DE102014019544A1 - Device for increasing the electrical insulation resistance - Google Patents

Abstract

The invention relates to a device for increasing the electrical insulation resistance in a cooling circuit (12) with in liquid coolant lines (18) flowing liquid coolant. The device according to the invention is characterized in that at at least one point of the cooling circuit (12) one of the coolant lines (18) terminates in the intended use in the direction of gravity above a liquid level (24) in a gas-filled container (21) in the cooling circuit (12) ,

Description

The invention relates to a device for increasing the electrical insulation resistance according to the preamble of claims 1 and 8. Moreover, the invention relates to the use of these methods.

Increasing the insulation resistance of liquid coolant flowing in a coolant line is of particular importance for vehicle applications, and in particular for applications with coolant-cooled high-voltage assemblies. These units may be fuel cell stacks, for example, which are used to generate electrical drive power in a vehicle. In these components, but partly also in traction batteries, the coolant is in contact with electrically conductive parts of the fuel cell or battery. On the other hand, the coolant is in contact with components which are connected to the vehicle chassis and thus "on ground". At operating voltages of more than 60 V DC increased demands on the electrical insulation between the operating voltage, such as the fuel cell stack, and the vehicle mass are required. A typical requirement is the legal minimum value of 100 ΩN, which is increased to 250 ΩN due to tolerances and operational safety, for example. The higher the operating voltage, the higher the required insulation resistance. At a maximum voltage of, for example, 500 V, an insulation resistance of at least 125 kΩ is required, which typically increases in the order of 300 to 500 kΩ due to tolerances and operational safety requirements. This results in particular, since the resulting insulation resistance ultimately arises from a parallel connection of all components present in the electrical system, so that a comparatively high individual value must be maintained.

Today, it is usually the case that this high resistance in the water-based coolant circuit can only be achieved by additional measures. These are, for example, a targeted extension of the coolant lines and an increased requirement for the electrical conductivity of the coolant. These measures require additional space and due to the increased pressure losses higher performance of the coolant pump. In addition, the coolant is typically passed through an ion exchanger to keep its electrical conductivity low. This also presents a certain disadvantage since the ion exchanger must be regularly maintained. Another problem, which occurs especially in fuel cell applications, now consists in the fact that this construction requires a comparatively large cooling circuit with a high volume of coolant. However, this is a considerable disadvantage in particular in the case of fuel cell systems in vehicles, which are in any case critical during cold starts, since the entire volume of the coolant must be heated as quickly as possible to the operating temperature of the fuel cell system in such a situation.

To counteract this problem, it is from the two Japanese patent applications JP 2004 335369 A and JP 2002 117884 A It is known to insert impellers either in the form of an impeller of the coolant pump and / or independently thereof into the volumetric flow of the coolant. Such impellers made of electrically insulating material temporarily separate individual parts of the volume flow of the coolant, and thus significantly increase the insulation resistance. As a result, correspondingly short coolant lines and, if appropriate, also the waiver of an ion exchanger are conceivable. However, the structure is, due to the moving parts, all in all comparatively complicated, especially since it typically requires a corresponding structure of this type both at the entrance to the high-voltage-carrying component and at the output from the high-voltage-carrying component. In addition, the wheels, if they are not actively driven, also increase the flow resistance and thus the power requirement for cooling the corresponding components. If they are actively driven, they increase the power requirement anyway.

The object of the present invention is now to provide a device which contributes to increase the electrical insulation resistance of a coolant flowing in a coolant line, without having the disadvantages mentioned.

According to the invention this object is achieved by a device having the features in claim 1. Advantageous embodiments emerge from the dependent subclaims. A particularly preferred use is specified in claim 10.

In the device according to the invention for increasing the electrical insulation resistance in a cooling circuit, it is now provided that at least one point of the cooling circuit one of the coolant lines ends in the intended use in the direction of gravity above a liquid level in a gas-filled container. It is thus achieved that the flowing coolant exits from the end of the coolant line and over a piece, for. B. free path through which the container falls before settling down in the container collects and flows out or is sucked off by the coolant conveyor. The simple and very compact measure already leads to a measurable increase in the insulation resistance.

The structure of the device according to the invention is so compact that it can easily be done twice in the cooling circuit. It is thus possible to provide both the coolant inlet and the coolant outlet of a high-voltage-carrying component. Preferably, the installation can even be carried out completely or partially in the housing of the high-voltage-carrying component. This represents a significant additional advantage in terms of packaging, especially when used in vehicles.

According to an advantageous continuation of the idea, it is now provided in particular that in the region in which the coolant line ends, a clocked switchable valve device is arranged. By such a clocked switchable valve device can be achieved that the flow of coolant into the container is interrupted again and again. Such a discontinuous flow of coolant through the gaseous atmosphere prevents a continuous electrical conduction in the coolant through the interruptions of the flow. The insulation resistance can thus be significantly increased again. Due to the structure in which the discontinuous stream flows into the container and collects there before the onward flow, the entry of harmful pressure pulsations into the cooling circuit can be prevented or at least minimized.

A particularly advantageous alternative to the aforementioned development provides that in the region in which the coolant line ends, a passively actuated by the flow pressure of the coolant locking device is arranged. Such a passive barrier device as an alternative solution has the advantage that an active control is necessary for this purpose. Both on a control unit and on control lines and actuators and possibly also sensors can therefore be dispensed with. This saves installation space and costs during production and assembly. The functionality and the effect are the same as in the development described above. The coolant flow is thus constantly released and interrupted again, so that a discontinuous flow is formed.

Such a passive barrier device can preferably be designed as a valve loaded by a spring against the direction of flow. With a suitable choice of the spring strength, the flap can interrupt the flow until a spring force has built up the forces of the spring. Then the flap releases the flow cross-section and the dynamic pressure builds up. Now the spring can close the flap against the pure flow pressure again, until again a sufficient back pressure has built up to open the flap.

A favorable embodiment of the device according to the invention may further provide that in the container between the end of the coolant line and the liquid level typically present in the container, a rocker is arranged. Instead of - or possibly also in addition to - a valve or locking device in or at the end of the coolant line is provided in this variant of the device, the rocker in the container to also periodically interrupt the falling into the container coolant flow and thus for a discontinuous Coolant flow through the gas atmosphere to provide.

A further possibility to create a discontinuous flow of coolant interrupted by electrically insulating parts is that an overshot water wheel is arranged in the container between the end of the coolant line and the liquid level typically present in the container. Such an overshot water wheel or overshot mill wheel is typically supplied from above with the liquid medium, in this case the coolant. Not by the flow, but only by gravity, the supershafted waterwheel then moves, as individual densely formed cells fill up with the coolant and, due to gravity, move one side of the waterwheel downwards and in turn the other upwards , Due to the rotational movement along the circumference of the water wheel, the individual cells empty at the lower end and release the coolant contained in them in the container. In this way, a structure is provided in which the individual sections of the discontinuous coolant flow are separated from each other, in this case by the walls forming the cells of the overshot water wheel. If these are formed from an electrically insulating material or an electrically not very good conductive material, a significant increase in the electrical insulation resistance is achieved by this structure.

A very favorable alternative or additional embodiment of the device according to the invention can also provide that at the end of the coolant line, a device for introducing the gas present in the container is arranged in the liquid flow. Such a device is extremely simple, robust and low maintenance. It can be constructed, for example, like a so-called jet regulator. Such aerators are used for mixing water and air at countless taps in sanitary facilities application. In the embodiment of the device according to the invention with such a device a very strong mixed with the gas from the container mixed coolant flow into the container. This also increases the insulation resistance both alone and in combination with one of the other embodiments.

An alternative device which also achieves the object is described by the features of claim 8. In this embodiment of a device according to the invention, it is such that two gas-filled containers or a gas-filled container with two separate sections are provided, wherein one of the containers or one section lies in the direction of gravity higher than the other container or the other section wherein the containers or sections are connected by an Archimedean screw. Such a connection of a lower-lying container or portion with a higher-lying container or portion via an Archimedean screw allows a promotion of the coolant from the lower-lying container or section in the higher-lying container or section. Unlike the previous embodiments, however, a drive of the Archimedean screw is necessary for this, but which requires relatively little power. The principle of the Archimedes screw is that the angle of the screw axis relative to the horizontal and the pitch of the screw is designed so that the liquid coolant flows with one revolution of the screw from one room to the next higher space of the thread and thereby altogether upwards promoted or lifted. This structure has been known for promoting water. Here, too, if the screw is formed in particular from an electrically non-conductive material, a structure in which ultimately the individual water-filled spaces of the spindle in the above the surface of the lower container or portion lying portion of the screw through the material of Screw and are separated by air. This also results in individual volumes of the coolant, which are not connected to each other and thus contribute to a significant increase in the electrical insulation resistance in the coolant circuit.

As a gas can be used in all versions of the device while various electrically insulating gases or as a very easily available alternative air.

The device according to the invention in both the first and in the second embodiment is particularly suitable for increasing the electrical insulation resistance in a coolant which circulates between a voltage or high-voltage source which flows through it and elements which are earthed. In this case, a correspondingly high electrical insulation resistance of the coolant must be ensured. To realize this with minimal effort and space, the two methods of the invention are very well suited. Since such requirements are typically directed to the coolant of a fuel cell system or an electric vehicle, the particularly preferred use of the inventive method is in its use for improving the electrical insulation resistance in a coolant flowing in a cooling circuit of a vehicle equipped with a fuel cell and / or traction battery ,

Further advantageous embodiments will become apparent from the embodiments, which are described below with reference to the figures.

Showing:

1 an indicated vehicle with a fuel cell system and a cooling circuit according to the prior art;

2 a detail of the cooling circuit with a device according to the invention in a first embodiment;

3 a section of the cooling circuit with a device according to the invention in a second embodiment;

4 a detail of the cooling circuit with a device according to the invention in a third embodiment;

5 a section of the cooling circuit with a device according to the invention in a fourth embodiment;

6 a detail of the cooling circuit with a device according to the invention in a fifth embodiment;

7 a detail of the cooling circuit with a device according to the invention in a sixth embodiment; and

8th a section of the cooling circuit with a device according to the invention in a seventh embodiment.

In the presentation of the 1 is a vehicle 1 with a fuel cell system 2 very strongly schematized indicated. The core of the fuel cell system 2 forms a fuel cell 3 , with a cathode area 4 and an anode area 5 , The fuel cell 3 in particular as a stack of single cells, as so-called Fuel cell stack to be constructed. Part of the fuel cell 3 is also a heat exchanger 6 , which of a coolant for temperature control of the fuel cell 3 is flowed through. This construction is a whole in a fuel cell housing 7 arranged. The fuel cell system 2 is shown very simplified, since its structure is familiar to the expert, and is to be understood purely by way of example here. Other constructions than shown here are also conceivable and possible.

The fuel cell 3 or their cathode compartment 4 Air is transferred via an air conveyor 8th supplied as an oxygen supplier. The air conveyor 8th conveys the compressed supply air via a gas / gas humidifier 9 in the cathode compartment 4 , In turn, exhaust air laden with deoxygenated oxygen flows through the gas / gas humidifier 9 and releases moisture to the supply air before the exhaust air flows into the environment. The anode compartment 5 the fuel cell 3 becomes hydrogen from a compressed gas storage 10 via a pressure regulating and dosing valve 11 fed. In the embodiment shown here, residual hydrogen and exhaust gas from the fuel cell system 2 in the nearby areas. Again, other structures such as turbines, burners or circulation of the anode exhaust gas would be conceivable. All of this is familiar to the person skilled in the art and of secondary importance for the present invention. Therefore, this will not be discussed.

Now it is the case that in the fuel cell the coolant is in direct communication with elements that are electrically under the voltage of the fuel cell. That in a cooling circuit 12 via a coolant pump 13 circulated coolant, which via a cooling heat exchanger 14 must therefore have a certain electrical insulation resistance, which is typically on the order of 250 ΩN voltage of the fuel cell 3 is used to take account of tolerances and collateral compared to the legal limit.

In the prior art constructions, the refrigeration cycle is 12 thereby often trained, as he in the representation of the 1 can be seen. The cooling circuit comprises two additional meander-shaped loops, which in the illustration of the figure by the reference numeral 15 are provided. These meandering loops serve the path length in the coolant between the live regions of the fuel cell 3 and areas of the refrigeration cycle 12 , which communicate with the environment or with the electrical ground of the vehicle chassis of the vehicle 1 are connected to increase accordingly. As a result, typically the necessary electrical insulation resistance between the fuel cell 3 and here exemplified potential equalization 16 ensured. In addition, to keep the conductivity of the coolant permanently low, typically is an optional ion exchanger 17 intended.

This structure is associated with corresponding disadvantages, as it is due to the very large cooling circuit 12 comprises a comparatively large amount of coolant. This is a decisive disadvantage in particular when cold starting and generally requires a higher drive power of the coolant delivery device 13 , which is also disadvantageous in terms of efficiency. It would be desirable now, ideally within the fuel cell housing 7 a way to find the insulation resistance in the shortest possible distance of a coolant line 18 of the cooling circuit 12 to increase so much that the equipotential bonding 16 directly to the fuel cell housing 7 could then be trained.

Such a construction is now possible by ideally at one or both in the illustration of 1 indicated by dashed lines and with the reference numeral 19 marked points a corresponding device 20 is used to increase the electrical insulation resistance. Such devices 20 are shown below by way of example in various embodiments.

In the presentation of the 2 is another embodiment of such a device 20 to recognize. The device 20 consists essentially of a container 21 , which is filled with an electrically insulating gas, for ease of construction and assembly, in particular with air. In this container 21 In the direction of gravity and in the direction of the representation of the upper area, a first part of the coolant line ends 18 in which, as by the arrow 22 indicated, coolant flows. Through a second part of the coolant line 18 flows as if through the arrow 23 indicated in the container 21 at the lower end collecting coolant then again. A liquid level of the collecting coolant is denoted by the reference numeral 24 Mistake. At one end 25 the upper part of the coolant line, which in the container 21 is at the in 2 illustrated embodiment, a valve device 26 arranged. This valve device 26 can now be switched clocked. This is shown by a magnetic coil 27 indicated, so that the valve device 26 is actuated electromagnetically and can be opened and closed periodically, for example by a clocked switching pulse. This ultimately results in a discontinuous flow through the air in the container 21 falling Coolant flow. This discontinuous part of the coolant flow is indicated by several individual areas with coolant, some of which are denoted by the reference numeral 28 are provided. By this periodic interruption of the coolant flow is a significant increase in the insulation resistance in the cooling circuit 12 achieved. Here is the device 20 so small and compact to realize that they can be easily connected to the two 19 each designated points can be provided once without unnecessarily increasing the size of the overall structure.

In the presentation of the 3 is an alternative structure to recognize, in which instead of the active clocked switched valve device 26 at the end 25 of the upper part of the conduit element 18 a flap 29 is arranged. This flap 29 is at her fulcrum 30 rotatably mounted and by a spring, for example a torsion spring in the region of the pivot point 30 designed so that they are by the force of this spring against the end 25 the upper part of the coolant line 18 is pressed. This will be the end 25 the coolant line 18 locked. As the coolant flows in, a back pressure builds up until it is greater than the force applied by the spring. Only then will the flap 29 open, as indicated by dotted lines. Coolant can escape and through the container 21 fall while the flap 19 back to the closed state. This is repeated and also leads to a discontinuous flow of coolant, which in turn by the designation of some sections by the reference numeral 28 is indicated.

Another alternative embodiment of the device 20 is in the representation of 4 to recognize. The core of the device 20 forms a rocker 31 which is in the container 21 centered under the end 25 the coolant line 18 is arranged. The coolant then flows into the one, shown in the solid line variant right with 32 designated chamber of the rocker 31 one. Once the coolant in this chamber 32 a corresponding gravity builds up, the rocker 31 tilt to the dashed position. The chamber 32 then runs over the opening 33 empty, while the other with 34 designated chamber now vertically below the end 25 the coolant line 18 lies and correspondingly full. After a while, the rocker tilts 31 from the position shown in dashed lines in the position shown in solid and back over the opening 33 the chamber 34 the coolant runs off as indicated by the arrow, the process starts again. As a result, a discontinuous discharge of the coolant is achieved in the coolant sump standing in the container, so that also by this structure with the rocker 31 an interruption of the coolant flow and thus a significant increase in the electrical insulation resistance is achieved.

In the presentation of the 5 Now a combination of the two last described structures can be seen. Instead of the two-piece rocker 31 as they are in 4 is shown, the structure is now designed so that a one-sided rocker 35 is arranged in the container. This can by the force of a spring or in particular by a counterweight 36 be brought into the position shown in solid.

Coolant, which via the coolant line 18 flows in, will be in one with 37 designated depression of the one-sided rocker 35 collect. Once the gravity of the water the force of the spring and / or the counterweight 36 exceeds, the coolant is discharged in a surge down, so that it comes to the discontinuous stream, which passes through the individual sections 28 the coolant flow is indicated accordingly.

In the presentation of the 6 a further alternative embodiment can be seen. Instead of the previous installations, such as the rockers 31 . 35 , now enters a so-called oberschlächtiges waterwheel 38 , The overshot waterwheel 38 is so in the container 21 arranged it with its axis of rotation slightly offset below the end 25 the coolant line 18 to come to rest. Now it is with a superficial water wheel so that the incoming water, which from the end 25 the coolant line 18 flows into individual cells of the waterwheel 38 collects. The individual cells, some of which are designated by the reference numeral 39 are provided, then ensure that the waterwheel moves due to the gravity of the water, and expressly not due to the flow of the coolant flow, according to the direction of rotation indicated by the arrow. The water in the individual cells 39 forms a discrete amount of water, which of the other amounts of water through which the cells 39 separating partitions is separated from each other. If these partitions are made of electrically insulating material, then the individual volumes of the coolant are in the individual cells 39 of the waterwheel 38 not in connection with each other, whereby the electrical insulation resistance increases accordingly. The further the individual cells 39 in the presentation of the 6 move the axis of rotation down to the right, the more water flows out of the individual cells 39 off so the cells on the opposite side of the perimeter of the waterwheel 38 empty up again. Without that a drive of the water wheel 38 is necessary, so a very consistent division of individual volumes of the coolant flow from each other, so that the insulation resistance increases significantly.

Another alternative embodiment of a device 20 to increase the electrical insulation resistance is in the representation of 7 to recognize. In the presentation of the 7 is purely an example of a single container 21 shown, which in the embodiment shown here, a lower portion 40 as well as an upper section 41 having. The inflowing coolant flows over the line 18 as indicated by the arrow 22 is indicated in the lower section. The water stands there as an example with the 24 marked filling height. Inside the container 21 is now a so-called Archimedean screw 42 arranged. This will be over with a 43 Rotated drive motor rotates, causing water along the pitch of its thread within a fixed thread circumferentially limiting tube 45 moved upwards. The individual volumes of the over the Archimedean screw 42 Upwardly moving coolant are separated from each other, so that by this structure, especially if the Archimedean screw or at least the threads are made of an electrically insulating material, the electrical insulation resistance is significantly increased. So from the bottom section 40 in the upper section 41 pumped coolant accumulates in the upper section 41 as determined by the local coolant surface 44 is indicated and flows through the coolant line 18 according to the 23 designated arrow in the cooling circuit 12 further.

In the presentation of the 8th are one or two further embodiments of the device 20 shown. These can be used both alone and in addition to the variants described above. In the most simple variant, it is provided that the structure is designed so that the end of the conduit element 25 free in the container 21 ends. The flow then falls through the container 21 which already leads to a measurable increase in the insulation resistance. To further increase this effect with very simple means, as shown in the representation of the 8th is executed, in the end 25 a so-called jet regulator 46 be installed. Such a jet regulator 46 , which is also referred to as an air nozzle or air mixing nozzle, is well known and common in the field of faucets in sanitary facilities. Its construction functions to extract gas from the environment, in this case gas from the vessel, based on a negative pressure caused by the flowing coolant 21 , sucks and this mixed with the coolant flow continues. Between the jet regulator 46 and the surface 24 which is in the container 21 collecting liquid coolant thus results in a mixture of coolant and air, which also contributes to an increase in the insulation resistance.

In particular, this last-described construction can be implemented extremely easily and efficiently. It can also be easily and simply combined with all the embodiments described above, so as to further increase the electrical insulation resistance.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• JP 2004335369 A [0004]
• JP 2002117884 A [0004]

Claims (10)

Contraption ( 20 ) for increasing the electrical insulation resistance in a cooling circuit ( 12 ) with in coolant lines ( 18 ) flowing liquid coolant, characterized in that at least one point of the cooling circuit ( 12 ) one of the coolant lines ( 18 ) in the intended use in the direction of gravity above a liquid level ( 24 ) in a gas-filled container ( 21 ) in the cooling circuit ( 12 ) ends. Device according to claim 1, characterized in that in the region ( 25 ), in which the coolant line ( 18 ), a clocked switchable valve device ( 26 ) is arranged. Device according to claim 1, characterized in that, (in the region 25 ), in which the coolant line ( 18 ), a passively actuated by the flow pressure of the coolant locking device ( 19 ) is arranged. Apparatus according to claim 3, characterized in that, the locking device as by a spring against the flow direction loaded flap ( 19 ) is trained. Device according to claim 1 or 2, characterized in that in the container ( 21 ) between the end ( 25 ) of the coolant line ( 18 ) and typically in the container ( 21 ) liquid level ( 24 ) a rocker ( 31 . 35 ) is arranged. Device according to claim 1 or 2, characterized in that in the container ( 21 ) between the end ( 25 ) of the coolant line ( 18 ) and typically in the container ( 21 ) liquid level ( 24 ) an overshot waterwheel ( 38 ) is arranged. Device according to one of claims 1 to 6, characterized in that, at the end of the coolant line ( 18 ) An institution ( 37 ) to the entry in the container ( 21 ) present gas is disposed in the liquid stream. Contraption ( 20 ) for increasing electrical insulation resistance in a cooling circuit ( 12 ) with in coolant lines ( 18 ) flowing liquid coolant, characterized in that two gas-filled containers or a gas-filled container ( 21 ) with separate sections ( 40 . 41 ), wherein one of the containers or the one of the sections ( 41 ) in the direction of gravity higher than the other container or the other section ( 40 ), the containers or sections ( 41 . 40 ) via an Archimedean screw ( 42 ) are connected. Device according to one of claims 1 to 8, characterized in that the (in the container 21 ), the containers or sections ( 40 . 41 ) present gas is air. Use of the device according to one of claims 1 to 9, for increasing the electrical insulation resistance in a cooling circuit ( 12 ), which in an electrically driven vehicle ( 1 ) for cooling a fuel cell ( 3 ) and / or a traction battery is used.

Images