Engine assembly for a motor vehicle

Abstract

The present invention relates to an engine assembly (1) for a motor vehicle, comprising a crankshaft (2), a casing (3) configured to at least partially house the crankshaft (2) and comprising at least one bearing for receiving a journal (4) of the crankshaft (2), the casing (3) comprising a groove (10) formed in a lateral face of a wall (9) of the casing which helps to delimit the receiving casing, the engine assembly further comprising at least one axial stop device (11) configured to be housed within the groove (10), characterised in that the axial stop device (11) comprises a first portion (12) and a second portion (13), both configured to be housed within the groove (10), each portion (12, 13) comprising a positioning heel configured to cooperate in a complementary manner with a notch formed at one end of the groove (10).

Description

[0001] DESCRIPTION

[0002] Engine assembly for a motor vehicle

[0003] The present invention relates to the field of thermal engines for thermal vehicles, and more particularly concerns an engine assembly for such a thermal engine.

[0004] The engine assembly includes a casing in which pistons are caused to move within engine cylinders under the effect of fuel combustion, this casing housing a crankshaft capable of transforming the translational movement of the pistons into a rotational movement of the crankshaft subsequently transmitted to the vehicle wheels.

[0005] In particular, the crankshaft comprises journals, which define the axis of rotation of the crankshaft and are supported by rotary bearings formed in the engine casing, and crankpins, which are offset from the journals and are connected to the pistons.

[0006] The rotational movement of the crankshaft is then transmitted to the vehicle's wheels via the pinions and secondary shafts of a gearbox. This arrangement results in micro-shocks during gear changes, which can generate micro-displacements of the crankshaft along its axis of rotation. It is therefore known to provide at least one axial stop to block the axial movement of a crankshaft journal in the corresponding reception bearing formed in the casing, the aim being to ensure that the crankpins of the crankshaft remain in line with the axis of translation of the engine pistons.

[0007] The axial stop is located in the bearing area of a journal, between a lateral bearing surface of the crankshaft axially delimiting the journal and a wall of the engine casing, in a groove formed for this purpose in the said wall.

[0008] This type of axial stop is installed manually on a thermal engine assembly line. However, several thermal engine models are sometimes assembled on the same assembly line. These different thermal engines may have different characteristics from one another, and in particular have crankshaft dimensions, including journal diameters, which may vary from one engine to another. Axial stops predestined to be installed on a crankshaft for one model of thermal engine are therefore potentially incompatible with other thermal engines, and the installation of the wrong axial stop may occur. The axial stop may not completely fill the groove because it is too small in relation to the aforementioned groove, generating the risk of axial instability of the crankshaft due to the journal not being locked axially in a uniform manner, or conversely, it may protrude from the groove because it is too large in relation to the said groove, generating the risk of blocking the assembly of the parts of the engine casing coming from either side of the crankshaft.

[0009] The present invention makes it possible to avoid such an installation error by proposing an engine assembly for a motor vehicle, comprising a crankshaft, a casing configured to house the crankshaft at least partially and comprising at least one bearing for receiving a journal of the crankshaft, the casing comprising a groove formed in a lateral face of a wall of the casing participating in delimiting the receiving bearing, the engine assembly also comprising at least one axial stop device configured so as to be housed within the groove between the said lateral face and the crankshaft, characterised in that the axial stop device comprises a first portion and a second distinct portion, both configured so as to be housed within the groove, each portion comprising a positioning heel configured so as to cooperate in a complementary manner with a notch formed at one end of the groove.

[0010] The two-part axial stop device avoids any confusion as to the type of axial stop to be fitted during assembly of the engine assembly. It can be decided that the two-part axial stop devices are intended for a first type of engine assembly, while other single-part axial stops are intended for a second type of engine assembly. This eliminates the risk of arranging the wrong axial stop and ensures that the crankshaft operates correctly.

[0011] The casing is specially adapted to receive the crankshaft, for example by being moulded to match the contours of the journals of said crankshaft and to form reception bearings defining the axis of rotation of the crankshaft, while allowing crankpins of the crankshaft, eccentric with respect to the journals and in engagement with pistons of the engine, to be set in motion. The casing is in two parts arranged on either side of the crankshaft, with each part comprising walls having a semi-circular shape allowing the formation of bearings to receive the crankshaft when the two parts are assembled. The groove is arranged on a lateral face of one of these walls, this lateral face being intended to face a lateral bearing surface of the crankshaft axially delimiting the journal.

[0012] The axial stop device is therefore arranged within this groove and follows the shape of a portion of the crankshaft journal around the axis of rotation of the latter. Once in place, the axial stop device is therefore located within the groove of the casing, axially interposed, with respect to the axis of rotation of the crankshaft, between the lateral face of a wall of the casing and a lateral bearing surface of the crankshaft and thus prevents any axial movement of the latter, i.e. any movement parallel to an axis of rotation of the crankshaft.

[0013] The groove runs the full length of the semicircle, and has notches at each of these ends of the groove, these notches forming an enlarged receiving area compared to the rest of the groove. Portions of the axial stop device are slid into the groove when the crankshaft is already in place and can penetrate via the notches. A locating heel for a portion of the axial stop device is arranged at the end of this portion and consists of an area of greater dimension, for example higher or thicker, than the corresponding dimension of the rest of the portion. The positioning heel provides an end stop for inserting the axial stop portion into the groove. A positioning heel is complementary in shape to the notch in the groove in which it is to abut, which ensures easy assembly of the axial stop device on the casing. This also makes it possible to check that the axial stop device is correctly in place.

[0014] According to one feature of the invention, each portion is in the shape of an arc of a circle. And according to another feature of the invention, the two portions have a dimension defining the extent of the arc of a circle which is identical from one portion to the other. The groove extends in a semicircle within the wall forming a bearing for receiving a crankshaft journal. In order that the two portions can be introduced into the same groove, and insofar as they have angular dimensions defining the extent of the arc of a circle which are similar from one portion to the other, they have at most a quarter-circle shape.

[0015] According to a characteristic of the invention, each portion comprises a rounded end opposite the positioning heel, the rounded ends of the two portions forming the axial stop device facing each other within the groove. The rounded ends make it possible to limit potential mechanical stresses due, for example, to design micro-defects.

[0016] According to a characteristic of the invention, each portion comprises an inner face oriented towards the casing and an outer face opposite the inner face and oriented towards the crankshaft, the outer face of each portion comprising a lubrication cavity. When the portions forming the axial stop device are arranged in the groove, the inner face is pressed against a bottom of the groove in the casing while the outer face is in contact with the crankshaft bearing once the engine assembly is fully assembled.

[0017] The lubrication cavity forms a gap between each of the portions and the crankshaft journal so that lubricating fluid can circulate in this area defining the axis of rotation of the crankshaft within the casing, thereby reducing crankshaft friction.

[0018] According to a feature of the invention, the first portion and the second portion respectively comprise a first positioning heel and a second positioning heel, the first positioning heel and the second positioning heel being of different shape and / or size to each other. The positioning heels enable the two portions of the axial stop device to be arranged in the correct position. The positioning heels therefore have a locating function, as each of them only cooperates with one of the notches in the groove by virtue of their complementary shape.

[0019] The coded function ensures that the external face, and therefore the lubrication cavity, faces the crankshaft journal so that the latter is correctly lubricated by the lubricating liquid.

[0020] According to a feature of the invention, the first positioning heel and the second positioning heel each have a connecting face connecting the inner face to the outer face, the first portion and the second portion being configured to be arranged in the groove so that the connecting face of each positioning heel is in the same plane relative to each other.

[0021] More particularly, these connection faces are flush with a joining surface of the part of the casing in which the groove is made, so that these connection faces extend as far as possible into the groove without interfering with the assembly of the two parts of the casing to enclose the crankshaft.

[0022] According to a feature of the invention, the axial stop device is made of metal. By way of example, the axial stop device may comprise a steel base and also contain an alloy of aluminium and tin.

[0023] According to a feature of the invention, the engine assembly may comprise two axial stop devices each configured to be arranged on either side of the crankshaft journal. In other words, the crankshaft journal is gripped by two axial stop devices, i.e. a total of four portions joined together in pairs. This configuration provides better support for the crankshaft in both axial directions.

[0024] The invention also covers a method of assembling an engine assembly as described above, comprising:

[0025] - a step for determining a crankshaft diameter,

[0026] - a step of arranging the axial stop device in two portions when the diameter of the crankshaft is compatible,

[0027] - a step of arranging an axial stop device of a type different from the type of axial stop device in two portions when the diameter of the crankshaft is not compatible with the axial stop device.

[0028] As mentioned earlier, the two-piece stop device is specific to one type of engine assembly. The latter can be identified by the diameter of the crankshaft journals, which can be a different dimension from one type of engine assembly to another. Once the dimension has been determined, the two portions of the axial stop device can be fitted if it is indeed the engine assembly with which this type of axial stop device interacts in two separate portions. If this is not the case, then another stop device must be fitted, for example a stop device consisting of a single portion.

[0029] According to a characteristic of the method, the first portion of the axial stop device is inserted through a first end of the groove and the second portion of the axial stop device is inserted through a second end of the groove. The two portions can be inserted one after the other or simultaneously. The complementary shape between the positioning heel of each portion and the notch at each end of the groove ensures optimum insertion of the axial stop device.

[0030] Other features and advantages of the invention will become apparent from the following description, on the one hand, and from a number of embodiments given by way of indication and without limitation with reference to the attached schematic drawings, on the other hand, in which :

[0031] [fig 1] shows an exploded view of a engine assembly according to the invention, [fig 2] is a front view of an axial stop device arranged within the engine assembly. Figure 1 is a partial exploded view of an engine assembly 1 according to the invention. The engine assembly 1 comprises in particular a crankshaft 2 and a casing 3 configured to house at least part of the crankshaft 2.

[0032] The crankshaft 2 comprises a shaft formed by a plurality of journals 4, spaced apart from one another and intended to be received respectively in a receiving bearing formed in the casing 3, and it comprises crankpins 6 interposed between the journals 4. The shaft and journals 4 define an axis of rotation 5 of the crankshaft and the crankpins 6 are off-centre with respect to this axis of rotation. As mentioned, the function of the journals 4 is to cooperate with bearings in the casing 3 to allow rotation of the crankshaft, and the crankpins 6 cooperate with pistons housed in cylinders formed in the casing 3 to transform the translational movement of the pistons into a rotational movement of the crankshaft.

[0033] The crankshaft 2 is connected to complementary drive means outside the engine assembly casing, for example gearbox drive shafts, not shown here.

[0034] The casing 3 delimits a recess 7 for at least partial reception of the crankshaft 2. Figure 1 illustrates part of the casing 3, intended to partially receive the crankshaft 2, it being understood that a second part of the casing is fixed to the first part of the casing to form a closed assembly within which the crankshaft in particular is housed. The casing 7 comprises, in particular, spaces 8 arranged in the axial extension of cylinders in which the pistons of the engine assembly slide, here not visible, these spaces 8 allowing freedom of movement of the crankpins 6 of the crankshaft 2, as well as walls 9 forming an arch in the shape of a semicircle making it possible to form half-bearings for receiving a journal 4 of the crankshaft

[0035] 2. It is understood that the second part of the casing 3, not visible here, comprises walls forming complementary arches enabling complementary half-bearings to be formed, the abutment of these two parts of the casing at the level of opposing joining surfaces enabling the journal-receiving bearing to be closed.

[0036] Compliance with the theoretical axial position of the crankshaft 2 is essential for the correct operation of the engine assembly 1 , so that the crankpins 6 are correctly positioned with respect to the translational movement of the pinions within the cylinders formed in the casing

[0037] 3. Thus, once the crankshaft 2 is installed in the casing 3, any movement, particularly axial movement of the crankshaft 2, i.e. in a direction parallel to the axis of rotation 5 of the shaft

[0038] 4. must be avoided at all costs. However, as has already been mentioned, the crankshaft is connected outside the engine assembly to the drive elements of a gearbox and the crankshaft may be subjected to micro-shocks along the axial direction at each gear change. In order to lock the crankshaft axially in the casing 3, the casing 3 comprises at least one groove 10 and the engine assembly 1 comprises at least one axial stop device 1 1 which can be inserted into the groove 10 to be interposed axially between a wall of the casing 3 and the crankshaft 2 in order to prevent any play of the latter in the axial direction, i.e. the direction parallel to the axis of rotation 5.

[0039] More particularly, the groove 10 is formed in a lateral face of the wall 9 forming the casing bearing 3. The crankshaft is configured in such a way that two lateral bearing surfaces 5 axially surround the journal 4 intended to be received in this reception bearing, these lateral bearing surfaces 5 being arranged on either side of the wall 9 of the casing and having a larger diameter than the journal 4 so as to face a lateral face of this wall 9. The groove 10 is cut into the material of this side face of wall 9 along the axial direction. In this way, the axial distance between the wall 9 of the casing and the lateral bearing surface 5 of the crankshaft is locally increased, this clearance zone being filled by the axial stop device which has antifriction properties and is dimensioned to ensure axial contact both with the wall of the casing and with the lateral bearing surface of the crankshaft.

[0040] The groove 10 is formed over the entire angular dimension of the reception bearing formed by wall 9, around the axis of rotation 5. In other words, here the groove has a semi-circular shape and the axial stop device 1 1 has a corresponding shape which will be described below. The axial stop device 1 1 can be made of metal, for example steel with an alloy of aluminium and tin.

[0041] The axial stop device 1 1 is installed during an assembly process for the engine assembly 1 . Such an installation is carried out manually within an assembly line for the engine assembly 1 , or even for the thermal engine as a whole. However, several types of engine assembly are sometimes assembled within these assembly lines, which can lead to confusion as to which axial stop device is suitable for which type of engine assembly. If the axial stop device is inserted into a non-compatible engine assembly, the axial stop device may float within the groove or protrude from the groove. This can lead to a number of negative effects, such as mounting difficulties or a lack of stability in the axial direction.

[0042] The engine assembly 1 according to the invention avoids any confusion as to the axial stop device 11 to be installed, as the latter comprises two distinct parts, namely a first portion 12 and a second portion 13, both intended to be inserted within the same groove 10. This axial stop device 11 in two portions 12, 13 is thus distinct from other types of axial stop devices in a single portion. It is thus understood that the axial stop device 1 1 in two portions 12, 13 is specific to the engine assembly 1 illustrated in Figure 1 , which avoids any confusion for operators responsible for assembling the engine assembly 1. There is thus no risk of arranging the wrong axial stop device 1 1 , as it is determined beforehand what type of axial stop device must be arranged within a given engine assembly.

[0043] Generally speaking, it is the diameter of the shaft and more specifically of the journals 4 of the crankshaft 2 that varies from one type of engine assembly to another. A first step in an assembly process is therefore to check the diameter of a journal 4, either by measurement or by checking a marking previously made by the crankshaft manufacturer. When the diameter of the journal requires it, i.e. when the engine assembly is of a first type, and once the crankshaft is in position against the casing, with the journals against the walls of the casing forming bearings for receiving these journals, the axial stop device 11 in two portions 12, 13 is arranged in the groove 10. Alternatively, when the verified diameter of the journal is specific to an engine assembly of a type other than the first type mentioned, a third stop device, for example a single-portion stop device, must be fitted.

[0044] The portions of the axial stop device are housed in the groove 10 while the journal 4 of the crankshaft 2 is against the wall 9 of the casing, with the lateral bearing surfaces 5 delimiting the journal 4 facing the lateral faces of this wall 9 of the casing. The portions 12, 13 of the axial stop device 1 1 are thus inserted through one end of the groove 10, their angular position within the groove 10 being defined by the cooperation, described below, of a heel for positioning a portion and a notch in the groove. It should be noted that only one groove 10 is shown in Figure 1 , on a side face of a wall 9 of the casing, but the casing 3 may comprise several grooves 10 each configured to receive an axial stop device 1 1 in two portions 12, 13. In particular, a groove 10 may be formed on each of the lateral faces of the same wall 9 of the casing intended to form a bearing for receiving a journal 4, so that an axial stop device 11 is arranged on either side of at least one of the journals 4 of the crankshaft 2.

[0045] Figure 2 is a sectional view, in a plane at the junction of a journal and the lateral bearing surface of the crankshaft, showing the axial stop device 1 1 in two portions 12, 13 inserted in the groove 10 formed in wall 9. Figure 2 also shows a second part of the casing, which completes the arch shape of wall 9 to close the bearing for the crankshaft journal 4.

[0046] The two portions 12, 13 are each in the shape of a quarter circle, the axial stop device 1 1 being in the shape of a semi-circle capable of completely filling the corresponding angular dimension of the groove around the axis of rotation 5.

[0047] More generally, the shape of the two portions 12, 13 is in the form of an arc of a circle, so that they at least partially match the shape of the crankshaft journal 4.

[0048] The first portion 12 and the second portion 13 respectively comprise a first positioning heel 14 and a second positioning heel 15 configured to cooperate by complementarity of shape with a notch 16. The groove comprises two notches 16 at each end, each of the notches 16 being designed to receive the positioning heel 14, 15 of one of the portions 12, 13.

[0049] From the positioning heel 14, 15, each portion 12, 13 extends in the shape of an arc of a circle to a rounded end 17. When the portions 12, 13 are housed in the groove 10, these rounded ends 17 are intended to be opposite, or even in contact, with each other. The rounded shape makes it possible to limit mechanical stresses that may, for example, be due to manufacturing tolerances of the portions 12, 13.

[0050] As mentioned previously, the portions 12, 13 of the axial stop device 11 are introduced through one end of the groove 10, i.e. through one of the notches. In other words, the assembly can be implemented so that the first portion 12 of the axial stop device 1 1 enters the groove via a first end of this groove 10 and the second portion 13 of the axial stop device 11 enters the groove via a second end of the groove 10, said ends corresponding to the notches 16.

[0051] More particularly, simultaneously or successively, each portion is inserted into the groove by first passing the rounded end of this portion into the notch dedicated to it, then sliding the portion into the groove until the positioning heel cooperates with the notch of complementary shape and blocks the insertion of the portion into the groove. When the positioning heel of a portion of the axial stop device is in contact with the edges delimiting the notch, the portion is in the desired angular position within the groove 10.

[0052] In addition, each portion 12, 13 comprises an inner face and an outer face 19, only the outer face 196 being visible in Figure 2. When the axial stop device 1 1 is arranged within the groove 10, the inner face is oriented towards the wall 9 forming the bearing for receiving the journal 4, so as to face the inside of the groove 10, while the outer face 19 is opposite the inner face and is configured so as to be oriented towards the lateral bearing surface 5, not visible in Figure 2 due to the cross-sectional view, axially delimiting the journal 4. The outer face 19 of each of the portions 12, 13 differs from the inner face in that it comprises a lubrication cavity 20 within which a lubricating fluid can flow.

[0053] The first positioning heel 14 and the second positioning heel 15 have different dimensions to each other. In particular, the positioning heels 14, 15 differ from each other in terms of length L14, L15 and height H14, H15. Alternatively, the positioning heels 14, 15 may differ in shape. Each notch 16 in the groove 10 is specifically sized to receive the first positioning heel 14 or the second positioning heel 15. In other words, one notch has a first dimension, for example a height, which is equal to the height H14 of the first positioning heel, while the other notch has a second dimension, for example a height, which is equal to the height H14 of the second positioning heel. In this way, the operator can easily check that the positioning heel of the portion he has just inserted is in the correct notch. This configuration ensures that each portion 12, 13 is positioned in the right place, so that the external face 19 of each portion 12, 13 faces the lateral bearing surface of the crankshaft and not the wall of the casing. The dimensions of the positioning heels 14, 15 therefore act as a locator to ensure that the lubrication cavity 20 of each portion faces the crankshaft so that the latter is correctly lubricated. Each portion 12, 13, more particularly each positioning heel 14, 15, comprises a connecting face 21 connecting the inner face to the outer face 19 and forming a thickness of each portion 12, 13. Once the portions 12, 13 are positioned in the groove 10, the connecting faces 21 are diametrically opposed with respect to the journal and must be arranged in the same plane P, which forms a junction plane with a complementary part of the casing to form the journal receiving bearing. In this way, the axial stop device 1 1 is arranged on only one side of the plane P, thus facilitating assembly of the engine assembly. In the context of what has been described above, if the connecting faces 21 are not flush with the plane P once the portions have been inserted into the groove, the operator may consider that the portions have not been inserted on the correct side of the groove and may restart the operation.

[0054] Of course, the invention is not limited to the examples just described and many adjustments can be made to these examples without departing from the scope of the invention.

[0055] The invention, as just described, achieves its intended purpose well, and makes it possible to offer an engine assembly comprising an axial stop device in two portions which can be identified as specifically having to be assembled within the said engine assembly. Variants not described here could be implemented without leaving the context of the invention, provided that, in accordance with the invention, they comprise an engine assembly according to the invention.

Claims

CLAIMS1 - Engine assembly (1 ) for a motor vehicle, comprising a crankshaft (2), a casing (3) configured to at least partially house the crankshaft (2) and comprising at least one bearing for receiving a journal (4) of the crankshaft (2), the casing (3) comprising a groove (10) formed in a side face of a wall (9) of the casing that helps to define the reception casing, the engine assembly further comprising at least one axial stop device (1 1 ) configured to be housed inside the groove (10) between said side face and the crankshaft (2), characterised in that the axial stop device (11 ) comprises a first portion (12) and a second distinct portion (13), both configured to be housed within the groove (10), each portion (12, 13) comprising a positioning heel (14, 15) configured to cooperate in a complementary manner with a notch (16) formed at one end of the groove (10).2- Engine assembly (1 ) as claimed in claim 1 , wherein each portion (12, 13) has the shape of an arc of a circle.3- Engine assembly (1 ) according to any one of the preceding claims, in which each portion (12, 13) comprises a rounded end (17) opposite the positioning heel (14, 15), the rounded ends (17) of the two portions (12, 13) forming the axial stop device (1 1 ) facing each other within the groove (10).4- Engine assembly (1 ) according to any one of the preceding claims, wherein each portion (12, 13) comprises an inner face oriented towards the casing (3) and an outer face (19) opposite the inner face and oriented towards the crankshaft (2), the outer face (19) of each portion (12, 13) comprising a lubrication cavity (20).5- Engine assembly (1 ) according to any one of the preceding claims, wherein the first portion (12) and the second portion (13) respectively comprise a first positioning heel (14) and a second positioning heel (15), the first positioning heel (14) and the second positioning heel (15) being of different shape and / or size from one another.6- Engine assembly (1 ) according to the preceding claim, combined with claim 4, in which the first positioning heel (14) and the second positioning heel (15) each have a connecting face (21 ) connecting the inner face to the outer face (19), the first portion (12) and the second portion (13) being configured to be arranged in the groove (10) so that the connecting face (21 ) of each positioning heel (14, 15) is in the same plane (P) relative to each other.7- Engine assembly (1 ) according to any of the preceding claims, wherein the axial stop device (11 ) is made of metal.8- Engine assembly (1 ) according to any of the preceding claims, comprising two axial stop devices (11 ) each configured to be arranged on either side of the journal (4) of the crankshaft (2).9- A method of assembling an engine assembly (1 ) according to any one of the preceding claims, comprising : a step to determine the diameter of the crankshaft (2), a step of arranging the axial stop device (1 1 ) in two portions when the diameter of the crankshaft (2) is compatible, a step of arranging an axial stop device of a type different from the type of axial stop device in two portions when the diameter of the crankshaft (2) is not compatible with the axial stop device (1 1 ).10- A method of assembling according to the preceding claim, during which the first portion (12) of the axial stop device (11 ) is inserted through a first end of the groove (10) and the second portion (13) of the axial stop device (11 ) is inserted through a second end of the groove (10).

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