Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F1/00—Springs
  • F16F1/36—Springs made of rubber or other material having high internal friction, e.g. thermoplastic elastomers
  • F16F1/366—Springs made of rubber or other material having high internal friction, e.g. thermoplastic elastomers made of fibre-reinforced plastics, i.e. characterised by their special construction from such materials
  • F16F1/368—Leaf springs

Definitions

• the invention relates to a leaf spring made of a fiber composite material according to the preamble of patent claim 1.
• Leaf springs are commonly used for suspensions on a vehicle to cushion it against uneven terrain conditions.
• Such vehicles may in particular be passenger cars, trucks and other commercial vehicles, but also rail vehicles and the like.
• Leaf springs made of steel have been known for a long time. In these individual, narrow steel sheets are superimposed with decreasing lengths to achieve a variable spring constant with increasing load. By clamping and / or screw the plates of the leaf springs are connected to form a package. When mounting a leaf spring in a motor vehicle, for example, this takes place transversely to the direction of travel, wherein the central region thereof is fixed to the vehicle body, while the two axial ends of the leaf spring in the region of the suspension of the right and left vehicle wheel are arranged.
• a metallic leaf spring is comparatively inexpensive to manufacture and reliable in operation, but such is disadvantageously difficult, which contributes to a relatively high vehicle weight and thus ultimately causes increased fuel consumption.
• leaf springs made of fiber composite materials, which are formed, for example, impregnated with synthetic resin glass or carbon fibers and have the same size and comparable spring properties considerably less weight than steel leaf springs.
• Such composite fiber leaf springs are made, for example, from individual resin-impregnated fiber layers known by the term "prepreg.” These prepregs are manufactured in made of the desired shape and / or cut and placed one above the other in a mold, which corresponds to the dimensions of the leaf spring. Subsequently, the green leaf spring is cured in the mold under the action of pressure and heat.
• a leaf spring made of a fiber composite material which consists of a central arc section and ends of peripheral sections in one piece.
• the peripheral portions have at their respective axial end an eyelet with an opening for receiving a bolt for the purpose of securing the leaf spring to the vehicle chassis.
• the disadvantage here is the introduction of the attachment eye in the leaf spring, which can only be realized by a structurally complex mold or by a severing the fibers punching process.
• the end portions are chamfered.
• the respective end section is cut to size after curing of the leaf spring of the bevelled shape. This has the consequence that also the fibers of the material are cut.
• the interfaces often lead to cracks, which emanate from the interfaces and extend substantially parallel to the longitudinal extent of the fibers at permanent alternating loads of the leaf spring. These cracks in turn can lead to breakage of the leaf spring.
• a leaf spring made of a fiber composite material which is narrower and thicker at its axial ends than in a central, rectangular section.
• the region of the axial ends of the leaf spring can be approximately trapezoidal in plan view.
• the area of rectangular cross sections of the leaf spring from one spring end to the other spring end may be constant according to another variant.
• the composite fibers are axiomatic from one to the other. alen end uncut.
• the geometry of the leaf spring is produced during its manufacture by compression molding.
• a leaf spring made of a fiber composite material with a central longitudinal portion and axial ends for a suspension on a vehicle in which the axial ends are formed with respect to the leaf spring width is tapered, and in the axially aligned Fibers of the fiber composite material are fed uncut to the end edge of the leaf spring.
• the leaf spring can be reinforced in its central region by geometrically simple, rectangular fiber layers in terms of their component thickness, while being used to form the V-shaped axial ends of the leaf spring appropriately trained and guided over the entire component length fiber layers.
• a leaf spring according to DE 10 2004 010 768 A1 has several advantages, since it has substantially constant cross-sectional areas over almost its entire length and a constant thickness with reduced width at the axial end, without having to cut it at its axial ends.
• leaf springs made of fiber composites In structural analysis of known leaf springs made of fiber composites has been shown that this is not always the by a Press mold predetermined rectangular cross section. Rather, these leaf springs have transversely to the longitudinal extent slightly concave curved upper and / or lower sides, whereby the longitudinal edges of the leaf spring projecting slightly upwards or downwards.
• the invention is therefore based on the object, a fiber composite leaf spring in such a way that the cracking or even an edge fracture described at the attachment points does not occur.
• the invention is based on the finding that despite a right-angled shaping cross-sectional geometry of a press mold for producing a fiber composite leaf spring, a non-rectangular cross-sectional geometry of the leaf spring can be established. In particular, often forms a concave upper and / or underside.
• a mold is used for producing a leaf spring according to the invention, which has concave curved molding surfaces in cross-section at least for the top and bottom of the leaf spring, so that as a result a leaf spring with convex surfaces can be produced.
• the invention therefore relates to a leaf spring made of a fiber composite material, which is characterized in that at least the top and / or bottom are curved transversely to the longitudinal extent of the same convex.
• the fiber composite leaf spring can also be formed with side surfaces that are convex in cross section, so that their edges have a particularly obtuse angle, which further reduces the risk of cracking or breaking of the edges.
• the convex curvature of at least the top and / or bottom of the leaf spring is formed so that fastening means which fix the leaf spring to a vehicle, the edges of the leaf spring during clamping at least not first touch.
• At least the upper side and / or the underside of the leaf spring, seen in the longitudinal direction, are convexly curved or convex only in the region of their attachment points.
• the convex curvature of at least the top and / or the underside of the leaf spring over the entire cross-sectional width or only in the region of the axially aligned edges thereof is formed.
• FIG. 1 is a schematic plan view of a leaf spring according to the invention
• Fig. 2 shows a cross section through the mounting portion of a conventional leaf spring at the point A-A of FIG. 1 and by an associated fastening device, and
• Fig. 3 is a representation as in Fig. 2, but with a formed according to the invention leaf spring.
• Fig. 1 shows a schematic plan view of a leaf spring 1, which consists of a fiber composite material and has a largely square bar-shaped peripheral contour 2.
• the fiber composite material consists essentially of substantially parallel aligned fibers 4, for example glass, carbon or aramid fibers, which extend unabridged from one axial end 3 to the opposite axial end 3 of the leaf spring and are embedded in a cured resin.
• This leaf spring 1 is provided by way of example for installation in a motor vehicle, such as city delivery vehicle, in which it is arranged transversely to the vehicle longitudinal axis.
• the leaf spring 1 is connectable with its attachment areas 5, 6, 6 'and 7 with vehicle parts, wherein the axially outer mounting portions 5 and 7 usually a suspension of a left or a right driving front wheel and the central attachment areas 6, 6 'are assigned twice eccentrically attachment points on the vehicle body.
• a leaf spring 15 according to the prior art takes place as shown in simplified manner in the cross-sectional view A-A shown in FIG. 2.
• a first fastening means 8 on the upper side 11 and a second fastening means 9 on the underside 12 of the leaf spring 15 using a contact force F are located in the fastening area 5. Since the leaf spring 15 according to the prior art due to production with slightly concave upper side 11 or slightly concave bottom 12 is formed acts on a first load of the leaf spring 15, the contact force F substantially on the longitudinal edges 10 thereof, so that they partially break or at least have cracks, which is indicated in Fig. 2 and should be avoided.
• FIG. 3 shows a cross section AA through the leaf spring 1 according to the invention as shown in FIG. 1.
• the leaf spring 1 has a convex upper side 13 and a convex underside 14.
• the curvature or crowning of the surfaces 13, 14 is preferably formed so small that the edges 10 of the leaf spring 1 are not acted upon first by the contact pressure F, but that a large-area central region is first charged. As a result, cracking in the leaf spring 1 is avoided and thus their life extended detectable.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Springs (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=37761968

Family Applications (1)

Country Status (6)

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• 2005
  • 2005-11-11 DE DE102005054335A patent/DE102005054335A1/de not_active Withdrawn
• 2006
  • 2006-11-04 US US12/093,327 patent/US20080284070A1/en not_active Abandoned
  • 2006-11-04 DE DE112006002662T patent/DE112006002662B4/de active Active
  • 2006-11-04 JP JP2008539237A patent/JP2009515123A/ja active Pending
  • 2006-11-04 WO PCT/DE2006/001938 patent/WO2007054068A1/de active Application Filing
  • 2006-11-04 CN CNA2006800411642A patent/CN101300434A/zh active Pending
  • 2006-11-04 EP EP06818042A patent/EP1948957A1/de not_active Withdrawn

Non-Patent Citations (1)

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