Vibration damper with pull stop

Abstract

Vibration dampers for vehicle chassis, including - a damper tube (1), - a piston rod (2) which can oscillate back and forth in the damper tube (1) in the axial direction, - a working piston (3) arranged on the piston rod (2), - a sealing assembly (4) closing the damper tube (1), through which the piston rod (2) is passed, - a spring element (6) arranged in the area between the working piston (3) and the locking assembly (4) with an annular base body (7) which encloses the piston rod (2) forming an annular space between the base body (7) and the piston rod (2) and which has a top surface (8) facing the locking assembly (4) and a bottom surface (9) facing the working piston (3), wherein the spring element (6) has a lip element (10) at least on the top surface (8) or on the bottom surface (9), wherein the spring stiffness of the lip element (10) is less than that of the base body (7), characterized in that a tension stop spring (5) is arranged between the working piston (3) and the locking assembly (4), and wherein the spring element (6) is arranged between the tension stop spring (5) and the locking assembly (4), wherein the spring stiffness of the lip element (10) or the lip elements (10) is less than that of the tension stop spring (5).

Description

[0001] The present invention relates to a vibration damper for chassis of motor vehicles according to the preamble of claim 1.

[0002] Such a vibration damper is known from publication DE 10 2006 005 621 A1. This publication describes in the Fig. 1 and Fig. 2 two differently designed spring elements, which are arranged between the tension stop spring and the locking assembly that closes the damper tube. The present invention derives from the in Fig. The embodiment shown in Figure 2 represents the closest prior art. A spring element designed as a circular elastomer body 31 is arranged between the rebound stop spring (coil spring 19) and the closure assembly (piston rod guide 5) that closes the damper tube (cylinder 3). The elastomer body 31 is supported axially on the spring plate 23, which also supports the rebound stop spring. The spring plate 23 has a circumferential annular web 49, which represents an axial stop for the hydraulic assembly 15 and thus determines its minimum compressed length.

[0003] During driving, road-induced vibrations occur which act on the vibration damper. During the wheel rebound process, the rebound stop spring engages at a defined amplitude, i.e. the elastomer body 31 comes into contact with the closure package and the rebound stop spring and the elastomer body are compressed. This engagement of the rebound stop spring leads to the vibrations spreading via the piston rod into the body and consequently into the passenger compartment. This can result in unwanted noises and / or oscillations and / or vibrations which, among other things, reduce driving comfort. In addition, unwanted noises also arise when the elastomer body detaches from the closure package again as part of a compression stage movement of the vibration damper (piston rod moves into the damper tube).This separation process also transmits vibrations and mechanical shocks via the piston rod into the body and passenger compartment, resulting in noise.

[0004] Further vibration dampers of this type are disclosed in the publications DE 695 03 887 T2, DE 10 2006 022 490 A1, DE 10 2007 037 954 A1, EP 0 335 201 A1, US 2 642 845 A and EP 2 600 029 A1. Disclosure of the invention

[0005] It is an object of the present invention to provide a vibration damper in which the noise generation and vibration transmission into the vehicle body described above is significantly reduced and ideally minimized.

[0006] This problem is solved by a vibration damper with the features of claim 1.

[0007] The starting point for solving the above-mentioned technical problem is the idea of ​​optimising the behaviour of the vibration damper with regard to the introduction of vibrations and shocks when the spring element or the rebound stop spring engages in a rebound movement of the piston rod and when the spring element or the spring element and the rebound stop spring detach in a compression movement of the piston rod.

[0008] Starting with a vibration damper having the features of the preamble of patent claim 1, the invention proposes that the spring element have a lip element at least on the top or bottom side, wherein the spring stiffness of the lip element is lower than that of the base body. Because, in addition to the base body, a lip element is provided on at least one side (top or bottom) of the base body, the spring stiffness of the lip element, the spring stiffness of which is lower than that of the base body, the vibrations and shocks are absorbed to a large extent. The elastically deformable lip element dampens the vibrations and shocks through its deformation, so that they are only transmitted to a significantly reduced extent via the piston rod and structural components into the vehicle body. In this way, noise generation is significantly reduced.A reduction in noise and vibration also leads to an increase in driving comfort.

[0009] According to one embodiment of the invention, the spring element has a lip element on both its upper and lower sides. This double-sided arrangement of the lip elements leads to an effective reduction in noise generation and thus to acoustic improvements during operation. Compared to a single-sided arrangement, the lip elements arranged on both sides result in greater damping and energy absorption of vibrations and shocks. Nevertheless, there may be applications (e.g., when using the spring element according to the invention in a vibration damper without an additional tension spring) where a lip element on only one side of the base body is sufficient to achieve the desired damping and absorption effect.

[0010] According to one embodiment of the invention, the lip elements are formed integrally with the annular base body. The spring element can then be manufactured as an injection-molded part, which is particularly advantageous for the cost-effective production of large quantities of spring elements according to the invention for series production.

[0011] According to one embodiment of the invention, the spring element has pressure equalization bores through which damping medium can flow out of or into the annular space during elastic deformation of the spring element. These pressure equalization bores effectively and simply prevent the spring element from becoming suctioned to the locking element of the vibration damper due to the formation of a vacuum in the annular space enclosed by the spring element. This ensures that the spring element always releases reliably from the locking assembly, especially after large deformations of the spring element.

[0012] According to one embodiment of the invention, the pressure equalization bores are arranged in the lip elements and in the base body. If the lip elements initially contact the closure assembly, for example during an extension movement of the piston rod (rebound movement), and then deform as the extension movement continues, the damping medium flows out of the annular space enclosed by the spring element through the pressure equalization bores in the lip elements. At the same time, the damping medium can also flow out through the pressure equalization bores arranged in the base body. If the lip elements are significantly deformed, the pressure equalization bores arranged in the lip elements can become closed; in this case, the damping medium can flow out of the annular space through the pressure equalization bores arranged in the base body.

[0013] The above description regarding the outflow of damping medium from the annular space also applies analogously to the inflow of damping medium into the annular space when the spring element relaxes from its compressed state. Adherence of the spring element to the sealing assembly due to a negative pressure arising in the annular space is reliably prevented by pressure equalization via the pressure equalization bores.

[0014] According to the invention, a tension stop spring is arranged between the working piston and the locking assembly, with the spring element being positioned between the tension stop spring and the locking assembly. Measurements on test benches have shown that vibrations and shocks are effectively dampened and the vibration and shock energy absorbed when a tension stop spring is present between the working piston and the locking assembly, provided the lip elements are arranged on both sides of the spring element, i.e., when a first lip element is arranged on the upper side facing the locking assembly and a second on the lower side of the base body facing the working piston. In this way, unwanted vibration transmission into the vehicle body and unwanted noise generation are effectively minimized.

[0015] If the vibration damper has a rebound spring between the working piston and the closure assembly, and the spring element is arranged between the rebound spring and the closure assembly, then, according to the invention, the spring stiffness of the lip elements should not only be lower than that of the base body of the spring element, but also lower than that of the rebound spring, in order to prevent a relatively undamped vibration transmission into the body via the rebound spring. In particular, mechanical coil springs, which are frequently used as rebound springs in vibration dampers, have only limited damping properties for damping the road-induced vibrations and shocks that occur during driving.According to the invention, the spring element, which has lip elements with a lower spring stiffness than that of the rebound spring, is inserted into the transmission path for the road-induced vibrations and shocks in such a way that the vibrations and shocks are largely dampened and the vibration and shock energy is largely absorbed. The lip elements, with a softer spring stiffness (often referred to as spring rate) compared to the base body and the rebound spring, ensure that the damping effect of the spring element according to the invention begins at significantly lower forces than if only an elastomer body with a comparatively high spring stiffness were arranged between the rebound spring and the closure assembly.

[0016] It can also be expressed as follows: the spring element according to the invention is interposed in the transmission path of the vibrations and shocks between the tension stop spring and the locking assembly in such a way that the damping effect of the spring element for the road-induced vibrations and shocks begins at significantly lower forces due to the lip elements with comparatively low spring stiffness than if an elastomer base body with comparatively high spring stiffness is arranged between the tension stop spring and the locking assembly.

[0017] In principle, the lip elements can be made of a different material than the base body of the spring element. With such a design of the spring element, the designer has the option of selecting the material of the lip elements so that it exhibits the desired spring stiffness for a given shape of the lip elements. For cost-effective production of large quantities of the spring elements according to the invention, manufacturing them as a one-piece injection-molded part is advantageous. In this case, the base body and lip elements are made of the same material. The spring stiffness of the lip elements can then be adjusted both by their geometric design and by suitable post-treatments (e.g., tempering, etc.).

[0018] The invention will be explained in more detail below with reference to a drawing. Short description of the drawings Fig. 1 shows a vibration damper according to the invention in half section; Fig. 2 shows the combination of rebound spring and spring element in a side view without damper tube; Fig. 3a, Fig. 3b show the spring element in a top view ( Fig. 3a) and in a half section ( Fig. 3b) along the section line AA from Fig. 3a; Fig. Figure 4 shows a force / displacement diagram in which the force / displacement behavior of the spring element according to the invention is compared to that of an elastomer body without lip elements known from the prior art (e.g. DE 10 2006 005 621 A1). Embodiments of the invention

[0019] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0020] In Fig. Figure 1 shows a vibration damper according to the invention. A piston rod 2, which can oscillate back and forth in the direction of the longitudinal axis of the damper tube (i.e., in the axial direction), is arranged in a damper tube 1. A working piston 3 is attached to the piston rod. The damper tube is filled with damping medium (e.g., hydraulic oil), and during operation, this medium flows through the working piston, generating damping forces when the piston rod moves out of the damper tube (so-called rebound movement of the piston rod) or into the damper tube (so-called compression movement of the piston rod). The working piston 3 divides the interior of the damper tube 1 into a working chamber on the piston rod side and a working chamber further away from the piston rod. The sealing assembly 4 is fixedly seated in the damper tube and seals it tightly against the environment. The sealing assembly 4 is penetrated by the piston rod 2.The movements of the piston rod are guided by the locking package 4. The locking package is therefore often referred to as a sealing and guide package.

[0021] Fig. 2 shows the vibration damper according to the invention according to Fig. Figure 1 is shown in a slightly enlarged representation for improved clarity and without the damper tube 1 and without other components of the vibration damper. In the working chamber on the piston rod side, a tension stop spring 5 is arranged between the working piston 3 and the locking assembly 4. In the illustrated embodiment, this spring is designed as a mechanical coil spring. The end of the tension stop spring 5 facing the working piston is supported by a spring plate 21, which in turn is axially supported by the piston rod 2. The end of the tension stop spring 5 facing the locking assembly 4 is supported by a spring plate 22, which in turn is axially supported by the piston rod 2. The spring element 6 is arranged between the tension stop spring 5 and the locking assembly 4.The spring element 6 has a base body 7, on the upper side of which, facing the locking assembly 4, and on the lower side of which, facing the working piston 3, a lip element 10 is arranged. The spring stiffness of the lip elements 10 is lower than that of the base body 7 and that of the rebound stop spring 5. From a predetermined amplitude, during an extension movement of the piston rod 2 (rebound movement), the upper lip element of the spring element 6 contacts the locking assembly 4. With a continued extension movement of the piston rod 2, the lip elements 10 are then compressed. This dampens vibrations and shocks, and the vibration and shock energy is converted into deformation energy and thus absorbed.The spring element 6, with its lip elements 10, thus prevents vibrations and shocks from being transmitted to an undesirable extent via the tension stop spring 5 into the piston rod 2 and from there into the vehicle body and thus into the passenger compartment.

[0022] Even when the spring element 6 detaches from the locking assembly 4 due to a compression movement of the piston rod 2 (piston rod 2 moves into the damper tube 1), vibrations and / or shocks are introduced into the piston rod and transmitted to the vehicle body. This also leads to undesirable noise in the passenger compartment. These vibrations and shocks are also effectively dampened and absorbed by the lip elements 10 of the spring element 6. The generation of undesirable noise during the detachment process of the spring element 6 from the locking assembly 4 is thus significantly reduced or minimized.

[0023] The spring element 6 has pressure equalization bores 11, which are arranged on one side in the base body 7 and on the other side in the lip elements 10. Damping medium can flow out of the annular space between the piston rod 2 and the spring element 6 through these pressure equalization bores 11 when the spring element 6 is compressed during a rebound movement of the piston rod 2. Likewise, damping medium can flow from the piston-rod-side working chamber of the vibration damper into the annular space between the piston rod 2 and the spring element 6 when the spring element 6 relaxes from a compressed state during a compression movement of the piston rod 2. The resulting pressure equalization ensures that the spring element 6 does not suction itself to or adhere to the locking assembly 4 and does not detach from it.

[0024] Fig. Figure 3a shows the spring element 6 in a top view. Visible is the upper surface 8 of the spring element 6, which in the installed state faces the locking assembly, and the lip element 10 arranged on the upper surface 8 with the pressure equalization bores 11 arranged therein. Fig. Figure 3b shows the spring element 6 according to Fig. 3a in axial half-section along the section line AA from Fig. 3a. The spring element 6 has a base body 7 which is bellows-shaped and curves radially outwards. Pressure equalization bores 11 are provided in the base body 7, one of which is located in Fig. Figure 3b shows that lip elements 10 are arranged on both sides of the base body 7. The lip elements 10 are integrally formed with the base body 7. Pressure equalization bores 11 are arranged in the lip elements 10. The spring element 6 is manufactured as an injection-molded part. The lip elements 10 have a significantly lower spring stiffness than the base body 7. This lower spring stiffness is achieved, on the one hand, by the considerably thinner wall thickness of the lip elements 10 compared to the base body 7. Additionally, post-treatment measures (e.g., tempering) can be carried out after injection molding to adjust the desired spring stiffness of the lip elements 10.

[0025] Fig.Figure 4 shows a force / displacement diagram for a combination of a rebound spring and a spring element 6. The diagram compares the force / displacement characteristic curve 30 (solid line) of a spring element 6 according to the invention and the force / displacement characteristic curve 31 (dashed line) of an elastomer base body without lip elements according to the prior art. It is very clearly evident that with the elastomer body according to the prior art, a rapid increase in force with a large gradient occurs even after short deformation paths. The force curve rises steeply and almost linearly even with relatively short deformation paths. With such a characteristic curve, vibration is introduced into the vehicle body with relatively undamped vibration. The hysteresis of the force / displacement characteristic curve of the spring element according to the prior art is relatively small.The force reduction when the spring element is relaxed according to the state of the art is essentially parallel and thus equally steep to the force increase during compression.

[0026] In contrast, with the spring element 6 according to the invention, the force build-up only begins at significantly larger deformation distances. In other words, with the spring element 6 according to the invention, a much lower force builds up over the same deformation distance compared to the spring element according to the prior art. Over a relatively large deformation distance (region A), only a very small force builds up in the spring element 6 according to the invention. This is the region in which the lip elements 10 deform. After the lip elements 10 have fully deformed, the deformation of the base body 7 begins (region B). In this region, the force / displacement characteristic curve is determined by the spring stiffness of the base body 7. The subsequent region C represents the region in which the tension stop spring reaches its limit.The force / displacement characteristic curve for the spring element 6 according to the invention has a significantly larger hysteresis compared to the characteristic curve for the spring element according to the prior art, which indicates a greater damping factor and thus a greater energy absorption capacity of the combination of tension stop spring 5 and spring element 6 than in the prior art. REFERENCE MARK LIST 1 spring element 2 piston rod 3 working pistons 4 closure pack 5 Tension stop spring 6 spring element 7 basic bodies 8 Top 9 Bottom 10 lip element 11 pressure equalization openings; pressure equalization bores 21 spring plates 22 spring plates 30 Force / Displacement Characteristic Curve 31 Force / Displacement Characteristic Curve Area Area B Area C

Claims

[1] Vibration dampers for chassis of motor vehicles, comprising - a damper tube (1), - a piston rod (2) which can be moved back and forth in an oscillating manner in the axial direction in the damper tube (1), - a working piston (3) arranged on the piston rod (2), - a closure package (4) closing the damper tube (1) through which the piston rod (2) is guided, - a spring element (6) arranged in the area between the working piston (3) and the closure assembly (4) with an annular base body (7) which encloses the piston rod (2) to form an annular space between the base body (7) and the piston rod (2) and which has an upper side (8) facing the closure assembly (4) and an underside (9) facing the working piston (3), wherein the spring element (6) has a lip element (10) at least on the upper side (8) or on the underside (9), wherein the spring stiffness of the lip element (10) is lower than that of the base body (7), characterized by that a rebound stop spring (5) is arranged between the working piston (3) and the closure package (4), and wherein the spring element (6) is arranged between the rebound stop spring (5) and the closure package (4), wherein the spring stiffness of the lip element (10) or the lip elements (10) is lower than that of the rebound stop spring (5). [2] Vibration damper according to claim 1, wherein the spring element (6) has a lip element (10) on both the upper side (8) and the lower side (9). [3] Vibration damper according to claim 1 or 2, wherein the lip elements (10) are formed integrally with the annular base body (7). [4] Vibration damper according to one of the preceding claims, wherein the spring element (6) has pressure equalization openings (11) through which damping medium can flow out of the annular space or into the annular space upon elastic deformation of the spring element (6). [5] Vibration damper according to claim 4, wherein the pressure equalization openings are designed as pressure equalization bores (11) which are arranged in the lip elements and in the base body (7).

Images