helical gears

Description

[0001] The present invention relates to a spur gear with at least two toothed spur gears according to the preamble of claim 1.

[0002] Spur gears of the generic type are known, for example, from WO 2012 / 028231 A1, WO 2015 / 177332 A1, WO 2017 / 207215 A1, and WO 2017 / 072211 A1. Such spur gears are used, for example, to drive compressor stages in the petrochemical, oil and gas industries, refrigeration technology, air separation plants, steel production, and geothermal energy. The present invention relates both to spur gears with only two shafts, one of which carries, for example, a large gear and the other, for example, a pinion, as well as to spur gears with three or more shafts, one of which, in particular, carries a large gear and the others each carries a pinion or an intermediate gear, wherein such an intermediate gear can operate to drive a pinion arranged further away from the large gear.The more pinion shafts are provided, the more compressor stages or compressors can be driven via the spur gear, for example by means of a single drive or even with several drives.

[0003] For example, at least one electric motor and / or a gas or steam turbine could be considered as the drive. In principle, the drive is provided by the shaft of the large gear or an intermediate gear, but a drive by a pinion shaft is also possible.

[0004] To reduce ventilation and flow losses, the housings of spur gears of this type have an inner housing, also called a casing, which tightly encloses the gears. The casing can be complete or partial. The inner housing or casing is in turn mounted in and enclosed by an outer housing. Depending on the number of shafts, the inner housing and / or the outer housing comprise one or more horizontal joints. Inner housings or even outer housings without horizontal joints can also be provided. Vertical joints are also provided if required. WO 91 / 05965 A1 discloses a spur gear with such an inner housing and a coolant injection system in the area of ​​the gear meshing.

[0005] The shafts are usually mounted in the outer housing. The gear teeth of the spur gears are lubricated and / or cooled, for which purpose appropriate lubricant or lubricant injection systems may be provided.

[0006] For the distribution and removal of such lubricant and / or coolant, openings may be provided in the inner housing through which the lubricant and / or coolant flows into the space between the inner housing wall and the outer housing wall and then drains into a sump in the outer housing. A coolant flow may also be directed over the surface of the inner housing wall or through channels within the inner housing wall to dissipate heat.

[0007] WO 2017 / 207215 A1 proposes providing cooling pipes with coolant outlet openings extending along a lateral surface of the inner housing covering the spur gears. Coolant can flow from the coolant outlet openings onto the lateral surface and cool it. Furthermore, axial openings are provided in the inner housing, which extend along the circumference of the large gear and are located in the area of ​​the gear teeth. A hot lubricant-air mixture emerges from these axial openings and flows freely into the space between the side wall of the inner housing and the inner wall surface of the outer housing.

[0008] In the area of ​​the casing surface axially outside the cooling tubes, sheet metal elements can be provided that project radially beyond the casing surface, defining channels extending laterally along the casing surface in the axial direction. A hot lubricant-air mixture also flows into the channels from radial openings arranged in the casing surface, with the channels being covered by the wall of the outer casing.

[0009] US 2013 / 0180803 A1 describes a spur gear with an inner housing and an outer housing of the generic type with deflector plates on the inner housing to divert oil flowing radially from drainage openings. DE 295 17 964 U1 describes another spur gear in which an oil sump is pumped out of the inner housing by a pump. The inner housing does not tightly enclose the gears; instead, the inner housing contains oil collecting plates in the immediate vicinity of the tooth tips, which are provided with through-openings over at least part of their circumference. Circulating or ejected oil droplets pass through these through-openings to the back of the collecting plates and from there into the oil sump. The through-openings preferably extend tangentially.The document DE 295 17 964 U1 discloses a spur gear with at least two spur gears whose toothings mesh with each other in pairs, wherein the spur gears each have a radially outer circumference and two axial sides facing away from each other and are enclosed by an inner housing, and wherein the inner housing has radial openings through which the lubricant can flow out of the inner housing at least indirectly; wherein at least one radial opening is covered by a shielding element arranged between the inner housing and the outer housing, and wherein the lubricant is deflected outside the inner housing by the shielding element.

[0010] Further spur gears are disclosed in DE 10 2015 221 234 A1 and US 2013 / 0025405 A1.

[0011] A disadvantage of the known embodiments is that the hot lubricant-air mixture flowing out of the axial openings and radial openings flows directly against the wall of the outer housing and thereby causes uneven heating of the outer housing and strong, locally limited thermal loads on the outer housing.

[0012] The present invention is therefore based on the object of specifying a spur gear which avoids the aforementioned unfavorable thermal load on the outer housing and at the same time retains the advantages of the close encapsulation of the spur gears with the inner housing and the dissipation of heat from the inner housing via a lubricant-air mixture from axial openings and / or radial openings.

[0013] The object of the invention is achieved by a spur gear having the features of claim 1. The dependent claims describe advantageous and particularly useful embodiments of the invention.

[0014] A spur gear according to the invention comprises at least two toothed spur gears, each arranged on a shaft, whose toothings mesh with each other in pairs. In particular, three or more spur gears, each with its own shaft, are provided.

[0015] The spur gears each have a radially outer circumference (or circumferential surface) in which the toothing is arranged, as well as two mutually opposite axial sides. Over most of their radially outer circumference and over most of their mutually opposite axial sides, the spur gears are enclosed by an inner housing. The inner housing encloses the spur gears comparatively tightly, so that the wall of the inner housing follows the contour of the spur gears and a gap remains in the radial direction and preferably also in the axial direction between the wall of the inner housing and the outer contour of the spur gears, which gap is preferably less than one-tenth, particularly preferably less than one-twentieth of the diameter of the respective spur gear.

[0016] The inner housing, in turn, is fully enclosed by a separate outer housing and is preferably mounted in the outer housing, meaning that the outer housing supports the inner housing. The shafts are also preferably mounted in the outer housing. Thus, the inner housing is preferably positioned between the shaft bearings and, advantageously, at an axial distance from them, relative to the axial direction of the shaft rotation axes, and the spur gears. On both axial sides, the distance between the inner housing and the spur gears in the axial direction is generally smaller than the aforementioned axial distance from the shaft bearings.

[0017] Preferably, the spur gears are at least one large gear and at least one pinion meshing with the large gear.

[0018] According to one embodiment, a single large gear and a single pinion are provided.

[0019] According to another embodiment, at least two pinions are provided which mesh with the large wheel, for example directly.

[0020] According to a particular embodiment, at least one pinion meshes directly with the large gear and at least one other pinion meshes with the large gear via an intermediate gear.

[0021] According to the invention, the spur gears are supplied with a lubricant in the region of their toothing. The inner housing has axial openings that face one or both axial sides of at least one spur gear, and / or the inner housing has radial openings that face the radially outer circumference of at least one spur gear, wherein the lubricant can flow out of the inner housing at least indirectly through the axial openings and / or radial openings.

[0022] The spur gears in the area of ​​their gear teeth can be supplied with a lubricant, for example, by means of a lubricant injection, whereby the injection can be carried out via nozzles with pressure or via lines at least comparatively pressureless or pressureless.

[0023] The injection of lubricant preferably into the tooth engagement areas can be provided, for example, with corresponding nozzles provided in or on the inner housing, in particular flat jet nozzles, wherein channels are preferably provided in the inner housing for the lubricant supply to the nozzles, in particular within the inner housing wall, for example in a jacket surface and / or in a side part of the inner housing.

[0024] According to the invention, at least one or several or all axial openings and / or radial openings are covered by a shielding element arranged between the inner housing and the outer housing, wherein the shielding element is arranged in such a way or at such a distance from the respectively covered axial opening or radial opening that lubricant flowing out of the axial opening or radial opening is deflected outside the inner housing by the shielding element.

[0025] Thus, the shielding element faces the hot lubricant flow or lubricant air flow exiting the axial or radial opening in such a way that this flow is prevented from flowing directly against the inner wall surface of the outer housing. Rather, the flow is completely deflected by the shielding element or at least distributed by the shielding element in such a way that the flow does not cause a locally limited temperature increase in the outer housing.

[0026] According to the invention, the outflowing lubricant, or the lubricant-air mixture stream, is deflected outside the inner housing by a coolant injection device associated with the opening, so that it does not flow directly against the opposing outer housing. For this purpose, the coolant injection device can introduce a more or less focused jet of coolant into the lubricant or lubricant-air mixture emerging from the opening, particularly by means of a nozzle or a spray nozzle, in order to achieve the desired deflection. At the same time, this advantageously cools the lubricant or lubricant-air mixture emerging from the inner housing.

[0027] In particular, at least one shielding element is arranged opposite the respectively covered axial opening or radial opening in such a way that lubricant flowing out of the axial opening or radial opening is deflected in a direction along an outer surface of the inner housing, more or less touching the inner housing. This means that the deflected lubricant flow (or lubricant air flow) flows at least substantially parallel to the outer surface of the inner housing, either directly on the outer surface or at a distance from it. Additionally or alternatively, at least one shielding element can also have openings and can in particular be designed as a perforated plate. The openings each have a maximum flow cross-section of one twentieth, one fiftieth, or one hundredth of the flow cross-section of the axial opening or radial opening covered by the respective shielding element.Thus, a distribution of the lubricant emerging from the axial opening or radial opening is achieved, so that the lubricant flowing out of the axial opening or radial opening is distributed over a comparatively larger area of ​​the outer housing, compared to an embodiment without a shielding element.

[0028] According to a preferred embodiment, at least one shielding element has an arcuate shape, in particular with a concave side facing the axial or radial opening. Such a shielding element can be designed with or without openings. If it is designed with openings, this promotes the distribution of the lubricant flow. If it is designed without openings, the deflection of the lubricant is promoted and, in particular, discharge from drain openings in the shielding element in two opposite directions is possible. Of course, the shielding element can be arranged such that lubricant discharges in only one direction, i.e., from a drain opening.

[0029] According to one embodiment of the invention, at least one shielding element rests with at least one or two lateral ends laterally to the axial or radial opening on an outer surface of the inner housing. This prevents lubricant from escaping in the region of these lateral ends between the shielding element and the inner housing. Furthermore, easy installation of the shielding element on the inner housing is possible.

[0030] The shielding element can, in particular, rest against the outer surface of the inner housing on two opposite sides of the axial or radial opening. This creates a tab that is open on both sides. For example, the aforementioned curved shape of the shielding element can be chosen for this purpose. Of course, another shape, in particular a beveled shape, is also possible.

[0031] According to an alternative embodiment, the shielding element rests with three of its four lateral ends on the outer surface of the inner housing, laterally facing the axial or radial opening, and is designed, in particular, as a deep-drawn gill in a side part of the inner housing. This deflects the lubricant flow in exactly one direction.

[0032] However, in both embodiments it is also possible to provide openings in the shielding element so that lubricant can also escape towards the outer housing.

[0033] According to one embodiment of the invention, the inner housing has a plurality of individual shielding elements which are provided for a plurality of axial openings and / or radial openings, wherein the shielding elements are each fastened to the inner housing or to the outer housing.

[0034] Furthermore, at least one shielding element can also be designed as a closed drainage channel, which extends along an outer surface of the inner housing with its longitudinal axis, which is completely enclosed in the circumferential direction by the inner housing and a channel wall. Such a drainage channel can, for example, extend with its longitudinal axis in the circumferential direction of a spur gear. Additionally or alternatively, at least one drainage channel extends vertically with its longitudinal axis. Other extensions are possible.

[0035] It is advantageous if at least some axial openings are arranged at a distance from one another in the circumferential direction of at least one spur gear along the toothing of the spur gear, i.e., radially in a region between the root diameter and the tip diameter of the toothing. The spacing between the axial openings can be irregular or regular, depending on where lubricant is desired to escape from the inner housing.

[0036] According to a further aspect of the invention, a coolant injection device is provided in the region of the axial openings and / or radial openings and / or on the shielding elements, with which a coolant is injected into the lubricant flowing out of the axial opening or radial opening. Such a coolant injection device not only allows the lubricant flow exiting the axial opening or radial opening to be cooled, but it is also possible to implement the coolant injection in such a way that it causes a distribution and / or redirection of the lubricant flow.

[0037] The outer housing advantageously includes an oil sump or lubricant sump, which collects oil or lubricant escaping from the bearings and / or the inner housing. The inner housing is preferably free of such an oil sump or lubricant sump.

[0038] Each pinion shaft can advantageously accommodate one or two compressor impellers to form a multi-stage compressor. In particular, up to five pinion shafts and 10 compressor stages are possible.

[0039] Spur gear diameters of more than one meter, and in the case of large gears, possibly more than three meters, are possible.

[0040] Gear ratios between the large gear and the pinions of more than 10 or more than 20, for example 24, are possible.

[0041] The spur gears can be straight-toothed, helical-toothed, or herringbone-toothed. Furthermore, a cooling groove can be formed in the circumferential direction of the gearing, particularly in the case of helical gearing.

[0042] Shafts mounted outside a parting joint can be designed as plug-in shafts.

[0043] In particular, the spur gear does not have the function of a gear pump and accordingly the spur gear can be free of a pressure connection to which pressure medium, in particular oil, pressurized and / or conveyed by the gears is applied.

[0044] The spur gears can be arranged entirely above an oil sump in the outer housing, thus not being immersed in the oil sump or generally not immersed in a fluid reservoir. Instead, lubricating fluid can be sprayed or directed onto the spur gears from above or from the side.

[0045] A design without an oil sump in the outer housing is also possible.

[0046] The following features and measures can also contribute to improving the efficiency and performance of a spur gear according to the invention, individually or in combination, but are not mandatory: Up to two impellers of a compressor or similar can be directly mounted on each pinion shaft. The impellers can be mounted directly to the pinion shaft, for example, using a conical connection, a flange, or a Hirth connection. The impellers are arranged outside the outer casing, but parts of the corresponding turbomachine can be integrated into the outer casing, for example, a spiral casing for the impeller.

[0047] An additional pump for supplying lubricating oil can also be arranged at a free shaft end, in particular via an additional gear stage for adjusting the pump speed.

[0048] Further designs are also possible which have an additional free shaft end on the large gear shaft, a pinion shaft or an intermediate shaft, i.e. an end without a compressor impeller, whereby further drive machines, gearboxes or working machines can be arranged or coupled to this free shaft end.

[0049] The shafts can preferably be supported by plain bearings, for example fixed-segment bearings or tilting-segment bearings, which can also be designed at least partially as hydrostatic bearings.

[0050] With the spur gear according to the invention, very high peripheral speeds of the gear teeth of up to 200 m / s or more can be achieved. With sufficient cooling, the gear temperature can be adjusted to a maximum of 125°C.

[0051] For maintenance work, the lower part of an inner housing with a horizontal joint preferably remains in the outer housing, meaning only the upper part of the inner housing is removed. An inspection option in the installed state is also advantageously provided, for example, through openings in the inner housing in the area of ​​the gear engagements.

[0052] The spur gears are preferably almost completely enclosed by the inner housing, in particular over at least approximately 360° (e.g. at least 330° or at least 340° or at least 350°), and openings for inspection are provided only in the area of ​​two meshing spur gears.

[0053] Cooling channels can be provided in the inner housing to conduct a coolant to cool the inner housing. Such a cooling channel, or the aforementioned drain channel, can be segmented. This can result in several individual channels for a spur gear, which are preferably arranged one behind the other in the circumferential direction and connected to each other by means of coolant or lubricant.

[0054] The inner housing is preferably designed as a welded construction. For better positioning during production, the sheet metal parts can be positioned and aligned using a tongue and groove system. This avoids complex downstream machining, especially in the area of ​​the gearing parts, as any form deviation is minimized and remains precisely within the specified design tolerances.

[0055] The distance between the rotating parts and the inner housing and / or outer housing (gearing, shafts and / or pressure comb) can be limited to 1 to 10 mm.

[0056] The cooling channel segments or drain channel segments can be connected to one another by connections within the parting joint of the inner housing, whereby a coolant flow, in particular cooling oil flow, or lubricant flow, in particular lubricant-air mixture flow, can be transferred from one housing part to the other housing part at the parting joint.

[0057] Temperature sensors can be arranged within the inner housing and / or in the cooling channels and / or in the drain channels to enable particularly needs-based control of the coolant flow. Furthermore, recesses and / or mounting options can be provided specifically on the inner housing for other sensors, for example, for detecting rotational speed, vibrations, acceleration, pressure, or for locating a rotary encoder (key phaser).

[0058] When using flat jet nozzles, it is advantageous to use nozzles with flattened side surfaces. This allows the contour to be prefabricated in the sheet metal parts of the inner housing. This eliminates the need for complex positioning and / or anti-rotation protection during the subsequent welding process during assembly of the inner housing. Other non-rotationally symmetrical geometries can also be used.

[0059] The lubricant for the gear teeth can be injected into the meshing and / or disengaging portions. When injected into both the meshing and disengaging portions, the same or different lubricant quantities can be used. This allows for an optimal lubricant film thickness to be achieved.

[0060] The assembly of an inner housing lower section is preferably carried out via tabs in the primary joint of the outer housing, preferably via tabs that are height-adjustable, for example, using adjusting screws and / or adjusting plates. To minimize the necessary machining at the outer housing joint or to enable the installation of a new inner housing in the event of a retrofit, the tabs are preferably designed with a cranked design to enable joint assembly with the outer housing joint.

[0061] An inner housing upper part is preferably screwed to an inner housing lower part.

[0062] A housing for additional spur gears which are not located at the level of the primary outer housing part joint can be provided by a second inner housing, which is preferably fastened in a second outer housing part joint or is screwed to the first inner housing via a second part joint.

[0063] Preferably, the position of the lower part of the inner housing, which is mounted in the primary parting joint of the outer housing, can be adjusted in the axial direction, for example by means of a toothing, with wedges and / or with adjusting screws.

[0064] Side walls of the inner housing can have an annular skimming edge in the area of ​​the openings for the shafts, which shields lubricant escaping from the openings, in particular oil from the plain bearings, or medium escaping from the ventilation slots of the inner housing from unwanted recirculation due to the suction effect of the toothed parts.

[0065] The side walls of the inner housing can have additional stiffening plates, which at the same time deflect the spray oil that forms in the space between the outer housing and the inner housing.

[0066] If cooling channels are provided on the inner housing for heat dissipation, flow velocity-increasing devices can be integrated, resulting in a preferably turbulent flow of the coolant, preferably oil, in the cooling channel. For this purpose, for example, fittings in the cooling channel are possible, which on the one hand increase the surface of the cooling channel over which the coolant flows and on the other hand temporarily increase the flow velocity of the coolant in the channel. For example, built-in sheets and / or cross-section-restricting bores can be provided, and / or inserted honeycomb structures and / or materials to improve the heat transfer coefficient, for example, made of copper, aluminum, copper alloys, or aluminum alloys. Such flow velocity-increasing devices are also possible in the drain channels.

[0067] The inlet and / or outlet of the coolant into the cooling channels can be selected depending on the direction of rotation in order to achieve an optimal cooling effect.

[0068] Openings, pipes, and / or hoses can be provided in the joint of the inner housing, establishing a flow-conducting connection between at least one cooling channel in the upper housing part and at least one cooling channel in the lower housing part of the inner housing. The same applies to a flow-conducting connection between a drain channel in the upper housing part and a drain channel in the lower housing part.

[0069] If several cooling channels are arranged next to each other in the axial direction, they can be completely separated from each other. Alternatively, openings in the axial direction are provided to connect the channels. The same applies to the drainage channels.

[0070] Cooling channels for the large gear or an intermediate gear can be provided separately from cooling channels of the pinions or can be connected to them.

[0071] Additional fittings may be provided in the channels to increase stiffness and achieve turbulent flows.

[0072] The flow in the cooling channels can be throttled at the inlet and / or outlet. The cooling medium is ideally drained into an oil sump in the outer casing or into an oil collecting tray.

[0073] In a design with closed cooling channels, it is not necessary for the coolant and lubricant to be identical or miscible. In such a design, the coolant can be fed into and out of the coolant channels in a closed manner. In addition to oil, possible coolants could include water, glycol, or other liquid or gaseous substances.

[0074] The advantage of using separate coolant and lubricant circuits is the use of different purity classes of the medium, such as the oil. This eliminates the need for constant filtering of the coolant, which has a positive impact on the required sizing of the filter system, especially the oil filter system.

[0075] When using separate lubricant and coolant circuits, the design with different temperature levels of the two media can also be advantageous with regard to the heat exchange or the lubricating behavior of the media.

[0076] The radial openings in the inner housing are preferably provided in a circumferential surface of the inner housing, which follows the contour of the tip circle of the corresponding spur gear, in particular a large gear, intermediate gear, or pinion. The radial openings can preferably be arranged in the region of the axially lateral ends of the circumferential surface and can be delimited or shielded axially on the outside by a side part of the inner housing that projects radially beyond the circumferential surface.

[0077] The shielding elements can be made in one piece with the inner housing or the outer housing, in particular, they can be integrally connected to them. The integral connection can be achieved through one-piece production or by welding or soldering; gluing is also possible. Alternative fastening is possible using screws, rivets, plugs, and the like. In general, any type of form fit is also possible. The shielding elements can be made of the same material as the inner housing and / or the outer housing, but a design using a different material than that from which the inner housing and / or the outer housing is made is also possible.

[0078] The shielding elements can be manufactured by folding or deep drawing material of the inner housing and / or the outer housing.

[0079] The shielding elements can be designed as one or more parts; in particular, in the case of asymmetrical geometries, the multi-part design is easier to implement technically.

[0080] The shielding elements do not have to be evenly distributed on both axial sides of the inner casing. Depending on the type of gearing, they can be arranged only on the pressure side or only on the suction side of the gearing, or the distribution, especially the spacing, can be different on both sides.

[0081] Shielding elements arranged on both axial sides of the inner housing can be arranged overlapping or offset from each other.

[0082] The axial or radial openings can have symmetrical or asymmetrical shapes. The same applies to the shielding elements.

[0083] The axial or radial openings can also be curved. However, triangular, square, polygonal, circular, or elliptical openings are particularly suitable.

[0084] The shielding elements can be bent and / or folded in several spatial directions.

[0085] The shielding elements can be designed in such a way that the lubricant-air mixture deflected by them is discharged in at least two different outflow directions via one or more discharge openings.

[0086] In particular, in the case of two opposing axial openings in the inner housing in the area of ​​the tooth engagement, one shielding element on the suction side can be used to supply cooling air into the tooth engagement and the other shielding element on the pressure side can be used to discharge the lubricant-air mixture from the tooth engagement.

[0087] The cooling channels or drainage channels can have connecting devices, such as flanges, threads, and the like, designed for connecting additional pipes, hoses, or shafts. These systems make it possible to direct the medium flowing in the channels to oil collection tanks, cooling tanks, lubricant systems, or cooling systems.

[0088] Optionally, at least one suction pump can be connected to at least one drainage channel and / or cooling channel, which causes a faster discharge of the medium flowing in the channel.

[0089] Axial openings can be found, particularly in the side section of the inner housing, in the area of ​​the meshing gears. This is where particularly hot lubricant escapes from the inner housing.

[0090] One or more axial openings can be arranged asymmetrically to the housing part joint, in particular horizontal housing part joint, of the inner housing.

[0091] The shielding elements can extend with their surface facing the side part obliquely or parallel to the side part in which a corresponding axial opening covered by the shielding element is provided.

[0092] Particularly good dispersion is achieved when the shielding elements have a curved, for example concave, surface onto which the lubricant emerging from the axial or radial opening impinges.

[0093] If the shielding element is designed with openings, in particular as a perforated plate or even as a grid or sieve, it can directly cover the axial opening or radial opening because this deflects the lubricant escaping from the axial opening or radial opening.

[0094] Instead of a sieve or perforated sheet, a sponge-like structure can also be provided.

[0095] The invention will be described below using exemplary embodiments and the figures.

[0096] They show: Fig. 1a-1d schematic representations of spur gears designed according to the invention; Figure 2 a top view obliquely from above of a spur gear designed according to the invention in a partial sectional view; Figure 3 a view of an inner housing of a spur gear designed according to the invention; Figure 4 a possible adjustable mounting of the inner housing in the outer housing; Figure 5 schematically possible inspection openings in the inner housing; Figure 6 an oblique top view of an inner housing with axial openings and radial openings; Figure 7 an axial top view of an inner housing with unevenly distributed axial openings; Figure 8 a radial top view of an inner housing with unevenly distributed radial openings; Figure 9 an oblique top view of an inner housing with axial openings covered according to the invention; Figure 10 an enlarged sectional view through the covered axial openings from the Figure 9 ; Figure 11 an embodiment according to the Figures 9 and 10 but with shielding elements only at two lateral ends; Figure 12 shows a schematic representation of an attachment of a shielding element to the inner housing; Figure 13 shows a schematic representation of an attachment of the shielding element to the outer housing; Figure 14 shows a shielding element with openings; Figure 15 shows a schematic representation with coolant injections on the shielding elements; Figure 16 shows an embodiment with shielding elements in the form of drainage channels in an axial plan view of an inner housing; Figure 17 shows an embodiment with drainage channels for the axial openings and radial openings; Figure 18 shows a cross-section through the embodiment according to the Figure 17 ; Figure 19 shows a further cross section through the embodiment according to the Figure 17; Fig. 20a-c shows a further embodiment for covered axial openings in different views; Fig. 21a-c shows a further embodiment for covered axial openings in different views; Fig. 22a-c shows a further embodiment for covered axial openings in different views; Fig. 23a-b shows an embodiment for the covering of axial openings; Figure 24 shows a further embodiment for the covering of axial openings; Figure 25 shows a sectional view of an embodiment for the covered axial opening; Figure 26 shows a sectional view of a further embodiment for covered axial openings.

[0097] The Figures 1a to 1b The spur gear units shown differ in the arrangement of impellers or pumps, the number of spur gears, and the corresponding number of shafts. These exemplary embodiments are not exhaustive, and other arrangements are possible.

[0098] According to the Figure 1a The spur gear comprises three spur gears 1, 2, 3, wherein the spur gear 1 is designed as a large gear 10 and the spur gears 2, 3 are each designed as pinions 11. The pinions 11 are arranged diametrically opposite one another with respect to the large gear 10 and mesh with the large gear 10. In particular, all shafts 5 of the spur gears 1, 2, 3 are mounted in a common joint of the outer housing 7.

[0099] Two impellers 26 of a compressor are positioned on the shaft 5 of the spur gear 2. The shaft 5 of the spur gear 3 is driven by an external drive 27. Thus, the drive power flow follows from the drive 27 via the spur gear 3 to the spur gear 1, then to the spur gear 2 and to the impellers 26.

[0100] The spur gears 1, 2, and 3 are positioned together in an inner housing 6 and are tightly enclosed by it. The inner housing 6 is arranged within an outer housing 7 and is supported by it.

[0101] The shafts 5 are mounted in the outer housing 7. In particular, the shaft 5 of the spur gear 1 is mounted in the outer housing 7 by a schematically illustrated radial bearing 17 and an axial-radial bearing 8, whereas the shaft 5 of the spur gear 2 is free of axial bearings and is mounted only in the outer housing 7 by radial bearings 17. Axial forces acting on the spur gear 2 are transmitted to the spur gear 1 via a thrust collar bearing 9 with two thrust collars 9.1, which are supported on both sides of the spur gear 1 in the axial direction, and are dissipated from its shaft, which is axially mounted in the outer housing 7, via the axial-radial bearing 8 to the outer housing 7.

[0102] The spur gear 3 can have an axial bearing in the outer housing 7 in addition to a radial bearing. According to one embodiment, however, axial forces can be additionally or alternatively absorbed by the drive 27.

[0103] The pressure comb bearing 9, here with the two pressure combs 9.1, is arranged within the inner housing 6 and is also tightly enclosed by the inner housing 6.

[0104] The design according to the Figure 1b corresponds to that of the Figure 1a with the difference that the drive 27 is provided on the shaft 5 of the large gear 10, and the spur gear 2 drives two impellers 26 of the compressor or several compressors via its shaft 5. Furthermore, a pump 28, in particular a lubricant pump and / or coolant pump, is arranged on the shaft 5 of the large gear 10.

[0105] In contrast to Figure 1a the spur gear 3 is not in direct drive connection with the spur gear 1, but a fourth spur gear 4 is provided, which is designed as an intermediate gear 29 and meshes with the spur gear 1 and the spur gear 3. However, this is not mandatory, as can be seen from the Figure 1c is evident.

[0106] To dissipate axial forces, the Figure 1b In the embodiment shown, the spur gear 3 is also mounted on the adjacent spur gear 4, here the intermediate gear 29, via a thrust collar bearing 9 with two thrust collars 9.1 in the axial direction, via which the spur gear 3, which is designed as a pinion 11, is driven by the spur gear 1, which is designed as a large gear 10. Alternatively, the spur gear 3 could again mesh directly with the spur gear 1 and be supported on the spur gear 1 via the thrust collar bearing 9, see the Figure 1c .

[0107] The spur gear 4 also has a shaft 5, which is preferably supported in the outer housing 7 via radial bearings and axial bearings, or a radial bearing and an axial-radial bearing (not shown). The pinions 11, however, can be free of axial bearings in the outer housing 7.

[0108] The inner housing 6 encloses all spur gears 1, 2, 3, 4 and the two thrust comb bearings 9.

[0109] The design according to the Figure 1c corresponds to that of the Figure 1b , only that here the intermediate gear 29 is omitted and, as explained, the spur gear 3 is supported on the spur gear 1 via the thrust bearing 9. For the rest, please refer to the description of Figure 1b referred to.

[0110] In the embodiment according to the Figure 1d Only two spur gears 1, 2 are provided, of which spur gear 1 is designed as a large gear 10 and spur gear 2 is designed as a pinion 11. The large gear 10 is driven by the drive 27 via the shaft 5 and drives the pinion 11 and, via its shaft 5, the impeller 26. The pinion 11 is axially mounted via the thrust collar bearing 9 with the two thrust collars 9.1 and does not require an axial bearing in the outer housing 7. The shaft 5 of the large gear 10 is axially and radially mounted in the outer housing 7. The inner housing 6 encloses the two spur gears 1, 2 and the thrust collar bearing 9.

[0111] In the Figure 2 a spur gear designed according to the invention is shown, comprising three shafts 5, of which the middle one carries the large gear 10 and the two outer shafts, which enclose the middle shaft 5 between them, each carry a pinion, which is not visible in the illustration because it is arranged within the inner housing 6. The cutouts in the outer housing 7 and in the inner housing 6 serve merely to illustrate various features and are not present in practice. In particular, it can be seen that the inner housing 6, in the area of ​​the large gear 10, has a jacket surface 30 which is radially opposite the toothing or the radially outer diameter of the large gear 10, with a comparatively small radial gap. Correspondingly, jacket surfaces 30 of the inner housing 6 are provided which are closely opposite the radially outer surface of the pinions and radially cover the pinions. In the Figure 2only one lateral surface 30 is visible.

[0112] When designing according to the Figure 2 A coolant channel 24 is placed on the outer surface 30 for the large gear 10 in order to actively dissipate heat with a coolant.

[0113] From the Figure 2 The bearing of the inner housing 6 is visible via tabs 31 in the parting line of the outer housing 7. This represents a preferred bearing concept. In particular, the position of the inner housing 6 is adjustable in the axial direction, i.e., in the direction of the shaft rotation axes 19 of the shafts 5.

[0114] In the Figure 3An inner housing 6 is shown as an example, which can accommodate five shafts (not shown), namely the shaft of a large gear (not shown) in the center, next to it the shaft of a pinion (not shown) and the shaft of an intermediate gear (not shown), beyond the intermediate gear the shaft of another pinion (not shown) and above the large gear the shaft of another pinion (not shown). Furthermore, axial openings 21 can be seen along the outer circumference of the upper housing half of the inner housing 6, through which hot lubricant, in particular oil, can be drained from the area of ​​the gears. The axial openings 21 are also referred to as ventilation openings.

[0115] The Figure 4 shows a device for adjusting the axial position of the inner housing 6 relative to the outer housing 7. The inner housing 6 can be moved within the outer housing 7 in the axial direction using adjusting screws 32.

[0116] The view of the Figure 5serves in particular to illustrate inspection openings 33 in the inner housing 6 in the area of ​​the tooth meshing of the spur gears (not shown here). In the area of ​​the large gear (not shown in detail), the intermediate gear and the pinion, axial openings 21, also called ventilation openings, can be seen, which are each arranged along the outer circumference in the area between the root circle and tip circle of the gearing. An additional, comparatively large axial opening 21 is shown in the area of ​​the gearing between the large gear (not shown here) and the intermediate gear. Coolant channels 24 are provided in the inner housing along the outer circumference around the individual spur gears. These coolant channels 24 could also be referred to as lubricant channels if the lubricating effect is the primary concern.These coolant or lubricant channels 24 can have nozzles 25 at their ends in the area of ​​the gear engagements in order to inject coolant and / or lubricant into the area of ​​the gearing.

[0117] In the embodiment shown, the inner housing 6 is designed in two parts and, as before, divided along a horizontal parting joint.

[0118] In the Figure 61 shows another inner housing 6 with two spur gears 1, 2, to which the present invention can be applied. The spur gear 1 is designed as a large gear 10, the spur gear 2 as a pinion 11. Both spur gears 1, 2 are each mounted on shafts 5 that protrude from side parts 20 of the inner housing 6. The side parts 20 are advantageously flat and extend in the radial direction beyond the outer surfaces 30 of the inner housing 6. Immediately adjacent to the side parts 20, at least in the outer surface 30 of the large gear 10, radial openings 16 are provided, through which hot lubricant or a lubricant-air mixture can flow out of the inner housing 6. Axial openings 21 for the same purpose are arranged in the side parts 20 in the region of the toothing of the large gear 10. The axial openings 21 accordingly extend along the circumference in the region of the toothing of the large gear 10 at a distance from one another in the circumferential direction.In the illustrated embodiment, the circumferential spacing between the axial openings 21 is identical, and the circumferential spacing between the radial openings 16 is identical. However, this is not mandatory. In the illustrated embodiment, the circumferential spacing between the radial openings 16 differs from the circumferential spacing between the axial openings 21. This could also be implemented differently.

[0119] The above description refers to an upper and lower half of the inner housing 6, which is joined together along the horizontal parting joint 38.

[0120] As can be seen, each side part 20 is constructed in one piece above and below the parting line 38. However, this is also not mandatory.

[0121] In the Figure 7An embodiment is shown in which the distance between the axial openings 21 in the upper part of the inner housing 6 is uneven. Furthermore, an additional axial opening 21 in the region of the parting line 38 is arranged asymmetrically to the parting line 38 and, in particular, is designed asymmetrically to a line of symmetry running radially to the shaft 5 of the large gear 10.

[0122] In the Figure 8 an embodiment of radial openings 16 in the inner housing 6 is shown, wherein the arrangement of the radial openings 16 in the region of one side part 20 is different from that in the region of the other side part 20.

[0123] The present invention can be used both in such inner housings 6 as shown in the Figures 6 to 8 are shown, but can also be used for other arrangements of axial openings 21 and radial openings 16.

[0124] In the Figure 9 the design is in accordance with the Figure 6with shielding elements 12 according to an advantageous embodiment of the invention. Only the axial openings 21 in the upper part of the inner housing 6 are covered with shielding elements 12. However, this is not mandatory; axial openings 21 in the lower part could also be covered. Furthermore, all axial openings 21 in the upper part are covered; here, too, only a portion of the axial openings 21 could be covered. The comparatively large additional axial opening 21 in the area of ​​the toothed engagement between the large gear 10 and the pinion 11 is not covered. Here, too, a corresponding cover could be provided by a shielding element 12.

[0125] In the illustrated embodiment, the shielding elements 12 are designed in the manner of gills 15. This can be seen again particularly in the enlarged illustration from the Figure 10 For example, the shielding elements 12 are manufactured by deep drawing the side parts 20.

[0126] Specifically, the shielding elements 12, which are essentially rectangular in shape, are connected by three lateral ends to the outer surface of the inner housing 6, so that a drainage opening 22 remains only in the region of the fourth lateral end. Along the further circumference of the axial openings, however, a seal is provided between the shielding elements 12 and the side part 20, or the shielding elements 12 are formed integrally with the side parts 20. A similar arrangement can be provided for shielding elements 12 of radial openings 16.

[0127] Due to the arrangement of the shielding elements 12, lubricant escaping from the axial openings 21 can no longer directly hit the axially opposite outer housing 7 (see for example the Figure 2 ) and a corresponding local heat input is avoided.

[0128] Figure 11shows an embodiment of an inner housing 6 with axial openings 21, one of which is covered by a shielding element 12, which is connected at two laterally opposite ends to the outer surface of the side part 20 or is formed integrally with it. This creates two opposing drainage openings 22, which are directed radially outward and radially inward, but could also be oriented circumferentially or diagonally.

[0129] In addition to the one axial opening 21 shown, further or all of the axial openings 21 could also be covered with such a shielding element 12 or a differently designed shielding element.

[0130] In the Figure 12 It is schematically shown that a shielding element 12 is attached to the inner housing 6, for example to the side part 20, for example, but not necessarily, with struts 23.

[0131] In the Figure 13In contrast, the shielding element 12 is attached to the outer housing 7, also by way of example, but not necessarily, with struts 23.

[0132] In the Figure 14 An optional aspect of the present invention is shown schematically, which is applicable to all embodiments. Here, the shielding element 12 has a plurality of openings 13, through which lubricant emerging from the axial opening 21 (or a radial opening) can flow in the direction of the outer housing (not shown here), but is distributed in order to enlarge the impact area of ​​the lubricant on the outer housing and thus reduce a locally limited heat input. Preferably, but not necessarily, the shielding element 12 is designed in an arc shape, with the concave side facing the axial opening 21 (or radial opening) in order to achieve an even better distribution of the lubricant deflected by the shielding element 12.

[0133] In the Figure 15 an optional feature of the invention is shown, according to which a coolant injection 18 is provided in the region of the axial openings 21 (or radial openings) in order to achieve the desired deflection of the lubricant emerging from the axial openings 21 (or radial openings) and thus to avoid a direct flow to the outer housing.

[0134] Such a coolant injection 18 can also be combined with a shielding element 12.

[0135] In the Figures 16 to 19 Embodiments are shown in which the shielding elements 12 have been further developed into drainage channels 14, so that the lubricant emerging from the openings (axial openings and / or radial openings) in the inner housing 6 is not only redirected but also discharged in a directed manner. Here, too, a coolant injection 18 can optionally, but not necessarily, be provided in the drainage channels 14.

[0136] In the embodiments shown, the drainage channels 14 extend with their channel longitudinal axis 14.1 in the circumferential direction, in particular of the large gear 10. However, this is not mandatory.

[0137] The drainage channels 14 are completely enclosed in the circumference around the channel longitudinal axis 14.1, on the one hand by the channel wall 14.2 and on the other hand by the outer surface of the inner housing 6, in particular the jacket surface 30 and the side part 20.

[0138] In the Figure 17 The channel arranged on the outer surface for the large gear 10 is designated 12, 14 because it receives and drains lubricant or lubricant-air mixture flowing out of invisible radial openings provided in the outer surface, which are positioned within the drain channel 14. At the same time, as indicated, further radial openings can be provided in the outer surface outside the drain channel 14.

[0139] Accordingly, axial openings could also be provided outside the drainage channels 14 on one or both side parts 20. Conversely, all radial openings and / or axial openings can also open into one or more drainage channels 14.

[0140] Furthermore, the Figure 17 The channel shown on the lateral surface can be designed as a coolant channel 24 arranged separately from the drain channels 14 and / or axial openings and / or radial openings, as is shown, for example, in the Figure 2 is shown.

[0141] Especially from the Figures 16 and 17It can be seen that the side parts 20 can advantageously be stabilized with reinforcing ribs 34. Furthermore, the upper housing part and the lower housing part each have a flange 35 for screwing the two housing parts together and for connecting, for example, the tabs 31 for mounting in the outer housing to these flanges 35. This can be provided in all embodiments and modifications thereof shown here, but is not mandatory.

[0142] The drainage channels 14 open into a space between the inner housing 6 and the outer housing (not shown in detail here) via drainage openings 22. Alternatively, a line 37 could be connected to the drainage channels 14, through which the medium conveyed in the drainage channels 14 is discharged. This is shown schematically in the Figure 16 This line 37 could, for example, be connected to a suction pump.

[0143] In the Figures 20a to 20cA further embodiment of a spur gear is shown, but without depicting the outer housing, in which the axial openings 21 distributed along the circumference in the upper part of the inner housing 6 are covered with shielding elements 12 of a first form, for example the aforementioned gill shape, and the comparatively larger axial opening 21 in the area of ​​the tooth engagement between the large gear (not visible here) and the pinion is covered with a shielding element 12 of a second embodiment. Figures 20a and 20b show the inner housing 6 from different perspective views, the Figure 20c shows a comparatively enlarged view in the area of ​​the gear engagement.

[0144] In the case of the Figure 20cFrom the exemplary embodiment of the shielding element 12 shown, it is clear that this shielding element 12 leads to an asymmetrical deflection of the lubricant or lubricant-air mixture flowing out of the axial opening 21. Several features will be explained with reference to this shielding element 12, which can be implemented individually or together. These features can also be implemented in other shielding elements 12 that cover axial openings 21 or radial openings 16.

[0145] The shielding element 12 can be designed in one piece or in several pieces.

[0146] Preferably, the shielding element 12 closes at least one side of the axial opening 21 (or radial opening 16).

[0147] The main surface of the shielding element 12 is preferably inclined at an angle between 0° and 45° to the surface or to the surface area of ​​the inner housing 6, here to the side surface of the inner housing 6, in which the axial opening 21 (or radial opening 16) is arranged.

[0148] The lateral surfaces of the shielding element 12 are preferably arranged at an obtuse angle to the main surface of the shielding element 12, that is to say at an angle of more than 90°.

[0149] In order to ensure better assembly and disassembly of the inner housing 6, the shielding element 12 is preferably only attached to the upper part or only to the lower part of the inner housing 6 and / or is detachably attached to the inner housing 6.

[0150] The shielding element 12 preferably covers the entire area of ​​the axial opening 21 (or radial opening 16), but preferably at least more than 10 percent of the area.

[0151] In the shielding element 12, which covers the axial opening 21 in the toothed engagement, according to the embodiment in the Figures 20a to 20c , the drain opening 22 at the lower end of the shielding element 12 is extended into one of the two side surfaces, here to the joint between the upper and lower parts of the inner housing 6, so that the outflow can be directed downwards and outwards on one side. This achieves the aforementioned asymmetrical deflection. Other embodiments are possible, in which the drain opening 22 is provided at the bottom and only on one side or only on opposite sides, with the shielding element 12 closed at the bottom.

[0152] When designing according to the Figures 21a to 21c , which in turn show various oblique views and an enlarged representation analogous to the Figures 20a to 20cAs shown, the shielding element 12 in the region of the toothed engagement is composed of two parts, each manufactured in one piece with the inner housing 6. Accordingly, the shielding element 12 also has a parting joint if the inner housing 6 has a parting joint and the shielding element 12 extends beyond the parting joint of the inner housing 6.

[0153] In this embodiment, but not necessarily, the main surface of the shielding element 12 is arcuate. Such an arcuate embodiment could also be provided in the other embodiments.

[0154] The cross-section enclosed by the shielding element 12 expands in the direction of the outflow. This is also not mandatory. Such an expansion is possible both with correspondingly expanding axial openings 21 or radial openings 16, but also with axial openings 21 or radial openings 16 that do not expand in this direction.

[0155] The embodiment according to the Figures 22a to 22c largely corresponds to each of the Figures 21a to 21c However, here the shielding element 12 covers the axial opening 21 only in the area of ​​the upper part of the inner housing 6 and can thus be designed in one piece.

[0156] When designing according to the Figures 23a and 23b One side half of the shielding element 12 has openings to achieve additional distribution of the lubricant-air mixture. For example, a perforated sheet metal can be used as the shielding element 12.

[0157] When designing according to the Figure 24It is shown by way of example that the main surface of the shielding element 12 can comprise partial surfaces arranged at an angle to one another in order to redirect the lubricant-air mixture more specifically. In the illustrated embodiment, although not necessarily, the shielding element 12 extends close to the lower edge of the inner housing 6 in order to be able to discharge the lubricant-air mixture into the oil sump in a targeted manner.

[0158] The design of the shielding element 12 with several mutually angled flat areas of the main surface prevents the lubricant-air mixture from rebounding off the shielding element 12. The arrangement of the surfaces is such that they are preferably inclined and thus not perpendicular to the flow direction of the lubricant-air mixture.

[0159] In the Figure 25It is shown by way of example that the shielding element 12 is double-walled to form a coolant channel 24. This allows the temperature of the outflowing lubricant-air mixture to be reduced in a targeted manner in this area. This is particularly advantageous in the area of ​​the gear mesh, since this is where the highest temperatures occur. According to an embodiment not shown, coolant can be injected from the coolant channel 24, which can also carry oil, into the lubricant-air mixture emerging from the axial opening 21 (or radial opening 16), or directly onto the gear mesh.

[0160] When designing according to the Figure 26It is shown by way of example that the shielding elements 12 on opposite sides of the inner housing 6, in particular for covering the axial openings 21 in the area of ​​the gear engagement, can be designed differently. Thus, on one side of the inner housing 6, which forms a suction side, air or a lubricant-air mixture can be sucked in through the axial opening 21 covered by the shielding element 12 and discharged through the opposite axial opening 21 on the other side of the inner housing 6 and redirected by the shielding element 12 there to the discharge opening 22. A coolant injection, in particular a cooling oil injection, could be provided on the suction side and / or the pressure side.

[0161] For example, as shown, on the suction side the shielding element 12 extends upwards from the axial opening 21 and on the pressure side it extends downwards from the axial opening 21. List of reference symbols

[0162] 1 Spur gear 2 Spur gear 3 Spur gear 4 Spur gear 5 Shaft 6 Inner housing 7 Outer housing 8 Axial-radial bearing 9 Thrust collar bearing 9.1 Thrust collar 10 Large gear 11 Pinion 12 Shielding element 13 Opening 14 Drain channel 14.1 Longitudinal channel axis 14.2 Channel wall 15 Gill 16 Radial opening 17 Radial bearing 18 Coolant injection 19 Shaft rotation axis 20 Side part 21 Axial opening 22 Drain opening 23 Strut 24 Coolant channel 25 Nozzle 26 Impeller 27 Drive 28 Pump 29 Intermediate gear 30 Shell surface 31 Lug 32 Adjusting screw 33 Inspection opening 34 Reinforcing rib 35 Flange 36Skimming edge 37Line 38Parting joint

Claims

1. Spur gear transmission having at least two toothed spur gears (1, 2, 3, 4) which are each arranged on a shaft (5) and the toothing systems of which mesh with one another in pairs; wherein the spur gears (1, 2, 3, 4) each have a radially outer circumference and two axial sides facing away from one another, and the spur gears (1, 2, 3, 4) are enclosed over most of their radially outer circumference and over most of their axial sides facing away from one another by an inner housing (6) which is in turn enclosed over its entire circumference by an outer housing (7) arranged separately thereto; wherein the spur gears (1, 2, 3, 4) are acted upon by a lubricant in the region of their toothing systems, and the inner housing (6) has axial openings (21) which are opposite one or both axial sides of at least one spur gear (1, 2, 3, 4), and / or radial openings (16) which are opposite the radially outer circumference of at least one spur gear (1, 2, 3, 4), through which the lubricant can flow out of the inner housing (6) at least indirectly; characterized in that at least one, a plurality of or all axial openings (21) and / or radial openings (16) are covered by a shielding element (12) arranged between the inner housing (6) and the outer housing (7), wherein the shielding element (12) is arranged in such a way or at such a distance from the respectively covered axial opening (21) or radial opening (16) that lubricant flowing out of the axial opening (21) or radial opening (16) is deflected outside the inner housing (6) by the shielding element (12); and at least one, a plurality of or all axial openings (21) and / or radial openings (16) are assigned a coolant injection means (18), by way of which coolant is injected into the lubricant flowing out of the axial opening (21) or radial opening (16) in such a way that the lubricant flowing out of the axial opening (21) or radial opening (16) is deflected outside the inner housing (6) by the coolant.

2. Spur gear transmission according to Claim 1, characterized in that the at least one shielding element (12) is arranged opposite the respectively covered axial opening (21) or radial opening (16) in such a way that lubricant flowing out of the axial opening (21) or radial opening (16) is deflected in a direction along an outer surface of the inner housing (6) so as to make contact with the inner housing (6) to a greater or lesser extent.

3. Spur gear transmission according to either of Claims 1 or 2, characterized in that the at least one shielding element (12) has openings (13) and is designed, in particular, as a perforated plate, wherein the openings (13) each have a maximum flow cross section of one twentieth, fiftieth or hundredth of the flow cross section of the axial opening (21) or radial opening (16) covered by the shielding element (12).

4. Spur gear transmission according to one of Claims 1 to 3, characterized in that the at least one shielding element (12) has an arcuate shape, in particular with a concave side facing the axial opening (21) or radial opening (16).

5. Spur gear transmission according to one of Claims 1 to 4, characterized in that the at least one shielding element (12) bears with at least one or two lateral ends against an outer surface of the inner housing (6) laterally with respect to the axial opening (21) or radial opening (16).

6. Spur gear transmission according to Claim 5, characterized in that the at least one shielding element (12) bears against the outer surface of the inner housing (6) on two opposite sides of the axial opening (21) or radial opening (16).

7. Spur gear transmission according to Claim 5, characterized in that the at least one shielding element (12) bears with three of four lateral ends laterally with respect to the axial opening (21) or radial opening (16) against the outer surface of the inner housing (6) and is configured, in particular, as deep-drawn jaws (15) in a side part (20) of the inner housing (6).

8. Spur gear transmission according to one of Claims 1 to 7, characterized in that a multiplicity of individual shielding elements (12) are provided for a multiplicity of axial openings (21) and / or radial openings (16), wherein the shielding elements (12) are each fastened to the inner housing (6) or outer housing (7).

9. Spur gear transmission according to one of Claims 1 to 7, characterized in that the at least one shielding element (12) is configured as a closed outflow duct (14) which extends along an outer surface of the inner housing (6) with a duct longitudinal axis (14.1) which is completely enclosed in the circumferential direction by the inner housing (6) and a duct wall (14.2).

10. Spur gear transmission according to Claim 9, characterized in that the at least one outflow duct (14) extends with its longitudinal axis (14.1) in the circumferential direction of a spur gear (1, 2, 3, 4).

11. Spur gear transmission according to either of Claims 9 or 10, characterized in that the at least one outflow duct (14) extends vertically with its longitudinal axis (14.1).

12. Spur gear transmission according to one of Claims 1 to 11, characterized in that at least some axial openings (21) are arranged at a distance from one another in the circumferential direction of at least one spur gear (1, 2, 3, 4) along the toothing system of the spur gear (1, 2, 3, 4).

13. Spur gear transmission according to Claim 12, characterized in that the distances are irregular.

14. Spur gear transmission according to Claim 14, characterized in that the at least one coolant injection means (18) is designed to bring about a distribution and / or deflection of the lubricant flow.

15. Spur gear transmission according to one of Claims 1 to 14, characterized in that, in the inner housing (6), in the region of a toothing engagement between two spur gears (1, 2, 3, 4), an axial opening (21) provided with a shielding element (12) on one axial side and with a second shielding element (12) on the other axial side is provided on each of the two axial sides of the toothing engagement, wherein the second shielding element (12) together with the inner housing (6) forms a suction duct for supplying a medium, in particular air, into the toothing engagement, and the shielding element (12) together with the inner housing (6) forms a pressure duct for discharging outflowing lubricant.

16. Spur gear transmission according to Claim 15, characterized in that the suction duct extends upwards starting from the axial opening (21), and the pressure duct extends downwards starting from the axial opening (21).