Viscosity torsional vibration damper or viscosity torsional vibration absorber

Description

[0001] The present invention relates to a viscous torsional vibration damper or viscous torsional vibration absorber according to the preamble of claim 1.

[0002] Viscous torsional vibration dampers or viscous torsional vibration absorbers of the generic type are known per se. Such dampers or absorbers are used to reduce torsional vibrations on the crankshafts of reciprocating piston engines, with flywheels or flywheel masses being mounted within the housing of such dampers or absorbers. Instead of a housing, a hub enclosed by a flywheel can also be used, as disclosed, for example, in DE 10 2016 113 719 A1. The housing or hub typically has a flange part that can be fastened to a crankshaft of an engine, in particular an internal combustion engine, with the flywheel being rotatable relative to the housing or hub, forming a shear gap filled with a liquid shear medium, such as the aforementioned silicone oil. Flanged bushings serve to guide and support the flywheel in this shear gap filled with silicone oil.However, other plain bearing components such as axial bearing rings or plain bearing plugs are also used to support the flywheel, possibly in combination with each other.

[0003] These plain bearing components, particularly in the form of flanged bushings, are usually inserted without preload between the two damper housings and the flywheel ring in order to allow the housing and ring to slide on the flanged bushings with as little friction as possible.

[0004] The problem with high temperatures, particularly temperatures above 130°C, which regularly occur in torsional vibration dampers due to the shearing of the silicone oil damping medium during operation, is that interactions often occur between the conventional flanged bushings, which are usually made of polyamide, and the silicone oil, leading to a very rapid degeneration of the silicone oil's viscosity. For example, tests with a viscous torsional vibration damper at an outside temperature of 160°C showed a 53% decrease in viscosity after approximately 20 hours. The service life of such viscous torsional vibration dampers is typically 20,000 hours. A wear rate of only 30% is targeted during this period.

[0005] To solve this problem, one could try to reduce the high operating temperature, but this does not seem likely due to space restrictions and higher peak pressures of the engines, so that the viscous torsional vibration dampers tend to have to be designed to withstand even higher temperatures and it therefore does not seem sensible to design the viscous torsional vibration dampers in such a way that they are not exposed to such high temperatures during operation.

[0006] DE 10 2013 006 751 A1 discloses a generic viscous torsional vibration damper or a viscous torsional vibration damper comprising flanged bushings made of a liquid crystal polymer. This material has proven generally well-suited for use in viscous torsional vibration dampers.

[0007] However, the availability of the material is limited. Furthermore, the material properties can vary depending on the order state of the respective batch and even the degree of order of the polymer structure, which also results in a variance between the crystalline and the disordered liquid state.

[0008] At the same time, however, when using LCP bushings, the interactions with the silicone oil are very low and therefore almost ideal, which overall makes the use of LCP bushings very advantageous for use in viscous torsional vibration dampers.

[0009] The object of the present invention is therefore to provide a viscous torsional vibration damper or a viscous torsional vibration absorber which, comparable to LCP material, ensures a longer service life than conventional viscous torsional vibration dampers or absorbers even at temperatures above 130°C and further improves the viscous torsional vibration damper or absorber with regard to its service life.

[0010] This object is achieved by a viscous torsional vibration damper or a viscous torsional vibration absorber having the features of claim 1.

[0011] A viscous torsional vibration damper or absorber according to the invention comprises a hub part that can be attached to a crankshaft of an engine, in particular an internal combustion engine, and a flywheel that is rotatably mounted relative to the hub part. The hub part can comprise a housing or, as shown in DE 10 2016 113 719 A1, merely an edge section of a hub. A shear gap filled with silicone oil is formed between the hub part and the flywheel, in which shear gap one or more plain bearing components are arranged for the sliding-guided mounting of the flywheel. The plain bearing component(s) are, according to the invention, formed at least in regions from a polyphthalamide-containing plastic with more than 50 wt.% PPA.

[0012] The viscous torsional vibration damper or absorber according to the invention is thus characterized, with reference to the embodiment of DE 10 2013 006 751 A1, in that the flanged bushings are made of polyphthalamide (PPA). According to the definition of the present invention, this term also includes a modified PPA, preferably an olefin-modified PPA. It has been shown that this material interacts more strongly with silicone oil than LCP, although these interactions are still significantly lower compared to conventional bearings, e.g., made of PA66 or the like.

[0013] At the same time, the material is characterized by good wear properties due to its smooth surface.

[0014] In particular, the friction properties of the PPA material are significantly better than most other materials.

[0015] The choice of PPA material over LCP material is surprising in that they represent a fundamentally different material class, exhibiting significantly lower interactions with silicone than previous PA bushings and, conversely, better frictional properties than LCP bushings. These frictional properties improve the overall service life of the plain bearing. Thus, the PPA material represents an optimized compromise between traditional PA66 plain bearing components and LCP plain bearing components in the field of viscous torsional vibration dampers or absorbers.

[0016] The use of such plain bearing components according to the invention in a viscous torsional vibration damper or absorber also enables a longer service life of the viscous torsional vibration damper or absorber than other torsional vibration dampers with conventional bushings or bearing materials.

[0017] The polyphthalamide used can be densified and / or heat-stabilized. PPA is a semi-crystalline, partially aromatic polyamide, so different densities are possible depending on the molecular weight and the crystalline content.

[0018] The preferred density of the PPA-containing plastic used according to the invention according to ISO 1183 (Method A) in the current version of May 2021 is between 1.10 and 1.20 g / cm 3< for the aforementioned application area as plain bearing components in viscous torsional vibration dampers and / or absorbers, particularly preferably 1.13 + / - (0.15) g / cm 3< .

[0019] The plain bearing components can be advantageously manufactured by injection molding.

[0020] The material of the plain bearing components can be fiber-reinforced, especially glass fiber-reinforced. However, a homogeneous PPA material without glass fibers also exhibits sufficiently high strength.

[0021] The shrinkage during production is less than 2.5% compared to the molten state according to ASTM D955 in the current version from May 2021. This enables a very precise production of the plain bearing component.

[0022] The glass transition temperature can exceed 150°C, which is outside the typical continuous operating temperature of a viscous vibration damper, which is usually between 110 and 130°C. Temperatures of approximately 150°C can occur briefly during use, but it has surprisingly been shown that the PPA material of the plain bearing component can withstand these short-term temperature peaks without extensive material changes.

[0023] Thus, polyphthalamide has proven to be an excellent compromise solution for improving friction properties and simultaneously reducing the deterioration of the interaction with silicone oil compared to LCP material, taking into account the boundary conditions of mechanical stability, vibration and temperature stability of plain bearing components for the application area of ​​viscous vibration dampers.

[0024] An embodiment of the invention is explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 is a perspective partial sectional view of a viscosity torsional vibration damper or viscosity torsional vibration absorber according to the invention; Fig. 2 is a cross-sectional view of the viscosity torsional vibration damper or viscosity torsional vibration absorber from Figure 1; and Fig. 3 a perspective view of a variant of a flange bushing.

[0025] In the following description of the figures, terms such as top, bottom, left, right, front, rear, etc., refer exclusively to the exemplary representation and position of the viscous torsional vibration damper, flanged bushing, flywheel, and the like chosen in the respective figures. These terms are not to be understood as limiting; i.e., these references may change due to different operating positions or the mirror-symmetrical design, etc.

[0026] In the Fig. 1Reference numeral 1 denotes an embodiment of a viscous torsional vibration damper or viscous torsional vibration absorber according to the invention. The viscous torsional vibration damper or absorber essentially comprises an annular housing 7, which is non-rotatably connected to the crankshaft M of an engine. Connected within the housing 7 is a flywheel 2, which is surrounded by a silicone oil serving as a damping medium and fills a shear gap 3 between the housing 7 and the flywheel 2.

[0027] As in Fig. 2 As can be clearly seen, the flywheel 2, which is loosely mounted on the housing 7, is guided radially and axially within the housing by plain bearing components 4 in the form of flanged bushings with a preferred L-shaped cross-section. The plain bearing components 4 are located in a shear gap 3 between the flywheel 2 and the housing 7, with the shear gap 3 being filled with silicone oil.

[0028] To minimize damage, particularly a reduction in viscosity, to the silicone oil caused by interactions with the material from which the flanged bushings are made, the flanged bushings are made of polyphthalamide. With such PPA-manufactured flanged bushings, a reduction in the viscosity decrease of the silicone oil is noticeable compared to PA66 flanged bushings, resulting in a significant extension of the service life.

[0029] The use of such flanged bushings made of polyphthalamide makes it possible to save materials such as fan disks, which in conventional viscous torsional vibration dampers or absorbers cool the silicone oil that heats up during operation, in order to minimize damage to the silicone oil with the flanged bushings made of polyamide compounds used previously in the state of the art.

[0030] At the same time, the improved friction properties of the material used compared to liquid crystal polymers extend the service life of the plain bearing component and the plain bearing as a whole.

[0031] The term “plain bearing component 4” in the context of the present invention is not limited to a flanged bushing from the Fig. 1 -3 The term can also be understood to refer to one or more axial bearing rings for the plain bearing of the flywheel or one or more plain bearing plugs for the plain bearing of the flywheel. Such alternative bearing elements are known to those skilled in the art from the field of viscous torsional vibration dampers.

[0032] The plain bearing component can also be manufactured as a composite component and have only one segment, e.g. in the design of an axial bearing ring, a plain bearing ring made of polyphthalamide and a support ring made of metal.

[0033] The plain bearing component is designed as a single piece and, in particular, is free of any coating, so that the plain bearing component is in contact with the silicone oil at least in some areas.

[0034] The sliding bearing component(s) are advantageously designed to be particularly thin. This allows them to be arranged in a shear gap with a gap width of less than 0.5 mm. At the same time, the choice of PPA material ensures high mechanical strength.

[0035] Specifically, the plain bearing component(s) may have an L-shaped cross-section, as is also the case Fig. 2 This allows the flywheel ring 2 to be supported from two sides – radially and axially. However, the PPA plain bearing component can easily withstand this double mechanical friction load over a long operating period.

[0036] The PPA can also be olefin-modified, particularly polyethylene or PE-modified, for example, at 10-20 wt.%. Additives of less than 7% can also be present in the plastic. The actual plastic of the plain bearing component can thus be pure PPA or a blend and / or copolymer of PPA and PE, although the predominant proportion, i.e., more than 50 wt.%, is always PPA. Therefore, in the context of the present invention, a plain bearing component made of PPA is to be understood as a plain bearing component with a plastic predominantly made of PPA. List of reference symbols

[0037] 1Viscosity torsional vibration damper or viscosity torsional vibration absorber 2Flying ring 3Shear gap 4Flange bushing 7Housing MCrankshaft

Claims

1. Viscous torsional vibration damper or absorber (1), having a hub part, which is fastenable to a crankshaft (M) of an engine, in particular an internal combustion engine, and a vibration damper ring (2) which is mounted rotatably relative to the hub part, wherein a shear gap (3), which is filled with a silicone oil, is formed between the hub part and the vibration damper ring (2), in which shear gap one or more plain bearing components (4) are arranged for the slidingly guided mounting of the vibration damper ring (2), characterized in that the one or more plain bearing components (4) are formed, at least in some regions, by a polyphthalamide-containing plastic, with a proportion of more than 50% by weight PPA.

2. Viscous torsional vibration damper or absorber (1) according to claim 1, characterized in that the one more plain bearing components (4) are formed as flange bushings, an axial bearing ring, and / or a plain bearing plug.

3. Viscous torsional vibration damper or absorber (1) according to any one of the preceding claims, characterized in that the plain bearing component (4) is formed as an injection-molded body.

4. Viscous torsional vibration damper or absorber (1) according to claim 1 or 2, characterized in that the material of the plain bearing ring (4) made from polyphthalamide has a density of between 1.10 and 1.20 g / cm3, most preferably 1.13±(0.15) g / cm3.

5. Viscous torsional vibration damper or absorber (1) according to any one of the preceding claims, characterized in that the plain bearing component (4) is formed as a single-piece and in particular to be coating-free, so that the plain bearing component (4) is in contact, in at least some regions, with the silicone oil.

6. Viscous torsional vibration damper or absorber (1) according to any one of the preceding claims, characterized in that the plain bearing component (4) is fiber reinforced, in particular glass-fiber reinforced.

7. Viscous torsional vibration damper or absorber (1) according to any one of the preceding claims, characterized in that the plain bearing component (4) consists of a homogeneous, in particular fiber-free, polyphthalamide material.

8. Viscous torsional vibration damper or absorber (1) according to any one of the preceding claims, characterized in that the material of the plain bearing component (4) has a shrinkage in comparison with a molten state of less than 2.5%.

9. Viscous torsional vibration damper or absorber (1) according to any one of the preceding claims, characterized in that the one or more plain bearing components (4) are arranged in the shear gap (3) with a gap width of less than 0.5 mm.

10. Viscous torsional vibration damper or absorber (1) according to any one of the preceding claims, characterized in that the one or more plain bearing components (4) have an L-shaped cross-section in order to mount the vibration damper ring (2) from two sides.