Pressure compensation device for electric machines, housing, electric machine and automotive
Patent Information
- Application Number
- JP2024539602
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-02-08
- Filing Date
- 2023-01-11
- Publication Date
- 2026-01-15
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to a pressure compensation device for an electric machine. The present invention further relates to a housing for an electric machine, the housing being equipped with a pressure compensation device. Furthermore, according to the invention, an electric machine with such a housing is proposed. In addition, the present invention relates to a motor vehicle, in particular made as a passenger car, equipped with such an electric machine. [Background technology]
[0002] In electrical structures with electric machines (e.g. as traction machines), such as electric drive assemblies, the liquid-filled liquid chamber of the electrical structure is often sealed liquid-tight to the air chamber, even though machine elements, such as a shaft, extend from inside the liquid chamber into the air chamber. For example, the rotor shaft extends from a liquid-filled stator chamber (liquid chamber) into an air-filled brush chamber (air chamber) of the electric machine, but the stator chamber and the brush chamber are sealed liquid-tight from each other along the rotor shaft. This means that the electric machines thus formed are so-called wet rotor machines. The rotor shaft in the case of dry-operating electric machines may likewise extend from an air-filled stator chamber (air chamber) into an oil-filled gear chamber (liquid chamber), but the stator chamber and the gear chamber are sealed liquid-tight from each other along the rotor shaft. In order to avoid liquid from undesirably leaking out of the liquid chamber into the air chamber, a radial shaft seal is used along the rotor shaft between the liquid chamber and the air chamber on the wall through which the rotor shaft extends. In order to keep this radial shaft seal as free of axial forces as possible, so that a particularly reliable sealing effect is guaranteed by the radial shaft seal, it is necessary that no positive or negative pressures arise in the corresponding chamber, i.e. for example in the liquid chamber, relative to the air chamber, which act in an adverse manner on the radial shaft seal in the axial direction, i.e. along the rotor shaft. When such a conventional drive assembly or such a conventional electrical structure or machine is equipped in a motor vehicle, it can happen that the air in the air chamber is heated or cooled due to the release of heat generated during the operation of the electric machine or due to external cooling of the electric machine, for example during standby operation. This causes a pressure change in the air chamber and, as a consequence, a pressure difference between the air chamber and the liquid chamber, according to the laws of thermodynamics.This results in unwanted axial loading of the radial shaft seals, ultimately causing a deterioration or reduction in the reliability of the sealing effectiveness of the shaft seat between the chambers.
[0003] To overcome this problem, for example from DE 10 200 03 133 A1 a generator housing is known, which housing comprises a plug socket and a pressure compensation conduit. The pressure compensation conduit connects the inside of the generator to the outside by means of a wire harness which is plugged into the plug socket and which also assumes the function of pressure compensation. However, combining the plug socket with the pressure compensation conduit is particularly complicated and the sealing effect depends on the correct seating of the plug element in the plug socket. Moreover, generator housings of this kind with plug sockets as well as wire harnesses for line-produced vehicles are difficult to handle, expensive and require particularly large assembly space outside the generator, which further complicates the packaging problems that are typical in vehicle construction.
[0004] From patent document 2 a cable is known which comprises electrical conductors which are integrated into the cable insulation material and enclosed in an electrically insulating and gas-tight outer cable jacket. A semi-permeable membrane permeable to air and water vapour is arranged in one place on the cable, the outer jacket being provided with a recess in the region of said membrane, so that ventilation of the cable through the membrane is ensured. However, such conventional cables are particularly complex in terms of manufacture, operation and handling, since the semi-permeable membrane is particularly prone to breakage, with the result that liquids can pass through a broken / damaged membrane and come into direct electrical contact with the electrical conductors. This can lead to short circuits.
[0005] In conventional electric machines or conventional housings, the radial shaft seal may be subject to critical operating conditions that weaken the sealing effect of the radial shaft seal due to pressure differences between the air and liquid chambers, especially between the stator and brush chambers. Depending on the actual operating temperature of the radial shaft seal, even a very small pressure difference may be sufficient for such a critical operating condition. If the sealing effect weakens due to a pressure difference, the liquid present in the liquid chamber (e.g. wet rotor liquid for cooling the stator and / or rotor in the stator chamber) can escape from the liquid chamber and leak past the no longer sufficient radial shaft seal into the air chamber, where it can cause damage or malfunction of the machine, such as a so-called insulation failure. [Prior art documents] [Patent documents]
[0006] [Patent Document 1] DE 102013200894 [Patent Document 2] German Patent No. 102017128532 Summary of the Invention [Problem to be solved by the invention]
[0007] SUMMARY OF THE DISCLOSURE The object of the invention is to provide a particularly efficient solution for avoiding pressure differences between a liquid chamber and an air chamber of an electric machine which are sealed fluid-tight from one another by a radial shaft seal. [Means for solving the problem]
[0008] This problem is solved by the subject matter of the independent patent claims. Features, advantages and possible embodiments described in the description for one of the subject matters of the independent claims can at least equally be regarded as features, advantages and possible embodiments of each of the subject matters of the other independent claims and of any combination of the subject matters of the independent claims. Further possible embodiments of the invention are disclosed in the dependent claims, the description and the drawings.
[0009] In order that pressure differences between the liquid and air chambers of the housing or the electric machine are not undesirably large, in particular are completely avoided, a pressure compensation device for an electric machine with a housing is proposed according to a first aspect of the invention. In the intended installation state, i.e. when the pressure compensation device is integrated or used for its designated purpose, the device forms part of the housing. Thus, an electric machine with a housing comprises the pressure compensation device by virtue of the housing comprising the pressure compensation device as a component. As a result, a motor vehicle comprises the pressure compensation device by virtue of the motor vehicle comprising its electric machine and thus the housing.
[0010] In an electric machine, a shaft, in particular a rotor shaft, extends from a liquid chamber, which is filled with liquid, into an air chamber. The air chamber is free of liquid and is filled with air (e.g. from the atmosphere). To prevent liquid from escaping from the liquid chamber (in particular along the rotor shaft) into the air chamber, the housing or the electric machine is provided with a radial shaft seal, which fits liquid-tight on the rotor shaft at its outer periphery at the point where the rotor shaft passes through the wall separating the air chamber from the liquid chamber, and which is itself surrounded liquid-tight on its outer periphery by the wall at this point.
[0011] The pressure compensation device includes three backflow preventers, each of which has an inlet side and an outlet side. Each backflow preventer allows a fluid (e.g., air) to flow through it from its inlet side to its outlet side. Conversely, each backflow preventer blocks or prevents flow from passing through it from its outlet side to its inlet side. Thus, when each backflow preventer is operating as intended, fluid can only flow through the backflow preventer if the fluid flows into the backflow preventer through its inlet side and flows out of the backflow preventer through its outlet side. Fluid cannot flow into the backflow preventer through its outlet side. Thus, each backflow preventer is a backflow prevention component that allows the flow of fluid (liquid, gas) in only one direction.
[0012] The outlet side of the first backflow preventer (hereinafter referred to as the "first outlet side") is fluidly connected to the inlet side of the second backflow preventer (the "second inlet side"). Furthermore, the first outlet side is configured to be fluidly connected to the air chamber of the housing. Thus, in the intended mounting state, the first outlet side is fluidly connected to the air chamber directly or indirectly, for example via a conduit. Here, the first outlet side and the second inlet side are in communication with each other, so that in the intended mounting state, the second inlet side and the air chamber are also fluidly connected to each other. The first inlet side, i.e. the inlet side of the first backflow preventer, is open to the surroundings of the pressure compensation device or the electric machine, for example to the atmosphere.
[0013] The outlet side of the second backflow preventer ("second outlet side") is connected to the inlet side of the third backflow preventer ("third inlet side"). Furthermore, the second outlet side is configured to be fluidly connected to the liquid chamber of the housing. In the intended installation state, the second outlet side is therefore fluidly connected to the liquid chamber either directly or indirectly, for example via a further conduit. Here, the second outlet side and the third inlet side are in communication with each other, so that in the intended installation state, the third inlet side and the liquid chamber are also fluidly connected to each other. The third outlet side is open to the surroundings of the pressure compensation device or the electric machine, i.e., for example to the atmosphere.
[0014] When properly installed, the backflow prevention devices regulate the flow direction of each fluid, so that air and other fluids - from the surroundings through the first backflow preventer and into the air chamber; - from the surroundings, through the first backflow preventer, through the second backflow preventer and into the liquid chamber; - exiting the air chamber, passing through a second backflow preventer, passing through a third backflow preventer and into the environment; - flowing out of the air chamber, through the second backflow preventer, and into the liquid chamber; - flowing out of the liquid chamber through a third backflow preventer into the surroundings; It is possible.
[0015] Here, in a properly implemented state, the fluids are prevented from flowing in the opposite direction by the backflow prevention bodies that define the flow directions of the respective fluids. - the air leaves the air chamber, passes through the first backflow preventer, and enters the surroundings; - flowing out of the liquid chamber, through the second backflow preventer, into the environment or into the air chamber; It is forbidden to do so.
[0016] This ensures that the radial shaft seal of the electric machine particularly reliably seals the air and liquid chambers from one another in a liquid-tight manner, since the pressure compensation device prevents the critical operating state of the radial shaft seal mentioned at the beginning. During operation of the electric machine, the radial shaft seal is not subjected to any or only very little axial deformations due to the absence of pressure differences, so that friction between the rotor shaft rotating during operation and the radial shaft seal is particularly low. An especially efficient efficiency is therefore possible with the electric machine equipped with a pressure compensation device. Furthermore, the electric machine advantageously has a particularly long service life and / or particularly long maintenance intervals due to the pressure compensation device, since the relatively lightly loaded radial shaft seal has a relatively long service life and requires relatively low maintenance due to the pressure compensation device.
[0017] The air chamber of the electric machine or the housing may be, for example, a brush chamber, in which case the liquid chamber is a stator chamber. The rotor shaft here extends into both the brush chamber and the stator chamber. The brush chamber and the stator chamber are sealed liquid-tight from each other by means of a radial shaft seal in cooperation with the rotor shaft on which it is fitted. Here, in the intended installation state, the first outlet side and the second inlet side are fluidically connected to the brush chamber, and the second outlet side and the third inlet side are fluidically connected to the stator chamber.
[0018] Furthermore, the liquid chamber may be formed by a chamber complex consisting of a stator chamber and a transmission chamber fluidly connected thereto, the rotor shaft extending into the brush chamber on the one hand and into the chamber complex on the other hand by penetrating the stator chamber and in particular projecting into the transmission chamber. The brush chamber and the stator chamber and thus the chamber complex are sealed fluid-tight from each other by using a radial shaft seal in cooperation with the rotor shaft on which it is fitted. In the intended installation state, the first outlet side and the second inlet side are fluidly connected to the brush chamber, and the second outlet side and the third inlet side are fluidly connected to the chamber complex forming the liquid chamber. For example, the second outlet side and the third inlet side are fluidly connected to the stator chamber and / or the transmission chamber.
[0019] Furthermore, the stator chamber may be formed by an air chamber, in which case the liquid chamber is formed by the transmission chamber. The rotor shaft then extends into both the stator chamber and the transmission chamber, which are sealed liquid-tight from each other by means of a radial shaft seal in cooperation with the rotor shaft on which it is fitted. In this case, in the intended installation state, the first outlet side and the second inlet side are fluidically connected to the stator chamber, and the second outlet side and the third inlet side are fluidically connected to the transmission chamber. In case the stator chamber and the brush chamber communicate with each other, the air chamber may be formed by a further chamber complex with the stator chamber and the brush chamber fluidically connected thereto. In that case, the first outlet side and the second inlet side may be fluidically connected to at least one of the brush chamber and / or the stator chamber. This further chamber complex, and thus the air chamber, may further comprise an inverter chamber in communication with the stator chamber and / or the brush chamber. The first outlet side and the second inlet side may then be fluidically connected with the stator chamber and / or the brush chamber and / or the inverter chamber. Alternatively, the inverter chamber is fluidically sealed with respect to the stator chamber and / or the brush chamber. In this case, the inverter chamber is evacuated by a separate pressure compensation element or the inverter chamber is fluidically connected with the first outlet side and the second inlet side.
[0020] In yet another form of the pressure compensation device, the second backflow preventer is configured to allow free flow of fluid or air from its (second) inlet side to its (second) outlet side when an opening pressure difference existing between the second inlet side and the second outlet side exceeds a pressure difference that is less than a pressure difference between the liquid chamber and the air chamber that may lead to the above-mentioned critical operating pressures. In this embodiment, therefore, the opening pressure difference, through which air can freely flow between the second inlet side and the second outlet side through the second backflow preventer, is set to be less than 10 mbar, in particular less than 5 mbar, preferably less than 1 mbar, which advantageously makes it possible to avoid even particularly small pressure differences between the liquid chamber and the brush chamber and air chamber.
[0021] The backflow preventers can be arranged freely (in particular individually and / or spatially separated from one another) depending on the available installation space around the housing and, if necessary, can be fluidly connected to one another and to the air and liquid chambers according to the arrangements described herein via a conduit system, a pipe system, a hose system, etc. In order to efficiently deal with a particularly onerous packaging problem at present, i.e. to efficiently utilize the small installation space available during the manufacture and / or design of the vehicle, in a further embodiment, at least two backflow preventers or all backflow preventers are provided together with one another as an assembled unit. This eliminates part of the conduit system, at least the conduits that interconnect the backflow preventers. In addition to the packaging advantage, this has the advantage that the pressure compensation device is particularly easily formed, which ultimately results in a vehicle that can be driven in a particularly energy-efficient and low-emission manner.
[0022] In a further possible embodiment, the pressure compensation device comprises a filter element through which the fluid can flow, the first flow-through side of which is fluidically connected to the inlet side of the second backflow prevention body. Furthermore, the second flow-through side of the filter element is designed to be fluidically connected to the air chamber of the housing, in particular the brush chamber, so that in the intended installation state the second flow-through side and the air chamber or the brush chamber are fluidically connected to each other. During operation of the electric machine, dust, in particular metallic dust, is generated in the brush chamber due to the rubbing of the rotor shaft against the brushes (sliding contact). This can lead to the air flowing out of the air chamber forming the brush chamber being mixed with metal dust and being carried away by the metal dust from the brush chamber. The filter element filters the dust-laden air flowing out of the air chamber, so that dust-free air can flow further to the second backflow prevention body. In this way, it is prevented that metal dust particles pass through the second backflow prevention body in an undesired manner and reach, in particular, the liquid chamber, in particular the stator chamber. This is because an electrically conductive or electrically conductive short circuit between the rotor and the stator and / or between the pole terminals (usually called U, V, W) must be avoided for unhindered operation. Furthermore, if the second outlet and the transmission chamber are connected to each other, it is avoided that metal dust particles reach into the transmission chamber. This also applies if the stator chamber and the transmission chamber are fluidically connected together in a chamber complex. In particular, metal dust particles can undesirably increase friction between the gear elements in the transmission chamber and / or damage the gear elements, for example the bearings. This can ultimately lead to a breakdown of the transmission and thus to a stoppage of the vehicle equipped with the electric machine.
[0023] The first through-flow side of the filter element and the first outflow side of the first backflow preventer are fluidly connected to each other, in particular as in the further embodiment. In this case, the filter element has a double function, i.e. firstly, it is used to filter brush dust from the air flowing out of the brush chamber, and secondly, it is used to filter dust etc. from the air flowing from the surroundings to the air chamber or the brush chamber. Further locations for incorporating the filter element and / or at least one further filter element may be envisaged, for example to prevent any dust etc. from the surroundings from reaching the liquid chamber or the housing of the electric machine. For this purpose, for example, a further filter element may be connected upstream of the first inflow side of the first backflow preventer.
[0024] In yet another aspect of the pressure compensation device, at least one or more backflow prevention bodies are formed as check valves, in particular umbrella valves. It may be provided that all backflow prevention bodies used in the pressure compensation device are formed as check valves. In general, other embodiments of the backflow prevention body are also conceivable, for example, swing type check valves, lift type check valves, ball type check valves, etc. In addition, it is also conceivable that the backflow prevention body or bodies are formed as shut-off valves that can be controlled (in particular electronically) as required.
[0025] The embodiment of the non-return valve for the non-return prevention body or bodies is advantageous in that the pressure compensation device is particularly easy to manufacture and the non-return valve provides a particularly reliable sealing function. Furthermore, non-return valves can now be manufactured and installed with particularly high efficiency in terms of installation space, which allows for a particularly advantageous packaging to a large extent. Umbrella valves also require little maintenance, which advantageously contributes to a particularly long service life of the pressure compensation device.
[0026] In yet another aspect of the invention, a housing for an electric machine is provided, the housing comprising a pressure compensation device formed as described above. The housing thus comprises or is at least partially formed from a liquid chamber and an air chamber. The liquid chamber and the air chamber are hereby fluidly connectable to one another such that air (or other fluid) can flow from the air chamber to the liquid chamber via the pressure compensation device, but cannot flow from the liquid chamber to the air chamber. The housing further comprises an opening fluidly connecting the liquid chamber and the air chamber to one another, the opening being formed to serve as a seat for a radial shaft seal. In the electric machine, the rotor shaft extends from the liquid chamber into the air chamber through the opening, i.e. for example from the stator chamber into the brush chamber and / or from the stator chamber into the transmission chamber. The air chamber and the liquid chamber are sealed liquid-tight from each other in the intended installed state (i.e. when the housing forms part of the electric machine ready for use) by a radial shaft seal inserted in the opening and through which the shaft of the electric machine, in particular the rotor shaft, extends.
[0027] In a possible development of the housing, the air chamber forms the brush chamber of the housing and the liquid chamber forms the stator chamber of the housing. Alternatively, the housing can be provided in such a way that the air chamber is formed by a chamber complex formed by a brush chamber and a stator chamber communicating with said brush chamber, and the liquid chamber forms the transmission chamber of the housing. In yet another possibility for realizing the housing, the air chamber forms the brush chamber of the housing and the liquid chamber is formed by a further chamber complex formed by a stator chamber and a transmission chamber communicating with said stator chamber.
[0028] In yet another aspect, the invention relates to an electric machine having a pressure compensation device with a housing as described above, the electric machine being configured in particular as an electric traction engine for a motor vehicle.
[0029] Moreover, the present invention relates in yet another aspect to a motor vehicle, in particular a car and / or truck, which is equipped with an electric machine formed as described above, and thus in particular a motor vehicle which can be at least partially electrically driven / moved or which can operate exclusively electrically.
[0030] Further features of the invention will become apparent from the claims, the drawings and the description of the drawings. All features and combinations of features described herein above and shown below in the description of the drawings and / or individually in the drawings can be used not only in the combinations described, but also in other combinations or individually without departing from the scope of the invention. [Brief description of the drawings]
[0031] [Figure 1] 1 is a schematic diagram of an electric machine having a pressure compensation device with a housing. [Diagram 2] FIG. 2 illustrates a graph of operating conditions of a radial shaft seal of an electric machine in which critical operating conditions are avoided by a pressure compensation device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] In the figures, identical and functionally identical elements are provided with the same reference numerals. The following description equally relates to the pressure compensation device DAV, the housing G, the electric machine EM and the vehicle (not shown).
[0033] In this regard, Fig. 1 shows in a schematic diagram an electric machine EM with a housing G having a pressure compensation device DAV with backflow prevention bodies V1, V2, V3. In this example, the individual backflow prevention bodies V1, V2, V3 are each configured as a check valve, in particular each in the form of an umbrella valve. The first outlet side AS1 of the first backflow prevention body V1 and the second inlet side ES2 of the second backflow prevention body V2 are fluidly connected to each other by the merging of a conduit C1 into a conduit C2, which in this example is used to fluidly connect the first outlet side AS1 to the housing G or the air chamber K1 of the electric machine (EM) to each other. In this example, the second outlet side AS2 of the second backflow preventer V2 and the inlet side ES3 of the third backflow preventer V3 are fluidly connected to each other by merging the conduit C3 into the conduit C4 used to fluidly connect the second outlet side AS2 to the liquid chamber K2 of the housing G or the electric machine (EM).
[0034] The liquid chamber K2 is at least partially filled with a liquid N (e.g. a lubricant such as oil, wet rotor liquid, etc.). The air chamber K1 is free of liquid and is filled with air L. The air chamber K1 comprises or consists of a brush chamber BK of the housing G or of the electric machine EM. The liquid chamber K2 comprises or consists of a stator chamber SK of the housing G or of the electric machine EM. The electric machine EM shown in FIG. 1 is thus a machine of the wet rotor type. The housing G comprises in this example a transmission chamber GK, which contains for example gear oil, in which gear elements (not shown) splash oil during operation of the electric machine EM. Here, the transmission chamber GK and the stator chamber SK may be in communication with each other and the gear oil may be the wet rotor liquid N or vice versa. The liquid chamber K2 may thus be formed from a first chamber complex KV1 with a stator chamber SK and a transmission chamber GK.
[0035] Although not shown, it is also within the scope of the invention that the electric machine EM can be configured as a dry-operating machine, in which case the stator chamber SK operates dry during operation of the electric machine EM, i.e. is free of liquid. In this case, the liquid chamber K2 consists of the transmission chamber GK, and the air chamber K1 consists of a second chamber complex KV2 with the (dry, i.e. liquid-free) stator chamber SK and the brush chamber BK, which communicate with each other.
[0036] In order to prevent the liquid N from leaking from the liquid chamber K2 to the air chamber K1 along the rotor shaft RW extending from the liquid chamber K2 into the air chamber K1, the rotor shaft RW is surrounded liquid-tight on the outer periphery by a radial shaft seal RWD. The radial shaft seal RWD is seated, for example, in an opening OE1 (in this specification, the symbol "OE" stands for "O umlaut") in a wall W1 of the housing G, and the brush chamber BK and the stator chamber SK are liquid-tight sealed from each other by this wall W1. In other words, the opening OE1 penetrates the wall W1 to connect the brush chamber BK and the stator chamber SK. Nevertheless, the radial shaft seal RWD liquid-tightly surrounds the rotor shaft RW on the outer periphery at the position of the opening OE1, and the radial shaft seal RWD itself is seated liquid-tight in the opening OE1, thereby preventing the liquid N from leaking out.
[0037] The radial shaft seal RWD may seat in an opening OE2 in a wall W2 of the housing G when the stator chamber SK is part of the air chamber K1. The stator chamber SK and the transmission chamber GK are sealed liquid-tight from each other by the wall W2. In other words, the opening OE2 penetrates the wall W2 and connects the stator chamber SK and the transmission chamber GK. Nevertheless, the radial shaft seal RWD surrounds the rotor shaft RW liquid-tight on the outer periphery side at the position of the opening OE2, and the radial shaft seal RWD itself is seated liquid-tight in the opening OE2, thereby preventing leakage of the liquid N.
[0038] The conduits C1, C2, C3, C4 allow a fluid (in particular, for example, air L or liquid N or any other fluid) to flow through them in both directions, whereas the individual non-return bodies or individual check valves V1, V2, V3, when used appropriately, allow a liquid to flow through them in only one direction, as illustrated by the possible flow directions R1, R2, R3 in Figure 1. The non-return bodies V1, V2, V3, which define the respective flow directions R1, R2, R3, therefore allow the supply and degassing of the chambers K1, K2 and the compensation of the pressure between the chambers K1, K2, by allowing the air L to flow as follows: from the housing G or from the periphery U of the electric machine EM through the first backflow prevention body V1 into the air chamber K1, - from the surroundings U through the first backflow preventer V1, through the second backflow preventer V2 and into the liquid chamber K2, - out of the air chamber K1, through the second backflow preventer V2, through the third backflow preventer V3 and into the surroundings U, - out of the air chamber K1, through the second backflow prevention body V2 and into the liquid chamber K2, - out of the liquid chamber K2, through the third backflow preventer V3 and into the surroundings U; At this time, the air L is - exiting the air chamber K1, passing through the first backflow prevention body V1 and into the surroundings U; - exiting the liquid chamber K2, passing through the second backflow prevention body V2 and into the surroundings U or into the air chamber K1; is prohibited.
[0039] In addition, in FIG. 1, an inverter chamber IK is arranged, and the brush chamber BK and the inverter chamber IK are fluidly connected to each other via a cable gland KD, which in this example is used to pass a cable (e.g., an SSM cable) extending in the brush chamber BK and the inverter chamber IK through the wall W3 of the housing G. Alternatively, in this case, the brush chamber BK and the inverter chamber IK may be sealed fluid-tight from each other, in that the cable gland KD and the cable are formed to prevent the ingress of liquid between the brush chamber BK and the inverter chamber IK. The stator chamber SK and the transmission chamber are fluidly connected to each other in this example, and the third inlet side ES3 and the second outlet side AS2 are fluidly connected to the transmission chamber GK, as shown in FIG. 1. Through an opening OE2 penetrating the wall W2, the rotor shaft RW extends from the stator chamber SK into the transmission chamber GK. The inverter chamber IK and the stator chamber SK or the transmission chamber GK are sealed liquid-tight from one another, and between the inverter chamber IK and the stator chamber SK an opening OE3 may be formed, through which the pole cables P run and are connected on the one hand to the stator S and on the other hand to the inverter I of the electric machine EM. To ensure a liquid-tight separation between the stator chamber SK and the inverter chamber IK at the opening OE3, a sealing ring DR, for example in the form of an O-ring, is arranged there (when the electric machine EM is formed as a wet-rotor machine so that the stator chamber SK is part of the liquid chamber K2). On the other hand, when the stator chamber SK is part of the air chamber K1, the sealing ring DR can be omitted.
[0040] If the liquid chamber K2 is partly formed by the stator chamber SK, the first outlet side AS1 and the second inlet side ES2 are fluidically connected to each other and to the air chamber K1 by being fluidically connected to the brush chamber BK and / or the inverter chamber IK. For this purpose, for example, the conduit C2 can open directly into the brush chamber BK and / or the inverter chamber IK. In this case, the second outlet side AS2 and the third inlet side ES3 are fluidically connected to each other and to the liquid chamber K2 by being fluidically connected to the stator chamber SK and / or the transmission chamber GK. For this purpose, the conduit C4 can open directly into the stator chamber SK and / or the transmission chamber GK.
[0041] If the air chamber K1 is partly formed by the stator chamber SK, the first outlet side AS1 and the second inlet side ES2 are fluidically connected to each other and to the air chamber K1 by being fluidically connected to the brush chamber BK, the stator chamber SK and / or the inverter chamber IK. For this purpose, for example, the conduit C2 can open directly into the brush chamber BK, the stator chamber SK and / or the inverter chamber IK. In this case, the second outlet side AS2 and the third inlet side ES3 are fluidically connected to each other and to the liquid chamber K2 by being fluidically connected to the transmission chamber GK. For this purpose, the conduit C4 can open directly into the transmission chamber GK.
[0042] At least the second backflow preventer V2 is configured, selected or manufactured so that air L flows freely as soon as the liquid pressure or air pressure on the second inlet side ES2 reaches or exceeds 1 mbar.
[0043] As can be seen from Fig. 1, the backflow prevention bodies V1, V2, V3 in this example form an assembly unit B, i.e. are combined into an assembly unit B. In this case, the conduit bodies C1, C3 can be particularly short or can be completely eliminated.
[0044] Furthermore, the pressure compensation device DAV in this example comprises a filter element F through which the air L can flow, the first through-flow side DS1 of which is fluidly connected both to the second inlet side ES2 and to the first outlet side AS1, and the second through-flow side DS2 of the filter element F and the brush chamber are fluidly connected to each other.
[0045] The pressure compensation device DAV, the housing G, the electric machine EM and the motor vehicle show respective possibilities for avoiding a pressure difference between the liquid chamber K2 and the air chamber K1 of the electric machine EM, which are sealed fluid-tight from each other by the radial shaft seal RWD. The current leakage problem between the chambers K1, K2 is thus effectively addressed. The evacuation and the supply of the two (also called oil or air chambers) chambers K1, K2 are separated. The supply of the system is carried out via the backflow preventer V1, which is connected to the air side, i.e. the air chamber K1 or the air chamber K1. The evacuation of the system is carried out via the backflow preventer V3, which is connected to the oil side, i.e. the liquid chamber K2. The two chambers K1, K2 are fluidly connected to each other in a one-way manner by a second backflow preventer V2, which can or can be passed through with a completely low opening pressure difference of less than 1 mbar. The through-flow direction, i.e. the flow direction, is determined by the second backflow prevention body V2, which is also determined from the air side to the oil side. This prevents oil from penetrating into the air or air chamber K1, in particular into the brush chamber BK and the inverter chamber IK. The second backflow prevention body V2 ensures that the liquid or air can flow freely in the direction R2 when the air chamber is under positive pressure or the oil chamber is under negative pressure. This avoids critical operating points of the radial shaft seal RWD thanks to the pressure compensation between the chambers K1, K2. The opening pressures to the outside or opening pressure differences of the backflow prevention bodies V1, V2, V3, which can each be formed in particular as umbrella valves, are set in such a way that high pressures in the system are avoided, thereby ensuring high system efficiency.
[0046] FIG. 2 shows, for example, operating states of the radial shaft seal RWD of an electric machine EM, where critical operating states KB are avoided by the pressure compensation device DAV. The horizontal axis represents the temperature T of the radial shaft seal RWD, and the vertical axis represents the pressure difference between the chambers K1, K2. The critical operating states KB appear as a function of the temperature T of the radial shaft seal RWD in the area below the limit curve C. By using the pressure compensation device DAV, the operating point of the radial shaft seal RWD is always above the limit curve C and is therefore non-critical. This is because the pressure between the chambers K1, K2 is compensated via the second backflow prevention body V2 even for pressure differences DZ below 10 mbar, and in particular even above a pressure difference DZ of 1 mbar. This is represented in the graph of FIG. 2 by the opening characteristic curve KL of the second backflow prevention body V2. As a result, the radial shaft seal RWD is only placed in non-critical operating points. [Explanation of symbols]
[0047] AS1 Outflow side AS2 Outflow side AS3 Outflow side B Assembly unit BK Brush Chamber C limit curve DAV Pressure Compensator DR Seal Ring DS1 Once-through side DS2 Once-through side DZ Pressure Difference EM Electrical Machinery ES1 Inlet side ES2 inflow side ES3 Inlet side F Filter material G Housing GK transmission chamber I Inverter IK inverter chamber K1 Air Chamber K2 Fluid Chamber KD Cable Gland KV1 chamber complex KV2 chamber complex L Air N liquid KL opening characteristic curve OE1 Opening (OE is O umlaut) OE2 Opening (OE is O umlaut) OE3 Opening (OE is O umlaut) P-pole cable R1 Flow direction R2 Flow direction R3 Flow direction RW rotor shaft RWD radial shaft seal S stator SK stator chamber T temperature V1 Backflow preventer V2 Backflow preventer V3 Backflow Prevention Body W1 wall W2 Wall W3 wall
Claims
1. A pressure compensation device (DAV) for an electric machine (EM) with a housing (G), comprising: Three backflow preventers (V1, V2, V3) are provided; the outlet side (AS1) of the first backflow preventer (V1) is fluidly connected to the inlet side (ES2) of the second backflow preventer (V2) and is further configured to be fluidly connected to the air chamber (K1) of said housing (G); The outlet side (AS2) of the second backflow preventer (V2) is connected to the inlet side (ES3) of the third backflow preventer (V3) and is further configured to be fluidly connected to the liquid chamber (K2) of the housing (G), which is sealed fluid-tight to the air chamber (K1) by a radial shaft seal (RWD). Pressure Compensation Device (DAV).
2. 2. The pressure compensation device (DAV) according to claim 1, The second backflow prevention body (V2) is configured so that fluid can flow freely from its inlet side (ES2) to its outlet side (AS2) when the opening pressure difference between its inlet side (ES2) and its outlet side (AS2) exceeds a certain pressure difference of less than 10 mbar, particularly less than 5 mbar, preferably less than 1 mbar.
3. 3. The pressure compensation device (DAV) according to claim 1 or 2, A pressure compensation device characterized in that at least two of the backflow preventers (V1, V2, V3) are joined together to form an assembly unit (B).
4. 3. The pressure compensation device (DAV) according to claim 1 or 2, A pressure compensation device characterized by a filter element (F) through which a fluid can flow, the filter element having a first flow-through side (DS1) fluidly connected to the inlet side (ES2) of the second backflow preventer (V2) and a second flow-through side (DS2) formed to be fluidly connected to the air chamber (K1) of the housing (G).
5. 5. A pressure compensation device (DAV) according to claim 4, A pressure compensation device, characterized in that the outflow side (AS1) and the first through-flow side (DS1) of the first backflow preventer (V1) are fluidly connected to each other.
6. 3. The pressure compensation device (DAV) according to claim 1 or 2, 10. A pressure compensation device, characterized in that one or more of the backflow prevention bodies (V1, V2, V3) are formed as individual check valves, in particular umbrella valves.
7. A housing (G) for an electric machine (EM), comprising: an air chamber (K1), a liquid chamber (K2) and a pressure compensation device (DAV) configured as claimed in claim 1 or 2, A housing in which chambers (K1, K2) are fluidly connected to each other via openings (OE1, OE2), and when radial shaft seals (RWD) are inserted into the openings (OE1, OE2) and a shaft (RW) of the electric machine (EM) extends through the radial shaft seal (RWD), the chambers (K1, K2) are fluid-tightly sealed to each other at the openings (OE1, OE2).
8. 8. The housing of claim 7, - the air chamber (K1) forms the brush chamber (BK) of the housing (G) and the liquid chamber (K2) forms the stator chamber (SK) of the housing (G), or - the air chamber (K1) is formed by a chamber complex formed by the brush chamber (BK) and the stator chamber (SK) communicating with it, and the liquid chamber (K2) forms the transmission chamber (GK) of the housing (G), or The air chamber (K1) forms the brush chamber (BK) of the housing (G), and the liquid chamber (K2) is formed by another chamber complex formed by the stator chamber (SK) and the transmission chamber (GK) communicating with it. A housing characterized by:
9. An electric machine (EM) comprising a housing (G) configured as claimed in claim 7.
10. A motor vehicle comprising an electric machine (EM) configured as claimed in claim 9.