Coolant circuit for a self-propelled working machine with a plurality of electric drive components

Abstract

To provide a cooling system which efficiently addresses cooling capacity requirements of different electric drive components in all-electric or hybrid-electric drive designs.SOLUTION: A coolant circuit (1) for a self-propelled work machine including multiple electric drive components (8-13) includes a coolant pump (2) for generating a flow of coolant which circulates in the coolant circuit, a heat exchanger (3) for dissipating thermal energy stored in the coolant, and at least two circuit lines (4-7) which extend parallel to each other and guide the coolant so as to pass through the drive components (8-13) respectively assigned to them, in order to absorb thermal energy. In addition, a self-propelled work machine, in particular a mobile crane, includes multiple electric drive components (8-13) and one or more such coolant circuits (1).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a refrigerant circuit for dissipating the heat power generated by and cooling the electric drive components of a self-propelled working machine, in particular a mobile crane, and also to a self-propelled working machine, in particular a mobile crane, equipped with one or more such refrigerant circuits. [Background technology]

[0002] In known working machines comprising mobile cranes, the individual (crane) functions are usually operated by so-called hydraulic drives, in which one or more hydraulic pumps, supplied with for example the machine (shaft) power, are fluidly connected to the hydraulic cylinders or hydraulic motors of the individual (crane) functions for the eventual drive. In hybrid electric or all-electric drive designs, these hydraulic drives are at least partially supplemented or replaced by electric drives. The electric drives usually comprise an electric motor with an associated inverter for power and position control. The required electrical power is provided by a generator, which is for example driven by an internal combustion engine in the undercarriage of the working machine or by inputting external electrical power. Likewise, the working machine can comprise its own energy storage device to supply electrical power, and combinations of said supply options are also conceivable. By decelerating the individual drives, energy is released with which the energy storage device can be charged. If the energy storage device is fully charged, this electrical power must often be reduced via an electrical resistor, a so-called brake chopper, whereby thermal energy is released. Energy storage and / or storage devices, electric motors and associated inverters, together with power electronics and controllers, have high requirements for maintaining an acceptable operating temperature. If the operating temperature exceeds or falls below the so-called operating temperature limit, the power of the associated components is reduced to protect the system. To avoid such a reduction in power, which is detrimental to the machine operation, said electric drive components are often cooled by sophisticated mechanisms. For this purpose, liquid cooling systems, i.e. cooling systems using a liquid cooling medium (often a water-glycol mixture), are widely used. For simplicity, in the following, reference is made to a mobile crane as a specific embodiment of a self-propelled working machine. The design described below can of course be applied to any type of self-propelled machine and is not limited to a mobile crane.

[0003] Drive components for the individual crane functions typically found on a crane include hydraulic pumps which drive hydraulic motors or hydraulic cylinders assigned to drive, for example, the luffing mechanism, the lifting mechanism, the telescopic mechanism, and the swing mechanism. Summary of the Invention [Problem to be solved by the invention]

[0004] It is an object of the present invention to provide a cooling system that efficiently addresses the cooling capacity needs of the different electric drive components in an all-electric or hybrid electric drive design. [Means for solving the problem]

[0005] The present invention recognises that during operation of a mobile crane, it is not common for all drives to be operating at high load factors simultaneously with associated cooling capacity demands, therefore intelligent cooling system design offers the potential for significant savings.

[0006] This object is achieved by the subject matter of independent claims 1 and 9.

[0007] According to the present invention, there is provided a refrigerant circuit for a self-propelled working machine having a plurality of electrical drive components, comprising: a refrigerant pump that generates a flow of refrigerant circulating in the refrigerant circuit; a heat exchanger for dissipating thermal energy stored in the refrigerant; at least two circuit lines extending parallel to one another and guiding a coolant through the drive components respectively assigned to them for absorbing thermal energy; A refrigerant circuit is provided comprising:

[0008] In other words, at least some regions of the refrigerant circuit according to the invention comprise several lines running parallel to one another for cooling respectively assigned drive components, which can be fed via a common supply flow and exit again into a common return flow. A refrigerant pump may be arranged in the supply flow. A heat exchanger / cooler may be arranged in the return flow.

[0009] According to the invention, by providing at least two circuit lines arranged in parallel with one another, the individual moving parts can be divided between the provided lines according to their cooling capacity requirements. Furthermore, the individual moving parts can be divided between the available circuit lines according to their heat input, so that the heat input is as uniform as possible over the entire refrigerant circuit. This avoids local excessive heat input.

[0010] In one embodiment, the circuit lines experience a substantially equal pressure drop throughout the refrigerant flow, and at least one of the circuit lines has a throttling element that adjusts the pressure drop in that circuit line to the pressure drop in at least one other circuit line.

[0011] In other words, the circuit lines are substantially equal in back pressure. This is made possible by targeted selection of the drive components arranged in each circuit line. That is, the flow rates of the refrigerant guided through each circuit line may be completely different from each other, although they are in a constant ratio during the operation of the crane. Even if the combination and arrangement of the drive components arranged in each crane does not allow the individual circuit lines to have sufficiently similar back pressures and / or pressure losses, throttling elements such as throttles, baffles or throttle valves can be used in the individual circuit lines to create sufficiently equal pressure losses and / or back pressures throughout the circuit lines.

[0012] According to another embodiment, in at least one of the circuit lines, the plurality of moving parts may be arranged in the direction of flow of the coolant starting from the lowest operating temperature limit according to the level of their respective operating temperature limits.

[0013] In other words, efficiency is further improved by directing the coolant flow first through at least one of the circuit lines to the driving components with the lowest operating temperature limit, i.e. those that are most likely to be the first to require a reduction in power due to their operating temperature being too high. If there are more than two driving components in one circuit line, they may be arranged so that the coolant guided through the circuit line first reaches the driving component with the lowest operating temperature limit, then the driving components with intermediate operating temperature limits, and finally the driving component with the highest operating temperature limit. By arranging the driving components in this way, the available coolant flow can be used efficiently and the coolant circuit, including the coolant pump and the piping, can be made smaller as a result.

[0014] The moving components in the circuit lines may be arranged according to heat dissipation and / or safety. In particular, the coolant may pass the most safety relevant components first, followed by the less safety relevant components. The components exhibiting the lowest heat dissipation may be passed first, followed by the components exhibiting the highest heat dissipation. It is also conceivable to arrange the components in the circuit lines according to at least two of the criteria of operating temperature limits, heat dissipation and safety relevance.

[0015] The circuit lines may be arranged between a coolant pump and a heat exchanger, as viewed in the flow direction of the coolant. The coolant pump may, for example, be arranged in the supply flow upstream of the respective circuit line, and the heat exchanger and / or the cooler may, for example, be arranged in the return flow downstream of the respective circuit line. Of course, it is also conceivable to arrange the heat exchanger in the supply flow and / or the coolant pump in the return flow.

[0016] According to another embodiment of the invention, the refrigerant circuit comprises at least one connecting line fluidly connecting at least two of the circuit lines and at least one valve for opening and closing the connecting line and / or for varying the flow rate of the refrigerant guided through the connecting line. Such a connecting line allows to transfer the refrigerant from one circuit line to another circuit line running in parallel therewith, supplying the drive parts with a refrigerant at a lower or higher temperature than is possible via its "own" circuit line. Such a "cross-supply" may be selectively performed when it is determined or expected that the operating temperature of the drive parts to be cooled is too low or too high. The connecting lines may be opened or closed by one or more selectively switchable valves. It is also conceivable that all or only a part of the flow of the refrigerant is drawn from the contributing circuit lines. It is also conceivable that the actual refrigerant supply via the supply flow is completely or only partially closed in the receiving circuit line.

[0017] In one embodiment, the connecting line connects a first circuit line downstream of at least one driving component in the first circuit line in the flow direction of the coolant with a second circuit line upstream of at least one driving component in the second circuit line in the flow direction of the coolant. With such an arrangement, waste heat from the individual driving components can be transferred to the coolant in the first circuit line and used to heat one or more driving components in the second circuit line. This is particularly useful if driving components for the operation of the crane must first reach the operating temperature in order to avoid a reduction in power. This is particularly conceivable in connection with batteries and / or accumulators, whereby any conceivable driving components already provided for the crane function can be used as heat source, but it is equally possible to provide a heating device, in particular an electrically operated heating device.

[0018] It is conceivable that the function of the at least one connecting line for at least one valve may be actuated manually by a crane operator, for example, but the at least one valve may also be configured to be actuated by a control device for automatically guiding the flow rate of the coolant through the connecting line depending on the cooling requirements of a driven part to which the coolant is supplied via the connecting line.

[0019] In another embodiment, the control device may include at least one sensor for detecting a temperature of a moving component and selectively open or close the at least one valve when the moving component falls below or exceeds a preset temperature threshold for the moving component.

[0020] This allows the (preferably electronic) control device to open the connecting line in order to utilize the waste heat from one driving part to heat another driving part if it is necessary for the driving part to be heated or if it is simply deemed advantageous for operation. When the required operating temperature is reached, the control device may close the connecting line again. This also applies if the driving parts have additional cooling requirements, which can be covered via the connecting line.

[0021] Another aspect of the invention relates to a self-propelled work machine, in particular a mobile crane, comprising a plurality of electric drive components and a refrigerant circuit according to an embodiment described above.

[0022] In another embodiment, the self-propelled working machine (in particular a mobile crane) comprises a plurality of the refrigerant circuits, which are configured independently of each other and are similarly or differently constructed. For a working machine and / or a crane comprising a lower structure and an upper structure rotatably arranged on the lower structure, it is conceivable, for example, to provide one refrigerant circuit running through the rotational connection between the upper structure and the lower structure. Conversely, it is also conceivable to provide the lower structure and the upper structure with respective refrigerant circuits independent of each other. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 shows a refrigerant circuit for the undercarriage of a crane. [Diagram 2] FIG. 1 shows a refrigerant circuit for the crane superstructure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The present invention will now be described in more detail based on preferred embodiments with reference to the accompanying drawings, in which: The present invention may comprise any of the features described herein, both individually and in any convenient combination.

[0025] FIG. 1 shows a refrigerant circuit 1 for a crane undercarriage. In addition to a supply flow with a refrigerant pump 2 and a return flow with a heat exchanger 3, the refrigerant circuit 1 comprises four circuit lines 4-7 running parallel to each other between the supply and return flows. The refrigerant delivered by the pump 2 is supplied to all circuit lines 4-7 for cooling (in other words dissipating their waste heat) the electric drive components 8-13 arranged in the respective circuit lines 4-7. The heated refrigerant is delivered via a common return flow to the heat exchanger 3, where the stored thermal energy is removed from the refrigerant again. An expansion tank 25 arranged between the heat exchanger 3 and the pump 2 in the refrigerant flow direction is used to compensate for the thermally induced changes in the volume of the refrigerant.

[0026] In the example shown in Fig. 1, all circuit lines 4-7 exhibit approximately equal pressure losses and / or generate approximately equal back pressures. This means that the flow rates of refrigerant guided through the respective circuit lines 4-7 have a constant magnitude ratio, and the individual circuit lines 4-7 are not over- or under-fed. As the circuit line 7 comprising the inverter of the intermediate circuit 12 of the electric energy supply and the inverter of the generator 13 exhibits the largest pressure losses, the other circuit lines 4-6 (whose assigned drive components 8-11 cause smaller pressure losses) are provided with throttle valves 20 in order to ensure that all circuit lines 4-7 exhibit approximately equal pressure losses and / or generate approximately equal back pressures.

[0027] Within each circuit line 4-7, the drive components 8-13 are arranged so that the flow of coolant passes first through the drive components with the lowest operating temperature limits, and then through the drive components with the higher operating temperature limits.

[0028] The refrigerant circuit 1 shown in FIG. 1 also comprises an electronic control device 23 which is connected in a signal-transmitting manner to the two valves 22 and to the temperature sensor 24 and which opens and closes the valve 22 depending on the temperature value transmitted from the sensor 24. In particular, if the sensor 24 detects that the temperature of the accumulator and / or the battery 9 is too low, the control device 23 opens the connecting line 21 and supplies the waste heat released into the refrigerant by the brake chopper 8 to the battery 9 via the connecting line 21 so that the battery 9 reaches its operating temperature. When the valve 22 is in this state, there is no direct connection between the circuit line 4 and the return flow and no direct connection between the circuit line 5 and the supply flow. As a result, all the refrigerant passing through the brake chopper 8 passes through the battery 9.

[0029] The brake chopper 8 converts the surplus energy, which arises for example from the braking recovery of the drive and which cannot be used to charge the battery 9 because the latter is fully charged, into thermal energy via an electrical resistor. This thermal energy is absorbed by the passing coolant.

[0030] Since it is not expected that high heat power will be dissipated from both the generator 10 and the inverter of the external power source 11 at the same time, these components can be placed on the same line 6 .

[0031] FIG. 2 shows a coolant circuit 1 for the crane superstructure, the essential components of which are the same as the coolant circuit 1 shown in FIG. 1. However, the coolant circuit 1 for the crane superstructure only comprises two parallel circuit lines 5, 6 which respectively supply coolant to three drive parts 14-16 and 17-19. In line 5 there are (in order of increasing permissible operating temperature limit) the electric motor of the lifting mechanism 14, the inverter of the first air-cooled slewing mechanism motor 15 and the inverter of the hydraulic pump 16. In line 6 there is, for example, a water-cooled motor of the hydraulic pump 17 which supplies hydraulic fluid to the luffing mechanism and the telescopic mechanism, another inverter of the second air-cooled slewing mechanism motor 18 and an inverter of the water-cooled lifting mechanism motor 19. Since in the basic mobile crane it is assumed that the lifting mechanism does not operate constantly together with the luffing mechanism and the telescopic mechanism (their drive parts simultaneously generate high levels of waste heat), their corresponding drive parts 14, 16, 17, 19 are supplied with coolant via the same circuit lines 5, 6. In order to avoid local "heat spikes", the individual drive parts 14, 16, 17, 19 of the lifting mechanism and the hydraulic pumps are "transversely" distributed between the circulation lines 5, 6.

Claims

1. A refrigerant circuit for a self-propelled working machine having a plurality of electric drive components (8 to 19), comprising: a refrigerant pump (2) that generates a flow of refrigerant circulating in the refrigerant circuit (1); a heat exchanger (3) for dissipating thermal energy stored in the refrigerant; at least two circuit lines (4-7) running parallel to one another and guiding a coolant through the drive components (8-19) respectively assigned to them for absorbing thermal energy; at least one connection line (21) that fluidly connects at least two of the circuit lines (4 to 7), including a first circuit line and a second circuit line, and is configured to be able to draw a refrigerant from the first circuit line and supply the refrigerant to the second circuit line; said at least one connecting line (21) comprises at least one valve (22) for opening and closing said connecting line (21) and / or for varying the flow rate of said refrigerant guided through said connecting line (21); Refrigerant circuit.

2. 2. A refrigerant circuit as claimed in claim 1, wherein the circuit lines (4-7) experience substantially equal pressure losses throughout the refrigerant flow, and at least one of the circuit lines (4-7) comprises a throttling element (20) adjusting the pressure loss of that circuit line (4-7) to the pressure loss of at least one other circuit line (4-7).

3. 2. The refrigerant circuit according to claim 1, wherein in at least one of the circuit lines (4-7), the plurality of moving parts (8-19) are arranged in the flow direction of the refrigerant according to their respective levels of operating temperature limits, heat dissipation and / or safety concerns, starting from the point with the lowest operating temperature limit, the lowest heat dissipation and / or the highest safety concern.

4. 2. The refrigerant circuit according to claim 1, wherein the circuit lines (4-7) are arranged in a flow direction of the refrigerant between the refrigerant pump (2) and the heat exchanger (3).

5. 2. The refrigerant circuit according to claim 1, wherein the connecting line (21) connects a first circuit line (4-7) downstream of at least one driving component (8-19) in the first circuit line (4-7) in the flow direction of the refrigerant with a second circuit line (4-7) upstream of at least one driving component (8-19) in the second circuit line (4-7) in the flow direction of the refrigerant.

6. 2. The refrigerant circuit according to claim 1, wherein the at least one valve (22) is configured to be actuated by a control device (23) for guiding the flow rate of the refrigerant through the connecting line (21) depending on the cooling requirements of the drive components (8-19) to which the refrigerant is supplied via the connecting line (21).

7. 7. The refrigerant circuit according to claim 6, wherein the control device (23) comprises at least one sensor (24) for detecting a temperature of the driving parts (8-19) and selectively opens or closes the at least one valve (22) when the driving parts drop below or exceed a temperature threshold preset for the driving parts (8-19).

8. A self-propelled working machine comprising a plurality of electric drive components (8 to 19) and a refrigerant circuit (1) according to any one of claims 1 to 7.

9. The self-propelled working machine according to claim 8, comprising a plurality of refrigerant circuits (1) according to any one of claims 1 to 7 configured independently of each other, wherein a first refrigerant circuit (1) is assigned to a lower structure of the working machine comprising a plurality of drive parts (8 to 19), and a second refrigerant circuit (1) is assigned to an upper structure of the working machine comprising a plurality of drive parts (8 to 19).

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