FR2755649A1 - Power unit mounting block for automobile - Google Patents

Abstract

The automobile consists of a chassis (3), which carries the power unit (2) by means of a series of mounting blocks (4, 5 & 6). The mounting blocks are designed to support the power unit and to dampen out the relative vibrational movement between the power unit and the chassis. The mounting blocks consist of a rigid support arm (7), fixed to the power unit, and which carries an anti vibration support (10), which consists of a primary rigid frame (11), fixed to the support arm, a second rigid frame (12), which is fixed to the chassis, and a elastomer body (13), which links the two frames together. A movement limiter (14) is designed to restrict the relative movement, parallel to axis (X) and consists of a rigid finger (16) with two elastomer pads (20), positioned between two stops (21).

Description

AUTOMOTIVE VEHICLE COMPRISING A DOTE DRIVE UNIT
OF A SUSPENSION WITH A LIMITED TRAVEL
The present invention relates to motor vehicles comprising a power unit equipped with a suspension with limited travel.

More particularly, the invention relates to motor vehicles comprising a chassis, a power unit and a plurality of fixing devices supporting the power unit and damping the relative vibrational movements between the power unit and the chassis parallel to a first substantially vertical axis, these fastening devices allowing movements of the powertrain relative to the chassis parallel to the first axis and at least parallel to a second axis perpendicular to the first axis, at least one of these fastening devices, called "first fastening device", comprising
- a rigid support arm secured to the power unit, the support arm and the chassis being hereinafter called one "first element" and the other "second element",
- an anti-vibration support which itself comprises a first rigid frame fixed to the support arm, a second rigid frame fixed to the chassis and an elastomer body connecting the first and second frames together and supporting the power unit by allowing the above-mentioned relative deflections between this powertrain and the chassis,
- And a travel limiter which is able to limit the relative displacements between the power unit and the chassis parallel to the second axis, the travel limiter comprising a rigid finger which extends in a longitudinal direction perpendicular to the second axis and which is integral of the first element, this finger being coated with elastomer and cooperating with two abutment faces integral with the second element to limit the relative deflections between the power unit and the chassis parallel to the second axis.

In known vehicles of this type, for example in the vehicle of the "CLIO" brand, manufactured by the Company
RENAULT, the finger is covered with a solid rubber mass which forms a block rigidly connected to said finger, and this finger is engaged in a recess in the support arm, two opposite walls of which constitute the abovementioned abutment faces.

 This known embodiment works properly, but has the disadvantage that, when the finger of the travel limiter is in abutment against the wall of the recess of the support arm, the significant friction which is thus generated between this finger and this wall interferes with the operation of the anti-vibration mount in the vertical direction.

 In particular, this friction tends to directly transmit the vibrational movements between the power train and the chassis of the vehicle, while the anti-vibration support is precisely provided to avoid such transmission as much as possible.

 The object of the present invention is in particular to overcome this drawback.

To this end, according to the invention, a motor vehicle of the kind in question is essentially characterized in that the finger supports two elastic buffers which each extend parallel to the second axis from said finger in two opposite directions, each of these buffers elastic including
- an inner layer of elastomer adhered to the finger,
- A connecting rod which comprises at least one rigid spacer and which has first and second opposite rigid faces which are oriented respectively towards the finger and towards the corresponding abutment face, each of these rigid faces having a convex and finished radius of curvature, at less in any plane parallel to the first and second axes which intersects said rigid face, the first rigid face of the link being adhered to the inner layer of elastomer, and the link having a certain length d parallel to the second axis and a certain height h parallel to the first axis, such that the ratio d / h is at least equal to 0.5,
- And an outer layer of elastomer which is directly opposite the corresponding abutment face, this outer layer of elastomer being adhered to the second rigid face of the link and being separated from the inner layer of elastomer by the link .

 Thanks to these provisions, a travel limiter is obtained which has a relatively great stiffness parallel to the second axis, so as to effectively limit the movements of the power unit parallel to this axis, while having very low stiffness in the vertical direction.

 These provisions therefore allow the travel limiter not to interfere with the operation of the anti-vibration support and therefore not to transmit the vibratory movements between the power train and the chassis of the vehicle.

 In addition, the elastic buffers have very good progressiveness: in other words, they provide effective but relatively gentle travel limitation, without imposing a shock on the power unit.

In preferred embodiments, use may optionally be made of one and / or the other of the following arrangements.
- The link of each elastic buffer comprises at least first and second rigid spacers aligned parallel to the second axis, the first spacer being disposed between the finger and the second spacer, each of the spacers having first and second opposite curved surfaces which are oriented respectively towards the finger and towards the corresponding abutment face, each of these curved surfaces having a convex and finite radius of curvature, at least in any plane parallel to the first and second axes which intersects with said curved surface, the first curved surface of the first spacer constituting the first rigid face of the link, the spacers being separated from each other by at least one intermediate layer of elastomer, each intermediate layer of elastomer being adhered respectively to the second curved surface of one of the spacers and to the first curved surface of another of the e ntretoises, and the second curved surface of the second spacer constituting the second rigid face of the link (if the link has additional spacers in addition to the first and second spacers, these additional spacers are interposed between the first and second spacers)
- Each elastic pad has a central axis parallel to the second axis, the above-mentioned radii of curvature of the curved surfaces of the spacers, in a vertical plane containing this central axis, being between 0.5 cm and 10 cm
- each link consists of a single rigid spacer
- the spacer has two end heads which define the first and second rigid faces of the rod and which are connected together by a narrower link arm
- Each elastic pad has a central axis parallel to the second axis, the radii of curvature of the convex rigid faces of the rod, in a vertical plane containing this central axis, being between 0.5 cm and 10 cm
- the length of the link is greater than 1 cm
- The elastomer body of the antivibration support has a bell shape extending by diverging from a top secured to the first frame to an annular base secured to the second frame, this elastomer body partially delimiting a working chamber which communicates through a constricted passage with a compensation chamber delimited by an easily deformable wall, the working chamber, the compensation chamber and the constricted passage forming a sealed volume filled with liquid
- the power unit is pendulum-suspended, this power unit extending longitudinally along a third horizontal axis perpendicular to the second axis and being connected to the chassis by the first fixing device associated with second and third fixing devices, the first and second fastening devices being substantially aligned parallel to the third axis and being fixed to the power unit at points located above the level of the center of gravity of this power unit, and the third fixing device being connected to the power unit at a point below first and second fixing devices.

 Other characteristics and advantages of the invention will appear during the following detailed description of several of its embodiments, given by way of nonlimiting examples, with reference to the accompanying drawings.

On the drawings
FIG. 1 very schematically shows a motor vehicle engine with pendulum suspension, known per se,
FIG. 2 is also a very schematic view of a motor vehicle of the prior art equipped with an engine such as that of FIG. 1, this figure showing in more detail one of the engine fixing devices,
FIG. 3 is a view in vertical section of a hydraulic antivibration support, known per se, belonging to the fixing device shown in FIG. 2,
- Figure 4 is a vertical sectional view of a travel limiter which, in a first embodiment of the invention, is intended to replace the travel limiter of the fixing device of the prior art shown in the figure 2, the rigid vertical finger of the travel limiter not being cut, for greater clarity,
FIG. 5 is a perspective view of one of the rigid spacers belonging to the travel limiter of FIG. 4,
FIG. 6 is a perspective view of a rigid spacer which can be used in place of that shown in FIG. 5, according to a variant of the invention,
- And Figure 7 is a view similar to Figure 4, for a second embodiment of the invention.

 In the different figures, the same references designate identical or similar elements.

 The invention applies preferably, but not exclusively, to a motor vehicle 1 comprising a powertrain 2 with pendular suspension, known per se and shown in FIGS. 1 and 2.

 In such a pendulum suspension, the longitudinal direction of the power unit 2 generally extends parallel to a horizontal transverse axis Y, which is perpendicular to a horizontal axis X corresponding to the longitudinal direction of the vehicle.

Furthermore, the power unit 2 is generally connected to the chassis 3 of the vehicle by means of three fixing devices, namely
first and second fastening devices 4, 5 aligned parallel to the Y axis and fixed to the longitudinal ends of the power train at points located above the center of gravity G of this power train,
- And a third fastening device 6 connected to the power train at a point located below the first and second fastening devices, for example on one of the sides of the power train or below this power train.

The three fastening devices generally include anti-vibration supports, each provided with an elastomer body which connects the power unit to the chassis of the vehicle, so as to allow movements of the power unit along a vertical axis Z, along the axis.
X, and in rotation around the Y axis (which results in movements along the X and Z axes).

 In particular, the power unit 2 rotates around the Y axis with each acceleration and each deceleration.

In addition, the anti-vibration supports of the first and second fixing devices 4, 5 are also provided, in a manner known per se, to support the weight of the power train 2 and to dampen the vibratory movements between the power train 2 and the chassis 3 according to the axis
Z.

 Finally, to limit the movements of the power unit 2, the fastening devices 4-6 include one or more limiters of movement.

Thus, in the example shown in FIG. 2, corresponding to the prior art, the first fixing device 4 comprises
- A rigid support arm 7 which is substantially horizontal, which is generally made of cast aluminum or cast iron and which is fixed to a longitudinal end of the power unit 2, in this case opposite the gearbox 8 of this block drive train, this support arm 7 being traversed vertically by a recess 9 located in a substantially median position between the two ends of said arm 7,
- An anti-vibration support 10 which in all cases comprises a first rigid frame 11 fixed under the support arm 7, a second rigid frame 12 fixed to the frame 3, and an elastomer body 13 connecting the first and second frames together and supporting the powertrain 2 by authorizing the aforementioned relative deflections between this powertrain and the chassis,
- And a travel limiter 14 which is able to limit the relative displacements between the power unit 2 and the chassis 3 parallel to the axis X (that is to say not only in translation along the axis X, but also in rotation around the Y axis, since such a rotation causes a displacement along the X and Z axes of any point of the power train not located on the axis of rotation), the travel limiter 14 comprising on the one hand a rigid horizontal base plate 15 in the shape of a horseshoe, which partially surrounds the elastomer body 13 and which is fixed to the frame 3, and on the other hand a rigid vertical finger 16 covered with solid rubber, which is integral with the plate base 15 and which extends upwards from this base plate by penetrating into the recess 9 of the support arm 7 by cooperating by abutment with the side walls of this recess.

 The antivibration support 10 may or may not be hydraulic. In particular, this anti-vibration support may be of the type shown in FIG. 3, known from document EP-AO 346 227, in which the elastomer body 13 has a bell-shaped shape extending by diverging from an apex secured to the first frame 11 to an annular base integral with the second frame 12, this elastomer body partially delimiting a working chamber A which communicates via a throttled passage 17 with a compensation chamber B delimited by a bellows 18 made of elastomer, the working chamber A, the compensation chamber B and the constricted passage 17 forming a sealed volume filled with liquid.

 Thus, the vibratory movements between the power unit 2 and the chassis 3, and in particular the vibratory movements of relatively large amplitude (for example greater than 0.1 mm) and of relatively low frequency (for example less than 20 Hz), cause liquid displacements between the chambers A and B via the throttled passage 17, which causes particularly effective damping of said vibratory movements.

 In addition, the chambers A and B are generally separated in part by a so-called "decoupling" valve 19, which may consist, for example, of a rubber strip interposed between two grids 19a, 19b, communicating with the chambers A, B. This valve 19 absorbs vibrations of relatively low amplitude (for example, less than 0.1 mm) and of relatively high frequency (for example greater than 20 Hz), generated by the power unit 2.

 The fastening device 4 of the prior art which has just been described works overall in a satisfactory manner, in particular thanks to the remarkable efficiency of the hydraulic antivibration support 10 which has just been described.

 However, when the finger 16 of the travel limiter is in abutment against the wall of the recess 9 belonging to the support arm 7, and in particular during the acceleration or deceleration phases of the vehicle, the significant friction existing between this finger 16 and the support arm 4 allows the vibratory movements to be transmitted directly between the power train 2 and the chassis 3 of the vehicle, without being attenuated by the anti-vibration support 10.

 To overcome this drawback, according to a first embodiment of the invention, a travel limiter 14 such as that shown in FIG. 4 is used, the other elements of the fixing device 4 remaining unchanged with respect to the arrangement shown in the figure 2.

 The travel limiter 14 of FIG. 4 always includes a base plate 15 identical to that described above, as well as a rigid vertical finger 16 identical or similar to that described above, having the shape of a vertical rod of any section or a vertical plate parallel to the Y and Z axes.

 Furthermore, the finger 16 carries two elastic pads 20 which each extend parallel to the axis X from said finger in two opposite directions, and which cooperate respectively with two abutment faces 21 formed by the walls which delimit the recess 9 of the support arm 7.

Each of the elastic pads 20 includes
an inner layer 22 of elastomer adhered to the finger 16,
two identical or similar rigid spacers 23 aligned along a central axis 28,
an intermediate layer of elastomer 24 interposed between the two spacers 23, and separated from the layer 22 by one of the two spacers 23,
- And an outer layer of elastomer 25 disposed opposite the corresponding abutment face 21.

 Each spacer 23 has first and second opposite curved faces 26, 27, clearly visible in Figure 5, which have a radius of curvature convex and finished in any vertical plane parallel to the axis X and intersecting said curved faces.

 This radius of curvature is preferably between 0.5 cm and 10 cm, at least in a vertical median plane containing the central axis 28 of the elastic pads.

 On the other hand, in the example of FIGS. 4 and 5, the curved faces 26, 27 of the spacers do not have any curvature (that is to say have an infinite radius of curvature) in any horizontal plane intersecting said curved faces.

 The first curved face 26 of the spacer 23 closest to the finger 16 in each elastic pad is adhered to the inner layer of elastomer 22, while the second curved face 27 of this spacer is adhered to the intermediate layer of elastomer 24.

 Similarly, the first curved face 26 of the spacer 23 furthest from the finger 16 inside each elastic pad is adhered to the intermediate layer of elastomer 24, while the second curved face 27 of this spacer is adhered to the outer layer of elastomer 25.

The elastic pads 20 make it possible to limit the deflections of the power train parallel to the X axis (that is to say both in translation along the X axis and in rotation about the Y axis, since these rotations cause powertrain movements, especially along the axis
X) with a relatively large elastic stiffness, but with good progressiveness.

 In addition, when one of the elastic pads 20 is in abutment against the corresponding abutment face 21, each of the spacers 23 undergoes rotational movements around the Y axis and the elastomer layers 22 and 24 work in shear when finger 16 moves vertically.

 The two spacers 23 and the intermediate elastomer layer 24 of each elastic pad 20 thus constitute a flexible and deformable link which facilitates the relative vertical movements between the finger 16 and the abutment faces 21.

 The length d of each of these links, measured along the central axis 28 of each pad 20, is advantageously at least equal to half the height h of said link.

 The length d may for example be greater than 1 cm, and in particular between 2 and 3 cm.

 To further facilitate these vertical displacements, the intermediate layer 24 of elastomer can also have a height along the axis Z less than the height h of the spacers 23, which accentuates the "elastic ball joint" effect of this layer 24.

 In all cases, even when the elastic pads 20 are in contact with the abutment faces 21, the fastening device 4 has a low elastic stiffness parallel to the axis Z, which allows it not to interfere with the operation of the anti-vibration mount 10.

 Optionally, as shown in FIG. 6, each spacer 23 could be replaced by a spacer 23a having a shape of revolution around the central axis 28, the spacer 23a having a section identical to the section of the spacer 23 already described. , in a vertical plane passing through the central axis 28.

 In this case, the two curved faces 26a, 27a of the spacer 23a have a convex radius of curvature in any plane passing through the central axis 28.

 Each elastic pad 20 may possibly comprise more than two spacers 23 or 23a, for example three or four spacers arranged one behind the other and connected to each other by intermediate layers of elastomer adhered to said spacers.

 Furthermore, as shown in FIG. 7, the number of spacers of each elastic pad 20 could be limited to one.

 In this case, each elastic pad comprises only an inner elastomer layer 22 adhered to the finger 16, a rigid spacer 29 which in itself constitutes a rigid link, and an outer elastomer layer 25.

 As in the examples described above, the spacer 29 has two opposite curved faces 30, 31 which are adhered respectively to the elastomer layers 22 and 25.

 As before, these two curved faces can have a convex curvature only in vertical planes, or even have a shape of revolution around the central axis 28, common to the two spacers, in which case the curved faces 30, 31 have convex curvatures in any plane passing through axis 28.

 Similarly, as described above, each spacer 29 completely separates the layers of elastomer 22 and 25.

 Finally, the length d of each spacer 29, measured along the central axis 28, is at least equal to half the total height h of the spacer 29 along the z axis.

 The above-mentioned length d may for example be at least 1 cm, and in particular between 2 and 3 cm.

 A relatively large lever arm is thus obtained between the curved faces 30, 31 of each spacer 29, so that, when the outer layer of elastomer 25 is in contact with the corresponding abutment face 21, the angular displacements of the spacer 29, which are due to the relative vertical movements between the finger 16 and said abutment face 21, cause relatively small shear deformations in the inner layer of elastomer 22.

 The elastic buffer 20 therefore induces a low elastic stiffness parallel to the axis Z, which allows it not to interfere with the operation of the anti-vibration support 10.

 Finally, to reduce the weight of each spacer 29, given the relatively large lever arm between the curved faces 30 and 31 of this spacer, it is advantageous to produce this spacer with two relatively wide end heads 32, 33 which form respectively the faces 30 and 31 and which are connected together by a relatively narrow rigid link arm 34.

Claims (10)

 1. Motor vehicle comprising a chassis (3), a power unit (2) and a plurality of fastening devices (4,5,6) supporting the power unit and damping the relative vibrational movements between the power unit and the chassis parallel to a first axis (Z) substantially vertical, these fastening devices (4,5,6) allowing movements of the power unit (2) relative to the chassis (3) parallel to the first axis (Z) and at least parallel to a second axis (X) perpendicular to the first axis, at least one of these fixing devices, called first fixing device "(4), comprising  - a rigid support arm (7) integral with the power unit (2), the support arm (7) and the chassis (3) being called hereinafter one "first element" and the other "second element,  - an anti-vibration support (10) which itself comprises a first rigid frame (11) fixed to the support arm (7), a second rigid frame (12) fixed to the frame (3) and an elastomer body (13) connecting together the first and second frames and supporting the power train (2) by authorizing the aforementioned relative deflections between this power train and the chassis,  - And a travel limiter (14) which is able to limit the relative displacements between the power train (2) and the chassis (3) parallel to the second axis (X), the travel limiter comprising a rigid finger (16) which extends in a longitudinal direction perpendicular to the second axis (X) and which is integral with the first element, this finger being coated with elastomer and cooperating with two abutment faces (21) integral with the second element to limit the relative deflections between the powertrain (2) and the chassis (3) parallel to the second axis (X), characterized in that the finger (16) supports two elastic pads (20) which each extend parallel to the second axis (X) from of said finger in two opposite directions, each of these elastic pads comprising:  - an inner layer of elastomer adhered to the finger (16),  - an outer layer of elastomer (25) which is located directly opposite the corresponding abutment face,  - And a link (23, 24, 23; 29) interposed between said inner and outer layers of elastomer, this link having first and second opposite rigid faces (26, 27; 30, 31) which are oriented respectively towards the finger (16) and towards the corresponding abutment face (21), each of these rigid faces having a radius of curvature which is convex and finite, at least in any plane parallel to the first and second axes (Z, X) which intersects said rigid face, the inner and outer layers of elastomer (22, 25) being adhered respectively to the first and second rigid faces (26, 27 30, 31), and the link having a certain length d parallel to the second axis (X) and a certain height h parallel to the first axis (Z) such that the ratio d / h is at least equal to 0.5.  2. Vehicle according to claim 1, wherein the link (23, 24, 23) of each elastic buffer (20) comprises at least first and second rigid spacers (23) aligned parallel to the second axis (X), the first spacer being arranged between the finger (16) and the second spacer, each of the spacers (23) having first and second opposite curved surfaces (26, 27) which are oriented respectively towards the finger (16) and towards the abutment face (21 ) corresponding, each of these curved surfaces having a convex and finite radius of curvature, at least in any plane parallel to the first and second axes (Z, X) which intersects with said curved surface, the first curved surface (26) of the first spacer constituting the first rigid face of the link, the spacers (23) being separated from each other by at least one intermediate layer of elastomer (24), each intermediate layer of elastomer being adhered placed respectively on the second curved surface (27) of one of the spacers and on the first curved surface (26) of another of the spacers, and the second curved surface (27) of the second spacer constituting the second rigid face of the link.  3. Vehicle according to claim 2, in which each elastic buffer (20) has a central axis (28) parallel to the second axis (X), the above-mentioned radii of curvature of the curved surfaces (26, 27) of the spacers (23), in a vertical plane containing this central axis, being between 0.5 cm and 10 cm.  4. Vehicle according to claim 1, wherein each link is constituted by a single rigid spacer (29).  5. Vehicle according to claim 4, wherein the spacer (29) has two end heads (32, 33) which define the first and second rigid faces (30, 31) of the link and which are connected together by a narrower link arm (34).  6. Vehicle according to claim 4 or claim 5, wherein each elastic pad (20) has a central axis (28) parallel to the second axis (X), the radii of curvature of the rigid convex faces (30, 31) of the connecting rod, in a vertical plane containing this central axis (28), being between 0.5 cm and 10 cm.  7. Vehicle according to any one of the preceding claims, in which the length (d) of the link is greater than 1 cm.  8. Vehicle according to any one of the preceding claims, in which the finger (16) is integral with the chassis (3), while the abutment faces (21) which cooperate with the elastic pads (20) form part of the arm of support (7).  9. Vehicle according to any one of the preceding claims, in which the elastomer body (13) of the antivibration support (10) has a bell shape extending diverging from a top secured to the first frame (11) up to to an annular base secured to the second frame (12), this elastomer body partially delimiting a working chamber (A) which communicates via a throttled passage (17) with a compensation chamber (B) delimited by an easily deformable wall (18), the working chamber, the compensation chamber and the constricted passage forming a sealed volume filled with liquid.  10. Vehicle according to any one of the preceding claims, in which the power unit (2) is pendularly suspended, this power unit extending longitudinally along a third horizontal axis (Y) perpendicular to the second axis (X) and being connected to the frame (3) by the first fixing device (4) associated with second and third fixing devices (5,6), the first and second fixing devices (4,5) being substantially aligned parallel to the third axis (Y ) and being fixed to the power unit at points located above the level of the center of gravity (G) of this power unit, and the third fixing device (6) being connected to the power unit at a point located below the first and second fastening devices.