Expansion tank for a coolant system and motor vehicle

Abstract

Expansion tank (10) for a coolant system, comprising a housing (12) whose internal volume is divided into several chambers (20) by at least one baffle (18) extending therein to dampen movement of a coolant (22) in the expansion tank (10), wherein the at least one baffle (18) has, with reference to a specified installation position of the expansion tank (10), a fluid-flowable lower passage (26) below a specified minimum fill level of the expansion tank (10) and an air-flowable upper passage (24) above a specified maximum fill level of the expansion tank (10), through which the chambers (20) are coupled to one another, wherein for a given medium the upper passage (24) has a greater flow resistance than the lower passage (26), characterized in thatthat the upper passage opening (24) and the lower passage opening (26) are matched to each other in such a way that the upper passage opening (24) offers the air flowing through it at least essentially the same flow resistance as the lower passage opening (26) offers the coolant (22) flowing through it.

Description

The present invention relates to an expansion tank for a coolant system, in particular for a motor vehicle. The invention further relates to a corresponding motor vehicle equipped with such an expansion tank. In automotive engineering, as in other technical fields, the cooling requirements of various systems or units can often only be met by liquid-based cooling. Such liquid-based cooling systems frequently include expansion tanks for a cooling medium or coolant circulating within the system. These expansion tanks serve, for example, as a vent point for the cooling system, for refilling with coolant, and can also accommodate volume changes in the coolant caused by temperature fluctuations. By design, a portion of the expansion tank integrated into the cooling system is empty or filled with air or gas, thus preventing damage to the cooling system from excessive pressure increases due to the incompressibility of typical coolants. However, if such a cooling system or expansion tank is used in applications where movement or acceleration of the expansion tank is possible, partial filling with coolant can cause the coolant to slosh around inside the tank. This can negatively affect, for example, a coolant or level sensor may falsely report a coolant loss or a low coolant level, and / or air may enter a downstream coolant line of the cooling system or be drawn in by a coolant pump. This can lead to damage or reduced effectiveness of the cooling system. JP 2014-66 250 A describes a coolant tank with a downwardly offset area in which a coolant tank outlet is located. A partition is also located within the coolant tank near this area. DE 10 2019 212 096 A1 describes a buffer tank with a plurality of adjacent chambers connected to each other in a lower section. Some adjacent chambers are also connected to each other via an opening located in an upper section, but at least two adjacent chambers are fluidically separated from each other in the upper section. The chambers can only be traversed by a fluid along a meandering flow path. DE 10 2013 001 681 A1 discloses an expansion tank for the cooling system of an internal combustion engine with welded tank shells having inner walls. DE 24 37 502 A1 describes an expansion tank connected on its inlet side by at least two vent lines and on its outlet side by a bypass return line. A vertically oriented internal partition divides the tank into a pre-chamber and an extraction chamber, with the vent lines opening into the pre-chamber and the bypass return line into the extraction chamber. The partition has a connection at the bottom of the tank for low-bubble coolant and a vent connection at the top of the tank between the pre-chamber and the extraction chamber. From DE 10 2018 102 235 A1, an expansion tank for cooling circuits with different temperature levels and pressure addition is known. To achieve rapid pressure build-up in all connected cooling circuits while simultaneously minimizing heat transfer between the different cooling circuits, the expansion tank described therein is divided into separate chambers by partitions. The expansion tank comprises at least two coolant chambers connected on the coolant and air sides, and a series connection of at least two air chambers for rapid pressure build-up by means of pressure addition. The coolant chambers can communicate via openings in the partitions. Thus, the coolant level can equalize across the multiple chambers via these openings.However, a potential problem is that such compensation can occur too quickly in practical applications, which could lead to continued problematic air intake. Another expansion tank, specifically for a motor vehicle cooling system, is described in EP 2 762 696 A1. The expansion tank described therein has a coolant chamber and an expansion chamber separated from it by a partition. The expansion chamber is located below the coolant chamber, with an upper section of the coolant chamber connected to a lower section of the expansion chamber by a transfer line. The expansion tank is to have a base body, formed as a section of an extruded profile, which is sealed fluid-tight by at least two cover elements. The coolant chamber and / or the expansion chamber may be penetrated by baffles to dampen coolant movement within the coolant chamber and / or the expansion chamber and to increase the rigidity of the expansion tank.However, even there, no solution is ultimately offered for the problems mentioned. The object of the present invention is to reduce the risk of air being drawn in from an expansion tank of a coolant system in a particularly space-saving manner. This problem is solved according to the invention by the subject matter of the independent claims. Possible embodiments and further developments of the present invention are specified in the dependent claims, in the description, and in the drawing. An expansion tank according to the invention for a coolant system, in particular of a motor vehicle, has a housing whose internal volume is divided into several chambers by at least one baffle wall located therein to dampen the movement of a coolant or cooling medium in the expansion tank. The at least one baffle wall has at least one lower opening through which fluid can flow and at least one upper opening through which fluid or air can flow. The lower opening is arranged, relative to a direction of gravity, below a predetermined minimum coolant level in the expansion tank when installed in the intended position.The upper opening, relative to the direction of gravity, is positioned above a predetermined maximum coolant level in the expansion tank when installed correctly. The chambers are interconnected via these openings. This allows communication between the chambers, enabling coolant level equalization within the expansion tank. This occurs, for example, during acceleration of the expansion tank or the vehicle equipped with it, or when the expansion tank is tilted relative to the direction of gravity. According to the invention, for a given medium, the upper passage opening has a greater flow resistance than the lower passage opening. In other words, at a given pressure, the upper passage opening can offer greater resistance to a substance flowing through it than the lower passage opening. At a given pressure, a lower volume flow rate of the given medium would therefore flow through the upper passage opening than through the lower passage opening. The upper and lower passage openings can be designed differently to achieve this. Various possibilities for this are explained in more detail below. In the present invention, the upper and lower passage openings are coordinated such that the upper passage opening offers at least substantially the same flow resistance to the air flowing through it as the lower passage opening offers to a coolant flowing through it. In other words, while the flow resistances of the upper and lower passage openings differ for a single medium, the flow resistances of the upper passage opening for air and the lower passage opening for a specific coolant can be at least substantially the same. This is achieved here by a corresponding design of the passage openings, which takes into account or compensates for the differences in flow behavior between air and coolant. For example, water, glycol, a salt solution, oil, and / or the like can be specified or used as the coolant.By coordinating the lower and upper passage openings as proposed here, an equilibrium with regard to pressure exchange between the chambers can be achieved in the practical use of the expansion tank. The baffles reduce coolant movement within the expansion tank during dynamic motion, such as when the vehicle is driven. A sufficient quantity of coolant is always present or supplied to the lower section of the expansion tank through the lower opening, which completely penetrates or extends perpendicular to the baffle's main plane. This coolant can then flow into an outlet or coolant line located there. The lower opening can be permanently or at least temporarily completely covered or filled with coolant.In such a situation, air above a certain fill level or level of coolant in the expansion tank can flow through the upper passage opening from one of the chambers into another, thereby enabling the level equalization of the coolant within the expansion tank, i.e. across all chambers. Due to the greater flow resistance of the upper opening compared to the lower opening, the time required for the coolant to equalize its level within the expansion tank is increased, for example, compared to identical upper and lower openings. Because of this greater flow resistance, the upper opening acts as a damper for the level equalization process, essentially throttling the airflow. This damping or throttling effect of the upper opening slows down the movement of the coolant within the expansion tank without completely stopping it.This prevents, for example, a lower area, such as an outlet or connection opening in the base of the expansion tank, from running dry due to a oscillating movement, i.e., a back-and-forth sloshing of the coolant in the expansion tank, during acceleration or tilting of the tank. This reduces the risk of air being drawn into the expansion tank, for example, by a coolant pump of the cooling system, compared to conventional expansion tanks without baffles or with identical upper and lower openings. The present invention is particularly advantageous for expansion tanks with a wide variety of geometries, including those with non-optimal basic geometries.Furthermore, since the present invention allows the expansion tank to be smaller overall than a conventional expansion tank without thereby increasing the risk of air intake, the expansion tank according to the invention can also meet demanding packaging requirements or utilize a limited or asymmetrical abdominal space for the arrangement of the expansion tank. In a possible embodiment of the present invention, the upper passage opening in the baffle wall occupies a smaller area than the lower passage opening. In other words, the upper passage opening is smaller than the lower passage opening, particularly or at least with respect to its area or extent in a principal plane of extension of the baffle wall. The upper and lower passage openings can have the same shape or be shaped differently. Identical shapes for the upper and lower passage openings can then allow for a particularly simple determination of their area or size ratio and are also particularly easy to manufacture. Different shapes for the upper and lower passage openings, on the other hand, allow for their different sizes to be achieved independently of, or adapted to, a complex or irregular shape of the baffle wall or the expansion tank.The smaller design of the upper passage opening represents a particularly easy way to adjust the greater flow resistance of the upper passage opening compared to the lower passage opening. In a further possible embodiment of the present invention, the lower passage opening is designed as a free opening through the respective baffle, with a partially permeable, in particular partially air-permeable, membrane arranged in the upper passage opening. The upper passage opening can therefore be filled or covered by the partially permeable membrane. Due to its partial permeability, such a partially permeable membrane can also enable pressure or level equalization between the chambers. At the same time, the partially permeable membrane offers a way to increase the flow resistance of the upper passage opening compared to the lower passage opening or a passage opening designed as a free opening.Designing a through-hole as a free opening means that the respective through-hole effectively represents a hole in the baffle plate that is not covered or filled by any other material of the expansion tank. This design of the lower through-hole ensures that coolant flow between the chambers is not obstructed or impaired, thus guaranteeing a sufficient flow of coolant from the chambers to, for example, an outlet or a coolant line connection in the cooling system. The possibilities for achieving the greater flow resistance between the upper passage opening compared to the lower passage opening can also be combined. In a further possible embodiment of the present invention, the internal volume of the housing is divided into more than two chambers. This can be achieved, for example, by several baffles that extend completely or partially through the housing or its internal volume. Several baffles can be arranged parallel or perpendicular to each other, or at another angle to each other. All pairs of adjacent chambers, i.e., chambers separated or delimited from each other only by exactly one of the baffles, are coupled to each other by a respective upper and a respective lower opening. In other words, each baffle, or each section of a baffle that forms a common wall or boundary between two chambers adjacent to the respective baffle or section, has both an upper and a lower opening.This allows coolant and air to flow directly from one chamber into all adjacent chambers, without first passing through any of the others. In this way, particularly good and reliable compensation for any acceleration or tilting direction of the expansion tank can be achieved or ensured. Therefore, in this design, there is no baffle separating two adjacent chambers that does not have at least an upper and lower opening and thus could not act as an impermeable barrier to the coolant or air. In a further possible embodiment of the present invention, the at least one baffle has several lower passage openings and / or several upper passage openings, particularly in the region of each of the chambers. The individual flow resistance of each upper passage opening arranged in the respective region is greater than the individual flow resistance of each lower passage opening arranged in this region. Furthermore, the combined flow resistance of all upper passage openings in the respective region is greater than the combined flow resistance of all lower passage openings in the respective region. This applies in each case to a given medium and / or a given pressure.By using multiple upper and / or lower flow openings, the intended functionality of the expansion tank, namely the ability to equalize the coolant level between the chambers, can be reliably ensured over the long term. For example, level equalization can continue even if one of the flow openings is blocked, since any two adjacent chambers are directly connected or coupled via multiple upper and / or lower flow openings, thus allowing them to communicate. The consistent design of the flow resistances of the flow openings proposed here ensures that the described damping or throttling effect of the upper flow openings is reliably achieved, despite the multiple upper and / or lower flow openings. In a further possible embodiment of the present invention, the expansion tank is designed as a pressure vessel. In other words, the expansion tank can be designed to be airtight or pressure-tight—at least up to an outlet or connection for the coolant system or a coolant line—so that it can maintain a pressure difference between its internal volume and its external environment. This allows the coolant to be held at a higher pressure than the external environment and retained in a particularly simple manner. The flow resistance of the openings, or the ratio of the flow resistance of the upper and lower openings, can then be adjusted for a specific predetermined internal pressure of the coolant system.The expansion tank may need to be adjusted, for example by appropriately adapting the design of the flow openings, in order to achieve the desired throttling effect of the upper flow openings particularly precisely and reliably. In a further possible embodiment of the present invention, the expansion tank has a connection opening for connecting to a coolant line. This connection opening is located below the lower through-hole in the intended installation position of the expansion tank, relative to the direction of gravity. During operation or use of the expansion tank or the coolant system, coolant can be drawn from the expansion tank through this connection opening, for example, by a coolant pump. The arrangement of the connection opening below the lower through-hole can help to limit coolant loss from the expansion tank, for example, in the event of a leak or damage to the expansion tank, and to ensure that sufficient coolant can reach the connection opening during normal operation.In particular, the connection opening can be surrounded all around by areas of the baffle walls remaining below the respective lower passage opening, so that even if the expansion tank is damaged in an adjacent chamber, at least a minimum supply of coolant can be retained in the area of ​​the connection opening. In a possible further development of the present invention, the connection opening is arranged in a central area of ​​the base of the expansion tank. For example, the connection opening can be located in or on a central chamber of the expansion tank, which can be surrounded by further chambers at least in the main extension directions of the base. This reliably prevents damage to the expansion tank in the area of ​​the connection opening and thus ensures that even in the event of such damage as described, at least a minimum supply of coolant can be retained in the area of ​​the connection opening. Furthermore, the central arrangement of the connection opening ensures a consistent coolant supply for all acceleration or tilting directions of the expansion tank. Another aspect of the present invention is a motor vehicle comprising a coolant system. This coolant system in turn comprises a coolant line and an expansion tank according to the invention, which is fluidly connected thereto. The coolant system of the motor vehicle according to the invention can, for example, be configured to cool an engine or a drive component and / or one or more other components of the motor vehicle. The motor vehicle according to the invention can, in particular, be the vehicle mentioned in connection with the expansion tank according to the invention and accordingly have some or all of the properties and / or features mentioned in this context. Further features of the invention may become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. The drawing shows in: Fig. 1 a schematic cross-sectional view of an expansion tank for a coolant system in a first direction; and Fig. 2 a schematic cross-sectional view of the expansion tank in a second direction. In the figures, identical and functionally equivalent elements are provided with the same reference symbols. Fig. 1 shows a first schematic cross-sectional view of an expansion tank 10, for example, for a motor vehicle's coolant system. Especially in today's increasingly common electric vehicles, accelerations and decelerations in the range of 1 g can regularly occur. This can cause fluids in the vehicle or its systems, such as the coolant system, to shift relative to the vehicle against the direction of acceleration due to their inertia and mobility. This can be problematic for various reasons. To address this problem, the expansion tank 10 shown here is proposed. The expansion tank 10 has an outer housing 12. This housing 12 can, for example, be made of several interconnected parts, such as an upper shell and a lower shell bonded or welded to it, and is made of a plastic material. In this case, the expansion tank 10 has a filling port 14 on its upper side, relative to a direction of gravity when the expansion tank 10 is installed in its intended position. The filling port 14 can, for example, be an opening in the housing 12 that can be tightly sealed by a lid or cap. Furthermore, the expansion tank 10 has a connection 16 on its underside, particularly on the side opposite the filling port 14, for connecting to a coolant system, i.e., for connecting a coolant line.The pipe connection 16 can therefore represent an inlet and an outlet. Likewise, a valve, for example, can be arranged at the pipe connection 16. The internal volume of the expansion tank 10 or the housing 12 is divided here by several baffles 18, which subdivide the internal volume of the housing 12 into several chambers 20. For example, the expansion tank 10 can have nine such chambers 20, of which the three middle ones are visible in the direction of view. Thus, for example, three further chambers 20 can be arranged in front of and behind each of these chambers. Accordingly, the filling point 14 and the pipe connection 16 can be located at a central chamber 20. In the situation depicted here, the expansion tank 10 is partially filled with a liquid coolant 22. As the temperature increases, this coolant 22 can expand into the remaining empty or air-filled portion of the chambers 20. During the aforementioned accelerations, as well as during tipping of the expansion tank 10, the coolant 22 within the expansion tank 10 can shift relative to it. This can change the fill level or coverage of the coolant 22 in the area of ​​the line connection 16, and in particular, ultimately reduce it. Simultaneously, a coolant pump (not shown here) can activate, drawing coolant 22 from the expansion tank 10. This creates a risk of air intake, which can be problematic and is therefore undesirable. In this case, the baffles 18 serve to reduce these fluctuating movements of the coolant 22 within the housing 12.However, since the coolant 22 should still be able to reach the line connection 16 regardless of the acceleration or position of the expansion tank 10, the baffle walls 18 each have at least one lower passage opening 26 through which the coolant 22 can flow. The expansion tank 10 is shown here in a rest position, in which a resting level 28 of the coolant 22 has been established across the chambers 20, specifically perpendicular to the direction of gravity in the intended installation position of the expansion tank 10. If the expansion tank 10 is now tilted, for example, in the plane of the drawing, or experiences a corresponding acceleration in the plane of the drawing perpendicular to the main extension direction of the baffles 18, i.e., perpendicular to an imaginary connecting line between the filling point 14 and the line connection 16, the coolant 22 will initially shift, so that, for example, intermediate fill levels 30 indicated here can be established in the individual chambers 20. To ensure the supply or coverage of the line connection 16 even in such acceleration or tilting situations, a level equalization of the coolant 22 across the chambers 20 is desirable.To enable this, the baffles 18 above the static fill level 28 each have at least one upper passage opening 24. These upper passage openings 24 allow air exchange between the chambers 20, ultimately enabling the level equalization of the coolant 22 across the chambers 20. After a certain period of acceleration or tilting or inclination of the expansion tank 10, an equalization fill level 32 of the coolant 22, also shown schematically here, will be established. The dynamic equalization of the coolant 22 between the chambers 20, i.e., the reaching of the equilibrium level 32, is to be delayed or dampened. For this purpose, the upper passage openings 24 have a greater flow resistance for a given medium than the lower passage openings 26. To achieve this, the upper passage openings 24 are smaller than the lower passage openings 26. The greater flow resistance of the upper passage openings 24 results in a correspondingly adjusted pressure loss characteristic to dampen fluctuations or sloshing movements of the coolant 22, or the level equalization of the coolant 22 between the chambers 20 under dynamic load. Fig. 2 shows the expansion tank 10 in a second cross-sectional view along the section line BB indicated in Fig. 1. In the different perspective shown in Fig. 2, it can be seen that the lower passage openings 26 are not only larger than the upper passage openings 24, but also shaped differently. In the present example, the upper passage openings 24 are round, while the lower passage openings 26 are formed as rounded rectangles. However, other shapes, particularly identical shapes, for the passage openings 24 and 26 are also possible. The exact sizes, size ratios, and / or shapes of the passage openings 24 and 26 can be determined, for example, for the coolant 22 intended for the respective application and / or a specific internal pressure of the expansion tank 10, by computer-aided or model-based simulation or optimization. When using the expansion tank 10, or...of the corresponding coolant system in a motor vehicle, the upper passage openings 26 for a water-based coolant 22 and otherwise air-filled chambers 20 can, for example, have a diameter in the range of 1.5 mm to 4 mm, preferably of approximately 2 mm. The expansion tank 10 also has a vent line 34, which extends towards the bottom of the expansion tank 10, where the pipe connection 16 is located, up to the area or height of the lower through-holes 26. At its other, upper end, the vent line 34 extends to an area of ​​the expansion tank 10 located above the static fill level 28, in particular to one of the chambers 20. For external venting, the vent line 34 is also connected to or provided with a vent nozzle 36 leading to the outside, i.e., into the vicinity of the expansion tank 10. The expansion tank 10 may also have further details or features, such as one or more vent openings and / or the like. Overall, the examples described show how swell damping for a coolant expansion tank, especially of a motor vehicle, can be achieved in a particularly simple way through an adapted geometric design. Reference symbol list 10 Expansion tank 12 Housing 14 Filling point 16 Line connection 18 Baffles 20 Chambers 22 Coolant 24 Upper flow openings 26 Lower flow openings 28 Resting level 30 Intermediate levels 32 Equalizing level 34 Vent line 36 Vent nozzle

Claims

Expansion tank (10) for a coolant system, comprising a housing (12) whose internal volume is divided into several chambers (20) by at least one baffle (18) extending therein to dampen movement of a coolant (22) in the expansion tank (10), wherein the at least one baffle (18) has, with reference to a specified installation position of the expansion tank (10), a fluid-flowable lower passage (26) below a specified minimum fill level of the expansion tank (10) and an air-flowable upper passage (24) above a specified maximum fill level of the expansion tank (10), through which the chambers (20) are coupled to one another, wherein for a given medium the upper passage (24) has a greater flow resistance than the lower passage (26), characterized in thatthat the upper passage opening (24) and the lower passage opening (26) are matched to each other in such a way that the upper passage opening (24) offers the air flowing through it at least essentially the same flow resistance as the lower passage opening (26) offers the coolant (22) flowing through it. Expansion tank (10) according to one of the preceding claims, characterized in that the upper passage opening (24) in the baffle wall (18) occupies a smaller area than the lower passage opening (26). Expansion tank (10) according to one of the preceding claims, characterized in that the lower passage opening (26) is designed as a free opening through the baffle wall (18) and a partially permeable membrane is arranged in the upper passage opening (24). Expansion tank (10) according to one of the preceding claims, characterized in that the internal volume of the housing (12) is divided into more than two chambers (20), wherein all pairs of adjacent chambers (20) are coupled to each other by a respective upper passage opening (24) and a respective lower passage opening (26). Expansion tank (10) according to one of the preceding claims, characterized in that the at least one baffle wall (18) has several lower passage openings (26) and / or several upper passage openings (24), in particular in the area of ​​each of the chambers (20), wherein in each of the areas of one of the chambers (20) the flow resistance of each of the upper passage openings (24) is greater than the flow resistance of each of the lower passage openings (26) and the flow resistance of all upper passage openings (24) together is greater than the flow resistance of all lower passage openings (26) together. Expansion tank (10) according to one of the preceding claims, characterized in that the expansion tank (10) is designed as a pressure vessel. Expansion tank (10) according to one of the preceding claims, characterized in that the expansion tank (10) has a connection opening (16) for connecting to a coolant line, wherein the connection opening (16) is arranged below the lower passage opening (26) with respect to a direction of gravity in the intended installation position of the expansion tank (10). Expansion tank (10) according to claim 7, characterized in that the connection opening (16) is arranged in a central area of ​​a base of the expansion tank (10). Motor vehicle comprising a coolant system comprising a coolant line and a fluid-conducting expansion tank (10) connected thereto according to one of the preceding claims.

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