DE4240775A1 - Spring element with variable resetting force - has suitably shaped extension arm to set desired resetting moment of rotary spring acting on swivel member. - Google Patents

Abstract

The spring element has a swivel member (11) swivelling about a swivel axis (12) and a rotary spring (14) set eccentric of the swivel axis to bias the swivel member against its swivel direction through an extension arm (15) supported on a supporting point (16). This extension arm (15) has over its longitudinal extension such a shape that with each swivel angle of the swivel member a desired resetting moment acts on the swivel member. The connecting point (17) of the rotary spring (14) is at a distance from the swivel member inside or outside the swivel radius of the same whilst the support point (16) for the extension arm lies on the swivel member. The extension arm can be formed by one arm end of the rotary spring. The other arm end is fixed on or near the spring attachment point. USE/ADVANTAGE - Opening spring for the bonnet or boot of a vehicle. A constant, non-constant, degressive, progressive or linear spring characteristic of the spring element can be achieved over the swivel angle of the swivel member.

Description

The invention relates to a spring element with the spring travel variable restoring force according to the preamble of Claim 1.

Such spring elements are used to the spring characteristic a torsion spring that increases linearly over the angle of rotation is to modify. Torsion springs are compared to tension springs preferred because they take up little space as well as cheap Have vibration properties.

In a known spring element of this type (DE-AS 11 81 082), which makes it easier to fold up one pivoted in the vertical direction Trunk lid or bonnet lid is inserted, the swivel link with swivel axis from one on Trunk or hood cover attached articulated arm formed, the pivot pin forming the pivot on the Vehicle body is held. The torsion spring is as Torsion spring or torsion bar running with parallel for pivoting the articulated arm extending rod axis also eccentrically on the vehicle body Pivot is held. The torsion bar lies with the straight boom on the articulated arm so that the  Folding up and closing movement of the cover one Relative movement between the point of application of the boom on Articulated arm and the axis of the torsion bar occurs in such a way that the point of attack during the closing movement to the axis of the torsion bar moves and the distance of the Point of attack from the axis of the torsion bar, the effective arm of the boom corresponds, towards the end of Folding up movement is greatest. By at the Folding up the lid and enlarging it Closing movement of the lid is effective The lever arm of the boom takes the one exerted on the articulated arm Return torque of the torsion bar to such an extent or to that the lid by the torsion bar alone each of his positions is kept in balance. At Such a spring element changes to that Restoring moment acting on the swivel link via the adjustment path only steadily, in such a way that with increasing swiveling of the Torsion bar (closing the cover) the restoring torque only grows.

The invention has for its object a spring element to create of the type mentioned, in which the Return torque of the torsion spring optional over the adjustment path can be specified in such a way that different Areas with a reset torque increase and / or decrease arise, areas with an increase in Restoring torque and areas with a decrease in Restoring torque and vice versa can follow each other and an inconsistent transition is also possible between the areas is.

The task is a spring element in the preamble of claim 1 defined genus according to the invention  by the features in the characterizing part of claim 1 solved.

By depending on the desired dependency of the Restoring torque caused by the swivel angle of the swivel link The shape of the boom is different from the stretched shape deviates and bends, bulges and curvatures can have, that for the restoring torque decisive relationship between the respectively effective Lever arm of the swivel link and the respectively effective lever arm of the boom can be changed within wide limits. This can a section with the travel of the spring element progressive spring characteristic and a section with degressive spring characteristic or sections degressive or progressive spring characteristics with different Progression or degression can be achieved. If necessary, the restoring torque can also be made zero.

Advantageous embodiments of the invention Spring element with useful training and Embodiments of the invention are in the further Claims specified.

The invention is described in more detail below with reference to exemplary embodiments shown in the drawing. There each show a schematic representation of Fig. 1 is a side view of a spring member to pivot member and torsion springs,

Fig. 2, the spring characteristic of the spring element in Fig. 1,

Fig. 3 to 7 are side views of various embodiments of a spring element,

Fig. 8 is an achievable spring characteristic of the spring element according to Fig. 7,

FIGS. 9 and 10 a side view detail of a wheel suspension with double wishbone and spring element according to the invention, namely in the rebound state (Fig. 9) and in the compressed state (FIG. 10),

Fig. 11 is a fragmentary side view of a wheel suspension with longitudinal and 12 or trailing arm and spring element according to the invention, namely in the rebound state (Fig. 11) and eingefedertem state (Fig. 12),

Fig. 13, the spring characteristic of the wheel suspension in Fig. 9 and 10 or 11 and 12,

Fig. 14 is a diagram for explaining the calculation of the spring characteristic of the spring element,

Fig. 15, a fragmentary boot of a motor vehicle with opening spring for the trunk lid,

Fig. 16 is an enlarged view of the opening spring of FIG. 15 in different pivoting positions,

Fig. 17, the spring characteristic of the opening spring in Fig. 15 and 16.

The spring element schematically sketched in FIG. 1 has a lever-like pivot member 11 which can be pivoted about a pivot axis 12 fixed to the housing, namely in the direction of the pivot angle ϕ _H , and a torsion spring 14 which loads the pivot member 11 . In the starting position shown in FIG. 1, the pivot member 11 bears against a stop 13 fixed to the housing under the action of the torsion spring 14 . The torsion spring 14 has a linearly increasing spring characteristic M _F = c _F · ϕ _F , where c _{F is} the spring constant and ϕ _{F is} the swivel angle of the torsion spring 14 . The torsion spring 14 is articulated eccentrically to the pivot axis 12 , the spring axis running parallel to the pivot axis 12 and the inner leg end 18 of the torsion spring 14 being fixed to the housing. The outer leg end of the torsion spring 14 is formed into a cantilever 15 which is supported at a support point 16 on the pivot member 11 and acts on it against the pivot direction ϕ _H thereof. Due to the eccentricity of the torsion spring 14 and the pivot axis 12 of the pivot member 11 , the distance between the spring pivot point 17 and the boom support point 16 on the pivot member 11 changes via the pivot angle ϕ _H of the pivot member 11 . In order to achieve a desired spring characteristic M _H = f (ϕ _H ) of the spring element, the extension 15 is now shaped over its longitudinal extent so that a desired restoring moment M _H acts on the pivot member 11 at each pivot angle ϕ _{H of} the pivot member 11 . The calculation bases for the shape of the boom 15 are outlined in FIG. 14. F _{F shows} the force effect of the torsion spring 14 on the pivot member 11 . The effective lever arms a _{H of} the swivel member 11 and a _{F of} the boom 15 result from this force direction F _F. The spring element is extended in two different positions and shown in dashed lines. In the dashed line position result from the changing force F _F 'other lever arms a _H ' and a _F '. By suitable shaping of the boom 15 , the ratio of the effective lever arm a _{H of} the swivel member 11 and the effective lever arm a _{F of} the boom 15 can be determined so that a very specific restoring moment M _H acts on the swivel member 11 . As can be seen from FIG. 2, the spring characteristic of the spring element can be designed as desired, with the restoring torque M _H decreasing with increasing pivoting angle ϕ _{H of} the pivoting member 11 in a certain pivoting angle range, the spring element thus showing degressive behavior, and the restoring moment in a subsequent pivoting angle range M _H again grows disproportionately with increasing swivel angle ϕ _H , so that the spring element here has a progressive spring characteristic.

In Fig. 3-6 different embodiments of a spring element are outlined, which correspond in their mode of operation. The same components are provided with the same reference numerals. In the spring element according to FIG. 3, the articulation point 17 (= spring axis) of the torsion spring 14 lies - just like in FIG. 1 - at a distance from the pivot member 11 within its pivot radius r _o . When spring element of Fig. 4, however, the pivot point located 17 of the torsion spring 14 outside the pivoting radius r _o of the pivot member 11. In both cases, the torsion spring 14 is articulated to the housing and is supported with its leg end 18 in a housing-fixed manner, and the support point 16 of the arm 15 lies on the pivot member 11 .

In the embodiment of FIG. 5, the torsion spring 14 is attached to the pivot member 11 so that its pivot point 17 (= spring axis) lies on the pivot member 11 . The leg end 18 of the torsion spring 14 which does not form the arm 15 is also fixed on the pivot member 11 . The support point 16 for the boom 15 is fixed to the housing and is arranged at a distance from the pivot axis 12 of the pivot member 11 . The support point 16 lies within the swivel radius r _{o of} the swivel member 11 .

The spring element in FIG. 6 is modified compared to the spring element in FIG. 5 only to the extent that the support point 16 for the arm 15 is also fixed to the housing but outside the pivot radius r _{o of} the pivot member 11 .

The spring element according to FIG. 7, the torsion spring is 'turn mounted on the pivot member 11, but so that it about the articulation point 17' 14 is rotatably (= spring axis) on the pivot member 11. One leg end of the torsion spring 14 'in turn forms the boom 15 , while the other leg end is not fixed as in Fig. 5 and 6 on the pivot member 11 , but is designed as a further boom 19 . The two arms 15 and 19 of the torsion spring 14 'are supported on two fixed support points 16 and 20 , one of which is a support point 16 within the swivel radius r _{o of} the swivel member 11 and the other support point 20 outside the swivel radius r _{o of} the swivel member 11 . However, both support points 16 , 20 can also be arranged inside or outside the swivel radius r _o . In the case of such a spring element, the spring characteristic can be designed as desired, and - as the spring characteristic in FIG. 8 shows - zero crossings are also possible. With a suitable design, this spring element can work with very little spring deflection, which increases the fatigue strength of the spring element.

The spring element described above is particularly suitable for use as a wheel spring in vehicles. A first exemplary embodiment of such a wheel suspension with the spring element according to the invention is shown in FIGS . 9 and 10. With a wheel suspension of this type, for reasons of comfort and safety, a compromise is sought between a soft suspension on a level road when the vehicle is unloaded in order to achieve a high level of rolling comfort and a tight suspension when loading and fast cornering, in order to ensure a spongy driving behavior when driving sharply for safety reasons avoid evasive action and / or heavily loaded vehicle. If one takes into account that a much greater deflection of the wheel spring occurs with a high load or fast cornering than with an unloaded vehicle on a level road, a wheel suspension can be achieved due to the possibility of adjusting the spring characteristic of the spring element described above, which has the spring characteristic shown in FIG. 13 . F denotes the spring force of the wheel spring with h the spring travel of the wheel spring, which is inversely proportional to the height h _{B of} the vehicle body 21 above the roadway 22 ( FIGS. 9 and 10). In area I there is only a very small change in spring force via the spring deflection. The characteristic curve only increases slightly linearly, the spring constant is small. Even low forces lead to large spring deflections. The vehicle is extremely comfortable to drive. In area II there is a major change in the spring force over the spring deflection. The spring constant is moderately large. The suspension is tight enough in terms of driving safety despite the load and still offers sufficient driving comfort. The characteristic curve area III sees a very tight suspension for high driving safety, e.g. B. in fast cornering and with extreme loads, before. Here, large forces only result in a small deflection. The spring constant is very large. Such behavior of the wheel suspension is achieved by appropriate design of the spring element described above.

In the wheel suspension shown in detail in FIGS . 9 and 10, the vehicle body 21 is coupled to the axle 24 of the wheel 25 via a double wishbone 23 . The double wishbone 23 consists of an upper wishbone 26 and a lower wishbone 27 which, on the one hand, are pivotably mounted on the vehicle body 21 at a distance from one another and, on the other hand, are pivotably connected to a coupling 28 which is fixedly connected to the axle 24 . The lower wishbone 27 forms the pivot member 11 of the spring element in FIG. 1 and carries a roller 29 which forms the support point 16 of the arm 15 of the torsion spring 14 in FIG. 1. The torsion spring 14 is articulated on the vehicle frame 21 and is also supported there with its leg end 18 . The shape of the boom 15 over its longitudinal extent is determined such that the wheel spring receives the spring characteristic specified in FIG. 13.

FIG. 9 shows the wheel spring when the vehicle is rebounded, FIG. 10 when the vehicle is rebounded. In both cases, the direction of force of the torsion spring 14 is shown on the lower wishbone 27 with F _F. A comparison with FIG. 14 clearly shows from FIGS. 9 and 10 that the ratio between the effective lever arm a _{H of} the lower wishbone 27 and the effective lever arm a _{F of} the boom 15 in the spring-loaded state of the wheel spring ( FIG. 9) is less than 1 and in the strongly compressed state of the wheel spring ( FIG. 10) is substantially greater than 1. Thus, the restoring torque M _H ( FIG. 14) applied by the torsion spring 14 is relatively low when the vehicle is rebound and the wheel spring has a soft response, while the restoring moment M _{H of} the torsion spring 14 is very large when the wheel spring is strongly deflected ( FIG. 10) and the wheel spring is very tight in this area.

In the wheel suspension shown in FIGS . 11 and 12, the axle 24 of the wheel 25 is coupled to the vehicle body 21 via a trailing arm or a semi-trailing arm 30 . The semi-trailing arm 30 is articulated both to the axle 24 and to the vehicle body 21 . It in turn carries a roller 31 which serves as a support point 16 for the arm 15 of the torsion spring 14 . The torsion spring 14 is fixed with its articulation point 17 and its leg end 18 on the vehicle body 21 . The direction of action of the spring force F _F acting on the trailing arm 13 is shown in FIGS. 11 and 12. Here too, the wheel spring is relatively soft when the vehicle is rebounded or slightly rebounded and ensures a high level of driving comfort when the vehicle is not heavily loaded and the road is level. In the case of an extremely loaded vehicle or extreme cornering, the vehicle is strongly deflected and the wheel spring is very tight, since the restoring torque is very large here due to the very large ratio between the effective lever arm a _H of the semi-trailing arm 30 and the effective lever arm a _{F of} the boom 15 .

The spring element described at the beginning can also be advantageous as an opening spring for the bonnet or the Trunk lid of a motor vehicle can be used. A Conventional trunk lid often opens due to low spring tension of the opening spring not quite what occurs especially in cold weather. However, if Opening spring tensioned more, so you have to raise one Purchase of force when closing the trunk lid to take. Here the spring element according to the invention can be extremely advantageous as an opening spring for the trunk lid be used, because with the help of this element the on Trunk lid acting torque individually over the Opening angle of the trunk lid can be adjusted.  

A schematic longitudinal section through the rear of a motor vehicle is shown in detail in FIG. 15. 32 the motor vehicle body, 33 the rear window and 34 the trunk lid. On the underside of the trunk lid 34 of the boot lid 34 is fixed to an articulated arm 35 preferably on each side, which is pivotable at its other end to a body-fixed pivot axis 36, which is located immediately below the rear window shelf of the motor vehicle body transverse to the vehicle longitudinal direction. With this articulated arm 35 , the trunk lid 34 can be pivoted upward from its closed position, in which apart from its rear part pulled down essentially horizontally, by an opening angle of approximately 90 °, as a result of which the trunk opening is maximally released.

In order to minimize the effort required to open and close the trunk lid 34 , an opening spring is usually provided, which applies a torque acting against the trunk force 34 to the trunk lid 34 . The spring element described above is used for this opening spring, the articulated arm 35 forming the pivot member 11 of the spring element. The torsion spring 14 is articulated at a distance from the pivot axis 36 of the articulated arm 35 , the spring axis running parallel to the pivot axis 36 and the inner leg end 18 of the torsion spring 14 being fixed to the housing. The outer leg end of the torsion spring 14 is in turn formed as an extension arm 15 , which is supported at a support point 16 on the articulated arm 35 . The support point 16 is designed here as a roller 37 which is arranged on the articulated arm 35 so as to be rotatable. Here too, the eccentricity of torsion spring 14 and swivel axis 36 of articulated arm 35 changes the distance between spring articulation point 17 and boom support point 16 via the swivel angle Schwenk _H of articulated arm 35 . As seen from an enlarged view of the support point 16 moves used as opening spring spring element in accordance with FIG. 16 can be seen in which the boom is of the torsion spring shown 15 14 in different positions during the opening movement of the trunk lid 34 to the pivot point 17 back, so that the distance between articulation point 17 and support point 16 shortened by the opening angle ϕ _H. In Fig. 16, the respectively effective lever arms a _H of articulated arm 35 and a _F of boom 19 are shown, the index 0 for the closed position of the trunk lid 34 and the index 6 for an opening angle of approximately 60 °. At a swivel angle of 90 °, the roller 37 assumes its uppermost position shown in dash-dot lines in FIG. 16, and the trunk lid 34 is approximately vertical. The equations mentioned above and compiled in FIG. 14 apply to the calculation of the different torques.

In Fig. 17, various torque characteristics over the opening angle of the trunk lid 34 and thus about the pivot angle φ _H of the articulated arm 35 shown. With I the torque characteristic on the pivot axis 36 of the articulated arm 35 is designated due to the weight of the trunk lid 34 . II shows a torque line on the pivot axis 36 that is desired to ensure smooth operation of the trunk lid 34 . This characteristic curve corresponds to the torque that the operator must apply to the trunk lid 34 . III represents the spring characteristic of the spring element used, which is required to achieve the desired torque characteristic II at the torque characteristic I predetermined by the weight of the trunk lid 34 . This characteristic curve III is achieved by suitable coordination of the articulation point 17 of the torsion spring 14 and the shape of the arm 15 of the torsion spring 14 , as is schematically outlined in FIG. 16. The torque of the spring element acting in the opening direction is approximately constant in the range from 0 ° to approximately 30 ° opening angle of the trunk lid 34 , increases in the range from approximately 30 ° to 50 ° / 60 °, and then again between 50/60 ° and 90 ° decrease sharply. For this purpose, the boom 15 is designed so that the ratio of the effective lever arms a _H and a _F ( FIG. 16) of the articulated arm 35 and the boom 15 decreases little over the pivot path of the articulated arm 35 in the range between 0 ° and about 30 °, in the range increases strongly between approximately 30 and 50 ° / 60 ° and decreases strongly again in the range between approximately 50 ° / 60 ° and 90 °. This ensures that the trunk lid 34 falls into the trunk lock due to its weight without external influences in the range between 0 ° and 30 °. The trunk lid 34 does not move from standstill between approximately 30 ° and 50 ° / 60 °. However, this area can be easily overcome if the trunk lid 34 is manually accelerated in one direction or the other. From approximately 50 ° / 60 °, the trunk lid 34 opens automatically up to the stop in the vertical position. In the end area (trunk fully open) there is still a slight drive effect by the torsion spring 14 . The trunk lid 34 is hardly accelerated; ie it runs against the stop at a relatively slow speed. As a result, the trunk lid 34 does not swing back too far.

If the extension arm 15 of the torsion spring 14 is provided with locking points 38 , 39 , as can be seen in FIG. 15, then an automatic swinging out of the trunk lid 34 from its end positions is prevented, the extension arm 15 assuming the position designated A and C, respectively. If one sees between the two final locking points 38 , 39, a further locking point 40 , in which the trunk lid 34 is pivoted out of the closed position by approximately 50 ° and in which the extension arm 15 of the torsion spring 14 assumes the position designated B, a likewise secured one is obtained Intermediate position of the trunk lid 34 , which allows handling in the trunk in rainy weather without rain getting into it.

Claims (16)

1.Spring element with resetting force which can be varied via the spring travel and which has a pivoting member which can be pivoted about a pivot axis and a torsion spring which is arranged eccentrically with respect to the pivot axis and which acts on the pivot member via a cantilever arm extending at a support point against its pivoting direction in such a way that the distance between the spring articulation point and the boom support point changes over the swivel angle of the swivel member, characterized in that the boom ( 15 ) has such a shape over its longitudinal extent that at each swivel angle (ϕ _H ) of the swivel member ( 11 ) a desired restoring torque (M _H ) acts on the swivel link ( 11 ). 2. Spring element according to claim 1, characterized in that the articulation point ( 17 ) of the torsion spring ( 14 ) at a distance from the pivot member ( 11 ) is inside or outside the pivot radius (r _o ) of the pivot member and the support point ( 16 ) of the boom ( 15 ) lies on the swivel link ( 11 ). 3. Spring element according to claim 1, characterized in that the articulation point ( 17 ) of the torsion spring ( 14 ) on the pivot member ( 11 ) and the support point ( 16 ) of the boom ( 15 ) at a distance from the pivot member ( 11 ) inside or outside of Swivel radius (r _o ) of the swivel member ( 11 ). 4. Spring element according to one of claims 1-3, characterized in that the boom ( 15 ) from one leg end of the torsion spring ( 14 ) is formed and that the other leg end ( 18 ) is fixed at or near the spring pivot point ( 17 ). 5. Spring element according to claim 1, characterized in that the articulation point ( 17 ) of the torsion spring ( 14 ') on the pivot member ( 11 ) is set such that the torsion spring ( 14 ') is pivotable about the articulation point ( 17 ) that the Boom ( 15 ) from one leg end of the torsion spring ( 14 ') is formed so that the other leg end ( 18 ) of the torsion spring ( 14 ') is formed into a further boom ( 19 ) and that the two support points ( 16 , 20 ) two brackets ( 15 , 19 ) are arranged away from the swivel member ( 11 ) inside and / or outside of its swivel radius (r _o ). 6. Spring element according to one of claims 1-5, marked by its use as a wheel spring of a vehicle, in particular a motor vehicle.   7. Spring element according to claim 6, characterized in that the shape of the boom ( 15 ) is predetermined in sections so that the spring constant of the wheel spring is small in the area (I) of a smaller spring travel, large in the area (II) and a medium spring travel and in the area ( III) a large spring deflection is extremely large, and that the spring constants are approximately constant over the respective range. 8. Spring element according to claim 6 and 7, characterized in that the pivot member ( 11 ) is formed by a wishbone ( 27 ) of a double wishbone ( 23 ) arranged between the wheel axle ( 24 ) and vehicle body ( 21 ). 9. Spring element according to claim 8, characterized in that the torsion spring ( 14 ) on the vehicle body ( 21 ) is articulated between the articulation points of the upper and lower wishbones ( 26 , 27 ) and is fixed there with its one leg end ( 18 ) and that the boom ( 15 ) is supported on a roller ( 29 ) mounted on the lower wishbone ( 27 ). 10. Spring element according to claim 6 or 7, characterized in that the pivot member ( 11 ) of a between the wheel axle ( 24 ) and vehicle body ( 21 ) articulated longitudinal or semi-trailing arm ( 30 ) is formed. 11. Spring element according to claim 10, characterized in that the torsion spring ( 14 ) on the vehicle body ( 21 ) above the trailing arm or semi-trailing arm ( 30 ) and articulated there with one leg end ( 18 ) and that the boom ( 15 ) itself is supported on a roller ( 31 ) mounted on the longitudinal or semi-trailing arm ( 30 ). 12. Spring element according to one of claims 1-5, characterized by its use as an opening spring for engine compartment or trunk lid ( 34 ) of motor vehicles, wherein its pivot member ( 11 ) of one on the motor vehicle body ( 32 ) pivotally mounted, at the end on the lid ( 34 ) rigidly attached, arcuate articulated arm ( 35 ) is formed. 13. Spring element according to claim 12, characterized in that the shape of the arm ( 15 ) of the torsion spring ( 14 ) is predetermined in sections so that on the in the closed state (opening angle = 0 °) lying approximately horizontally and pivoted in the open state by about 90 ° approximately vertically standing cover ( 34 ) acts in the opening direction, which is approximately constant in an opening range from 0 ° to 30 °, increasing in an opening range of approximately 30 ° to 50 ° and decreasing in an opening range of approximately 50 ° to 90 ° is. 14. Spring element according to claim 2 and 13, characterized in that the articulation point ( 17 ) of the torsion spring ( 14 ) in relation to the pivot axis ( 36 ) of the articulated arm ( 35 ) and the shape of the boom ( 15 ) is made such that the ratio of the effective lever arms (a _H , a _F ) of the articulated arm ( 35 ) and the extension arm ( 15 ) decreases little over the swivel angle (ϕ _H ) of the articulated arm ( 35 ) in the range between 0 ° and approximately 30 °, in the range between approximately 30 ° to 50 ° increases sharply and decreases sharply in the range between approximately 50 ° and 90 °. 15. Spring element according to one of claims 13 or 14, characterized in that the boom ( 15 ) of the torsion spring ( 14 ) is provided with catches ( 38 , 39 , 40 ) in which the support point ( 16 ) on the articulated arm ( 35 ) in defined positions of the cover ( 34 ) occurs. 16. Spring element according to claim 15, characterized in that the detents ( 38 , 39 , 40 ) are arranged at the front end and / or at the end near the articulation point and / or approximately in the middle of the boom ( 15 ), such that the cover ( 34 ) takes one and / or other end position and / or a middle position.