Self-regulating damping unit

Abstract

The present invention relates to a self-adjusting damping unit (10) comprising a cylinder (12) having a first working chamber (18) and a second working chamber (20), a piston (14), a piston rod (22), and a through hole (34, 36, 38, 40) between the first working chamber (18) and the second working chamber (20). The damping unit (10) further comprises a movable counterweight (26) that alters the cross-sectional area (42) of the through hole (34, 36, 38, 40), wherein the movable counterweight (26) is movably mounted such that a delay in the piston (14) causes an expansion of the cross-sectional area (42). The invention also relates to a seatbelt unit comprising a seatbelt and the damping unit (10).

Description

Technical Field

[0001] The present invention relates to a self-adjusting damping unit, comprising: a cylinder filled with fluid; a piston dividing the interior of the cylinder into a first working chamber and a second working chamber and disposed displaceably within the cylinder; a piston rod connected to the piston and protruding from the cylinder at one end; and at least one through hole adapted to allow fluid communication between the first working chamber and the second working chamber. Background Technology

[0002] There are various applications in which damping units are expected to adjust themselves independently. For example, in industrial applications, it might be desirable to use a single damping unit to uniformly cushion masses of varying sizes. In another example, in modern vehicles, various safety systems intervene to protect occupants in the event of a collision. These systems include, for example, belt tensioners, airbags, or belt force limiters. First, a belt tensioner ensures pre-tensioning of a belt that may be too loosely fastened relative to the occupant. Then, the airbag deploys very rapidly. To protect the occupant's shoulder area while simultaneously utilizing the airbag with maximum effect, a belt force limiter ensures that the occupant's head contacts the airbag after a certain time and / or distance, and does not exceed a critical load on the shoulder area, by allowing the belt to yield (i.e., deploy) a predetermined distance.

[0003] However, systems known from the prior art are not suitable, or are only suitable by adding additional sensors, to respond to different occupant weights and adjust the force required to restrain the occupant on the force limiter to ensure that the occupant is not injured or at least to reduce the risk of injury. Summary of the Invention

[0004] Therefore, the object of the present invention is to provide a self-adjusting damping unit that can be used, for example, as a force limiter and is designed to adapt to the weight of the occupant.

[0005] This task is solved by a self-adjusting damping unit according to the invention, which includes a fluid-filled cylinder, a piston dividing the interior of the cylinder into a first working chamber and a second working chamber and movably disposed within the cylinder, a piston rod connected to the piston and protruding from the cylinder at at least one end of the cylinder, and at least one through-hole adapted to allow fluid communication between the first working chamber and the second working chamber. The damping unit is characterized by further including a movable counterweight adapted to change the available channel cross-section of the at least one through-hole allowing fluid passage due to relative movement with respect to the at least one through-hole. The movable counterweight is movably mounted relative to the at least one through-hole such that retardation of the moving piston or the moving piston rod causes an expansion of the channel cross-section of the at least one through-hole.

[0006] It should be noted that the phrase "changing the available channel cross-section" can include both partial opening / closing of the channel cross-section and complete opening / closing of the channel cross-section. In other words, the movable counterweight can be positioned in a first position (e.g., a resting position) to at least partially close the orifice, thereby reducing the flow rate of fluid from one working chamber to another to a value corresponding to the available channel cross-section of the orifice (or preventing the flow), and can be positioned in a second position (e.g., a release position) in which the movable counterweight is displaced maximally away from the resting position to at least partially, and particularly completely, release the orifice, thereby increasing the flow rate of fluid from one working chamber to another.

[0007] To explain the principle using the example of a force limiter, a movable counterweight can be configured on the piston rod such that, during initial acceleration of the piston rod, the movable counterweight is held in its rest position, the damping unit has a damping force corresponding to the cross-sectional area of ​​at least one through-hole through which fluid can flow, and once the acceleration of the piston rod decreases, the movable counterweight displaces from its rest position toward the release position due to its inertia, causing the cross-sectional area of ​​the through-hole to increase and the damping force of the corresponding damping unit to decrease. Of course, the damping unit according to the invention can be suitably configured for pressure loads on the piston rod, i.e., pushing the piston rod into the cylinder of the damping unit.

[0008] This provides a damping unit capable of maintaining a constant acceleration of the piston rod; that is, in the case of a force limiter, it maintains a constant belt acceleration regardless of speed and / or the force acting upon it. Therefore, the available damping distance can be utilized with optimal effect. With a force limiter, the damping unit according to the invention allows a heavier person to bear a greater force on their shoulder than a lighter person through the belt, but regardless of the person's weight, the belt speed decreases by the same amount for the same damping distance. Therefore, the damping unit can be made sensitive to the occupant.

[0009] For example, the damping unit according to the invention may have a stroke of 150 mm and / or allow a travel speed of 15 m / s.

[0010] It should also be noted that the damping unit according to the invention can operate without any power source. Therefore, a fully functional damping unit can be provided even in the event of a complete failure of the vehicle's power supply. This means that there is no need to operate the sensor devices with electricity. Nor is any information from the vehicle's sensor system required to adjust and operate the damping unit based on occupant needs.

[0011] It is also conceivable that the piston rod protrudes from the cylinder at both longitudinal ends. In such an embodiment, the piston is not positioned at the longitudinal ends of the piston rod, but rather can be positioned, for example, approximately centered relative to the length of the piston rod. Thus, for example, the cylinder of the damping unit can be completely filled with fluid. This reduces turbulence of the damping fluid (e.g., oil) during the operation of the damping unit, allowing the damping unit to be used regardless of its position, since the cylinder essentially no longer contains any gas.

[0012] In addition, a compensation reservoir, diaphragm reservoir, or the like can be provided. If the reservoir is used in a pressurized working chamber, a valve can be added separately. This means that the damping unit can operate in any position even if the piston rod protrudes from only one end, because the volume compensation is located outside the working chamber. This may be particularly feasible for dual-tube dampers, diaphragm dampers, etc.

[0013] In another embodiment of the invention, a seal may be provided on the outer periphery of the piston to seal the piston against the cylinder. This prevents fluid from flowing from one working chamber to another across the outer periphery of the piston.

[0014] Advantageously, an elastic element, particularly a spring, can be connected to the movable counterweight, which is adapted to push the movable counterweight into its rest position. On the one hand, this ensures that the movable counterweight is actually in its rest position when the piston rod begins to move; on the other hand, the spring stiffness of the elastic element can be used to set a delay required to allow the movable counterweight to move from its position against the spring force of the elastic element toward the release position. It should generally be noted that the rest position and / or release position can be defined relative to the through-hole. The elastic element also allows the damping unit to be used multiple times by displacing the movable counterweight back to the rest position after the damping unit has been triggered.

[0015] The elastic element connected to the movable counterweight can also be adapted to apply a predetermined force to the movable counterweight when it is in a stationary position. This allows a predetermined preload to be applied to the movable counterweight in its stationary position, in particular, so that the force required to move the movable counterweight away from its stationary position can be defined very precisely.

[0016] Specifically, a stop can be provided, on which an elastic element connected to the movable counterweight presses the movable counterweight. With the aid of such a stop, the resting position of the movable counterweight can be defined, and the resting position of the movable counterweight can be repeatedly approached by means of the elastic element. For example, the stop can be configured as a protrusion projecting radially outward from the piston rod, which can be integrally formed with the piston rod, or the stop can be configured as a spring washer engaging in a groove in the piston rod.

[0017] Furthermore, when the movable counterweight is in its stationary position, a predetermined portion of at least one through-hole can remain open to allow fluid passage. This can be achieved, in particular, by the movable counterweight not completely closing the through-hole in its stationary position. However, a fluid connection may also exist between the two working chambers, which is not obstructed by the movable counterweight. This allows for defining the initial fluid flow at the start of movement of the piston rod or piston within the damping unit's cylinder. However, the movable counterweight can also completely close the through-hole. For this purpose, an additional overflow cross-section should be added at another point in the piston system. Specifically, this should correspond to the channel cross-section, which in turn corresponds to the movable counterweight in its fully closed position. This allows for an expansion of the corresponding cross-section for a given installation space.

[0018] The remaining open cross-section of the through hole associated with the resting position of the movable counterweight can be, for example, 1 mm. 2 Up to 4mm 2 Especially around 2.5mm 2 The fully open cross-section of the through-hole can be, for example, 4mm. 2 Up to 10mm 2 Especially about 6mm 2 The ratio of the fully open cross-section of the through-hole to the cross-section of the through-hole associated with the resting position of the movable counterweight can be, for example, 1 to 10, particularly 1 to 4. Of course, this depends heavily on the proportions of the damping unit and the intended use, and deviations from the foregoing cross-sections and ratios are also possible within the scope of this invention.

[0019] It is also conceivable that, with the movable counterweight in a stationary position, no through-hole remains (or even partially) open between the two working chambers. In this case, a compressible damping fluid (e.g., a gas such as air) can be used in the cylinder of the damping unit according to the invention to provide initial damping. Furthermore, the first portion of the working chamber may include a compressible damping fluid, and the second portion of the working chamber may include an incompressible damping fluid, allowing these two functions to be combined.

[0020] Advantageously, the piston rod may have a longitudinal bore extending over at least a portion of its length. Thus, this longitudinal bore can form part of a through-hole. Specifically, the longitudinal bore may be coaxial with the longitudinal central axis of the piston rod. Furthermore, the longitudinal bore may extend particularly into the region on the piston rod where the piston is mounted. In the region at the end of the longitudinal bore opposite the piston, at least one transverse bore may extend radially outward relative to and from the longitudinal bore to allow fluid communication between the two working chambers via the longitudinal bore and at least one transverse bore. In such an embodiment, the transverse bore can therefore be considered a through-hole at least partially covered by a movable counterweight in a resting position.

[0021] Additional through-holes can also be provided, which are partially or completely closed by the movable counterweight in its rest position, and opened by displacement of the movable counterweight from its rest position to allow fluid passage. These additional through-holes can be implemented either by the aforementioned plurality of transverse holes or by additional connecting portions of the two working chambers (e.g., through-holes in the piston), in which, in the rest position of the movable counterweight, the through-holes in the piston can be, for example, at least partially covered by the movable counterweight simultaneously with at least one transverse hole.

[0022] Specifically, an additional stop can be provided, against which the movable counterweight rests when it has been displaced to its maximum displacement from its rest position. At this position of maximum orifice (referred to above as the "release position"), a larger channel cross-section is released for fluid flow between the two working chambers, compared to when the movable counterweight is in its rest position. For example, the stop can be constructed as a tube protruding from the piston toward the movable counterweight, with a portion of the piston rod passing through the interior of the tube.

[0023] The damping unit may also include an impact absorber that contacts the movable counterweight in its initial rest position. Within the scope of this invention, the impact absorber is a mass body capable of absorbing the initial impact applied to the movable counterweight to prevent release of the movable counterweight's mass from a stop associated with its rest position during the initial acceleration of the piston rod. For example, the impact absorber may be annular. In this case, the impact absorber can be mounted with its inner diameter in a tube protruding from the piston toward the movable counterweight, forming a stop for the release position. A predetermined gap may be maintained between the outer diameter of the impact damper and the inner surface of the wall of the damping unit's cylinder to allow fluid located between the piston and the impact damper to flow through the impact damper. For this purpose, the impact absorber may also have a through-hole and / or have a circumferentially non-circular inner and / or outer diameter, such as a notch.

[0024] For this purpose, the shock absorber can be connected to an elastic element that pushes the shock absorber toward the movable counterweight. This means that the impact applied to the movable counterweight can be transmitted to the shock absorber according to the principle of conservation of momentum, thereby ensuring that the movable counterweight displaces from the rest position toward the release position only after a correspondingly large delay in the piston rod, without due to the initial impact displacement on the piston rod or the movable counterweight. The shock absorber can be supported relative to the piston, specifically by means of a spring, which is radially disposed outside the aforementioned tube, which serves as a stop for the movable counterweight in the release position. Thus, in an exemplary embodiment, the radial sequence can begin with the piston rod, then the elastic element connected to the movable counterweight, followed by the stop for the release position of the movable counterweight, the elastic element connected to the shock absorber, and finally the wall of the damping unit's cylinder. In particular, the spring stiffness of the elastic element of the shock absorber can be much smaller than the spring stiffness of the elastic element connected to the movable counterweight. The preload force by which the elastic element pushes or presses the shock absorber against the movable counterweight can be configured, for example, such that it just exceeds the force caused by the weight of the shock absorber. This ensures that the shock absorber rests against the movable counterweight regardless of the orientation of the damping unit in the installed state. This further ensures that after displacement from the position where the shock absorber rests against the movable counterweight, it can move back to that position.

[0025] Simultaneously, the surface of the displaceable counterweight suitable for contacting the shock absorber and / or the surface of the shock absorber suitable for contacting the displaceable counterweight may have a texture, thereby defining surface adhesion between the displaceable counterweight and the shock absorber. This texture of at least one of the two contact surfaces should be particularly suitable for reducing surface contact and thus reducing the adhesion between the two surfaces, because if an impact is transmitted from the displaceable counterweight to the shock absorber, the shock absorber must be able to easily separate itself from the displaceable counterweight. For example, at least one of the two contact surfaces may have a texture in the form of a faceted spline profile.

[0026] It may also be desirable that the shock absorber does not immediately separate from the movable counterweight upon receiving the initial impact. For example, a predetermined setting of the surface adhesion force between the shock absorber and the movable counterweight can ensure that the movable counterweight is "carried" by the shock absorber at least within the initial range, so that the movable counterweight can be removed from its rest position once the initial impact begins.

[0027] In this respect, it should be noted that the features and effects described regarding the shock absorber / displaceable counterweight can also be applied to the surface contact between the displaceable counterweight and the stop.

[0028] The movable counterweight can be non-rotatably mounted on the piston rod, and / or the movable counterweight can have a groove on its inner surface, which is adapted to establish fluid communication between the through-hole and the working chamber where the movable counterweight is disposed, regardless of the rotational orientation of the movable counterweight relative to the piston rod. Due to this construction of the damping unit, the movement or acceleration of the movable counterweight from and / or to a rest position can be clearly defined, as unintentional obstruction of at least one through-hole can be avoided.

[0029] In order to enable the movable counterweight to be non-rotatably mounted on the piston rod, the movable counterweight may have a protrusion that engages with a recess, particularly a groove, provided on the piston rod.

[0030] On the other hand, the present invention relates to a seat belt unit, particularly for a vehicle, comprising a seat belt and a self-adjusting damping unit according to the invention, wherein the seat belt is directly or indirectly connected to one of a piston rod and a cylinder, and the other of the piston rod and cylinder is connected to an advanced component, particularly the vehicle body. Referring to the description given at the beginning, the self-adjusting damping unit according to the invention can be used as a force limiter for the seat belt in a vehicle, wherein the damping unit according to the invention provides occupant-sensitive damping, that is, damping that automatically adjusts according to the occupant's weight.

[0031] The phrase "directly or indirectly connected" should be understood to mean, for example, that as long as there is a force-transmitting connection between the two elements, the piston rod does not need to be in direct contact with the seat belt. Therefore, for example, with a three-point belt, the connection between the seat belt and the damping unit according to the invention can be achieved at at least one seat belt anchor point. More specifically, in the first example, the damping unit can be used for the attachment of the belt (to the lower part of the motor vehicle) and / or in the area of ​​the buckle and / or in the portion associated with the belt retractor. In the portion associated with the belt retractor, the damping unit according to the invention can, for example, be disposed between the vehicle body and the housing, which may also include other conceivable components of the seat belt unit, such as a belt tensioner, a check valve, etc. The housing can be displaced within a guide (e.g., a slider guide). Attached Figure Description

[0032] The invention will now be described in more detail with reference to the accompanying drawings. These drawings show:

[0033] Figure 1 This is a side sectional view of an embodiment of the damping unit according to the present invention. Detailed Implementation

[0034] exist Figure 1In this invention, the damping unit is generally indicated by reference numeral 10. The damping unit 10 includes a cylinder 12, within which a piston 14 is disposed. The piston 14 includes a sealing device 16 on its outer periphery that seals against the inner surface of the wall of the cylinder 12, such that the internal space of the cylinder 12 is divided by the piston 14 into a first working chamber 18 and a second working chamber 20. The internal space of the cylinder 12, including the two working chambers 18 and 20, is filled with a fluid, such as oil.

[0035] In further description Figure 1 Before illustrating the embodiment of the damping unit 10 according to the present invention, it should be noted that, according to Figure 1 The damping unit 10 is adapted to receive a pressure load, that is, to push the piston rod 22 connected to the piston 14 into the cylinder 12 (and the piston 14 toward...). Figure 1 (Right-side displacement).

[0036] At the end of the cylinder 12 where the piston rod 22 protrudes from the cylinder 12, the first working chamber 18 is sealed in a fluid-tight manner relative to the outside of the damping unit 10 by an additional sealing device 24.

[0037] A movable counterweight 26 is disposed on the piston rod 22 such that it can be displaced in the longitudinal extension direction of the piston rod 22. In the exemplary embodiment shown, the movable counterweight 26 is also configured to be rotatable relative to the piston rod 22. The movable counterweight 26 is pressed against a stop 30 by a spring 28, which is supported at one longitudinal end by the movable counterweight 26 and at the other longitudinal end by the piston 14. When the movable counterweight 26 contacts the stop 30, the stop 30 defines and restricts the resting position of the movable counterweight 26. The stop 30 is configured here as a spring washer that engages in a groove extending circumferentially in the piston rod 22. The spring 28 surrounds the piston rod 22 directly, rather than resting against it.

[0038] The tube 32 is connected to and extends from the piston 14 toward the movable counterweight 26, thereby defining and restricting the release position of the movable counterweight 26 when it has been moved from the release position to contact the tube 32. A spring 28 is disposed within the tube 32 when viewed in the radial direction of the damping unit 10.

[0039] A longitudinal hole 34 is provided coaxially with the center line X of the piston rod 22. On the one hand, the longitudinal hole 34 leads to the second working chamber 20 at the end of the piston rod 22 where the piston 14 is mounted. On the other hand, the longitudinal hole 34 terminates as a blind hole in the area of ​​the piston rod 22 that is radially covered by the movable counterweight 26 in its resting position. Through holes 36 extend radially outward from the longitudinal hole 34 to the piston rod 22, such that in the resting position of the movable counterweight 26, they are partially covered by the movable counterweight 26 (in this embodiment).

[0040] The movable counterweight 26 has a circumferential groove 38 inside, from which a hole 40 extends radially. In this way, the hole 40, groove 38, through hole 36, and longitudinal hole 34 provide fluid communication between the first working chamber 18 and the second working chamber 20. The channel cross-section 42 associated with the resting position of the movable counterweight 26 is defined by only a partial overlap between the movable counterweight 26 and the through hole 36. Due to the circumferential groove 38, the overlapping function is separated from the rotational orientation of the movable counterweight 26 relative to the piston rod 22.

[0041] If a sudden impact is applied to piston rod 22 now, causing piston 14 to... Figure 1 When the damping unit 10 is displaced to the right, the movable counterweight 26 is pressed against the stop 30 due to its inertia and the preload of the spring 28, and fluid flows from the second working chamber 20 into the first working chamber 18, the flow rate being limited by the channel cross-section 42. If the displacement of the piston rod 22 and therefore the displacement of the movable counterweight 26 is delayed due to its inertia, the movable counterweight 26 displaces from its rest position toward its release position, that is, it disengages from the stop 30. Therefore, the channel cross-section 42 increases because, due to the displacement of the movable counterweight 26, the hole 40 or groove 38 of the movable counterweight 26 overlaps more greatly with the through hole 36. Thus, relative to the rest position of the movable counterweight 26, the through hole 36 is positioned closer to the piston 14 than the hole 40 or groove 38 of the movable counterweight 26. In the release position where the movable counterweight 26 rests against the tube 32, the hole 40 or groove 38 overlaps with the through hole 36 to the maximum extent.

[0042] The increase in the channel cross-section 42 causes an increase in the flow velocity of the fluid flowing from the second working chamber 20 into the first working chamber 18, thereby reducing the overall damping force of the damping unit 10. When the delay at the piston rod 22 decreases, the movable counterweight 26 moves back toward the rest position due to the action of the spring 28, thereby reducing the channel cross-section 42 again and increasing the damping force of the damping unit 10.

[0043] To prevent the initial impact introduced into the piston rod 22 from displacing the movable counterweight 26 away from the stop 30 (particularly due to the elasticity of the material (e.g., metal) used for the movable counterweight 26 and / or the stop 30), the embodiment shown here includes an impact absorber 44 that contacts the movable counterweight 26 when it is in a rest position, and is adapted to absorb the initial impact introduced into the movable counterweight 26 and move away from it toward the piston 14 due to the impact, so that the movable counterweight 26 can be held in its rest position (at that point in time). For this purpose, to ensure that the impact absorber 44 rests against the movable counterweight 26, the impact absorber 44 is preloaded toward the movable counterweight 26 by a spring 46, which is supported on the piston 14 at its end opposite the impact absorber 44.

[0044] Here, the shock absorber 44 is annular and mounted with its inner diameter on the outer surface of the tube 32, allowing it to move translationally and rotationally. A spring 46 connected to the shock absorber 44 is radially disposed on the outside of the tube 32.

[0045] In order to connect piston 14 to piston rod 22, a limiting element 48 is provided on piston rod 22. This limiting element 48 is also configured here as a spring washer engaging in a groove in piston rod 22. The limiting element 48 is adapted to limit the displacement of piston 14 toward movable counterweight 26. On the side of piston 14 opposite to the limiting element 48, piston 14 is secured in its position against the limiting element 48 by a fixing element 50 such as a nut.

[0046] It should be added that the movable counterweight 26 here is essentially bell-shaped, such that it has a larger diameter in the region where the movable counterweight 26 rests against the shock absorber 44 than in the region where the movable counterweight 26 rests against the stop 30. This prevents the fluid flow into or out of the first working chamber 18 from being restricted by an excessively narrow gap between the orifice 40 (other than the channel cross-section 42) and the inner surface of the wall of the cylinder 12, and the restriction therefrom may be greater than that imposed by the channel cross-section 42, which may adversely affect or even prevent the operation of the damping unit 10 according to the invention.

Claims

1. A self-adjusting damping unit (10), comprising: The cylinder (12) is filled with fluid. A piston (14) divides the interior of the cylinder (12) into a first working chamber (18) and a second working chamber (20), and is displaceably disposed within the cylinder (12). A piston rod (22), which is connected to the piston (14) and protrudes from the cylinder (12) at at least one end of the cylinder (12), and At least one through hole adapted to allow fluid communication between the first working chamber (18) and the second working chamber (20), Its features are: The damping unit (10) further includes a movable counterweight (26) adapted to change the channel cross-section (42) of the at least one through hole that can be used for fluid passage due to relative movement with respect to the at least one through hole. The movable counterweight (26) is movably mounted relative to the at least one through hole such that a delay in the movement of the piston (14) or the piston rod (22) causes an enlargement of the channel cross-section (42) of the at least one through hole. The damping unit (10) further includes an impact absorber (44) in contact with the movable counterweight (26) in its initial rest position, the impact absorber (44) being connected to an elastic element (46) that pushes the impact absorber (44) toward the movable counterweight (26).

2. The self-adjusting damping unit (10) according to claim 1, characterized in that, A sealing element (16) is provided on the outer periphery of the piston (14), and the sealing element (16) abuts against the cylinder (12) to seal the piston (14).

3. The self-adjusting damping unit (10) according to claim 1 or 2, characterized in that, An elastic element (28) is connected to the movable counterweight (26), the elastic element being adapted to push the movable counterweight (26) into its rest position.

4. The self-adjusting damping unit (10) according to claim 3, characterized in that, The elastic element (28) is a spring.

5. The self-adjusting damping unit (10) according to claim 4, characterized in that, The elastic element (28) connected to the movable counterweight (26) is also adapted to apply a predetermined force to the movable counterweight (26) when the movable counterweight (26) is in the stationary position.

6. The self-adjusting damping unit (10) according to claim 3, characterized in that, A stop (30) is provided, and the elastic element (28) connected to the movable counterweight (26) pushes the movable counterweight (26) onto the stop (30).

7. The self-adjusting damping unit (10) according to claim 1 or 2, characterized in that, When the movable counterweight (26) is in the stationary position, a predetermined portion of the at least one through hole remains open to allow fluid to pass through.

8. The self-adjusting damping unit (10) according to claim 1 or 2, characterized in that, The piston rod (22) has a longitudinal hole extending over at least a portion of its length.

9. The self-adjusting damping unit (10) according to claim 1 or 2, characterized in that, An additional through-hole is provided, which is partially or completely closed by the movable counterweight (26) in its rest position, and is opened by displacement of the movable counterweight (26) from the rest position to allow fluid to pass through.

10. The self-adjusting damping unit (10) according to claim 1 or 2, characterized in that, An additional stop (32) is provided, which rests against the movable counterweight (26) when the movable counterweight (26) has been displaced to its maximum displacement from its rest position.

11. The self-adjusting damping unit (10) according to claim 1, characterized in that, The surface of the movable counterweight (26) adapted to contact the shock absorber (44) and / or the surface of the shock absorber (44) adapted to contact the movable counterweight (26) are textured, thereby defining surface adhesion between the movable counterweight (26) and the shock absorber (44).

12. The self-adjusting damping unit (10) according to claim 1 or 2, characterized in that, The movable counterweight (26) is non-rotatably mounted on the piston rod (22), and / or The movable counterweight (26) has a groove on its inner surface, the groove being adapted to establish fluid communication between the through hole and the working chamber (18) where the movable counterweight (26) is disposed, regardless of the rotational orientation of the movable counterweight (26) relative to the piston rod (22).

13. The self-adjusting damping unit (10) according to claim 12, characterized in that, When the movable counterweight (26) is fixed to prevent rotation relative to the piston rod (22), the movable counterweight (26) has a protrusion that engages in a recess provided on the piston rod (22).

14. The self-adjusting damping unit (10) according to claim 13, characterized in that, When the movable counterweight (26) is fixed to prevent rotation relative to the piston rod (22), the movable counterweight (26) has a protrusion that engages in a groove provided on the piston rod (22).

15. A seatbelt unit, the seatbelt unit comprising a seatbelt and a self-adjusting damping unit (10) according to any one of claims 1 to 14, wherein, The seat belt is directly or indirectly connected to one of the piston rod (22) and the cylinder (12), and the other of the piston rod (22) and the cylinder (12) is connected to the vehicle body.

16. The seatbelt unit according to claim 15, characterized in that, The seat belt unit is a seat belt unit used in vehicles.

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