Casing for a reduction gear of a rotary electric machine

Abstract

The invention relates to a casing (10) for a reduction gear (1) of a rotary electric machine, comprising an inner wall (11) which forms a cavity (12) for receiving the reduction gear (1), for example a toothed wheel (20) of the reduction gear, the cavity (12) having on its periphery one or more facets (15) which each partially delimit a recess (17) of the inner wall (11) of the casing, the facet (15) being inclined with respect to an axis (Z) which is parallel to an axis of rotation of the reduction gear in order to divert a flow of lubricant to flow out of the recess (17) when the reduction gear (1) is in operation.

Description

[0001] Description

[0002] Title: Housing of a rotating electrical machine gearbox

[0003] The present invention claims priority from French application 2409713 filed on September 12, 2024, the content of which (text, drawings and claims) is incorporated herein by reference.

[0004] technical field

[0005] The present invention relates to the field of gearboxes for rotating electrical machines, and in particular the lubrication of these gearboxes for rotating electrical machines.

[0006] The machines can be synchronous or asynchronous, and alternating current. They can be traction or propulsion machines for electric (Battery Electric Vehicle) and / or hybrid (Hybrid Electric Vehicle - Plug-in Hybrid Electric Vehicle) motor vehicles, such as passenger cars, vans, trucks, or buses. The invention also applies to rotating electrical machines for industrial and / or power generation applications, particularly in the marine, aeronautical, or wind power sectors.

[0007] Previous technique

[0008] Lubrication of the gearboxes of rotating electrical machines is essential for their proper functioning and reliability, in order to reduce friction and wear generated by the movements of the different elements within them.

[0009] However, during gearbox operation, the lubricant used can tend to accumulate in certain areas, particularly in the immediate vicinity of the gearbox teeth, for example, in cavities designed to house the gears. This phenomenon can increase friction between the lubricant and the teeth, potentially leading to further losses. Furthermore, some of the lubricant is lost and cannot be replenished in sufficient quantity to the upper part of the gearbox to ensure proper lubrication of the various components.

[0010] To minimize losses, systems for recovering or guiding lubricant within gearboxes have been proposed. Patent application EP 4 325 092 describes a gearbox equipped with a smooth plate for oil insulation, allowing the oil deposited at the bottom of the gearbox housing to be isolated in order to reduce losses due to oil agitation. The plate prevents oil from escaping.

[0011] Patent application CN 117287501 relates to a gearbox with an arched guide rib designed to increase the amount of oil sprayed. This patent application does not seek to divert the oil away from the gear teeth.

[0012] Document CN 221591710 U describes a guide element whose wall includes several projections designed to slow the flow of lubricant, projected by a gear, towards the reservoir of a crankcase. The aim of this document is not to evacuate the lubricant, but to slow its flow in order to increase its quantity in the crankcase without increasing its level in the reservoir.

[0013] US patent application 2022 / 154814 discloses a system for channeling oil over the gears of the reducer.

[0014] US patent 10955 041 B2 describes a housing with a guiding surface designed to direct lubricant sprayed by a gear to a reservoir located near the gear. The reservoir serves as a temporary accumulation zone for the lubricant before its discharge, under the influence of gravity, through drainage channels. This discharge is neither direct nor rapid, being limited by the flow rate permitted by the channels.

[0015] There is a need to facilitate the evacuation of lubricant to the lower part of a reducer, and to limit friction losses at the level of the teeth.

[0016] Description of the invention

[0017] The invention aims to meet all or part of this need and achieves this, according to one of its aspects, by means of a housing for a rotating electrical machine reducer, comprising an inner wall providing a cavity for receiving the reducer, for example a toothed wheel of the reducer, the cavity having on its periphery one or more facets each partially delimiting a recess in the inner wall of the housing, the facet being inclined with respect to an axis Z parallel to an axis of rotation of the reducer to deflect the flow of a lubricant flow out of the recess during the operation of the reducer.

[0018] By 'axis of rotation of the reducer', we mean an axis of rotation of at least one element of the reducer, for example of the gear of the reducer.

[0019] By 'inclined facet', we mean that the facet is neither parallel nor perpendicular to the axis of rotation of the reducer, nor to the Z-axis parallel to the axis of rotation, nor to the plane of the reducer. The facet can therefore extend in a plane that is neither parallel nor perpendicular to the axis of rotation of the reducer, nor to the Z-axis parallel to the axis of rotation, nor to the plane of the reducer.

[0020] 'Indentation of the inner wall of the crankcase' refers to a hollow shape from inside the crankcase.

[0021] The recess in the inner wall of the housing allows the lubricant to be evacuated from the receiving cavity of the reducer, directly and quickly, without the lubricant being forced to flow or circulate in an intermediate space or element before being evacuated.

[0022] The facet is configured to deflect the lubricant flow in a direction with an axial component. An 'axial component' is defined as a component parallel to the Z-axis of the gearbox or a gearbox element, such as a gear. The direction of lubricant flow deflection may also include a tangential component, meaning a component parallel to a plane normal to the Z-axis and parallel to an axis of rotation of the gearbox or a gearbox element.

[0023] The facet(s) divert the flow of lubricant away from the recess corresponding to each facet during the operation of the gearbox, for example, during the rotation of the corresponding gear. This prevents lubricant from accumulating around the gear teeth, which would result in a loss of lubricant. Thus, power losses in the gearbox are minimized by limiting friction between the lubricant and the teeth. The invention increases the efficiency of the gearbox.

[0024] In addition, for example in the case where the toothed wheel is a pinion wheel associated with a rotating drive rotor, the facet(s) allow the flow of lubricant to be diverted towards a bearing of the rotor to lubricate it.

[0025] The invention is also advantageous due to its ease of implementation. It significantly reduces the total power losses of the gearbox without requiring any additional machining. The recess(es) can be formed in the inner wall of the housing during its molding, for example, in aluminum. The recess(es) may not need to be machined. The facet(s) may also not need to be machined.

[0026] A gearbox may include at least one primary input shaft, a secondary shaft or transmission stage, an output shaft, optionally a lubrication channel, and a housing in which the primary, secondary, and output shafts are housed. The transmission stage may include one or more secondary shafts, for example, one or two, so that motion is transmitted between the primary shaft and the output shaft. The secondary shaft may drive a toothed output wheel, which in turn drives a differential.

[0027] A reduction element can be chosen from: a bearing, a pinion, a gear, a cogwheel, a toothed wheel, a primary shaft, a secondary shaft of a transmission stage, an output shaft, a housing, a seal, a lubrication channel, this list is not exhaustive.

[0028] The gearbox housing may include an inner wall.

[0029] The term "cavity" refers to a hollow space that houses the reducer, extending deep into the inner wall. The cavity may generally be circular or partially circular, for example, with a cross-section perpendicular to an axis of rotation.

[0030] The gearbox housing can contain the lubricant necessary for the lubrication of the gearbox components during its operation.

[0031] The lubricant can be a fluid lubricant, for example a liquid. Preferably, it is an oil, for example a gearbox oil.

[0032] The reducer can be lubricated by "splash" lubrication or by "active" lubrication using a pump.

[0033] The reducer can be lubricated by spraying lubricant upwards by rotating different elements within the reducer, for example by rotating a gear of a differential of the reducer.

[0034] Summary of the invention

[0035] Facets The housing may have several facets, each partially defining a recess in the inner wall of the housing. Each facet may be inclined with respect to a Z-axis parallel to the axis of rotation of the gearbox to deflect the flow of lubricant away from the recess during gearbox operation.

[0036] The number of facets can range from 1 to 20, or even from 1 to 10, ideally from 1 to 4, for example, 2 or 4 facets. At least one facet, or even a majority of the facets, or all of them, can be as described below.

[0037] The facet(s) can be flat or curved. A facet can be concave, flat, or convex. The facet(s) can extend along a director plane P. By 'direction plane', we mean the average plane of elongation of the facet. The facet can be flat and extend entirely within its director plane P, or it can be concave or convex and extend tangentially to its director plane P.

[0038] The facet(s) can extend along a director plane P forming a non-zero angle α with the Z-axis parallel to the axis of rotation of the reducer. The angle α can, for example, be between 10° and 80°, or even between 20° and 70°, better between 30° and 60°, or even between 40° and 50°, being, for example, on the order of 45°.

[0039] The facet(s) can extend along a director plane P containing an axis X' forming with a radial axis X parallel to a radial axis of the reducer an angle [1. The angle P can be for example between -40° and +40°, or even between -30° and +30°, better between -20° and +20°, or even between -10° and +10°, being for example of the order of 0°.

[0040] The 'radial axis of the reducer' refers to a radial axis for a gear of the reducer located near the recess and the facet. The radial axis X passes through a point O at the end of the facet.

[0041] The term 'end point O of the facet' refers to a point O at which the facet connects to a cylindrical inner surface of the housing surrounding the gear. Point O is the point of the recess on the cylindrical inner surface of the housing surrounding the gear. It is the point where the recess begins to be cut. Point O is the innermost point of the recess in the housing.

[0042] Thus, the facet can extend along a director plane P close to the radial direction of the gear of the reducer.

[0043] The shortest distance d between the facet and the gear can be between 1 and 20 mm, or even between 3 and 15 mm, preferably between 5 and 12 mm. A length L of the facet measured parallel to the gear can be between 10 and 70 mm, or even between 20 and 60 mm, preferably between 30 and 50 mm. Such a length L can be on the order of the width of a gear tooth. The length L is measured in a plane Q parallel to the Z-axis, which is parallel to an axis of rotation, with the plane Q being perpendicular to the radial X-axis.

[0044] The width 1 of the facet, measured perpendicular to the gear, can be between 10 and 70 mm, or even between 20 and 60 mm, and ideally between 30 and 50 mm. Such a width 1 can be on the order of magnitude of the width of a gear tooth. The width 1 is measured in a plane Q parallel to the Z-axis, which is parallel to an axis of rotation, with the Q plane being perpendicular to the radial X-axis.

[0045] The maximum height h of the facet, measured parallel to a radial axis X, can be between 1 and 15 mm, or even between 2 and 12 mm, and preferably between 3 and 10 mm. The maximum height h is measured along the radial axis X, perpendicular to a plane Q parallel to the Z axis, which is itself parallel to an axis of rotation, with the plane Q being perpendicular to the radial axis X.

[0046] The facet(s) may be generally triangular in shape. The facet may extend along a director plane P with a generally triangular shape, taking on a form that widens towards the outside of the housing.

[0047] Sinks

[0048] The recess defined by the facet can also be defined by a bottom connecting to the facet and to a cylindrical inner surface of the housing surrounding the gear, the bottom of the recess being for example away from the cylindrical inner surface by a minimum depth a zero or non-zero.

[0049] In one embodiment, the minimum depth a is zero.

[0050] Alternatively, the minimum depth *a* is non-zero, for example, between 0 mm (exclusive) and 17 mm, or even between 1 and 15 mm, or between 2 and 12 mm, or preferably between 3 and 10 mm. A non-zero minimum depth *a* can increase the surface area of ​​the facet, for example, across its entire width and length, and thus the resulting deflection. Lubricant evacuation can also be improved. The bottom of the recess can be flat or, alternatively, non-flat, for example, concave or convex. It can, for example, be partially curved, following the inner surface of the housing surrounding the gear.

[0051] In one embodiment, the housing may include a single indentation with an associated facet, positioned towards the bottom of the housing.

[0052] In one embodiment, the housing may have two recesses, each with an associated facet, the two recesses being made on the same side of the housing, i.e. on the same side of the lower part of the housing, i.e. on the same side of a vertical plane containing the Z axis.

[0053] Alternatively, the housing may have two or more recesses, each with an associated facet. These two or more recesses are located on both sides of the housing, i.e., on either side of the lower part of the housing, or on either side of a vertical plane containing the Z-axis parallel to the axis of rotation of the gearbox. For example, the recesses and their associated facets may be arranged symmetrically on each side of the housing, on either side of the vertical plane containing the Z-axis parallel to an axis of rotation. The two recesses may be oriented in the same direction, i.e., evacuating the lubricant in the same direction.

[0054] Preferably, the indentations are located in the lower part of the cylindrical section of the crankcase because lubricant accumulates in this area.

[0055] In one embodiment, the housing may include a plurality of recesses and associated facets, which are distributed symmetrically on each side of the housing, on either side of a vertical plane containing the Z axis parallel to an axis of rotation.

[0056] For example, the housing may have four recesses, each with an associated facet, the four recesses being made on both sides of the housing in pairs, for example, being arranged symmetrically to each other on each side of the housing, on either side of the vertical plane containing the Z axis parallel to an axis of rotation.

[0057] The symmetrical configuration allows for lubricant deflection regardless of the direction of rotation. This configuration is therefore advantageous for a machine with two directions of rotation. The machine can thus be positioned in any orientation, and the choice of orientation may not depend on the issue of lubricant deflection. Alternatively, at least one recess can be defined by two facets inclined relative to the Z-axis, parallel to a rotation axis of the gearbox, to deflect the lubricant flow away from the recess during gearbox operation. This configuration allows for lubricant deflection regardless of the direction of rotation. This configuration is therefore advantageous for a machine with two directions of rotation, as explained above.

[0058] Carter

[0059] The housing can have a virtually constant thickness at the point of insertion, the insertion being formed in the inner wall of the housing, and an outer wall of the housing possibly having a relief corresponding to the insertion. Maintaining a constant thickness for the housing is advantageous in order to avoid adding weight.

[0060] Alternatively, the recess can be made in the thickness of the casing, with an outer wall not having any extra thickness at the point where the recess is made in the inner wall.

[0061] In one embodiment, the gear of the reducer can be a primary shaft pinion and / or a driven gear on a secondary shaft. In this embodiment, the invention is applied to a first meshing of the reducer, which makes it possible to overcome significant power losses due to a high tangential speed at the teeth of the primary shaft pinion and / or the driven gear on the secondary shaft.

[0062] Alternatively or additionally, the invention can be applied to another gearing of the reducer, for example a secondary shaft pinion and / or a differential ring gear.

[0063] The recess can be formed in a section of the housing attached to the rest of the housing. In this case, the attached section of the housing is a deflector piece attached to the housing.

[0064] The added section can be fixed to the rest of the housing after assembly, for example, during machine operation. This section facilitates the deflection of lubricant around the gear, while preventing lubricant from being sprayed onto gear teeth located outside the meshing area. The gear is thus protected from external splashes and internal buildup, reducing friction between the lubricant and the gear.

[0065] Using an added housing component can be advantageous when the housing is located further from the gear. This added housing component can be positioned on a shaft, for example, as a primary shaft gear and / or a secondary shaft gear. In these situations, the housing may be further radially away from the gear, and using an added housing component can then be beneficial.

[0066] The added part of the crankcase can be made by molding, for example from plastic material.

[0067] Alternatively, the housing can be a single piece. A single-piece configuration can be advantageous in terms of the overall size of the housing and the manufacturing process, which can be simplified.

[0068] The invention also relates to a reduction gear for a motor vehicle comprising a housing as described above. The reduction gear according to the invention may have a single transmission stage. Alternatively, it may have several transmission stages, for example two or three.

[0069] The invention also relates to a propulsion device for a motor vehicle, comprising a reducer as described above and a rotating electric machine.

[0070] The invention also relates to a motor vehicle comprising a propulsion device as described above. The vehicle may have at least two drive wheels, each of the drive wheels being driven in rotation by the reduction gear, for example by an output shaft thereof.

[0071] The drive wheels can be arranged on either side of the gearbox. Each drive wheel can have a shaft connected to an output shaft of the gearbox. The device can include a first drive wheel fixed in rotation to a first output shaft of the gearbox. The device can include a second drive wheel fixed in rotation to a second output shaft of the gearbox.

[0072] Brief description of the drawings The invention will be better understood by reading the detailed description that follows, by non-limiting examples of its embodiment, and by examining the attached drawing.

[0073] [Fig 1] Figure 1 is a schematic and partial perspective view of a gearbox housing.

[0074] [Fig 2a] Figure 2a shows a detailed, schematic and partial view of the gear wheel and inclined facets of the housing.

[0075] [Fig 2b] Figure 2b is a schematic and partial front view of the housing in Figure 2a showing the arrangement of the facets.

[0076] [Fig 2c] Figure 2c presents a schematic and partial perspective view of the casing of figure 2a.

[0077] [Fig 3a] Figure 3a is a schematic and partial perspective view of an alternative embodiment.

[0078] [Fig 3b] Figure 3b illustrates the angles and dimensions of the facets of the housing in Figure 3a.

[0079] [Fig 4] Figure 4 is a view analogous to figure 2b of an alternative embodiment.

[0080] [Fig 5] Figure 5 is a view analogous to figure 3a of an alternative embodiment.

[0081] [Fig 6a] Figure 6a presents a schematic and partial perspective view of an alternative embodiment.

[0082] [Fig 6b] Figure 6b shows a schematic and partial perspective view of part of the crankcase with facets.

[0083] [Fig 6c] Figure 6c illustrates another schematic and partial perspective view of the crankcase part of Figure 6b.

[0084] Detailed description

[0085] Figure 1 illustrates a gearbox 1 for a motor vehicle, mounted on the shaft of a rotor 2 of a rotating electrical machine. The gearbox 1 has a primary shaft pinion 3, meshed with a secondary shaft driven gear 4. The secondary shaft also has a secondary shaft pinion 5, meshed with a differential ring gear 6, which is integral with a differential 7. Figures 2a to 2c illustrate a housing 10 of the gearbox 1 for a rotating electrical machine, for example, a motor vehicle. The housing 10 of the gearbox 1 of a rotating electrical machine has an inner wall 11. This inner wall 11 provides a cavity 12 for receiving the gearbox 1, for example, a gear 20 of the gearbox.

[0086] The cavity 12 has on its periphery one or more facets 15, here two facets 15. Each facet partially delimits a recess 17 in the inner wall 11 of the housing.

[0087] The facet 15 is inclined with respect to a Z-axis parallel to an axis of rotation of the reducer. This allows the flow of lubricant to be diverted away from the recess 17 during the operation of the reducer 1. The facets 15 are configured to divert the flow of lubricant away from the recess 17 corresponding to each facet, in a direction having an axial component, parallel to the Z-axis parallel to the axis of rotation of the reducer, and a tangential component, parallel to a plane normal to the Z-axis.

[0088] The facets 15 extend along a director plane P, as illustrated in Figure 2c, which director plane P forms a non-zero angle α with the Z-axis parallel to the axis of rotation of the reducer. The angle α is, for example, between 40° and 50°.

[0089] The facet 15 extends along the director plane P containing an axis X' which forms an angle p with a radial axis X parallel to a radial axis of the reducer. The angle P is for example of the order of 0°.

[0090] The direction plane P passes through a point O and contains the axes Z' and X', which are perpendicular to each other, as illustrated in Figure 2c. The Z' axis is the axis of the OYZ plane passing through O and forming an angle α with the Z axis. The X' axis is the axis perpendicular to the Z' axis passing through O and forming an angle P with the X axis.

[0091] The shortest distance d between facet 15 and gear 20 is between 5 and 12 mm, as illustrated in figure 2c.

[0092] The length L of facet 15, measured parallel to gear 20, is between 30 and 50 mm. This length L is on the order of the width of one tooth of gear 20. The length L is measured in a plane Q parallel to the Z-axis. Plane Q is perpendicular to the radial X-axis.

[0093] The width 1 of facet 15, measured perpendicular to gear 20, is between 30 and 50 mm. This width 1 is on the order of magnitude of the width of a tooth of gear 20. The width 1 is measured in a plane Q parallel to the Z-axis. Plane Q is perpendicular to the radial X-axis.

[0094] The maximum height h of facet 15, measured parallel to the radial axis X of gear 20, is between 3 and 10 mm. The maximum height h is measured along the radial axis X. It is perpendicular to a plane Q parallel to the Z-axis. The plane Q is perpendicular to the radial axis X.

[0095] The facet 15 is generally triangular in shape, with a shape that widens towards the outside of the housing, as illustrated in figure 2a.

[0096] The recess 17 defined by the facet 15 is also defined by a bottom 19. This bottom connects to the facet 15 and to a cylindrical inner surface 25 of the housing surrounding the gear 20. The bottom 19 of the recess 17 is located away from the cylindrical inner surface by a minimum depth a, which may be zero or non-zero. In the embodiment shown in Figures 2a-2c, the minimum depth a is zero.

[0097] Alternatively, as illustrated in Figures 3a and 3b, the minimum depth a is non-zero. For example, it is between 3 and 10 mm. A non-zero minimum depth a allows for an increase in the surface area of ​​facet 15, particularly along its entire width and length.

[0098] In the embodiments just described, the housing 10 has two recesses 17, each with an associated facet 15, located towards the bottom of the housing. The two recesses 17 are formed on the same side of the housing, that is to say, on the same side of a vertical plane containing the Z-axis.

[0099] Alternatively, as illustrated in Figure 4, the housing 10 has four recesses 17, each with an associated facet 15. The four recesses 17 are formed on both sides of the housing in pairs. They are arranged symmetrically on each side of the housing, on either side of a vertical plane containing the Z-axis.

[0100] Alternatively, as illustrated in Figure 5, each recess 17 is delimited by two facets 15 inclined with respect to the Z-axis parallel to the axis of rotation of the gearbox. This diverts the flow of lubricant away from the recess during gearbox operation. Such a configuration allows for lubricant diversion regardless of the direction of rotation. Generally, the housing 10 has a substantially constant thickness at the recess 17. The recess 17 is formed in the inner wall 11 of the housing.

[0101] In the examples just described, the housing can be a single piece. Alternatively, the recess 17 is formed in a section of the housing attached to the rest of the housing. In this case, the attached section is a deflector piece attached to the housing, as illustrated in Figures 6a to 6c. The attached section is fixed to the rest of the housing after assembly, particularly during machine operation. The attached section of the housing can be made by molding, for example, from plastic.

Claims

Demands 1. Housing (10) of a gearbox (1) of a rotating electrical machine, comprising an inner wall (11) providing a cavity (12) for receiving the gearbox (1), for example a toothed wheel (20) of the gearbox, the cavity (12) having on its periphery one or more facets (15) each partially defining a recess (17) in the inner wall (11) of the housing, one or more facets (15) being inclined with respect to an axis (Z) parallel to an axis of rotation of the gearbox to deflect the flow of a lubricant flow out of the recess (17) during the operation of the gearbox (1).

2. Housing according to the preceding claim, comprising several facets (15) partially delimiting a recess (17) in the inner wall of the housing, each facet (15) being inclined with respect to an axis (Z) parallel to an axis of rotation of the reducer to deflect the flow of a lubricant stream out of the recess during operation of the reducer, the number of facets (15) being between 1 and 20, or even between 1 and 10, better between 1 and 4, being for example 2 or 4 facets.

3. Carter according to any one of the preceding claims, one or more facets (15) extending along a director plane (P) forming with the axis (Z) parallel to the axis of rotation of the reducer a non-zero angle (a), the angle (a) being for example between 10° and 80°, or even between 20° and 70°, better between 30° and 60°, or even between 40° and 50°.

4. Carter according to any one of the preceding claims, one or more facets (15) extending along a director plane (P) containing an axis X' forming with a radial axis (X) parallel to a radial axis of the reducer an angle (P), the angle (P) being for example between -40° and +40°, or even between -30° and +30°, better between -20° and +20°, or even between -10° and +10°.

5. Housing according to any one of the preceding claims, a shorter distance (d) between one or more facets (15) and the toothed wheel (20) being between 1 and 20 mm, or even between 3 and 15 mm, better between 5 and 12 mm.

6. Housing according to any one of the preceding claims, a length (L) of one or more facets measured parallel to the toothed wheel (20) being between 10 and 70 mm, or even between 20 and 60 mm, better between 30 and 50 mm.

7. Housing according to any one of the preceding claims, a width (1) of one or more facets (15) measured perpendicular to the toothed wheel (20) being between 10 and 70 mm, or even between 20 and 60 mm, better between 30 and 50 mm.

8. Housing according to any one of the preceding claims, a maximum height (h) of one or more facets (15) measured parallel to a radial axis X parallel to a radial axis of the gear (20) being between 1 and 15 mm, or even between 2 and 12 mm, better between 3 and 10 mm.

9. Housing according to any one of the preceding claims, the recess (17) defined by one or more facets (15) also being defined by a bottom (19) connecting to the facet(s) (15) and to a cylindrical inner surface (25) of the housing surrounding the gear (20), the bottom (19) of the recess (17) being for example away from the cylindrical inner surface by a minimum depth (a) of zero or non-zero.

10. Housing according to any one of the preceding claims, comprising a plurality of recesses (17) and associated facets (15), which are distributed symmetrically on each side of the housing, on either side of a vertical plane containing the axis (Z) parallel to the axis of rotation of the reducer.

11. Housing according to any one of the preceding claims, at least one recess (17) being delimited by two facets (15) inclined with respect to the axis (Z) parallel to the axis of rotation of the reducer to deflect the flow of lubricant out of the recess during operation of the reducer.

12. Housing according to any one of the preceding claims, having substantially constant thickness at the indentation (17), the indentation (17) being provided in the inner wall (11) of the housing, and an outer wall of the housing having a relief corresponding to the indentation.

13. Housing according to any one of the preceding claims, the gear (20) of the reducer being a primary shaft pinion and / or a driven gear of a secondary shaft.

14. Housing according to any one of the preceding claims, the recess (17) being provided in a part of the housing attached to the rest of the housing.

15. Reducer (1) for motor vehicle comprising a casing (10) according to any one of the preceding claims.

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