Torsional damping device

Abstract

The invention relates to a torsional damping device (1) comprising an input element (6), an output element (8), a mechanical energy storage member (9), a torque limiter (4) adapted to apply friction between a first metal element (10) and a second metal element (11, 12, 13) wherein the first and second metal elements comprise first and second coatings (101, 111, 121, 131) wherein the first and second coatings are oxide or friction layers, the friction layer comprises at least one element selected from the group consisting of zinc phosphate, manganese phosphate, iron phosphate, nickel, nickel-zinc, molybdenum disulfide, graphite and polytetrafluoroethylene, understood that the first coating (101) is formed directly on the metal substrate (100) of the first metal element (10) when the first coating (101) is an oxide layer.

Description

Technical Field

[0001] The invention relates to a torsional damping device, in particular suitable for integration into a drive train of a vehicle. Background Art

[0002] Motor vehicles often include such torsional damping devices to filter out the non-periodic behavior of the engine and allow smooth transmission. The filtering is usually performed by one or more spring-damper assemblies that work in torsion and allow relative rotational movement of a first rotating element of a driving element coupled to the transmission upstream of the damping device relative to a second rotating element of a driven element coupled to the transmission downstream of the damping device as torque is transmitted.

[0003] It is known practice to equip such a torsional damping device with a torque limiter configured to allow torque to be transmitted from the first rotating element to the second rotating element in normal operation and to limit this transmission when excessive torque is applied to the drive train, that is to say when this torque exceeds a certain value. These shocks are caused by abnormal maneuvers that may occur on the vehicle, such as braking during passage over an obstacle.

[0004] Friction elements or linings are arranged between the solid parts of the torque limiter, the purpose of these linings being to ensure a stable and controlled friction level whatever the conditions of use.

[0005] Motor vehicle manufacturers and equipment suppliers seek to make torsional damping devices as compact as possible in order to limit, among other things, the axial bulk and the effect on the amount of space required for the drive train. In this context, particular efforts are made to limit the thickness of the lining, which can result in two solid components (one on each side of the lining) rubbing together undesirably, in particular when one of the components exhibits flatness defects and / or local wear of the lining.

[0006] In order to obtain a device that is as compact as possible at low cost, efforts can also be made to eliminate friction linings and create metal-to-metal friction. However, this has the disadvantage of obtaining an unstable friction coefficient.

[0007] The invention therefore aims to obtain a device that is as compact as possible and has a stable coefficient of friction. Summary of the invention

[0008] Therefore, the present invention aims to provide a torsional damping device, comprising:

[0009] an input member configured to be fixed to the drive shaft for common rotation about the rotation axis,

[0010] an output member, configured to be fixed to the driven shaft for common rotation,

[0011] A mechanical energy storage member arranged between the input element and the output element,

[0012] a torque limiter adapted to apply friction between a first metal element and a second metal element pressed against the first metal element,

[0013] wherein the first metal element comprises a first coating, the second metal element comprises a second coating,

[0014] Wherein the first and second coatings are oxide layers or friction layers,

[0015] The friction layer comprises at least one element selected from zinc phosphate, manganese phosphate, iron phosphate, nickel, nickel-zinc, molybdenum disulfide, graphite and polytetrafluoroethylene,

[0016] It is understood that when the first coating is an oxide layer, it is formed directly on the metal substrate of the first metal element.

[0017] The invention makes it possible to generate a friction torque between the first and second metal elements due to the coating on the two metal elements. It is therefore not necessary to provide the friction material as a separate element. The axial volume and the costs are thus reduced due to the elimination of the friction lining. This also makes it possible to obtain a high heat resistance, since the metal elements are very heat resistant.

[0018] Finally, the friction damping device of the present invention can achieve a metal-to-metal friction coefficient that is greater than the metal-to-friction lining friction coefficient. This increased friction coefficient makes it easier to achieve the desired slip torque, as it will ultimately reduce the load on the elastic element and, therefore, the mechanical stress in the component. The choice of coating is important because it addresses the stability of the metal-to-metal friction coefficient. In particular, the latter can vary significantly depending on the operating time, the type of load (pressure, speed) and the environmental conditions (temperature, humidity).

[0019] The friction between the first and second metal elements is generated especially between the first coating and the second coating. Specifically, the first coating is arranged facing the second coating.

[0020] Advantageously, the device further comprises a hardening layer, the first coating being formed on the hardening layer. Thus, the hardening layer is an inner layer and the first coating is an outer layer. Preferably, the hardening layer is formed on the metal substrate of the first metal element.

[0021] Advantageously, the first and second coatings are friction layers.

[0022] Advantageously, the friction layer comprises zinc phosphate or manganese phosphate, and the friction layers may be the same or different.

[0023] Advantageously, the first friction layer consists of manganese phosphate and the second friction layer consists of zinc phosphate.

[0024] In one variant, the first coating is an oxide layer and the second coating is a friction layer.

[0025] In one variation, the first coating is an oxide layer and the second coating is an oxide layer.

[0026] Advantageously, the first metal element is a disk. Advantageously, the second metal element is a cover, a pressure plate or a resilient element.

[0027] Advantageously, the torque limiter comprises a third metal element pressed against the first metal element.The first metal element is thus axially interposed between the second and third metal elements.

[0028] Advantageously, the third metal element is one of the cover, the pressure plate and the elastic element, and the second metal element is another of the cover, the pressure plate and the elastic element. In other words, the second and third metal elements are two different parts.

[0029] Preferably, when the second metal element is one of the pressure plate or the cover and the third metal element is the other of the pressure plate or the cover, the torque limiter further includes an elastic element configured to press the second metal element against the first metal element.

[0030] In a variant, when one of the second and third metal elements is an elastic element, the other metal element is a cover. This makes it possible to eliminate the pressure plate, so that the elastic element directly abuts against the disk. The axial volume and cost are further reduced.

[0031] Preferably, the elastic element comprises at least one Belleville washer placed between the inner face of the output element and the pressure plate or disc. The Belleville washer makes it possible to obtain a height range for which the load variations are small. This allows the torque limiter slip torque to remain very stable, regardless of the manufacturing tolerances of its components and the wear in operation.

[0032] According to an optional feature of the invention, the torque limiter is disposed in an axial volume defined by the input element and the output element.

[0033] Advantageously, the third metal element comprises a third coating, which is an oxide layer or a friction layer. The friction between the first and third metal elements is generated particularly between the first coating and the third coating. Specifically, the first coating is arranged facing the third coating.

[0034] Thus, the first metal element comprises a first coating facing both the second coating of the second metal element and the third coating of the third metal element.

[0035] Advantageously, the coating corresponds to the friction surface of the torque limiter.

[0036] Advantageously, the torque limiter is arranged radially inside the mechanical energy storage member.It should be understood here that the term "radial" is intended to encompass directions perpendicular to the rotational axis of the input element, which is most typically the rotational axis about which the torsional damping device is arranged.

[0037] Advantageously, the torque limiter is fixed to the output element. More specifically, the cover is fixed to the output element. The torque limiter is thus positioned as close as possible to the gearbox, which makes it possible to limit the inertia downstream of the torque limiter and therefore the level of excessive torque to which the transmission is subjected. According to an optional feature of the invention, the torque limiter comprises two covers, the output element forming one of the two covers. In this way, the number of components is reduced, thereby reducing the manufacturing costs.

[0038] According to an optional feature of the invention, the torque limiter is a dry torque limiter. The torque limiter is located outside any space containing lubricants (such as grease). This positioning of the torque limiter achieves dry friction, allowing full operational control of the slip torque with minimal axial volume.

[0039] Another subject of the invention is a method for producing a torsional damping device as described above, wherein the oxide layer is obtained by a passivation process.

[0040] Advantageously, the hardened layer is obtained by a heat treatment process advantageously selected from the following heat treatments: induction hardening, quenching+tempering, case hardening, carbonitriding, nitrocarburizing and nitriding, preferably carbonitriding and nitriding.

[0041] Another subject of the invention is a vehicle drive train comprising a device as described above.

[0042] The driveline may form part of a vehicle powertrain which may include a hybrid engine or an electric motor, preferably a hybrid engine.

[0043] “Vehicle” is to be understood as a motor vehicle, which includes not only passenger cars but also industrial vehicles, in particular heavy goods vehicles, public transport vehicles or agricultural vehicles, but also any transport unit which is able to move living beings and / or objects from one point to another. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The invention will be better understood by reading the following description and examining the accompanying drawings which are provided only as a complete non-limiting illustration of the invention.

[0045] Figure 1 A cross-sectional view showing a torsional damping device equipped with a torque limiter according to a first embodiment of the present invention.

[0046] Figure 2 Shows Figure 1A more detailed cross-sectional view of a portion of the torsional damping device.

[0047] Figure 3 Shows Figure 1 A cross-sectional view of a torsional damping device showing only the resilient elements, pressure plates and covers on either side of the disc of the torque limiter of the first embodiment.

[0048] Figure 4 A cross-sectional view of a torsional damping device according to a second embodiment is shown, showing only the pressure plates and covers on either side of the disc of the torque limiter.

[0049] Figure 5 A cross-sectional view schematically illustrating the internal composition of the first metal element is shown.

[0050] Figure 6 : is a graph showing the change of the slip torque of the torque limiter according to the first example of the present invention as a function of the load amount.

[0051] Figure 7 : is a graph showing the change of the slip torque of the torque limiter according to the second example of the present invention as a function of the load amount.

[0052] Figure 8 : is a graph showing the change of the slip torque of the torque limiter according to the third embodiment of the present invention as a function of the load amount.

[0053] Fig. 9 : is a graph showing the change of the slip torque of the torque limiter according to the fourth embodiment of the present invention as a function of the load amount.

[0054] Identical, similar or like elements retain the same reference from one figure to another. DETAILED DESCRIPTION

[0055] Figures 1 to 4 A torsional damping device 1 for a vehicle drive train is shown, which comprises, in particular, a torque limiter 4 .

[0056] The torsional damping device comprises, in particular, an input element 6 , an output element 8 and at least one, preferably a plurality of mechanical energy storage components arranged between masses forming the input element and the output element, respectively.

[0057] Both the input element 6 and the output element 8 are rotatable about an axis of rotation X. The input element 6 may be a primary flywheel rotationally connected to a drive shaft, in this case a crankshaft of an internal combustion engine (not shown). The input element 6 is fixed to the drive shaft using a first connecting member.

[0058] The output member 8 may in particular comprise a hub 81. The output member 8 may further comprise a mounting plate 82 perpendicular to the rotation axis X. The hub 81 is located in the center of the mounting plate 82 and has an internal spline suitable for connecting to a driven shaft (not shown here) which can be used to connect the torsional damping device 1 to a gearbox (not shown here).

[0059] like Figure 1 As can be clearly seen in FIG. 8 , the mounting plate 82 for the output element 8 is bordered by a covering element 83 .

[0060] In the example discussed, each mechanical energy storage member arranged between the input element 6 and the output element 8 comprises a spring 9, which is configured to resist the pivoting of the input element relative to the output element. The spring 9 can be curved. As an alternative, the spring 9 can be a straight spring. Each spring 9 is alternately connected to the input element 6 and the output element 8 at one of the ends.

[0061] The torsional damping device 1 comprises an annular web which is arranged such that its periphery is contacted, where appropriate, by an intermediate web of a spring 9. The web can transmit torque between the spring 9 and the torque limiter 4. The spring 9 is axially accessible via openings 64, 84 formed in the first input and output element and is radially held in place by the peripheral edge of the input element 6 and the annular web so that they cannot become disengaged.

[0062] The torque limiter 4 is arranged radially inside the mechanical energy storage member 9 .

[0063] like Figure 3 and 4 As shown, the torque limiter 4 comprises a first metal element 10 and second metal elements 11, 12, 13 pressed against the first metal element 10. The disk 10 may coincide with the web just mentioned. The torque limiter 4 further comprises third metal elements 11, 12, 13.

[0064] like Figure 3 As shown, the first metal element 10 is a disk, the second metal element 11, 12 is one of the cover 14 and the pressure plate 16, and the third metal element 11, 12 is the other of the cover 14 and the pressure plate 16. Arbitrarily, consider that the second metal element 11 is the pressure plate 14 and the third metal element 12 is the cover. In a variant, it is entirely possible that the second metal element 12 is the cover 16 and the third metal element 11 is the pressure plate 14.

[0065] The second metal member 11 (pressing plate 14 ) and the third metal member 12 (cover 16 ) are arranged to be opposed to each other with the first metal member 10 (disk 10 ) sandwiched therebetween.

[0066] The torque limiter 4 further comprises at least one elastic element 20 configured to ensure the axial positioning of the components of the torque limiter relative to each other. The elastic element may in particular comprise a Belleville washer 20 placed between the inner face of the mounting plate 82 associated with the hub 81 and the pressure plate 16. In the example shown, the elastic element comprises two Belleville washers, but this does not limit the invention.

[0067] The cover 14 of the torque limiter includes a radial receiving portion 22 which is arranged perpendicular to the rotation axis X and axially faces the disc 10, a fixing portion 24 which is firmly pressed against the inner face of the mounting plate 82 of the output element 8, and a return portion 26 which axially connects the receiving portion 22 to the fixing portion 24, so that the radial receiving portion extends a distance from the mounting plate 82 of the output element 8, thereby defining a housing for the disc 10, the pressure plate 16 and the Belleville washer 20.

[0068] The fixing portion 24 is fixed to a mounting plate 82 associated with the hub 81 by means of a plurality of rivets 26 .

[0069] The torque limiter is axially delimited at one axial end by a cover 14 and at the other axial end by a mounting plate 82, and the cover 14 is arranged between this mounting plate 82, which forms part of the output element 8, on the one hand, and the input element 6, on the other hand. Thus, according to the invention, the torque limiter 4 is internal to the device, that is to say integrated into the axial volume delimited by the input element and the output element. The torque limiter is located in the drive train as close as possible to the gearbox, which makes it possible to limit the inertia downstream of the torque limiter and thus the excessive torque reaching those components of the drive train that are located between said torque limiter and the vehicle wheels. This configuration also makes it possible to obtain a compact device that is particularly suitable for the drive train of a hybrid engine.

[0070] As especially in Figure 2 As can be seen more clearly in FIG. 8 , the components of the torque limiter 4 , except the cover 14 , are arranged between the cover 14 and the mounting plate 82 in such a way that the radial receiving portion 22 of the cover 14 , the disc 10 , the pressure plate 16 and the Belleville washer 20 are arranged axially one after the other.

[0071] The pressure plate 16 , which is rotatable about the axis X, is able to move axially, in particular under the effect of the stress exerted by the Belleville washer 20 , so as to move closer to the radial housing portion 22 of the cover 14 and clamp the disk 10 .

[0072] The pressure plate 16 comprises at least one guide tongue 17 which projects radially on its inner periphery and which is dimensioned to be received in a recess formed in the return portion 26 of the cover 14. The cooperation between the guide tongue 17 and the recess allows, on the one hand, a correct angular positioning of the two solid parts of the torque limiter relative to each other and, where applicable, a good transmission of the rotational torque, and, on the other hand, an axial guidance of the pressure plate 16 under the effect of the stress exerted by the Belleville washer 20.

[0073] As previously mentioned, one or more Belleville washers 20 are axially interposed between the mounting plate 82 associated with the hub 81 of the output element 8 and the pressure plate 16. More specifically, the Belleville washers 20 here abut on the side of the pressure plate 16 opposite to the face of the pressure plate 16 facing the disc 10. The Belleville washers 20 allow the pressure plate 16 to remain pressed against the disc and the radial receiving portion 22 of the cover to remain pressed against the same disc. More specifically, each Belleville washer 20 is preloaded so that it constantly applies a predetermined axial pressure to the pressure plate 16, making it possible to clamp the disc 10 between the pressure plate 16 and the cover 14, since the cover 14 is fixed to the mounting plate 82 associated with the hub 81.

[0074] Figure 4 A torque limiter 4 according to a second embodiment is shown, which is similar to Figure 3 The torque limiter in FIG. 1 differs in that it does not comprise a pressure plate 16. Therefore, the elastic element 20 rests directly against the disc 10 without an intermediate component.

[0075] In this example, the first metal element 10 is a disk, the second metal elements 11 , 13 are one of the cover 14 and the elastic element 20 , and the third metal elements 11 , 13 are the other of the cover 14 and the elastic element 20 .

[0076] The metal elements 10, 11, 12 may be made of iron, rolled steel or other commercially available steel materials which ensure a predetermined stiffness generally required for the torsional damping device 1. Preferably, the metal elements 10, 11, 12 include a steel material combined with carbon, manganese, aluminum, chromium, silicon, titanium, boron and / or vanadium.

[0077] Now we will use Figures 3 to 5 The coating of metal components is described in more detail.

[0078] As described above, the first metal element 10 and the second metal element 11, 12, 13 will be pressed against each other to obtain friction. The first metal element 10 is a disk, and the second metal element 11, 12, 13 is a cover 14, a pressure plate 16 or an elastic element 20.

[0079] In the context of the present invention, the first metal element 10 comprises a first coating 101 and the second metal element comprises a second coating 111 , 121 , 131 .

[0080] The first coating layer 101 is formed on the outermost surface of the first metal element 10. The second coating layers 111, 121, 131 are formed on the outermost surfaces of the second metal elements 11, 12, 13.

[0081] When the torque limiter 4 is in operation, the second metal element 11, 12 continues to rotate relative to the first metal element 10. Friction forces will then be generated between these two elements, in particular between the first coating 101 and the second coating 111, 121, 131.

[0082] The first coating 101 is an oxide layer or a friction layer. The second coatings 111, 121, 131 are also oxide layers or friction layers.

[0083] The friction layer is composed of at least one element selected from zinc phosphate, manganese phosphate, iron phosphate, nickel, nickel-zinc, molybdenum disulfide, graphite and polytetrafluoroethylene.

[0084] When the first coating 101 is an oxide layer, it is always formed directly on the metal substrate 100 of the first metal element 10. In other words, there is no intermediate layer between the oxide layer 101 and the metal substrate 100 of the first metal element 10 to which the first coating 101 is applied.

[0085] Figure 5 Schematic internal composition of the first metal element 10 according to one embodiment is shown. The first metal element 10 includes a metal substrate 100 on which a hardening layer 100 ′ is formed. The hardening layer 100 ′ is formed on the entire metal substrate 100 .

[0086] The hardened layer 100 ′ is obtained by a heat treatment process which is advantageously selected from the following heat treatments: induction hardening, quenching+tempering, surface hardening, carbonitriding, nitrocarburizing and nitriding.

[0087] Depending on the heat treatment used, such as when quenching is used, the entire metal substrate 100 may become a hardened layer 100'. Specifically, quenching is a process that increases the hardness across the entire thickness, including the core of the substrate material.

[0088] Then, the first coating layer 101 is formed on the hardened layer 100'. The first coating layer 101 is also formed on the entire hardened layer 100'.

[0089] The first coating layer 101 is an outer layer because it is formed on the outermost surface of the first metal element 10, while the hardening layer 100' is considered to be an intermediate layer or an inner layer.

[0090] In the example under discussion, the first coating 101 is a friction layer.

[0091] In a variation, for example Figure 3 As shown in FIG. 4 , the first metal element 10 does not include the hardening layer 100 ′. Then, a first coating 101 which may be a friction layer or an oxide layer is directly formed on the metal substrate 100. The oxide layer may be obtained by a passivation process.

[0092] As mentioned above, in addition to the friction between the first and second metal elements, there may also be friction between the first and third metal elements. In the same way as the second metal element, the third metal element 11, 12, 13 includes a third coating 111, 121, 131, which is an oxide layer or a friction layer.

[0093] The following examples of damping devices according to the invention are particularly advantageous:

[0094] In a first example, the first metal element 10 comprises a metal substrate 100 made of steel, a hardened layer 100 ′ obtained by carbonitriding, a first coating 101 composed of manganese phosphate, and the second metal element 11 comprises a second coating 111 , 121 , 131 composed of zinc phosphate.

[0095] In the second example, the first metal element 10 comprises a metal substrate 100 made of steel, a hardened layer 100 ′ obtained by carbonitriding, a first coating 101 of manganese phosphate, and the second metal element 11 comprises a second coating 111 , 121 , 131 which is an oxide layer.

[0096] In a third example, the first metal element 10 comprises a metal substrate 100 made of steel, a hardened layer 100 ′ obtained by nitriding, a first coating 101 of manganese phosphate, and the second metal element 11 comprises a second coating 111 , 121 , 131 of zinc phosphate.

[0097] In the fourth example, the first metal element 10 includes a metal substrate 100 made of steel, a hardened layer 100 ′ obtained by carbonitriding, a first coating 101 as an oxide layer, and the second metal element 11 includes second coatings 111 , 121 , 131 as oxide layers.

[0098] Figure 6 , 7 , 8 and 9 are graphs showing the variation of the slip torque of the torque limiter according to the present invention as a function of the load amount for the above-mentioned first, second, third and fourth examples, respectively.

[0099] These results are derived from durability tests on a laboratory test bench designed to reproduce the loads to which the torque limiter is subjected during its entire period of use on a vehicle. These results illustrate that the choice of composition according to the invention leads to stable values ​​of slip torque during the entire period of use. The variation of slip torque is considered acceptable when it does not exceed 20% of the difference between its minimum and maximum values, which is the case here.

[0100] Furthermore, different features, variants and / or embodiments of the present invention may be combined with one another in various combinations, as long as they are not compatible or mutually exclusive.

Claims

1. A torsional damping device (1), comprising: an input member (6) configured to be fixed to the drive shaft for common rotation about an axis of rotation (X), An output member (8) is configured to be fixed to the driven shaft for common rotation, A mechanical energy storage component (9) is arranged between the input element (6) and the output element (8), A torque limiter (4) adapted to apply friction between a first metal element (10) and a second metal element (11, 12, 13) pressed against the first metal element (10), The first metal element (10) comprises a first coating (101), the second metal element comprises a second coating (111, 121, 131), Characterized in that the first coating and the second coating (101, 111, 121, 131) are oxide layers or friction layers, The friction layer comprises at least one element selected from zinc phosphate, manganese phosphate, iron phosphate, nickel, nickel-zinc, molybdenum disulfide, graphite and polytetrafluoroethylene, preferably zinc phosphate and manganese phosphate. It is understood that when the first coating (101) is an oxide layer, the first coating is directly formed on the metal substrate (100) of the first metal element (10).

2. The torsional damping device (1) according to claim 1, characterized in that: The first coating and the second coating (101, 111, 121, 131) are friction layers, the first friction layer comprises manganese phosphate, and the second friction layer comprises zinc phosphate.

3. The torsional damping device (1) according to any one of the preceding claims, characterized in that The torsional damping device comprises a hardened layer (100'), and the first coating (101) is formed on the hardened layer (100').

4. A torsional damping device (1) according to any one of the preceding claims, characterized in that The first metal element (10) is a disk, and the second metal element (11, 12, 13) is a cover (14), a pressure plate (16) or an elastic element (20).

5. The torsional damping device (1) according to any one of the preceding claims, characterized in that The torque limiter (4) comprises a third metal element (11, 12, 13) pressed against the first metal element (10).

6. The torsional damping device (1) according to claim 5 and claim 4, characterized in that The third metal element (11, 12) is one of the cover (14), the pressure plate (16) and the elastic element (20), and the second metal element (11, 12) is the other of the cover (14), the pressure plate (16) and the elastic element (20).

7. The torsional damping device (1) according to claim 5 or 6, characterized in that: The third metal element (11, 12, 13) comprises a third coating (111, 121, 131), and the third coating is an oxide layer or a friction layer.

8. A torsional damping device (1) according to any one of the preceding claims, characterised in that The torque limiter (4) is radially arranged inside the mechanical energy storage component (9).

9. A torsional damping device (1) according to any one of the preceding claims, characterised in that The torque limiter (4) is fixed to the output element (8).

10. A method for producing a torsional damping device (1) according to any one of the preceding claims, characterized in that The oxide layer is obtained by a passivation process.

11. A method for manufacturing a torsional damping device (1) according to claim 3, characterized in that The hardened layer (100') is obtained by a heat treatment process, which is advantageously selected from the following heat treatments: induction hardening, quenching+tempering, surface hardening, carbonitriding, nitrocarburizing and nitriding, preferably carbonitriding and nitriding.

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