioned are preferably fluidically connected to one another in an open hydraulic circuit which includes a tank. The working pump is preferably designed as an axial piston pump with a swash plate design, it most preferably having a continuously adjustable displacement volume. The setting of the displacement volume is preferably controlled at least indirectly by the control device. The pressure fluid used in the working hydraulics is preferably a liquid and most preferably hydraulic oil.

Said endlessly circulating chain can be composed of a large number of chain links which are movable relative to one another. However, it can also be an endless elastic band, the running surface of which is designed analogously to a link chain. Said elastic band is preferably made of rubber, with the rubber enclosing endless traction cables, in particular steel cables.

It is conceivable that a DC/AC voltage converter is connected to the high-voltage grid, with which the AC voltage (50 Hz, single-phase or three-phase, 230 V or 400 V) customary in the public power grid can be provided. This AC voltage is preferably provided at a standardized socket, for example a CEE socket.

The control device preferably comprises at least one programmable digital computer, which is most preferably set up, in particular programmed, in such a way that it executes the control functions described in the context of the present application.

The high-voltage battery is preferably connected to the high-voltage grid when the mobile working machine is in use, while it is not connected during the rest of the standby time. In the standby time, however, the control device is supplied with electrical energy via the low-voltage battery. An operating element, for example a rotary switch, is preferably provided, with which the mobile working machine can be switched on and off, the switching status of the operating element being monitored by the control device, a switching device being provided via which the high-voltage battery can be connected to the high-voltage network, wherein the switching device is closed by the control device when the operating element is switched on. The switching device preferably has a switch, in particular a contactor, for both electrical conductors of the high-voltage network.

The high and low voltage batteries are preferably each a single battery assembly. It is conceivable that a number of such battery assemblies are connected in series or in parallel in order to increase the maximum voltage or the maximum current of the relevant high or low voltage battery. It goes without saying that the battery assemblies mentioned are each composed of a plurality of battery cells on the inside.

Advantageous developments and improvements of the invention are specified in the dependent claims.

It can be provided that the low-voltage battery can be charged from the associated first or second low-voltage network, with the corresponding electrical energy being able to be drawn from the high-voltage battery via the third or fourth voltage converter via the high-voltage network. It is therefore sufficient if the high-voltage battery alone can be charged from the outside. A charging device with which the low-voltage battery can be charged directly from the public power grid can be omitted.

Provision can be made for the first and the second low-voltage network to have a common ground conductor which is electrically connected to at least one electrically conductive chassis of the mobile working machine, with the third and the fourth voltage converter each being designed as a DC/DC converter with electrical isolation, so that the high-voltage network has no defined potential with respect to said ground conductor, the high-voltage network being electrically isolated from the chassis with both electrical poles. This results in a high level of electrical safety for the mobile working machine. The control device is preferably set up to monitor the electrical insulation between the high-voltage network and the chassis, for example by measuring the ohmic resistance between the chassis and the two high-voltage conductors network is measured. If one of the two measured ohmic resistances falls below a specified limit value, the desired electrical insulation is no longer given. The high-voltage battery is then preferably immediately disconnected from the high-voltage network, with the relevant switches, which are preferably designed as a contactor (https://de.wikipedia.org/wiki/Sch%C3%BCtz_(Switch)), being arranged immediately adjacent to the high-voltage battery .

Provision can be made for the third and/or the fourth voltage converter to be designed in such a way that electrical energy can only flow from the high-voltage network to the relevant first or second low-voltage network. This should in particular avoid discharging the low-voltage battery associated with the second low-voltage network, so that the control device can be supplied with electrical energy in standby mode for as long as possible before the relevant low-voltage battery is discharged.

Provision can be made for the mobile working machine to include a charging device which can be connected to the high-voltage battery in order to charge it from another power grid, the charging device being controllable at least indirectly by the control device. According to the invention, the control device is permanently supplied with electrical energy. It can therefore recognize that a charging plug has been plugged into a charging connection of the charging device, so that the charging process can preferably be started by this alone, provided that the mobile work machine is not in operation or in standby mode. If the mobile working machine is in operation, as soon as the charging plug is plugged into the charging socket on the mobile working machine, it is preferably deactivated by the control device in such a way that at least the at least one first and the second electric motor can no longer be supplied with electric power from the high-voltage network be supplied with energy so that they no longer move. The additional power grid is preferably the public power grid, which is operated with AC voltage, with three phases being used most preferably. It is conceivable that the additional power grid is operated with DC voltage. The charging socket or the charging plug are preferably designed according to the CCS standard (https://de.wikipedia.org/wiki/Combined_Charging_System). The charging device charges the high-voltage battery until it is full or until the driver uses a control to stop charging. During charging, the control device preferably monitors the mobile working machine for compliance with electrical safety. In the event of a fault, the high-voltage battery is preferably disconnected from the high-voltage network at two poles, with the control device switching off the charging device.

Provision can be made for the at least one cooling device to comprise a first cooling device, with which pressure fluid circulating in the working hydraulic system can be cooled. Cooling devices are common in hydraulic circuits. The inventive connection of the third electric motor in question to the electrical system of the mobile working machine achieves the lowest possible electrical energy consumption for the first cooling device, so that the mobile working machine can be operated for a long time without the high-voltage battery having to be recharged.

It can be provided that the at least one cooling device comprises a second cooling device, with which the first electric motor and/or the second electric motor and/or the first voltage converter and/or the second voltage converter and/or the charging device can be cooled. As a result, the maximum electrical power that can be converted can be significantly increased. In particular, the second electric motor and the second voltage converter must convert a high level of electrical power in a very small space in order to provide the mechanical power required to drive the working pump. The second cooling device preferably uses a cooling liquid to cool the components mentioned. The second and/or the third cooling device preferably includes a cooling pump which is drive-connected to a sixth electric motor, the sixth electric motor being connected to the first low-voltage network. The inventive connection of the third electric motor in question to the electrical system of the mobile working machine achieves the lowest possible electrical energy consumption for the second cooling device, so that the mobile working machine can be operated for a long time without the high-voltage battery having to be recharged.

Provision can be made for the mobile working machine to have a closed driver's cab, with the air temperature in the driver's cab being adjustable to a predetermined temperature by means of an air conditioning system, with the at least one cooling device comprising at least a third cooling device which is part of the air conditioning system. The inventive connection of the third electric motor in question to the electrical system of the mobile working machine achieves the lowest possible electrical energy consumption for the third cooling device, so that the mobile working machine can be operated for a long time without the high voltage having to be recharged battery is required. In addition to the third cooling device, the air conditioning system can also include a heating device, so that the driver's cab can also be cooled and heated. The heating device can preferably be supplied with electrical energy directly from the high-voltage circuit. The waste heat occurring in the second cooling device is preferably used to heat the driver's cab. The air conditioner can set the desired temperature by means of temperature regulation or temperature control.

Provision can be made for the first electric motor to be drive-connected to the at least one wheel and/or to the at least one endlessly circulating chain via a gear, with the gear being able to be lubricated by means of a lubricating pump, the lubricating pump being drive-connected to a fourth electric motor , wherein the fourth electric motor can be supplied with electrical energy directly from the first low-voltage network, with its rotational movement being controllable at least indirectly by the control device. The inventive connection of the fourth electric motor to the electrical system of the mobile working machine achieves the lowest possible electrical energy consumption for lubricating the transmission, so that the mobile working machine can be operated for a long time without the high-voltage battery having to be recharged.

Provision can be made for a rotational speed and/or a torque of the first electric motor to be taken into account when controlling the rotational movement of the fourth electric motor. In this way, adequate lubrication of the transmission and consequently less wear on the transmission can be ensured in every operating state of the mobile working machine. As a result of the electrical connection according to the invention, the quantities mentioned, speed and torque of the first electric motor are available in the control device anyway, so that they can be used as proposed without any problems.

Preferably, the variables mentioned, speed or torque of the first electric motor, are considered over a predetermined period of time in order to determine the lubricating volume flow or the rotational movement of the fourth electric motor. For example, an average of the speed or torque can be formed over the period of time mentioned.

When controlling the fourth electric motor, a temperature of the lubricant and/or a temperature of the environment can be taken into account, which is preferably measured in each case by means of a temperature sensor. In this way, a temperature-dependent lubricating effect of the lubricant can be taken into account, which is caused, for example, by a temperature-dependent viscosity. Furthermore, the preferably liquid lubricant can be used to cool the transmission if required. It is conceivable that the flow of lubricant or the speed of the fourth electric motor is increased beyond what is absolutely necessary for lubrication in order to reduce the noise caused by the transmission. Here, the vibration-damping effect of the lubricant is used. The lubricant preferably circulates in a lubricating circuit that includes the lubricating pump. It is conceivable that the lubrication circuit includes a cooling device for the lubricant.

Immediately after the mobile working machine has been started up, a lubricant flow is preferably set which is at least 30%, preferably at least 50%, of a maximum lubricant flow in order to fill all the lubrication channels and lubrication points with lubricant. Furthermore, the lubricant is to be heated in this way so that it reaches the ideal operating temperature without the mobile work machine having to be moved for this purpose. The lubrication pump or the fourth electric motor is preferably provided with a speed sensor which is connected to the control device. This allows the control device to check whether the lubricating pump actually reaches the speed requested by the control device. This can happen once when the mobile working machine is started up and/or periodically at predetermined time intervals. After the mobile working machine has been shut down, the fourth electric motor or the lubricating pump preferably continues to run for a predetermined period of time in order to cool down the transmission.

Insofar as the mobile working machine includes, in addition to the transmission, further components which require lubrication, these are preferably likewise lubricated with the named lubricating pump, so that only a single lubricating pump is required.

Provision can be made for the working hydraulics to be designed as an open hydraulic circuit which includes a tank, with at least one auxiliary pump being provided, via which pressurized fluid can be drawn in from the tank, with the at least one auxiliary pump each being drive-connected to an associated fifth electric motor , wherein the fifth electric motor can be supplied with electrical energy directly from the first low-voltage network, with its rotational movement being controllable at least indirectly by the control device. The formwork according to the invention By connecting the fifth electric motor to the electrical system of the mobile working machine, the lowest possible electrical energy consumption for providing auxiliary pressure with the auxiliary pump is achieved, so that the mobile working machine can be operated for a long time without the high-voltage battery having to be recharged.

The pressure side of the at least one auxiliary pump can, for example, provide an auxiliary pressure that is independent of the working pressure of the working pump. With this, for example, pilot valves of the working hydraulics can be actuated. Furthermore, a hydraulic steering of the mobile work machine can be supplied with the auxiliary pressure. A hydraulic power brake can also be supplied with the auxiliary pressure. The power brake can be designed as a service brake or as a parking brake. In particular, a service brake enables the moving mobile working machine to be braked, which is not the case with a parking brake. The auxiliary pressure can also be used to hydraulically adjust a displacement volume of the working pump. This is advantageous, for example, when the working pump can be adjusted beyond the displacement volume of zero, so that the working pressure, particularly when the setting is zero, cannot be readily used to adjust the displacement volume.

A separate auxiliary pump can be provided for each of the functions mentioned. However, a common auxiliary pump can also be used, which serves all of the functions mentioned. Mixed forms are also conceivable, with the respectively most favorable variant being selected on the basis of the energy consumption to be expected and the production costs to be expected. The auxiliary pressure can be connected to a hydraulic accumulator so that the auxiliary pressure is still available for a predetermined minimum period of time even if the associated auxiliary pump fails. This is particularly advantageous when the auxiliary pump supplies the steering or the service brake, ie functions that are intended to work particularly safely and reliably. Said hydraulic accumulator can be designed as a diaphragm accumulator. If the first low-voltage network supplies safety-related functions such as the steering or the service brake, the first low-voltage network is preferably also connected to an associated low-voltage battery, with the two electrical conductors of the low-voltage network preferably being directly and permanently connected to the relevant low-voltage battery.

An additional valve can be installed as a redundancy for supplying the control pressure, which supplies the control pressure circuit from the high-pressure circuit as soon as the auxiliary pump fails. To do this, the working pressure must be reduced to the control pressure. The valve then also fills the hydraulic accumulator. Preferably the valve is set to operate only when the control pressure falls below the minimum pressure of the auxiliary pump.

If an auxiliary pump supplies several functions, a check valve is preferably assigned to each function, which only allows a flow of fluid from the auxiliary pump to the relevant function. If an overload occurs on one function, the other functions are not disturbed.

It can be provided that at least one auxiliary pump is connected to a hydraulic accumulator with its pressure side, a pressure sensor being provided with which the pressure in the hydraulic accumulator can be measured, the pressure sensor being at least indirectly connected to the control device, the fifth electric motor in question being the control device is only rotated when the pressure measured by the pressure sensor falls below a predetermined limit value.

The functions mentioned above, which are preferably supplied by the at least one auxiliary pump, often only require hydraulic energy for a short time, and it can then happen that a high level of hydraulic power is required. With the proposed system, the functions mentioned can be supplied with a comparatively small and inexpensive fifth electric motor. The maximum electrical power requirement to be served from the first low-voltage network is particularly low. The fifth electric motor can be switched on and off in the manner of a two-point control. However, it is also conceivable for the fifth electric motor to be operated at a continuously variable speed, in order to enable power control, for example. A pressure reducing valve can be provided, with an input side of the pressure reducing valve being connected to a pressure side of the working pump, with an output side of the pressure reducing valve being connected to an associated auxiliary pressure. As a result, an exceptionally high power requirement for a short period of time in relation to the auxiliary pressure in question can be served.

The fifth electric motor is preferably switched off again when the pressure measured by the pressure sensor exceeds a further predetermined limit value.

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

• 1 eine grobschematische Seitenansicht einer erfindungsgemäßen mobilen Arbeitsmaschine;
• 2 einen Schaltplan, welcher das Hochspannungsnetz und das erste und das zweite Niederspannungsnetz umfasst;
• 3 einen Schaltplan der Kühlanordnung; und
• 4 einen hydraulischen Schaltplan, welcher die Hilfspumpe umfasst.

The invention is explained in more detail below with reference to the accompanying drawings. It shows:

• 1 a highly schematic side view of a mobile working machine according to the invention;
• 2 a circuit diagram which includes the high-voltage network and the first and the second low-voltage network;
• 3 a circuit diagram of the cooling arrangement; and
• 4 a hydraulic circuit diagram that includes the auxiliary pump.

1 shows a roughly schematic side view of a mobile working machine 10 according to the invention. The mobile working machine 10 is designed, purely by way of example, as a telehandler, ie in the manner of a forklift truck which includes a telescoping arm 17 . The mobile work machine 10 has a chassis 11, which typically consists of electrically conductive steel. In the present case, four wheels 22 are rotatably attached to the chassis 11, the front wheels 22 preferably being steerable. The wheels 22 can preferably be braked with a hydraulic power brake.

The working hydraulics 30 of the mobile working machine 10 in the present case includes three actuators 33, which are each designed as hydraulic cylinders. An actuator 33 moves the telescoping arm 17 in and out. Another actuator 33 raises the telescoping arm 17 or lowers it. With a further actuator 33, the fork at the end of the telescoping arm 17 can be moved.

A driver's cab 15 is fastened to the chassis 11, in which the driver of the mobile working machine sits. Accordingly, operating elements 13 are provided there, with which on the one hand the travel movement and on the other hand the movement of the working hydraulic system 30 can be controlled. The operating elements 13 can include at least one joystick, a steering wheel, at least one pedal, at least one rotary switch, at least one button and/or a touch screen.

2 shows a circuit diagram showing the high-voltage network 70 and the first and the second low-voltage network 81; 82 includes. The high-voltage network 70 comprises a plus and a minus conductor 71; 72. A high voltage battery 73 is connected to this via contactors (not shown). The high-voltage battery 73 has a nominal voltage of 800 V, for example. It is charged by a charging device 74, which is also connected to the high-voltage network 70, with the electrical energy required for this being taken from the public electricity network, for example. The charging device 74 includes a charging socket 75, which is designed, for example, according to the CCS standard. The charging socket 75 can include DC voltage contacts, so that the DC voltage required for landing can be fed 76 directly into the high-voltage network 70 .

Next are a first and a second voltage converter 61; 62 connected to the high-voltage network 70. These convert the DC voltage of the high-voltage network 70 into a preferably three-phase AC voltage, with which the first and the second electric motor 51; 52 can be operated. The first and second electric motors 51; 52 are preferably each designed as a permanently excited synchronous motor. The first electric motor 51 drives at least part of the wheels (no. 22 in 1 ) of the mobile working machine.

The second electric motor 52 drives a working pump 31, which is preferably designed as an axial piston pump with a swash plate design. The working pump 31 is part of an open hydraulic circuit, which the actuators (No. 33 in 1 ) and a tank (No. 32 in 4 ) includes. All tank symbols in the 2 and 4 same tank. Each actuator is assigned a control valve with which its direction of movement and its speed of movement can be controlled. The control valves are preferably combined to form a valve block 34 .

Next are a first and a second low-voltage network 81; 82 provided. These have a common ground conductor 83, which is connected to the electrically conductive chassis (No. 11 in 1 ) connected. They also have a first and a second work leader 84; 85. The first low-voltage network 81 carries an electrical direct voltage of 24 V, for example, with the second low-voltage network carrying an electrical direct voltage of 12 V. The first and the second low-voltage network 81; 82 are each connected to an associated low voltage battery 86 which has a corresponding DC voltage rating. The first low-voltage network 81 is supplied with electrical energy from the high-voltage network 70 via a third voltage converter 63 . The second low-voltage network 82 is a fourth voltage converter 64 from the High-voltage network 70 indirectly supplied with electrical energy. It is conceivable for the second low-voltage network 82 to be supplied with electrical energy from the first low-voltage network 81 via a voltage converter. The third and the fourth voltage converter 63; 64 each bring about a potential separation, whereby they preferably only allow electrical energy to flow from the high-voltage network 70 to the relevant first or second low-voltage network 81; allow 82.

A fourth electric motor 54 is connected to the first low-voltage network 81 and drives an auxiliary pump 35 via which the transmission 20 is supplied with liquid lubricant, in particular lubricating oil. Next several third electric motors 53 are connected, each driving a fan wheel 45 of a cooling device, wherein in 2 only a single third electric motor 53 is shown. The third electric motors 53 and the fourth electric motor 54 are preferably in the form of DC motors.

A control device 12 is connected to the second low-voltage network 82 in such a way that it is permanently supplied with electrical energy if the associated low-voltage battery 86 is sufficiently charged. The control device 12 preferably comprises a programmable digital computer.

The thermal management 90 includes in addition to the in 3 Components shown other components that are connected to the high-voltage network 70. Namely, a heater 92 so that the air conditioner can not only cool but also heat. Furthermore, an air conditioning compressor 91, which liquefies the coolant circulating in the air conditioning system, so that it can develop its cooling effect through evaporation.

The various fuses 14, which interrupt the respective flow of current if the current there exceeds a predetermined limit value, should also be pointed out. Each fuse 14 is assigned to an electrical consumer on the high-voltage network 70 .

3 shows a circuit diagram of the cooling arrangement 40. The cooling arrangement 40 comprises a first, a second and a third cooling device 41; 42; 43. The first cooling device 41 comprises a finned heat exchanger 46, which is part of the above-mentioned open hydraulic circuit, it being preferably arranged in a bypass flow. It is blown on by a fan wheel 45 so that pressure fluid flowing through the lamellar heat exchanger 46 is cooled. The cooling effect can be influenced, among other things, by the speed and the duty cycle of the relevant third electric motor (No. 53 in 2 ) can be set.

The second cooling device 42 is used to cool various electrical components of the mobile working machine. It also includes a lamellar heat exchanger 46 which is blown on by a fan wheel 45 . In the present case, the corresponding coolant circuit has a total of four cooling pumps 44 which are each driven by a sixth electric motor 56 . The sixth electric motors 56 are preferably each connected to the first low voltage circuit (No. 81 in 2 ) connected. The corresponding cooling circuit has a branched design, with the first and the second electric motor 51; 52, the first, second, third and fourth voltage converters 61; 62; 63; 64 and the transmission 21 includes. The various branches of the cooling circuit are brought together in the coolant collector 48 so that the coolant flow can flow back to the finned heat exchanger 46 in a collected form. The coolant circulating in the second cooling device 42 is liquid, and it remains permanently in the liquid phase.

The third cooling device 43 is part of an air conditioning system with which the driver's cab (No. 15 in 1 ) is air-conditioned. The third cooling device 43 includes two lamellar heat exchangers 46 which are each blown on by a fan wheel 45 . The coolant is circulated by means of a cooling pump 44, being liquefied and vaporized again during one circulation in order to achieve the cooling effect.

A separate circuit is assigned to the heating device 92 . Reference should also be made to the reservoirs 47, each of which is assigned to a cooling circuit. The coolant supply there is used to replace coolant lost through leaks.

4 FIG. 12 shows a hydraulic circuit diagram that includes the auxiliary pump 35. FIG. The auxiliary pump 35 is designed, for example, as an external gear pump. It draws in pressurized fluid from a tank 32 and subjects it to an auxiliary pressure 39 which can be used for the purposes explained above. The auxiliary pump 35 is connected to the auxiliary pressure 39 via a non-return valve 38 , the non-return valve 38 only allowing a volume flow from the auxiliary pump 35 to the auxiliary pressure 39 . The auxiliary pressure 39 is connected to a hydraulic accumulator 36, which is preferably designed as a diaphragm accumulator.

With the pressure sensor 37, which is connected to the control device 12, the auxiliary pressure 39 is measured. The controller 12 switches the fifth electric motor 55, which drives the auxiliary pump 35, on and off in the simplest case. A speed adjustment in several speed levels or infinitely variable is also possible. In the present case, the fifth electric motor 55 is supplied with DC voltage from the first low-voltage network 81, this being a DC voltage motor.

Reference List

10

mobile working machine

11

chassis

12

control device

13

control element

14

fuse

15

driver's cabin

16

air conditioner

17

telescopic arm

20

traction drive

21

transmission

22

wheel

23

lubrication pump

30

working hydraulics

31

working pump

32

tank

33

actuator

34

Valve block with control valve

35

auxiliary pump

36

hydraulic accumulator

37

pressure sensor

38

check valve

39

auxiliary pressure

40

cooling arrangement

41

first cooling device

42

second cooling device

43

third cooler

44

cooling pump

45

fan wheel

46

finned heat exchanger

47

reservoir

48

coolant collector

51

first electric motor for traction

52

second electric motor for working pump

53

third electric motor for fan wheel

54

fourth electric motor for lubrication pump

55

fifth electric motor for auxiliary pump

56

sixth electric motor for cooling pump

61

first voltage converter

62

second voltage converter

63

third voltage converter

64

fourth voltage converter

70

high voltage grid

71

Plus conductor of the high-voltage network

72

Negative conductor of the high-voltage network

73

high voltage battery

74

loading device

75

charging socket

76

DC feed

81

first low-voltage grid

82

second low-voltage network

83

Ground conductor of the first and the second low-voltage network

84

Work manager of the first low-voltage network

85

Work manager of the second low-voltage network

86

low voltage battery

90

thermal management

91

air conditioning compressor

92

heating device

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102015111926 A1 [0002]
• DE 102019203723 A1 [0003]
• US5474428A [0004]
• DE 102017221754 A1 [0005]
• US6595330B1 [0005]

Claims (12)

Mobile working machine (10) with a travel drive (20), working hydraulics (30) and a cooling arrangement (40), wherein the travel drive (20) comprises at least one first electric motor (51), which is each equipped with at least one rotatable wheel (22) and /or is drive-connected to at least one endlessly revolving chain, the working hydraulic system (30) comprising a working pump (31) and at least one actuator (33), each with an associated control valve (34), the named components of the working hydraulic system (30) in are fluidically connected to one another in a hydraulic circuit, the working pump (31) being drive-connected to a second electric motor (52), the cooling arrangement (40) comprising at least one cooling device (41; 42; 43), the cooling device (41; 42 43) comprises a lamellar heat exchanger (46) with a rotatable fan wheel (45), the fan wheel (45) being in drive connection with an associated third electric motor (53). t, characterized in that a high-voltage battery (73) is provided, the electrical nominal direct voltage of which is greater than 100 V, preferably greater than 300 V, and which can be electrically connected to a high-voltage network (70), the first and second electric motors (51; 52) can be supplied with electrical energy directly from the high-voltage network (70) via an assigned first or second voltage converter (61; 62), with a first and a second low-voltage network (81; 82) being provided, which are each supplied at least indirectly via a assigned third or fourth voltage converter (63; 64) can be supplied with electrical energy from the high-voltage network (70), the first low-voltage network (81) carrying an electrical direct voltage which is greater than an electrical direct voltage of the second low-voltage network (82) and less than is the nominal DC voltage of the high-voltage battery (70), with the third electric motor (53) being able to be supplied with electrical energy directly from the first low-voltage network (81), with at least one control device (12) being supplied with electrical energy directly from the second low-voltage network (82). is supplied, with the control device (12) of the at least one first, the second ite and the third electric motor (51; 52; 53) can be controlled at least indirectly, with the second low-voltage network (82) being permanently connected to an associated low-voltage battery (86) in such a way that the control device (12) is permanently supplied with electrical energy, provided the relevant low-voltage battery (86) is sufficiently charged. Mobile work machine (10) after claim 1 , wherein the low-voltage battery (86) can be charged from the associated first or second low-voltage network (81; 82), the corresponding electrical energy being taken from the high-voltage battery ( 73) can be removed. Mobile working machine (10) according to one of the preceding claims, wherein the first and the second low-voltage network (81; 82) have a common ground conductor (83) which is electrically connected to at least one electrically conductive chassis (11) of the mobile working machine (10). , wherein the third and the fourth voltage converter (63; 64) are each designed as DC/DC converters with potential isolation, so that the high-voltage network (70) has no defined potential with respect to the said ground conductor (83), the high-voltage network (70) is electrically isolated from the chassis (11) with both electrical poles. Mobile working machine (10) according to one of the preceding claims, wherein the third and/or the fourth voltage converter (63; 64) is designed in such a way that electrical energy can only flow from the high-voltage network (70) to the relevant first or second low-voltage network (81). is. Mobile working machine (10) according to one of the preceding claims, wherein the mobile working machine comprises a charging device (74) which can be connected to the high-voltage battery (73) in order to charge it from a further power supply system, the charging device (74) being at least indirectly operated by the control device (12) can be controlled. Mobile work machine (10) according to one of the preceding claims, wherein the at least one cooling device comprises a first cooling device (41) with which in the working hydraulic system (30) circulating pressure fluid can be cooled. Mobile working machine (10) according to one of the preceding claims, wherein the at least one cooling device comprises a second cooling device (42) with which the first electric motor (51) and/or the second electric motor (52) and/or the first voltage converter (61) and/or the second voltage converter (62) and/or the charging device (74) can be cooled. Mobile working machine (10) according to one of the preceding claims, wherein the mobile working machine (10) comprises a closed driver's cab (15), the air temperature in the driver's cab (15) being adjustable to a predetermined temperature by means of an air conditioning system (16), the at least one cooling device comprises at least a third cooling device (53), which is part of the air conditioning system (16). Mobile working machine (10) according to one of the preceding claims, wherein the first electric motor (51) is drive-connected via a gear (21) to the at least one wheel (22) and/or to the at least one endlessly circulating chain, the gear ( 21) can be lubricated by means of a lubricating pump (23), wherein the lubricating pump (23) is drive-connected to a fourth electric motor (54), wherein the fourth electric motor (54) can be supplied with electrical energy directly from the first low-voltage network (81), wherein its rotational movement can be controlled at least indirectly by the control device (12). Mobile work machine (10) after claim 9 , A speed and/or a torque of the first electric motor (51) being taken into account when controlling the rotational movement of the fourth electric motor (54). Mobile working machine (10) according to one of the preceding claims, wherein the working hydraulic system (30) is designed as an open hydraulic circuit which comprises a tank (32), wherein at least one auxiliary pump (35) is provided, via which pressure fluid from the tank (32 ) can be sucked in, with the at least one auxiliary pump (35) being in drive connection with an associated fifth electric motor (55), with the fifth electric motor (55) being able to be supplied with electrical energy directly from the first low-voltage network, with its rotational movement being controlled at least indirectly by the Control device (12) can be controlled. Mobile work machine (10) after claim 11 , at least one auxiliary pump (35) being connected to a hydraulic accumulator (36) with its pressure side, a pressure sensor (37) being provided with which the pressure in the hydraulic accumulator (36) can be measured, the pressure sensor (37) being connected to the control device (12) is connected at least indirectly, with the relevant fifth electric motor (55) only being rotated by the control device (12) when the pressure measured by the pressure sensor (37) falls below a predetermined limit value.

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