Coolant circuit for a self-propelled work machine with multiple electric drive components

Abstract

Coolant circuit for a self-propelled work machine with multiple electric drive components (8-19), including: - a coolant pump (2) for generating a flow of coolant circulating in the coolant circuit (1); - a heat exchanger (3) for the removal of heat energy stored in the coolant; - at least two parallel circuits (4-7) designed to circulate the coolant past their respective drive components (8-19) for the purpose of absorbing heat energy; and - at least one connecting line (21) fluidically connecting at least two of the circuits (4-7) and designed to transfer coolant from a first circuit (4-7) to a second circuit (4-7) with at least one valve (22) for opening and closing the connecting line (21) and / or for varying the volume flow of the coolant passing through the connecting line (21).

Description

[0001] The present invention relates to a coolant circuit by means of which the thermal power generated by the electrical drive components of a self-propelled drive machine, in particular a mobile crane, is dissipated, thus cooling the electrical drive components. The present invention further relates to a self-propelled work machine, in particular a mobile crane, with one or more such coolant circuits.

[0002] In known work machines, including mobile cranes, it is common practice to operate the individual (crane) functions using so-called hydraulic drives. In these drives, one or more hydraulic pumps, powered, for example, by mechanical (shaft) power, are fluidly connected to hydraulic cylinders or hydraulic motors of the individual (crane) functions to ultimately drive them. In hybrid-electric or fully electric drive concepts, these hydraulic drives are at least partially supplemented or replaced by electric drives. Electric drives typically comprise electric motors with associated inverters for power and position control. The required electrical power is provided by a generator, which is driven, for example, by an internal combustion engine in the undercarriage of the work machine, or by an external electrical power supply.A machine's own energy storage unit can also be provided to supply power, although a combination of the aforementioned supply options is also conceivable. Braking individual drives releases energy, which can then be used to charge the energy storage unit. If the energy storage unit is fully charged, this power often has to be dissipated via an electrical resistor, a so-called brake chopper, which releases heat energy. Energy storage units or accumulators, electric motors and associated inverters, including their power electronics and control systems, place high demands on compliance with permissible operating temperatures. If so-called limit operating temperatures are exceeded or not met, the performance of the relevant components is reduced to protect the system.To avoid these power reductions, which are detrimental to machine operation, such electric drive components are cooled using often complex mechanisms. Liquid cooling systems, i.e., cooling systems with a liquid coolant (usually water-glycol mixtures), are widely used for this purpose. For the sake of simplicity, the following refers to a mobile crane as a specific embodiment of a self-propelled machine. The concepts described below are, of course, applicable to any type of self-propelled machine and are therefore not limited to mobile cranes.

[0003] The drive components typically found in cranes for the individual crane functions include hydraulic pumps, which drive associated hydraulic motors or hydraulic cylinders to operate, for example, luffing gear, hoisting gear, telescopic gear, and slewing gear. The publications DE 102015 007 235 A1 and DE 10 2021 200 734 A1 describe cooling circuits for cooling the electrical drive components of a moving machine.

[0004] The object of the present invention is to provide a cooling system that efficiently meets the cooling power requirements of various electric drive components in fully electric or hybrid-electric drive concepts. The present invention recognizes that in mobile crane operation, not all drives are typically operated simultaneously at high utilization and the associated cooling power requirements. An intelligent design of the cooling system therefore offers considerable savings potential.

[0005] This problem is solved by the subject matter of independent patent claim 1 and co-ordinate patent claim 8.

[0006] According to the present invention, a coolant circuit for a self-propelled work machine with several electric drive components is proposed, wherein the coolant circuit comprises the following: - a coolant pump for generating a flow of coolant circulating in the coolant circuit; - a heat exchanger for removing thermal energy stored in the coolant; - at least two circuit strands running parallel to each other, which are designed to guide the coolant past the drive components assigned to them in order to absorb thermal energy; and - at least one connecting strand fluidically connecting at least two of the circuit strands and designed to transfer coolant from a first circuit strand to a second circuit strand, with at least one valve for opening and closing the connecting strand and / or for varying a volume flow of the coolant guided through the connecting strand.

[0007] In other words, the coolant circuit according to the invention comprises, in at least one partial area, several parallel lines for cooling the drive components assigned to them. These lines can be fed via a common supply line and flow into a common return line. The coolant pump can also be arranged in the supply line, while the heat exchanger / cooler can be arranged in the return line.

[0008] By providing at least two circuit lines arranged parallel to each other, the present invention makes it possible to distribute the individual drive components among the provided lines according to their cooling power requirements. This makes it possible to distribute the individual drive components among the available circuit lines according to their heat input in such a way that the heat input is as uniform as possible throughout the coolant circuit. Locally excessive thermal input is thus avoided.

[0009] In one embodiment, the circuit strands can cause a substantially equal pressure loss in the coolant flow over their extent, in particular wherein at least one of the circuit strands has a throttle element by means of which the pressure loss of the circuit strand in question is adjusted to the pressure loss of the at least one further circuit strand.

[0010] In other words, an essentially identical backpressure is generated in each circuit train. This is made possible by a targeted selection of the drive components arranged in the respective circuit trains. This makes it possible to ensure that the coolant volume flows passed through the respective circuit trains remain in a fixed ratio throughout crane operation, but can have considerably different amounts between them. If, even with a clever combination and arrangement of the drive components provided for the respective crane, it is not possible to generate sufficiently similar backpressures or pressure drops in the individual circuit trains, throttling elements such as throttles, orifices, or throttle valves can be used in individual circuit trains to generate satisfactorily identical pressure drops or backpressures across the circuit trains.

[0011] According to a further example, the drive components in at least one of the circuit strands can be arranged according to the level of their respective limit operating temperature and in the flow direction of the coolant starting with the lowest limit operating temperature.

[0012] In other words, a further increase in efficiency is achieved by first directing the coolant flow in at least one of the circuit lines past the drive components whose limit operating temperature is the lowest, i.e., where a necessary power reduction due to excessive operating temperature is first expected. With more than three drive components in a circuit line, their arrangement can be as follows: First, the coolant flowing through the circuit line reaches the drive component with the lowest limit operating temperature, then the drive component with a medium limit operating temperature, and finally the drive component with the highest limit operating temperature.This arrangement of the drive component allows the available coolant flow to be used more efficiently and consequently the coolant circuit, including the coolant pump and the piping, can be dimensioned smaller.

[0013] Furthermore, the drive components within a circuit can be arranged according to their heat loss and / or their safety relevance. Specifically, this could mean that the coolant passes through the most safety-relevant component first, followed by less safety-relevant components. Components with the lowest heat loss could also be divided first, followed by components with higher heat loss. It is also conceivable that the arrangement of components within a circuit could be based on at least two of the criteria: operating temperature limit, heat loss, and safety relevance.

[0014] The circuit lines can be arranged between the coolant pump and the heat exchanger, viewed in the direction of coolant flow. For example, the coolant pump can be located in the supply line upstream of the individual circuit lines, and the heat exchanger or cooler can be located in the return line downstream of the individual circuit lines. Of course, it would also be conceivable to arrange the heat exchanger in the supply line and / or the coolant pump in the return line.

[0015] The connecting line makes it possible to transfer coolant from one circuit line to another running parallel to it in order to supply drive components with coolant at a lower or higher temperature than would be possible via the "separate" circuit line. Such a "cross-supply" can be provided whenever an excessively low or excessively high operating temperature of the drive component(s) to be cooled is detected or possibly expected. The opening and closing of the connecting line can be accomplished by one or more optionally switchable valves. It is also conceivable that all or only a portion of the coolant flow is taken from the donating circuit line. It is also conceivable that in the receiving circuit line, the actual coolant supply via the supply line is completely or only partially closed.

[0016] In one embodiment, the connecting line connects, in the direction of flow of the coolant, a first circuit line downstream of at least one drive component in the first circuit line with a second circuit line upstream of at least one drive component in the second circuit line. With such an arrangement, it is possible to use the waste heat from individual drive components, which was transferred to the coolant in the first circuit line, to heat one or more drive components in the second circuit line. This is particularly useful when drive components for crane operation must first be brought up to operating temperature in order to avoid performance reductions. This is particularly conceivable in connection with battery storage systems or accumulators.All conceivable drive components already present for the crane functions can serve as the heat source, but it is also possible to provide heating devices, in particular electrically operated heating devices.

[0017] Although it is conceivable for the function of the at least one connecting line that the at least one valve is operated manually, for example by crane personnel, the at least one valve can be designed to be controllable, in particular by means of a control device, in order to automatically guide a volume flow of coolant via the connecting line in accordance with the coolant requirement of a drive component supplied with coolant via the connecting line.

[0018] In a further embodiment, the control device can have at least one sensor that detects the temperature of a drive component and can selectively cause the at least one valve to open or close when the temperature falls below or exceeds a predefined temperature threshold for the drive component.

[0019] If it is determined that heating a drive component is necessary or even beneficial for operation, the connecting line can be opened using the preferably electronic control unit to use the waste heat from one drive component to heat another drive component. Once the required operating temperature is reached, the control unit can close the connecting line again. The same applies if drive components require additional cooling that can be met via the connecting line.

[0020] A further aspect of the present invention relates to a self-propelled work machine, in particular a mobile crane, with a plurality of electric drive components and a coolant circuit according to one of the embodiments described above.

[0021] In a further embodiment, the self-propelled work machine, in particular the mobile crane, can have several such coolant circuits, which can have the same, similar, or different configurations. For a work machine or crane with an undercarriage and a superstructure rotatably mounted thereon, it would initially be conceivable to provide a single coolant circuit, extending, for example, through the rotary union between the superstructure and undercarriage. Alternatively, it is conceivable to provide separate, independent coolant circuits for the undercarriage and the superstructure.

[0022] The present invention is explained in more detail below using preferred embodiments and with reference to the accompanying figures. The invention may include all features described herein individually or in any meaningful combination.

[0023] They show: Fig. 1: a coolant circuit for a crane undercarriage; Fig. 2: a coolant circuit for a crane superstructure.

[0024] In the Fig. 1 shows a coolant circuit 1 for a crane undercarriage, which, in addition to a supply line comprising the coolant pump 2 and a return line comprising the heat exchanger 3, has four parallel circuit branches 4 to 7 which extend between the supply line and the return line. The coolant pumped by the pump 2 is supplied to all circuit branches 4 to 7 in order to cool the electrical drive components 8 to 13 arranged in the respective circuit branches 4 to 7, in other words to dissipate their waste heat. The heated coolant is supplied via a common return line to the heat exchanger 3, in which the stored thermal energy is extracted from the coolant. An expansion tank 25 arranged in the direction of flow of the coolant between the heat exchanger 3 and the pump 2 serves to compensate for thermally induced volume changes of the coolant.

[0025] In the Fig. 1, all circuit branches 4 to 7 have approximately the same pressure loss or generate approximately the same back pressure. This ensures that the coolant volume flows guided through the respective circuit branches 4 to 7 are in a fixed size ratio, without individual circuit branches 4 to 7 being oversupplied or undersupplied. Since circuit branch 7 with the inverter 12 for an intermediate circuit of the electrical power supply and the inverter 13 of the generator 10 has the greatest pressure loss, the remaining circuit branches 4 to 6, whose associated drive components 8 to 11 cause a lower pressure loss, are provided with throttle valves 20, so that all circuit branches 4 to 7 have approximately the same pressure loss or generate approximately the same back pressure.

[0026] Within the individual circuit lines 4 to 7, the drive components 8 to 13 are arranged in such a way that the coolant flow first passes the drive components with the lowest limit operating temperature and only then the subsequent drive components with a higher limit operating temperature.

[0027] The one in the Fig. The coolant circuit 1 shown in Figure 1 further comprises an electronic control device 23, which is signal-connected to two valves 22 and a temperature sensor 24 and causes the valves 22 to open or close in accordance with a temperature value transmitted by the sensor 24. In the example shown, this means specifically that if the sensor 24 detects that the temperature of the accumulator or battery storage unit 9 is too low, the control device 23 causes the connecting line 21 to open, so that the waste heat released by the brake chopper 8 to the coolant is fed via the connecting line 21 to the battery storage unit 9 in order to bring it up to operating temperature. In this state of the valves 22, there is no direct connection between the circuit line 4 and the return line, nor is there a direct connection between the circuit line 5 and the supply line.All coolant passing the brake chopper 8 is consequently also passed the battery storage unit 9.

[0028] The brake chopper 8 converts excess energy, which arises, for example, from recuperation by braking a drive and cannot be used to charge the battery storage 9 due to a sufficiently high charge state of the battery storage 9, into heat energy via an electrical resistor, which is absorbed by the passing coolant.

[0029] Since it is not expected that both the generator 10 and the inverter of the external power supply 11 will have to dissipate high heat output at the same time, these components can be arranged in the same string 6.

[0030] In the Fig. 2 shows a coolant circuit 1 for a crane superstructure, which in its essential components is identical to the one shown in the Fig.1 is identical to the coolant circuit 1 shown. However, the coolant circuit 1 provided for the crane superstructure has only two parallel circuit lines 5 and 6, each of which supplies three drive components 14 to 19 with coolant. In line 5, these are, in order of increasing permissible limit operating temperature, the electric motor 14 of the hoist, the inverter 15 of a first air-cooled slewing gear motor, and the inverter 16 for the hydraulic pump 17. In line 6, these are the water-cooled electric motor for the hydraulic pump, which supplies, for example, the luffing gear and the telescopic gear with hydraulic fluid, another inverter 18 for a second air-cooled slewing gear motor, and the inverter 19 for the water-cooled hoist motor 14.Since it cannot be assumed that the hoisting gear of the underlying mobile crane will be continuously operated together with the luffing or telescopic gear, and their drive components therefore generate high levels of waste heat simultaneously, their corresponding drive components 14, 16, 17, and 19 are supplied with coolant via the same circuit lines 5 and 6. To avoid local "heat peaks," the individual components 14, 16, 17, and 19 of the hoisting gear and the hydraulic pump are distributed "crosswise" across circuit lines 5 and 6.

Claims

[1] Coolant circuit for a self-propelled machine with several electric drive components (8-19), with: - a coolant pump (2) for generating a flow of coolant circulating in the coolant circuit (1); - a heat exchanger (3) for dissipating thermal energy stored in the coolant; - at least two circuit strands (4-7) running parallel to one another, which are designed to guide the coolant past the drive components (8-19) assigned to them in order to absorb thermal energy; and - at least one connecting strand (21) fluidically connecting at least two of the circuit strands (4-7) and designed to transfer coolant from a first circuit strand (4-7) to a second circuit strand (4-7), with at least one valve (22) for opening and closing the connecting strand (21) and / or for varying a volume flow of the coolant guided through the connecting strand (21). [2] Coolant circuit according to claim 1, wherein the circuit strands (4-7) cause an equal pressure loss in the coolant flow over their extent. [3] Coolant circuit according to one of claims 1 and 2, wherein the drive components (8-19) in at least one of the circuit strands (4-7) are arranged in accordance with the height of their respective - Limit operating temperature; - heat loss performance; and / or - Safety relevance; and in the flow direction of the coolant starting with the - lowest limit operating temperature; - lowest heat loss; and / or - highest security relevance; are arranged. [4] Coolant circuit according to one of claims 1 to 3, wherein the circuit strands (4-7) are arranged in the flow direction of the coolant between the coolant pump (2) and the heat exchanger (3). [5] Coolant circuit according to claim 1, wherein the connecting line (21) connects the first circuit line (4-7) after at least one drive component (8-19) in the first circuit line (4-7) with the second circuit line (4-7) before at least one drive component (8-19) in the second circuit line (4-7) in the flow direction of the coolant. [6] Coolant circuit according to one of claims 1 to 5, wherein the at least one valve (22) is designed to be controllable in order to guide a volume flow of coolant via the connecting line (21) in accordance with a coolant requirement of a drive component (8-19) supplied with coolant via the connecting line (21). [7] Coolant circuit according to claim 6, wherein the control device (23) has at least one sensor (24) detecting a temperature of a drive component (8-19) and, when the temperature falls below or exceeds a temperature threshold predefined for the drive component (8-19), selectively causes the at least one valve (22) to open or close. [8] Self-propelled work machine, with several electric drive components (8-19) and a coolant circuit (1) according to one of claims 1 to 7. [9] Self-propelled working machine according to claim 8, with several coolant circuits (1) designed independently of one another according to one of claims 1 to 7.

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