Expansion tank for cooling circuits with different temperature levels and pressure addition

Description

[0001] The invention relates to an expansion tank for coolant in a cooling system with at least two cooling circuits operating at different temperature levels. In particular, the invention relates to an expansion tank comprising a plurality of chambers separated by partition walls. Furthermore, the invention relates to a vehicle, preferably a commercial vehicle, and / or a stationary system with such an expansion tank.

[0002] Coolant expansion tanks of the type mentioned above fulfill several functions in closed cooling circuits. In addition to venting the cooling circuit, they serve to compensate for volume changes in the coolant circulating in the cooling circuit, e.g., water, oil, or a water-coolant additive mixture. For this purpose, the expansion tank, which is connected to the corresponding cooling circuit via a supply and return line, is not completely filled with coolant, but rather contains a defined air volume. If the coolant volume expands due to heating of the system, coolant is directed into the expansion tank and temporarily stored there.The pressure regulator integrated into the expansion tank prevents an excessive pressure increase in the closed cooling circuit, especially during operating conditions with high coolant temperatures. Without such a regulator, this would lead to bursting of the radiator or hoses due to the limited component strength. To fulfill this coolant storage or pressure-regulating function even at maximum coolant temperatures, the air volume of the expansion tank or the possible coolant reservoir should be designed accordingly.

[0003] However, a large design for the expansion tank's air volume is counteracted by the desire to pressurize the expansion tank's air volume as quickly as possible after the cooling circuit is started up (e.g., 0.6 to 0.9 bar overpressure relative to ambient pressure) in order to maintain sufficient pressure on the suction side of the coolant pump to prevent cavitation. The occurrence of cavitation would reduce the efficiency of the coolant pump(s) in the cooling circuits and can also lead to damage to the pump components (cavitation corrosion). Therefore, to build up the increased system pressure in the cooling system as quickly as possible, even under partial load and at low outside temperatures, the expansion tank's air volume should be designed to be correspondingly small.

[0004] This optimization problem in the design of the expansion tank is further complicated if the cooling system contains multiple cooling circuits at different temperature levels. For example, it is common in hybrid vehicles to use a high-temperature circuit for cooling the combustion engine, with a temperature level of over 90 °C during normal operation, and a low-temperature circuit for cooling the electric drive system at a lower temperature level. In order to effectively utilize the available installation space in these cases and to facilitate filling the various cooling circuits, it is usually planned to use only one common expansion tank for several of the cooling circuits. On the one hand, this can save components (filler necks, silicate reservoirs, etc.), and on the other hand, an air-side connection between the cooling circuits in the expansion tank enables pressure equalization between the various systems.Due to the rapid heating of the high-temperature circuit and the resulting pressure increase, the air-side coupling of the circuits simultaneously achieves a rapid pressure increase in the low-temperature circuit. Without such coupling, the pressure build-up would take significantly longer due to the low temperature in the low-temperature circuit.

[0005] A disadvantage of using a shared expansion tank, however, is that it can also lead to mixing of coolants with different temperatures. "Too warm" coolant would then be introduced from the shared expansion tank into a cooling circuit with a lower temperature level via the corresponding supply line, which could limit its functionality or cause damage to the connected components. Consequently, in the case of a shared coolant expansion tank in a cooling system with at least two cooling circuits with different temperatures, it is desirable, on the one hand, to allow the fastest possible pressure buildup and pressure equalization between the different cooling circuits, while, on the other hand, to prevent the introduction of "too warm" coolant into the cooling circuit with a lower temperature level.

[0006] To solve this problem, the published patent application DE 2 063 298 A1 proposes an expansion tank whose interior is divided by a partition into two coolant receiving areas, each of which is assigned to a cooling circuit. However, the partition is not continuous but has a connecting opening on the air side. This ensures pressure equalization between the two areas without the coolants of the two connected cooling circuits mixing. However, since the coolants of the two circuits have no connection to one another, both filling and introducing additives into the coolants are made more difficult because all components (connectors, silicate reservoir, etc.) have to be designed multiple times. Another disadvantage of this design is that the system pressure builds up only slowly because the entire volume of air in the expansion tank has to be compressed.

[0007] A further development of the aforementioned expansion tank is known from published patent application DE 10 2007 054 855 A1. In addition to the air-side connection below the tank ceiling, it also features an additional expansion opening in the partition wall for the exchange of coolant and additives. This expansion opening is designed to be small enough to allow for level compensation of the heat transfer media and diffusion of additives between the two areas, while preventing heat transfer between the two cooling circuits as much as possible. However, even with this expansion tank, the entire air volume must be compressed to build up pressure. The document DE102015015198 A1 presents another relevant system.

[0008] The object of the invention is therefore to provide an improved expansion tank for coolant in a cooling system with at least two cooling circuits operating at different temperature levels compared to the prior art. In particular, the object of the invention is to provide an expansion tank that enables rapid coolant pressure buildup and immediate pressure equalization between the connected cooling circuits. Furthermore, the exchange of coolant and the distribution of additives between the various cooling circuits should be enabled, while simultaneously keeping heat transfer as low as possible.

[0009] This object is achieved by a device having the features of the independent claim. Advantageous embodiments and applications of the invention emerge from the dependent claims and are explained in more detail in the following description, with partial reference to the figures.

[0010] According to general aspects of the invention, an expansion tank for coolant is provided in a cooling system with at least two cooling circuits, wherein at least two of the cooling circuits are operated at different temperature levels and can comprise other components known per se, including coolant pumps, coolant coolers, heat exchangers and fluid lines. The interior of the expansion tank is divided by partition walls into separate chambers, comprising a first coolant chamber with a first inlet and a first outlet for connecting the first coolant chamber to a first cooling circuit and a second coolant chamber with a second inlet and a second outlet for connecting the second coolant chamber to a second cooling circuit. The volume of the first and second cooling chambers can differ.The coolant chambers can preferably be connected to the respective cooling circuits via fluid lines, for example, pipe and / or hose connections, which enables the exchange of coolant, air or an air-coolant mixture, as well as gases generated during operation through evaporation processes, between the cooling circuits and the expansion tank. Any medium suitable for heat transport that circulates at least partially in a liquid state through the cooling circuits and coolant chambers can be used as the coolant. The coolant is preferably oil, water, or a water-cooling water additive mixture.

[0011] The expansion tank comprises a first passage opening, preferably in a partition separating the first and second coolant chambers, particularly preferably in the lower region thereof, to enable an exchange of coolant between the first and second coolant chambers. Furthermore, the expansion tank comprises a second passage opening, preferably in a partition separating the first and second coolant chambers, particularly preferably in the upper region thereof, to enable an exchange of air between the first and second coolant chambers. The terms "top" and "bottom" and variations thereof (e.g., "above" and "below") refer to the orientation with respect to the direction of gravity. Consequently, the first passage opening can be arranged in a region below the coolant fill level in the first and second coolant chambers during normal operation, particularly near the bottom of the expansion tank.In order to prevent both cooling circuits from running dry in the event of damage, the first passage opening in the lower region of the partition wall can be arranged at a distance from the bottom of the expansion tank. This advantageously ensures that a minimum amount of coolant remains in the intact cooling circuit. The second passage opening can be arranged in an area above the coolant fill level in the first and second coolant chambers during normal operation, in particular close to the ceiling of the expansion tank. Due to their corresponding positions, the first passage opening thus enables a flow of coolant from the first to the second coolant chamber and vice versa, and the second passage opening enables a flow of air from the first to the second coolant chamber and vice versa, whereby the term air is understood here to represent all types of gases and / or vapors present in the cooling circuit.

[0012] The two coolant chambers can thus communicate via the passage openings, enabling level adjustment and immediate pressure equalization in the first and second coolant chambers. Additional passage openings can also be provided in the partition wall.

[0013] In addition to the coolant chambers just mentioned, the claimed expansion tank comprises further air chambers, including a first air chamber which is connected to the second coolant chamber via a first overflow connection, and a second air chamber which is connected to the first air chamber via a second overflow connection and a first pressure valve attached thereto. The first and second overflow connections can be fluid lines, for example a pipe and / or hose connection. Preferably, the first overflow line connects an upper region of the second coolant chamber to a lower region of the first air chamber, and the second overflow line connects an upper region of the first air chamber to a lower region of the second air chamber.The overflow lines can also be designed in the form of a channel formed by a partition wall and another wall or a through opening, whereby the openings in the partition wall required for this purpose can be regarded as the inlet opening of the overflow line and thus as part of the overflow line.

[0014] The second air chamber also comprises a second pressure valve, via which the interior of the second air chamber is connected to the exterior. This second pressure valve is designed for a relative opening pressure that corresponds to a pressure difference between a relative opening pressure of the first pressure valve and a predetermined increased relative opening pressure, resulting in a pressure addition between their relative opening pressures. For example, if an overpressure of 0.9 bar relative to the exterior is not to be exceeded in the first air chamber, the first pressure valve can open at an overpressure of 0.4 bar in the first air chamber relative to the second air chamber, and the second pressure valve can open at an overpressure of 0.5 bar in the second air chamber relative to the pressure in the exterior.The pressure addition can therefore also be understood as a series connection of the two pressure valves, whose respective relative opening pressures are summed up due to the series connection. The two pressure valves can each be a pressure relief and / or vacuum valve, whereby only the respective relative vacuum and over-opening pressures are added for the pressure addition. As will be described in more detail later, this arrangement of air chambers and pressure valves advantageously allows for a rapid pressure build-up in the expansion tank during normal operation, while at the same time a sufficiently large volume is provided to accommodate the expanding coolant even at maximum coolant temperature, thus preventing any loss or ejection of coolant during operation.

[0015] The indefinite articles "ein" and "eine" and their declensions do not exclude a majority of the characteristics they denote. Thus, both the previous and the following statements with "ein" and "eine" are to be understood as "at least one" or "at least one." Specifically, the expansion tank thus comprises at least one first / second inlet, at least one first / second outlet, at least one first / second passage opening, etc.

[0016] According to one embodiment of the invention, the first passage opening is arranged in a lower half, preferably in a lower third, of the partition separating the first and second coolant chambers, and the second passage opening is arranged in an upper half, preferably in an upper third, of the partition separating the first and second coolant chambers. This is intended to ensure that the first passage opening enables an exchange of coolant, which collects in a lower region of the cooling chambers due to gravity, and the second passage opening enables an exchange of air, which collects in the upper region of the cooling chambers due to its lower density. Preferably, the first passage opening is arranged in the region of an outlet of one of the coolant chambers, and the second passage opening is arranged in the region of an inlet of one of the coolant chambers.Particularly preferably, the first passage opening is located below the minimum permissible fill level during normal operation, and the second passage opening is located above the maximum permissible fill level during normal operation. Furthermore, the first passage opening can be designed so small compared to the size of the coolant chamber that, although level compensation of the coolant and diffusion of additives between the first and second coolant chambers can occur, no large amounts of heat can be exchanged between the two coolant chambers. For this purpose, the first passage opening can preferably be arranged in a flow-calmed region of the first and second coolant chambers.

[0017] In order to further reduce the heat exchange between the first and second coolant chambers, a preferred embodiment provides that the first passage opening additionally comprises a shut-off device for interrupting the exchange of coolant between the first and second coolant chambers, wherein the shut-off device is designed as a pressure valve and / or float valve and / or thermostatic valve and / or gate valve or butterfly valve. This has the advantage that an exchange of coolant is possible for the purpose of filling and / or leveling of the coolants in the two coolant chambers, but during normal operation the heat transfer only takes place via the partition wall. This can have a low thermal conductivity due to its material, e.g. plastic, or for structural reasons, whereby no significant heat transfer can take place between the differently temperatured cooling circuits.The shut-off device in the form of a pressure valve can open when a certain coolant pressure difference occurs between the first and second cooling chambers, e.g. due to significantly different fill levels, and thus enable pressure reduction or equalization of the fill levels. The shut-off device in the form of a float valve can be closed in the normal state and only open if a certain fill level in the first and / or second chamber is exceeded or undercut. Once the target fill level is reached, the float valve can close again. A shut-off device in the form of a thermostatic valve can be designed so that the thermostatic valve closes when the temperature difference between the media in the coolant chambers increases. Furthermore, a manually or electrically operated gate valve or a manually or electrically operated butterfly valve can be provided.These shut-off devices can be opened, for example, for filling, but otherwise closed to prevent heat exchange between the chambers.

[0018] Furthermore, it is preferably provided that the partition separating the first and second coolant chambers is designed in the form of a flow-calmed third coolant chamber. Alternatively, the third coolant chamber can also be designed as a further component in addition to the partition. The exchange of coolant and air between the first and second coolant chambers takes place via the third coolant chamber, wherein convection can be effectively avoided or at least reduced due to its structural design. In other words, coolant and additives dissolved therein can pass from the first via the third to the second coolant chamber and vice versa after filling, but this preferably takes place diffusively and not in the form of directed coolant and thus heat flows.The exchange of coolant between the first and second coolant chambers "via the third coolant chamber" is to be understood in such a way that coolant from the first coolant chamber first enters the third coolant chamber and then reaches the second coolant chamber, or coolant from the second coolant chamber first enters the third coolant chamber and then reaches the first coolant chamber.

[0019] The same applies to the exchange of air. Configuring the partition separating the first and second coolant chambers as a third coolant chamber, i.e., by constructing a partition separating the first and third coolant chambers on the one hand and a partition separating the third and second coolant chambers on the other, entails a corresponding adaptation of the first and second passage openings. Consequently, both the partition separating the first and third coolant chambers comprises a first and second passage opening, and the partition separating the third and second coolant chambers comprises a first and second passage opening. The same also applies if the third coolant chamber is configured as a further component in addition to the partition.

[0020] In order to effectively prevent the back-and-forth flow of coolant and thus heat exchange between the first and second coolant chambers, a further development of the embodiment provides that the third coolant chamber comprises one or more baffles for flow calming and / or one or more flow-calming elements. The baffle can be formed integrally with the wall of the expansion tank and / or a partition wall and / or have fluid-permeable openings. The baffle can dampen movements of the coolant within the third coolant chamber and preferably increase the rigidity of the expansion tank and thus its stability. Such baffles can also be arranged in the coolant chambers.The flow-calming elements can be in the form of flow obstacles and / or built-in components and / or flow-around bodies which, through their shape, restrict the coolant flow or reduce its speed. The third coolant chamber also comprises one or more fill level probes. This is particularly advantageous because the calmed flow in this chamber enables the fill level to be reliably measured and / or read without major fluctuations. The fill level probe can comprise a float and / or an inductive and / or magnetostrictive sensor. The fill level probe can comprise a vibration sensor and / or a pressure sensor. Furthermore, the fill level probe can comprise a visual display and / or an output of an electrical signal. The third coolant chamber is preferably arranged at a geometrically central location on the expansion tank in order to ensure reliable level control even in the event of inclined positions oraccelerations to sense an average coolant level.

[0021] According to a further aspect, at least one of the partition walls is double-walled and includes a thermally insulating air gap. The advantage of this is that it reduces heat transfer between the chambers, preferably between the coolant chambers. Furthermore, the air gap between the two walls can be filled with additional thermally insulating material.

[0022] According to one embodiment, the first and / or second air chamber comprises a connection for external pressurization and / or pressure relief. By means of external pressurization, which can be implemented in any technical form, an increased pressure can be set in the expansion tank already at the time of commissioning, whereby cavitation and / or boiling of coolant can be avoided in the (partial) cooling circuits connected to the expansion tank and the components and pumps contained therein. This is particularly advantageous if the connected cooling circuits have low temperature levels even during normal operation and a regular pressure build-up would therefore only occur slowly. The connection for external pressure relief can, for example, be connected to an area of ​​a cooling circuit connected to the expansion tank in which unintentionally high pressures occur.The external pressure relief can also be used to dissipate pressure surges or pressure pulsations, for example, generated by a water retarder. Alternatively, the external pressurization can also be arranged at the first and / or second coolant chamber.

[0023] To further enable safe opening of the expansion tank during operation, an external pressure relief device is provided, by means of which the excess pressure present in the expansion tank during normal operation can be quickly released. The external pressure relief device can be integrated into the cover and / or the filler opening and can be activated, for example, via a manually or automatically activated valve. Furthermore, the external pressure relief device can be implemented via a pressure relief opening in the cover and / or the filler opening, whereby the pressure relief opening is only released when the cover is opened. This is intended to specifically discharge the pressure, including any coolant carried within it.

[0024] According to one embodiment, which is not a variant of the present invention, it is provided that an air chamber arrangement, comprising the first and second air chambers, is directly adjacent to a coolant chamber arrangement, comprising the first and second coolant chambers. This means that the air chamber arrangement and coolant chamber arrangement can be in direct mechanical contact with one another and can therefore be regarded as a single component. According to the invention, however, the air chamber arrangement, comprising the first and second air chambers, is designed as a separate container part at a distance from the coolant chamber arrangement comprising the first and second coolant chambers and is connected to the coolant chamber arrangement via the first overflow connection. For this purpose, the overflow connection can comprise an additional fluid line section, for example a pipe and / or hose connection.The advantage of this design is that the available installation space can be used more effectively due to the more flexible arrangement of the chambers.

[0025] In a further preferred embodiment, the first air chamber has a smaller volume than the second air chamber to ensure rapid pressure build-up. Due to the small air volume, even a slight expansion of the coolant can cause a significant increase in pressure in the expansion tank, which advantageously results in increased coolant pressure in the cooling circuits shortly after commissioning. The first air chamber therefore preferably serves primarily to build up pressure during normal operation, while the larger volume of the second air chamber is dimensioned to accommodate the entire expanding quantity of coolant even at maximum coolant temperature, thereby preventing ejection or loss of coolant. In addition, the larger volume of the second air chamber ensures that the pressure level remains as constant as possible even when coolant temperatures fluctuate during operation.

[0026] According to a further aspect of the invention, the expansion tank is made of a transparent material. This advantageously enables visual monitoring of the coolant levels in the individual chambers. Alternatively, the expansion tank is made of a non-transparent material.

[0027] In a further embodiment of the expansion tank, it also includes a viewing window for visual fill level monitoring. The viewing window is preferably located on a coolant chamber. The expansion tank may also include multiple viewing windows.

[0028] The expansion tank further comprises one or more level probes. The level probe may comprise a float and / or an inductive and / or magnetostrictive sensor. The level probe may comprise a vibration sensor and / or a pressure sensor. Furthermore, the level probe may comprise a visual indicator and / or an output of an electrical signal.

[0029] To ensure a reliable and stable hose connection between the cooling circuits and the cooling chambers, a preferred embodiment provides for the inlet and / or outlet of the first and / or second coolant chamber to be designed as a hose connector or hose coupling. The inlet is understood to be the opening for supplying the coolant into the first or second coolant chamber, and the outlet is understood to be the opening for the coolant to escape from the first or second coolant chamber. The first and second coolant chambers can also comprise more than one inlet and more than one outlet. Alternatively, the inlet and / or outlet can also comprise a pipe coupling and / or flange connection.

[0030] In addition, the expansion tank can comprise one or more silicate reservoirs for introducing additives into the coolant. These are preferably arranged in the first and / or second coolant chamber. The silicate reservoirs can be permanent or refillable silicate reservoirs that release soluble additives, such as corrosion-inhibiting additives, into the coolant over time.

[0031] The expansion tank further comprises a filler opening for coolant with a corresponding cover. The filler opening is preferably arranged in the region of the partition wall separating the first and second coolant chambers in order to enable easy filling of both coolant chambers. Alternatively, the filler opening is arranged only in the region of the first or second cooling chamber, and the other chambers are filled via the first passage opening. The filler opening can preferably be arranged in the region of the expansion tank cover. In addition, the expansion tank can - if advantageous for the filling process during assembly - also comprise filler openings through which filling takes place during assembly, but which are subsequently closed so that they cannot be opened.

[0032] To connect additional cooling circuits, the expansion tank comprises additional coolant chambers connected in parallel to the first and second coolant chambers, each with corresponding inlets and outlets for connecting to additional cooling circuits. The additional coolant chambers can be connected via corresponding passage openings in the corresponding partition walls, thus enabling an exchange of coolant and air between the first, second, and additional coolant chambers.

[0033] The expansion tank further comprises additional air chambers connected in series with the first and second air chambers, each with corresponding overflow connections and pressure valves. Preferably, the respective relative opening pressures of the pressure valves are summed due to the series connection. Each of the two pressure valves can be an overpressure and / or a vacuum valve, with only the respective relative vacuum and overpressure pressures being added for the pressure summation.

[0034] The invention further relates to a motor vehicle, preferably a commercial vehicle (e.g., a truck, tractor unit, other motor vehicle, etc.), with an expansion tank as described in this document. For example, the commercial vehicle can be a construction machine (excavator, crawler, etc.) or an agricultural machine (tractor, combine harvester, etc.). The motor vehicle can comprise an internal combustion engine and / or electric motor and / or a fuel cell.

[0035] Furthermore, the invention relates to a stationary system with an expansion tank as described in this document. The stationary system can also comprise an internal combustion engine and / or electric motor and / or a fuel cell.

[0036] The disclosure further includes the following aspects: A first independent aspect relates to an expansion tank for coolant in a cooling system having at least two cooling circuits operating at different temperature levels, wherein an interior of the expansion tank is divided into separate chambers by partition walls. The expansion tank comprises: a) a first coolant chamber, having a first inlet and a first outlet for connecting the first coolant chamber to a first cooling circuit, b) a second coolant chamber, having a second inlet and a second outlet for connecting the second coolant chamber to a second cooling circuit, c) a first passage opening in a partition wall separating the first and second coolant chambers, preferably in the lower region thereof, to enable an exchange of coolant between the first and second coolant chambers, d) a second passage opening in a partition wall separating the first and second coolant chambers, preferably in the upper region thereof, to enable an exchange of air between the first and second coolant chambers, e) a first air chamber, which is connected to the second coolant chamber via a first overflow connection, f) a second air chamber,which is connected to the first air chamber via a second overflow connection and a first pressure valve attached thereto and is connected to the outside space via a second pressure valve, wherein g) the second pressure valve is designed for a relative opening pressure which corresponds to a pressure difference between a relative opening pressure of the first pressure valve and a predetermined increased relative opening pressure, so that a pressure addition results between their relative opening pressures.

[0037] According to a second aspect dependent on the first aspect, the first passage opening is arranged in a lower half, preferably in a lower third, of the partition wall separating the first and second coolant chambers and the second passage opening is arranged in an upper half, preferably in an upper third, of the partition wall separating the first and second coolant chambers.

[0038] According to a third aspect, dependent on the first or second aspect, the first passage opening additionally comprises a shut-off device for interrupting the exchange of coolant between the first and second coolant chambers, wherein the shut-off device is designed as a. pressure valve and / or b. float valve and / or c. thermostatic valve and / or d. gate valve or butterfly valve is trained.

[0039] According to a fourth aspect dependent on the first aspect, the partition wall separating the first and second coolant chambers is designed in the form of a flow-calmed third coolant chamber, wherein the exchange of coolant and air between the first and second coolant chambers takes place via the third coolant chamber.

[0040] According to a fifth aspect dependent on the fourth aspect, the third coolant chamber comprises a. one or more baffles to calm the flow and / or b. one or more flow-calming elements and / or c. one or more level probes.

[0041] According to a sixth aspect dependent on one of the aspects one to five, at least one of the partition walls is double-walled and comprises a thermally insulating air gap.

[0042] According to a seventh aspect, dependent on any one of aspects one to six, the first and / or second air chamber comprises a connection for an external a) pressurization and / or b) pressure relief.

[0043] According to an eighth aspect, which depends on one of the aspects one to seven a) an air chamber arrangement comprising the first and second air chambers directly adjoins a coolant chamber arrangement comprising the first and second coolant chambers; or b) an air chamber arrangement comprising the first and second air chambers is spaced apart from the coolant chamber arrangement comprising the first and second coolant chambers, is designed as a separate container part and is connected to the coolant chamber arrangement via the first overflow connection.

[0044] According to a ninth aspect, which depends on one of the aspects one to eight, the first air chamber has a smaller volume than the second air chamber for rapid pressure build-up.

[0045] According to a tenth aspect, which depends on one of the aspects one to nine a1) the expansion tank is made of a transparent material or a2) the expansion tank is made of a non-transparent material and / or b1) the expansion tank includes a viewing window for optical level control and / or b2) the expansion tank includes one or more level probes.

[0046] According to an eleventh aspect, which depends on one of the aspects one to ten a) the inlet and / or outlet of the first and / or second coolant chamber is designed as a hose nozzle or hose coupling and / or b) the expansion tank comprises one or more silicate depots for introducing additives into the coolant, which are preferably arranged on the first and / or second coolant chamber and / or c) the expansion tank has a filling opening for coolant with a corresponding lid.

[0047] According to a twelfth aspect, which depends on one of the aspects one to eleven, the expansion tank comprises a. further air chambers connected in series with the first and second air chambers, with corresponding overflow connections and pressure valves; and / or b. further coolant chambers connected in parallel with the first and second coolant chambers, with corresponding inlets and outlets for connection to further cooling circuits.

[0048] A thirteenth aspect relates to a motor vehicle, preferably a commercial vehicle, and / or a stationary system with an expansion tank according to one of aspects one to twelve.

[0049] The above-described preferred embodiments and features of the invention can be combined with one another as desired. Further details and advantages of the invention are described below with reference to the accompanying drawings. They show: Figure 1: a schematic longitudinal section of an expansion tank for coolant in a cooling system with at least two cooling circuits according to one embodiment (not an embodiment of the invention); Figure 2: an embodiment of an expansion tank according to an embodiment of the invention, in which the air chamber arrangement, comprising the first and second air chambers, is designed as a separate tank part; Figure 3: an embodiment (not an embodiment of the invention) of an expansion tank according to an embodiment, which comprises a further coolant chamber.

[0050] Figure 1shows an expansion tank according to one embodiment, the interior of which is divided into four chambers K 1 , K 2 , L 1 and L 2 by three partition walls 3a, 3b and 3c. The chambers K 1 and K 2 , which are referred to below as the coolant chamber, each have an inlet 1a, 2a and an outlet 1b, 2b, via which the two coolant chambers K 1 , K 2 are connected to cooling circuits (not shown) by means of corresponding supply and return lines, e.g. pipe or hose connections. In order to function properly, the cooling circuits can comprise components known per se, including coolant, coolant pumps, coolant coolers, heat exchangers, components around which coolant flows and other fluid lines. The two cooling circuits preferably have a different operating temperature during normal operation.Thus, the cooling circuit assigned to the first coolant chamber K 1 has a lower coolant temperature level than the cooling circuit connected to the second coolant chamber K 2. During normal operation, the two coolant chambers K 1 and K 2 are partially filled with coolant 10, with the coolant temperature level shown in . Figure 1 The coolant fill level shown by way of example is approximately 85% of the respective coolant chamber volume and is sensed by a fill level probe 9. The remaining volume of the coolant chambers K 1 and K 2 is filled with air 20, whereby the term air 20 is understood to represent all types of gases and / or vapors present in the cooling circuit. Coolant 10 can be understood to be any medium suitable for heat transport which circulates at least partially in the liquid state through the cooling circuits and coolant chambers K 1 , K 2 . The coolant 10 is preferably a water-cooling water-additive mixture.

[0051] The heat-insulating partition wall 3a separating the first and second coolant chambers K 1 and K 2 is not continuous, but has two small passage openings 4a and 4b. The first passage opening 4a is located near the bottom of the expansion tank 100, i.e. below the minimum permissible fill level of coolant 10, and enables an exchange of coolant 10 and substances dissolved therein, e.g. additives for corrosion protection. In order to prevent excessive heat exchange, the passage opening 4a is advantageously arranged in a region with calm flow. The second passage opening 4b is located just below the tank ceiling and thus in an area above the maximum permissible fill level of coolant 10. This second passage opening 4b enables an exchange of air 20 and thus also pressure equalization between the two coolant chambers K 1 and K 2.In other words, the same air pressure is present in the areas of the first and second coolant chambers K 1 and K 2 filled with air 20, and the same coolant pressure is present in the areas of the expansion tank 100 filled with coolant 10. Furthermore, the expansion tank 100 comprises a filler opening 7a for coolant 10 with a corresponding cover 7b. The filler opening 7a is arranged in the tank ceiling in the region of the partition wall 3a. Advantageously, both coolant chambers K 1 and K 2 can thus be filled with coolant simultaneously.

[0052] In addition to the two coolant chambers K 1 and K 2 , the expansion tank 100 comprises a first small air chamber L 1 , which is formed by the tank walls (including the lid and base) and the partition walls 3b and 3c. This air chamber L 1 is connected to the second coolant chamber K 2 via a first overflow connection 5a. By way of example, the air chamber L 1 is shown next to and in connection with the coolant chamber K 2. In the present example, the first overflow connection comprises an opening in the partition wall 3b just below the tank ceiling and a channel formed by the partition wall 3b and a further first wall 51. The overflow connection 5a opens into the first air chamber L 1 in a lower area, i.e. near the base of the expansion tank 100. This first air chamber L 1 is followed by a further second large air chamber L 2 , the volume of which is determined by the tank walls (including the lid and base) and the partition walls 3b and 3c.cover and base) and the partition walls 3c and which has a larger volume than the first air chamber L 1. The connection between the first and second air chambers is made via a first pressure valve 6a arranged in the upper region of the partition wall 6a and an adjoining second overflow connection 5b. Similar to the first overflow connection 5a, the second overflow connection 5b is also formed in this case by a partition wall 3c and a further second wall 52 and ends in a lower region, ie near the base of the expansion tank 100, in the second air chamber L 2. The first pressure valve 6a opens on the one hand at an overpressure of 0.4 bar in the first air chamber L 1 relative to the pressure in the second air chamber L 2 and on the other hand at a underpressure of 0.03 mbar in the first air chamber L 1 relative to the pressure in the second air chamber L 2.In addition, the second air chamber L 2 comprises a second pressure valve 6b, through which air can escape into the outside space from an overpressure of 0.5 bar in the second air chamber L 2 relative to the outside pressure and can enter the second air chamber from the outside space if there is a negative pressure of 0.03 mbar in the second air chamber relative to the pressure in the outside space.

[0053] In the following, the effect of the pressure addition of the two air chambers L 1 and L 2 is explained with reference to Figure 1 described in more detail, whereby in the initial state none of the cooling circuits should be in operation. In all four chambers there is an air pressure of 0 bar relative to the external pressure and the coolant chambers K 1 and K 2 are filled with coolant 10 up to the Figure 1Filled to the fill level shown. If the cooling circuits are now put into operation, the coolant 10 in both cooling circuits begins to heat up. As a result of the resulting expansion of the coolant 10, it is forced into the expansion tank 100 and displaces or compresses the air volume present there. This is composed of the small air volume above the initial coolant fill level in the coolant chambers K 1 , K 2 and the small air volume in the first air chamber L 1 .

[0054] As a result of thisDue to the relatively small air volume, a rapid pressure build-up in both cooling circuits up to an overpressure of 0.4 bar relative to the second air chamber L 2 or external pressure advantageously occurs, since the second air chamber L 2 is still at a pressure of 0 bar relative to the external pressure. In the course of this pressure build-up, coolant 10 can also be pressed into the first air chamber L 1 via the overflow connection 5a. The advantage of the arrangement is that, due to the air-side coupling via the passage opening 4b, an overpressure preventing cavitation and boiling of the coolant is generated even in the cooling circuit with a low temperature level shortly after commissioning, which would otherwise occur much more slowly due to the lower temperature level of the cooling circuit.

[0055] With further heating of the cooling circuits and the associated expansion of the coolant 10 in the cooling circuits, a further pressure buildup occurs in the system, although this now occurs more slowly, since from an overpressure of 0.4 bar relative to the second air chamber L 2, its volume is also available via the pressure valve 6a. Accordingly, a pressure buildup subsequently occurs in both the first and second air chambers, with the pressure in the first air chamber L 1 always being 0.4 bar higher than that in the second air chamber L 2.

[0056] This increase continues until an overpressure of 0.5 bar is reached in the second air chamber L2 compared to the outside. From this point on, air escapes from the expansion tank into the outside, and no further pressure buildup occurs to protect the components. The advantage of the two-stage pressure buildup using the two air chambers L1 and L2 is that, in the event of an interim pressure drop due to transiently fluctuating coolant temperatures, a rapid pressure buildup can occur again, since only the small volume of the first air chamber L1 needs to be compressed instead of the entire air volume of the expansion tank 100.

[0057] The advantage of the second air chamber L 2, instead of a direct outlet to the outside through a pressure valve with a correspondingly increased opening pressure, is that the second air chamber L 2 can be dimensioned such that it can accommodate the entire expanding coolant volume even at maximum coolant temperature. This prevents any loss or ejection of coolant 10 during operation.

[0058] Compressed in the Figure 1If the coolant 10 is released from the expansion tank 100 shown after the end of operation due to the falling coolant temperature, a negative pressure is created in the air chambers L 1 and L 2, which transports any coolant 10 present in the air chambers back into the coolant chambers K 1 and K 2 via the overflow connection 5a, 5b. In addition, in the present example, pressure equalization takes place via the pressure valves 6a and 6b if there is a negative pressure of 0.03 mbar in the first air chamber L 1 relative to the second air chamber L 2 or if there is a negative pressure of 0.03 mbar in the second air chamber L 2 relative to the external pressure.

[0059] Figure 2 shows an embodiment of the expansion tank 100 according to the invention, which also comprises two coolant chambers K 1 and K 2 and two air chambers L 1 and L 2. In contrast to the previous embodiment from Figure 1the air chambers L 1 and L 2 are designed as an air chamber arrangement spaced apart from the coolant chambers K 1 and K 2, which is connected to the coolant chambers K 1 and K 2 via the first overflow connection 5a. The overflow connection 5a comprises an opening formed as a hose and / or line connection in the partition wall 3b just below the container ceiling as well as a channel formed by the partition wall 3b and a further first wall 51. In contrast to the embodiment from Figure 1The first passage opening 4a in the partition wall 3a separating the first and second coolant chambers K 1 , K 2 is arranged below the minimum permissible coolant fill level, but not directly near the bottom of the expansion tank 100. This has the advantage that in the event of a leak in one of the cooling circuits, a complete draining of the other cooling circuit is prevented. In addition, the passage opening 4a comprises a shut-off device 6c. This is designed in the form of a valve and, when closed, interrupts the exchange of coolant 10 between the two cooling circuits. This effectively prevents heat transfer between the differently tempered cooling circuits. The air chamber arrangement consisting of the two air chambers L 1 and L 2 has, in addition to the embodiment of the Figure 1a connection 8a for external pressurization and a connection 8b for external pressure relief. By means of the pressurization, it is possible to apply excess pressure to the expansion tank 100 already when the cooling circuits are started up, thereby eliminating and / or accelerating the otherwise existing pressure build-up phase. By means of the pressure relief, any unwanted excess pressure, pressure surges and / or pulsations occurring in the cooling system can be diverted from the cooling system, thereby providing an additional safety mechanism. Furthermore, the expansion tank comprises a fill level probe 9 arranged in the second coolant chamber for sensing the coolant fill level.

[0060] In the Figure 3In the embodiment shown (not an embodiment of the invention), the partition wall 3a separating the first and second coolant chambers K 1 , K 2 is designed in the form of a flow-calmed third coolant chamber K 3. Due to the severely suppressed exchange of coolant 10 between the first and second cooling chambers K 1 , K 2, undesired heat transfer between the two differently tempered cooling circuits is prevented. Due to the small movements of the coolant 10 in the third chamber, this location is particularly suitable for level measurement. For this reason, in the exemplary embodiment shown, a level probe 9 is arranged in the third coolant chamber K 3, which measures the level of the coolant in the third coolant chamber K 3. Furthermore, the fill opening 7a is not arranged in the region of the partition wall, but exclusively in the region of the first coolant chamber.However, due to the first passage opening 4a passing through the third coolant chamber K 3 , when the first chamber K 1 is filled, coolant is simultaneously introduced into the second and third chambers K 2 , K 3 . List of reference symbols

[0061] K 1 First coolant chamber K 2 Second coolant chamber K 3 Third coolant chamber L 1 First air chamber L 2 Second air chamber 1aFirst inlet 1bFirst outlet 2aSecond inlet 2bSecond outlet 3aPartition between first and second coolant chamber 3bPartition between second coolant chamber and first air chamber 3cPartition between first and second air chamber 4aFirst passage opening 4bSecond passage opening 5aFirst overflow connection 5bSecond overflow connection 6aFirst pressure valve 6bSecond pressure valve 6cShut-off device 7aFill opening 7bFill opening cover 8aConnection for external pressurization 8bConnection for external pressure relief 9Fill level probe 10Coolant 20Air 51First wall 52Second wall 100Expansion tank

Claims

1. Compensation tank (100) for coolant (10) in a cooling system having at least two cooling circuits which are operated at different temperature levels, wherein an inner space of the compensation tank (100) is divided into separate chambers (K1, K2, L1, L2) by partition walls (3a, 3b, 3c), comprising: a) a first coolant chamber (K1) comprising a first inlet (1a) and a first outlet (1b) for connecting the first coolant chamber (K1) to a first cooling circuit, b) a second coolant chamber (K2) comprising a second inlet (2a) and a second outlet (2b) for connecting the second coolant chamber (K2) to a second cooling circuit, c) a first passage opening (4a) in a partition wall (3a) separating the first and second coolant chambers (K1, K2), preferably in the lower region thereof, for enabling an exchange of coolant (10) between the first and second coolant chambers (K1, K2), d) a second passage opening (4b) in a partition wall (3a) separating the first and second coolant chambers (K1, K2), preferably in the upper region thereof, for enabling an exchange of air (20) between the first and second coolant chambers (K1, K2), e) a first air chamber (L1), which communicates with the second coolant chamber (K2) via a first overflow connection (5a), f) a second air chamber (L2), which communicates with the first air chamber (L1) via a second overflow connection (5b) and a first pressure valve (6a) attached thereto and communicates with the external space via a second pressure valve (6b), wherein g) the second pressure valve (6b) is configured for a relative opening pressure corresponding to a pressure difference between a relative opening pressure of the first pressure valve (6a) and a predetermined increased relative opening pressure, so that a pressure addition results between their relative opening pressures; wherein an air chamber assembly, comprising the first and second air chambers (L1, L2), is arranged at a distance from the coolant chamber assembly, comprising the first and second coolant chambers (K1, K2), as a separate container part and is in communication with the coolant chamber assembly via the first overflow connection (5a).

2. Compensation tank (100) according to claim 1, characterized in that the first passage opening (4a) is arranged in a lower half, preferably in a lower third, of the partition wall (3a) separating the first and second coolant chambers (K1, K2), and the second passage opening (4b) is arranged in an upper half, preferably in an upper third, of the partition wall (3a) separating the first and second coolant chambers (K1, K2).

3. Compensation tank (100) according to claim 1 or 2, characterized in that the first passage opening (4a) further comprises a shut-off device (6c) for interrupting the exchange of coolant (10) between the first and second coolant chambers (K1, K2), wherein the shut-off device (6c) is configured as a. pressure valve and / or b. float valve and / or c. thermostatic valve and / or d. gate valve or butterfly valve.

4. Compensation tank (100) according to claim 1, characterized in that the partition wall (3a) separating the first and second coolant chambers (K1, K2) is configured as a flow-calmed third coolant chamber (K3) and the exchange of coolant (10) and air (20) between the first and second coolant chambers (K1, K2) occurs via the third coolant chamber (K3).

5. Compensation tank (100) according to claim 4, characterized in that the third coolant chamber (K3) comprises a. one or more baffles for flow-calming and / or b. one or more flow-calming elements and / or c. one or more filling level probes (9).

6. Compensation tank (100) according to any one of the preceding claims, characterized in that at least one of the partition walls (3a, 3b, 3c) is double-walled and comprises a thermally insulating air gap.

7. Compensation tank (100) according to any one of the preceding claims, characterized in that the first and / or second air chamber (L1, L2) has a connection for an external a) pressurization (8a) and / or b) pressure relief (8b).

8. Compensation tank (100) according to any one of the preceding claims, characterized in that for rapid pressure build-up, the first air chamber (L1) comprises a smaller volume than the second air chamber (L2).

9. Compensation tank (100) according to any one of the preceding claims, characterized in that the compensation tank (100) is a1) is made of a transparent material or a2) is made of a non-transparent material and / or b1) comprises a viewing window for optical filling level control and / or b2) comprises one or more filling level probes (9).

10. Compensation tank (100) according to any one of the preceding claims, characterized in that a) the inlet (1a, 2a) and / or outlet (1b, 2b) of the first and / or second coolant chamber (K1, K2) is configured as a hose nozzle or hose coupling and / or b) the compensation tank (100) comprises one or more silicate depots for introducing additives into the coolant (10), which are preferably arranged at the first and / or second coolant chamber (K1, K2) and / or c) has a filling opening (7a) for coolant (10) with a corresponding cover (7b).

11. Compensation tank (100) according to any one of the preceding claims, wherein the compensation tank (100) comprises a. further air chambers connected in series with the first and second air chambers (L1, L2) and having corresponding overflow connections and pressure valves and / or b. further coolant chambers connected in parallel with the first and second coolant chambers (K1, K2) and having corresponding inlets and outlets for connecting to further cooling circuits.

12. Motor vehicle, preferably commercial vehicle, and / or stationary installation having a compensation tank (100) according to any one of claims 1 to 11.