EP1948957A1 - Leaf spring comprising an upper and lower face with a convex cross-section - Google Patents

Leaf spring comprising an upper and lower face with a convex cross-section

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Publication number
EP1948957A1
EP1948957A1 EP06818042A EP06818042A EP1948957A1 EP 1948957 A1 EP1948957 A1 EP 1948957A1 EP 06818042 A EP06818042 A EP 06818042A EP 06818042 A EP06818042 A EP 06818042A EP 1948957 A1 EP1948957 A1 EP 1948957A1
Authority
EP
European Patent Office
Prior art keywords
leaf spring
vehicle
convex
leaf
section
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06818042A
Other languages
German (de)
French (fr)
Inventor
Clemens Aulich
Rainer Förster
Heiko Kempe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
IFC Composite GmbH
Original Assignee
IFC Composite GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by IFC Composite GmbH filed Critical IFC Composite GmbH
Publication of EP1948957A1 publication Critical patent/EP1948957A1/en
Withdrawn legal-status Critical Current

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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)

Abstract

The invention relates to a leaf spring (1) consisting of a fibre-composite material for use in a vehicle. To prevent cracking or the escape of leaf spring material on the longitudinal edges (10) of said leaf spring (1) when the latter is fixed to a vehicle, according to the invention at least the upper face (13) and/or the lower face (14) of the leaf spring (1) are convex transversally to the longitudinal extension of said spring.

Description

Blattfeder mit im Querschnitt konvexer Ober- und Unterseite Leaf spring with convex top and bottom
Die Erfindung betrifft eine Blattfeder aus einem Faserverbundwerkstoff gemäß dem Oberbegriff des Patentanspruchs 1.The invention relates to a leaf spring made of a fiber composite material according to the preamble of patent claim 1.
Blattfedern werden üblicherweise für Radaufhängungen an einem Fahrzeug verwendet, um dieses gegen unebene Gelände- bzw. Fahrwegbeschaffenheiten abzufedern. Solche Fahrzeuge können insbesondere Personenkraftwagen, Lastkraftwagen und andere Nutzfahrzeuge, aber auch Schienenfahrzeuge und dergleichen sein.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.
Seit langem bekannt sind Blattfedern aus Stahl. Bei diesen sind einzelne, schmale Stahlbleche mit kleiner werdenden Längen übereinander gelegt, um eine variable Federkonstante bei zunehmender Belastung zu erreichen. Durch Klammerungen und/oder Schraubverbindungen sind die Bleche der Blattfedern zu einem Paket verbunden. Bei der Montage einer Blattfeder in einem Kraftfahrzeug erfolgt diese beispielsweise quer zur Fahrtrichtung, wobei der mittlere Bereich derselben an der Fahrtzeugkarosserie festgelegt ist, während die beiden axialen Enden der Blattfeder im Bereich der Aufhängung des rechten bzw. des linken Fahrzeugrades angeordnet sind. Wenngleich eine metallische Blattfeder vergleichsweise kostengünstig herstellbar und zuverlässig im Betrieb ist, so ist eine solche jedoch nachteilig schwer, welches zu einem relativ hohen Fahrzeuggewicht beiträgt und damit letztlich einen erhöhten Kraftstoffverbrauch verursacht.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. Although 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.
Bekannt sind auch Blattfedern aus Faserverbundmaterialien, welche beispielsweise aus mit Kunstharz getränkten Glas- oder Kohlenstofffasern gebildet sind und bei gleicher Größe sowie vergleichbaren Federeigenschaften erheblich weniger Gewicht aufweisen als Stahl-Blattfedern. Solche Faserverbund-Blattfedern werden beispielsweise aus einzelnen harzgetränkten Faserlagen hergestellt, die unter dem Begriff „Prepreg" bekannt sind. Diese Prepregs werden in der gewünschten Gestalt gefertigt und/oder zugeschnitten und übereinander in eine Pressform eingelegt, die den Abmessungen der Blattfeder entspricht. Anschließend wird die Roh-Blattfeder in der Pressform unter Einwirkung von Druck und Wärme ausgehärtet.Also known are 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.
Aus der DE 102 21 589 A1 ist eine Blattfeder aus einem Faserverbundmaterial bekannt, die einstückig aus einem zentralen Bogenabschnitt und end- seitig aus peripheren Abschnitten besteht. Die peripheren Abschnitte besitzen an ihrem jeweiligen axialen Ende eine Öse mit einer Öffnung zur Aufnahme eines Bolzens zum Zwecke der Befestigung der Blattfeder am Fahrzeugchassis. Nachteilig hierbei ist die Einbringung der Befestigungsöse in die Blattfeder, die nur durch eine konstruktiv aufwendige Pressform oder durch einen die Fasern durchtrennenden Stanzvorgang zu realisieren ist.From DE 102 21 589 A1, a leaf spring made of a fiber composite material is known, 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.
Bei anderen Blattfederkonstruktionen aus Faserverbundwerkstoffen sind die Endabschnitte angeschrägt. Dabei wird der jeweilige Endabschnitt nach dem Aushärten der Blattfeder der angeschrägten Form entsprechend zurechtge- schnitten. Dies hat zur Folge, dass auch die Fasern des Werkstoffes angeschnitten werden. Die Schnittstellen führen bei Dauerwechselbelastungen der Blattfeder häufig zu Rissen, die von den Schnittstellen ausgehen und im Wesentlichen parallel zur Längserstreckung der Fasern verlaufen. Diese Risse wiederum können zum Bruch der Blattfeder führen.In other leaf spring structures made of fiber composite materials, the end portions are chamfered. In this case, 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.
Aus der EP 0 093 707 B1 beziehungsweise der dazu parallelen US 4,557,500 B1 ist eine Blattfeder aus einem Faserverbundmaterial bekannt, die an ihren axialen Enden schmaler und dicker als in einem zentralen, rechteckigen Abschnitt ausgebildet ist. Der Bereich der axialen Enden der Blattfeder kann in Draufsicht dabei etwa trapezförmig ausgebildet sein. Die Fläche von rechtwinkligen Querschnitten der Blattfeder von einem Federende bis zu dem anderen Federende kann gemäß einer anderen Variante konstant sein. Bei einer anderen Bauart dieser Blattfeder sind die Verbundfasern von einem bis zum anderen axi- alen Ende ungeschnitten. Die Geometrie der Blattfeder wird während deren Herstellung durch Pressformen erzeugt.From EP 0 093 707 B1 or the US 4,557,500 B1 parallel thereto, a leaf spring made of a fiber composite material is known, 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. In another type of this leaf spring, 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.
Außerdem ist aus der DE 10 2004 010 768 A1 der Anmelderin eine Blattfeder aus einem Faserverbundwerkstoff mit einem zentralen Längsabschnitt und axialen Enden für eine Radaufhängung an einem Fahrzeug bekannt, bei der die axialen Enden hinsichtlich der Blattfederbreite sich verjüngend ausgebildet sind, und bei der axial ausgerichtete Fasern des Faserverbundwerkstoffs ungekürzt bis zur Abschlusskante der Blattfeder geführt sind. Außerdem ist bei dieser Blattfeder vorgesehen, dass sie aus harzgetränkten Faserlagen aufgebaut ist, die bei der Herstellung der Blattfeder an ihren axialen Enden in einer Draufsicht eine V- förmige Geometrie bzw. einen V-förmigen Einschnitt aufweisen und somit jeweils zwei quer zur Längserstreckung der Blattfeder ausgebildete Schenkel bilden. Diese beiden Schenkel werden im Herstellprozess eng aneinandergelegt und ausgehärtet, so dass die fertig gestellte Blattfeder im Bereich ihrer Enden etwa trapezförmig ausgebildet ist und keine Materialaufdickung in diesem Bereich aufweist.In addition, from DE 10 2004 010 768 A1 of the applicant a leaf spring made of a fiber composite material with a central longitudinal portion and axial ends for a suspension on a vehicle is known 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. In addition, it is provided in this leaf spring that it is constructed of resin-impregnated fiber layers, which have in the manufacture of the leaf spring at its axial ends in a plan view of a V-shaped geometry or a V-shaped notch and thus two transverse to the longitudinal extent of the leaf spring forming trained thighs. These two legs are placed close together and hardened in the manufacturing process, so that the finished leaf spring is approximately trapezoidal in the region of its ends and has no material thickening in this area.
Aus dieser Druckschrift ist zudem bekannt, dass die Blattfeder in ihrem zentralen Bereich durch geometrisch einfache, rechteckige Faserlagen hinsichtlich deren Bauteildicke verstärkt werden kann, während zur Ausbildung der V- förmigen axialen Enden der Blattfeder entsprechend ausgebildete und über die gesamte Bauteillänge geführte Faserlagen verwendet werden.From this document it is also known that 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.
Eine Blattfeder gemäß der DE 10 2004 010 768 A1 ist mit einigen Vorteilen verbunden, da diese über beinahe ihre gesamt Länge im Wesentlichen konstante Querschnittsflächen sowie eine konstante Dicke mit am axialen Ende verringerter Breite aufweist, ohne dass dieselbe an ihren axialen Enden beschnitten werden muss.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.
Bei bauteilkundlichen Untersuchungen an bekannten Blattfedern aus Faserverbundwerkstoffen hat sich gezeigt, dass diese nicht immer den durch eine Pressform vorgegebenen rechtwinkligen Querschnitt aufweisen. Vielmehr haben diese Blattfedern quer zur Längserstreckung leicht konkav gekrümmte Ober- und/oder Unterseiten, wodurch die längsgerichteten Kanten der Blattfeder etwas nach oben beziehungsweise unten hervorstehen.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.
Wenn solche konventionellen Blattfedern an ihren Befestigungsstellen mit diesbezüglichen Befestigungsmitteln an einem abzufedernden Bauteil eingespannt werden, bilden sich an den Befestigungsstellen Risse oder es brechen die Kanten der Blattfeder an diesen Befestigungs- beziehungsweise Einspannstellen teilweise ab. Derartige Risse oder Bruchstellen wirken sich ungünstig auf die Lebensdauer der Blattfeder aus, da an diesen Feuchtigkeit in dieselbe eindringen und deren Verbundgefüge negativ beeinträchtigen kann.If such conventional leaf springs are clamped at their attachment points with related fasteners on a component to be absorbed, cracks are formed at the attachment points or the edges of the leaf spring at these attachment or clamping points partially break off. Such cracks or fractures have an unfavorable effect on the life of the leaf spring, since moisture can penetrate into it and negatively affect its composite structure.
Der Erfindung liegt daher die Aufgabe zugrunde, eine Faserverbund- Blattfeder derart weiterzubilden, dass die beschriebene Rissbildung oder gar ein Kantenbruch an den Befestigungsstellen derselben nicht auftritt.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.
Die Lösung dieser Aufgabe ergibt sich aus den Merkmalen des Anspruchs 1. Vorteilhafte Ausgestaltungen und Weiterbildungen der Erfindung sind den Unteransprüchen entnehmbar.The solution of this problem arises from the features of claim 1. Advantageous embodiments and modifications of the invention are the dependent claims.
Der Erfindung liegt die Erkenntnis zugrunde, dass sich trotz einer rechtwinkligen formgebenden Querschnittsgeometrie einer Pressform zur Herstellung einer Faserverbundblattfeder eine nicht rechtwinklige Querschnittsgeometrie der Blattfeder einstellen kann. Insbesondere bildet sich häufig eine konkav gewölbte Ober- und/oder Unterseite. Um dem entgegenzuwirken, wird zur Herstellung einer Blattfeder gemäß der Erfindung eine Pressform genutzt, welche im Querschnitt konkav gewölbte Formflächen zumindest für die Oberseite und die Unterseite der Blattfeder aufweist, so dass im Ergebnis eine Blattfeder mit konvexen Oberflächen herstellbar ist. Die Erfindung betrifft daher eine Blattfeder aus einem Faserverbundwerkstoff, welche dadurch gekennzeichnet ist, dass zumindest deren Oberseite und/oder Unterseite quer zur Längserstreckung derselben konvex gewölbt sind. Bei einem Einspannen derselben in diesbezügliche Befestigungsvorrichtungen an einem Fahrzeug stehen daher die Kanten der Blattfeder nicht mehr nach o- ben oder unten vor, weshalb diese auch nicht mehr befestigungsbedingt einreißen und/oder abbrechen können.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. To counteract this, 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. When clamping the same in this respect fastening devices on a vehicle, therefore, the edges of the leaf spring are no longer to oben or below, which is why these no longer tearing due to fastening and / or can break off.
Vorteilhaft kann die Faserverbundblattfeder auch mit im Querschnitt konvexen Seitenflächen ausgebildet sein, so dass deren Kanten einen besonders stumpfen Winkel aufweisen, welches die Gefahr der Rissbildung oder des Ab- brechens der Kanten weiter verringert.Advantageously, 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.
Bevorzugt ist vorgesehen, dass die konvexe Wölbung zumindest der Ober- und/oder Unterseite der Blattfeder so ausgebildet ist, dass Befestigungsmittel, welche die Blattfeder an einem Fahrzeug fixieren, die Kanten der Blattfeder beim Einspannen zumindest nicht zuerst berühren.It is preferably provided that 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.
Gemäß einer anderen Weiterbildung der Erfindung ist vorgesehen, dass zumindest die Oberseite und/oder die Unterseite der Blattfeder, in Längsrichtung gesehen, nur im Bereich ihrer Befestigungsstellen konvex gewölbt beziehungsweise ballig ausgebildet sind. Dadurch lässt sich ein erhöhter Materialaufwand axial zwischen den genannten Einspannstellen vermeiden.According to another embodiment of the invention, it is provided that 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. As a result, an increased material expenditure can be avoided axially between said clamping points.
Zudem kann vorgesehen sein, dass die konvexe Wölbung zumindest der Oberseite und/oder der Unterseite der Blattfeder über die gesamte Querschnittsbreite oder nur im Bereich der axial ausgerichteten Kanten derselben ausgebildet ist.In addition, it can be provided that 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.
Selbstverständlich könnten zur Erreichung des gleichen technischen Effekts, also der Vermeidung der Rissbildung bzw. des Abbrechens der Längskanten der Blattfeder, auch die Kontaktflächen der die Blattfeder einspannenden Befestigungsvorrichtungen eine konkave Oberfläche aufweisen. Ein unmittelbarer Kontakt der Kanten der Blattfeder mit der jeweiligen Befestigungsvorrichtung käme dann ebenfalls nicht zustande. Die Herstellung solcher Befestigungsvorrichtungen würde jedoch in einem spanenden Herstellvorgang erfolgen, welcher aufwendiger ist als der Formvorgang mit der nur leicht modifizierten Pressform zur Herstellung der Faserverbund-Blattfeder.Of course, to achieve the same technical effect, ie the prevention of cracking or breaking off of the longitudinal edges of the leaf spring, and the contact surfaces of the leaf spring chucking Fastening devices have a concave surface. A direct contact of the edges of the leaf spring with the respective fastening device would then also not materialize. However, the production of such fastening devices would take place in a cutting manufacturing process, which is more expensive than the molding process with the only slightly modified mold for producing the fiber composite leaf spring.
Zur Verdeutlichung der Erfindung ist der Beschreibung eine Zeichnung beigefügt. In dieser zeigtTo clarify the invention, the description is accompanied by a drawing. In this shows
Fig. 1 eine schematische Draufsicht auf eine Blattfeder gemäß der Erfindung,1 is a schematic plan view of a leaf spring according to the invention,
Fig. 2 einen Querschnitt durch den Befestigungsbereich einer konventionelle Blattfeder an der Stelle A-A gemäß Fig. 1 sowie durch eine zugeordnet Befestigungsvorrichtung, undFig. 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 eine Darstellung wie in Fig. 2, jedoch mit einer gemäß der Erfindung ausgebildeten Blattfeder.Fig. 3 is a representation as in Fig. 2, but with a formed according to the invention leaf spring.
Demnach zeigt Fig. 1 eine schematische Draufsicht auf eine Blattfeder 1 , die aus einem Faserverbundwerkstoff besteht und eine weitgehend vierkantstab- förmigen Umfangskontur 2 aufweist. Der Faserverbundwerkstoff besteht im Wesentlichen aus weitgehend parallel zueinander ausgerichteten Fasern 4, beispielsweise Glas-, Kohlenstoff- oder Aramidfasern, welche sich ungekürzt von einem axialen Ende 3 zu dem gegenüberliegenden axialen Ende 3 der Blattfeder erstrecken und in einem ausgehärteten Kunstharz eingebettet sind. Diese Blattfeder 1 ist beispielhaft zum Einbau in ein Kraftfahrzeug, wie etwa Stadtlieferfahrzeug vorgesehen, in welchem diese quer zur Fahrzeuglängsachse angeordnet wird.Accordingly, 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.
Die Blattfeder 1 ist mit ihren Befestigungsbereichen 5, 6, 6' und 7 mit Fahrzeugteilen verbindbar, wobei die axial äußeren Befestigungsbereiche 5 und 7 üblicherweise einer Radaufhängung eines linken bzw. eines rechten Fahr- zeugvorderrades und die mittleren Befestigungsbereiche 6, 6' zweifach außermittig Befestigungspunkten an der Fahrzeugkarosserie zugeordnet sind.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.
Die Befestigung einer Blattfeder 15 gemäß dem Stand der Technik an den genannten Fahrzeugteilen erfolgt so, wie dies vereinfacht in der Querschnittsdarstellung A-A gemäß Fig. 2 gezeigt ist. Dabei liegt im Befestigungsbereich 5 ein erstes Befestigungsmittel 8 an der Oberseite 11 sowie ein zweites Befestigungsmittel 9 an der Unterseite 12 der Blattfeder 15 unter Anwendung einer Anpresskraft F auf. Da die Blattfeder 15 gemäß dem Stand der Technik produktionsbedingt mit leicht konkaver Oberseite 11 bzw. leicht konkaver Unterseite 12 ausgebildet ist, wirkt bei einer erstmaligen Belastung der Blattfeder 15 die Anpresskraft F im Wesentlichen auf die längsgerichteten Kanten 10 derselben, so dass diese teilweise abbrechen oder zumindest Risse aufweisen, welches in Fig. 2 angedeutet ist und vermieden werden soll.The attachment of a leaf spring 15 according to the prior art to said vehicle parts takes place as shown in simplified manner in the cross-sectional view A-A shown in FIG. 2. In this case, 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 zeigt einen Querschnitt A-A durch die erfindungsgemäße Blattfeder 1 gemäß Fig. 1. Darin ist deutlich erkennbar, dass die Blattfeder 1 eine konvexe Oberseite 13 und eine konvexe Unterseite 14 aufweist. Die Wölbung bzw. Balligkeit der Oberflächen 13, 14 ist dabei bevorzugt so gering ausgebildet, dass die Kanten 10 der Blattfeder 1 nicht als erstes mit der Anpresskraft F beaufschlagt werden, sondern dass ein großflächiger mittlerer Bereich zuerst belastet wird. Dadurch wird eine Rissbildung in der Blattfeder 1 vermieden und so deren Lebensdauer feststellbar verlängert. FIG. 3 shows a cross section AA through the leaf spring 1 according to the invention as shown in FIG. 1. It can clearly be seen that 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.
Bezugszeichenreference numeral
1 Blattfeder1 leaf spring
2 Umfangskontur der Blattfeder2 Circumferential contour of the leaf spring
3 Axiales Ende der Blattfeder Faser3 Axial end of the leaf spring fiber
5 Seitlicher Befestigungsbereich5 Side mounting area
6 Mittlerer Befestigungsbereich 6' Mittlerer Befestigungsbereich6 Middle mounting area 6 'Middle mounting area
7 Seitlicher Befestigungsbereich7 Side mounting area
8 Befestigungsmittel8 fasteners
9 Befestigungsmittel9 fasteners
10 Kante10 edge
11 Oberseite der Blattfeder, konkav11 top of the leaf spring, concave
12 Unterseite der Blattfeder, konkav12 underside of the leaf spring, concave
13 Oberseite der Blattfeder, konvex13 top of the leaf spring, convex
14 Unterseite der Blattfeder, konvex14 underside of the leaf spring, convex
15 Blattfeder, Stand der Technik F Anpresskraft 15 leaf spring, prior art F contact pressure

Claims

Patentansprüche claims
1. Blattfeder (1) aus einem Faserverbundwerkstoff, dadurch gekennzeichnet, dass zumindest die Oberseite (13) und/oder die Unterseite (14) der Blattfeder (1) quer zur Längserstreckung derselben konvex gewölbt sind.1. leaf spring (1) made of a fiber composite material, characterized in that at least the top (13) and / or the bottom (14) of the leaf spring (1) are curved transversely to the longitudinal extent of the same convex.
2. Blattfeder nach Anspruch 1 , dadurch gekennzeichnet, dass auch die Seitenflächen der Blattfeder (1) konvex gewölbt sind.2. Leaf spring according to claim 1, characterized in that the side surfaces of the leaf spring (1) are convexly curved.
3. Blattfeder nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass zumindest die Oberseite (13) und/oder die Unterseite (14) der Blattfeder (1) nur in deren Befestigungsbereichen (5, 6, 6', 7) konvex gewölbt sind.3. Leaf spring according to claim 1 or 2, characterized in that at least the upper side (13) and / or the underside (14) of the leaf spring (1) are convexly curved only in their attachment areas (5, 6, 6 ', 7).
4. Blattfeder nach zumindest einem der Anspruch 1 bis 3, dadurch gekennzeichnet, dass die konvexe Wölbung so ausgebildet ist, dass Befestigungsmittel (8, 9), welche die Blattfeder (1) an einem Fahrzeug fixieren, die Kanten (10) der Blattfeder (1) beim Einspannen nicht zuerst berühren.4. leaf spring according to at least one of claim 1 to 3, characterized in that the convex curvature is formed so that fastening means (8, 9) which fix the leaf spring (1) to a vehicle, the edges (10) of the leaf spring ( 1) do not touch first when clamping.
5. Blattfeder nach zumindest einem der Anspruch 1 bis 4, dadurch gekennzeichnet, dass die konvexe Wölbung zumindest der Oberseite (13) und der Unterseite (14) über die gesamte Querschnittsbreite der Blattfeder (1) oder nur im Bereich der Kanten (10) ausgebildet ist.5. leaf spring according to at least one of claims 1 to 4, characterized in that the convex curvature of at least the top (13) and the bottom (14) over the entire cross-sectional width of the leaf spring (1) or only in the region of the edges (10) is.
6. Blattfeder nach zumindest einem der Anspruch 1 bis 5, dadurch gekennzeichnet, dass die konvexe Wölbung zumindest die Oberseite (13) und/oder die Unterseite (14) der Blattfeder (1) durch eine Werkzeugform mit konkaven Formflächen erzeugt ist. 6. leaf spring according to at least one of claims 1 to 5, characterized in that the convex curvature at least the top (13) and / or the underside (14) of the leaf spring (1) is generated by a mold with concave mold surfaces.
EP06818042A 2005-11-11 2006-11-04 Leaf spring comprising an upper and lower face with a convex cross-section Withdrawn EP1948957A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102005054335A DE102005054335A1 (en) 2005-11-11 2005-11-11 Leaf spring with convex top and bottom
PCT/DE2006/001938 WO2007054068A1 (en) 2005-11-11 2006-11-04 Leaf spring comprising an upper and lower face with a convex cross-section

Publications (1)

Publication Number Publication Date
EP1948957A1 true EP1948957A1 (en) 2008-07-30

Family

ID=37761968

Family Applications (1)

Application Number Title Priority Date Filing Date
EP06818042A Withdrawn EP1948957A1 (en) 2005-11-11 2006-11-04 Leaf spring comprising an upper and lower face with a convex cross-section

Country Status (6)

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US (1) US20080284070A1 (en)
EP (1) EP1948957A1 (en)
JP (1) JP2009515123A (en)
CN (1) CN101300434A (en)
DE (2) DE102005054335A1 (en)
WO (1) WO2007054068A1 (en)

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Publication number Priority date Publication date Assignee Title
DE102005054376A1 (en) * 2005-11-12 2007-05-24 Ifc Composite Gmbh Leaf spring made of a fiber composite material
DE102005055050B4 (en) * 2005-11-16 2007-09-27 Ifc Composite Gmbh Segmented fiber composite leaf spring and method of making the same
RU2707856C1 (en) * 2016-03-15 2019-11-29 Нхк Спринг Ко., Лтд. Clearance retaining element and multilayer leaf spring provided with such element

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FR2266058B1 (en) * 1974-03-27 1977-07-08 Nord Ressorts
JPS5818539B2 (en) * 1980-12-22 1983-04-13 日本発条株式会社 leaf spring
JPS5854241A (en) * 1981-09-29 1983-03-31 Hino Motors Ltd Leaf spring of fiber reinforced plastics
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Also Published As

Publication number Publication date
DE102005054335A1 (en) 2007-05-24
US20080284070A1 (en) 2008-11-20
WO2007054068A1 (en) 2007-05-18
DE112006002662B4 (en) 2013-03-28
CN101300434A (en) 2008-11-05
JP2009515123A (en) 2009-04-09
DE112006002662A5 (en) 2008-07-10

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