JP2009509774A - Apparatus and method for manufacturing a closed cross-section member with adjustable length punch and / or mold - Google Patents

Abstract

Tooling for the fabrication of a crosspiece with a closed section for connecting two longitudinal arms of a motor vehicle axle comprises a die (3) cooperating with a punch (2) for forming on the closed section of the crosspiece a lengthwise zone of torsion (L) and a mechanism for retaining the crosspiece in position. The die and/or the punch are adaptable in length to enable the length of the zone of torsion to be adapted. An independent claim is also claimed for the fabrication of a crosspiece with a closed section.

Description

The field of the invention is that of automobiles. In particular, the invention relates to a non-rigid axle for an automobile.
Non-rigid axle is a term generally used to mean an axle designed to form a torsion element between two wheels.

Traditionally, non-rigid axles have been provided with two longitudinal arms each having a support for mounting wheels, which are connected by a transverse connecting element known as a cross member or profile. ing.
During axle design, there are two parameters that are specifically considered to assess axle quality. They are bending and twisting.

The principle of a non-rigid axle makes it possible to combine a large bending stiffness with a relative torsional flexibility. In general, the desired balance between bending stiffness and (relative) torsional flexibility is achieved because the cross-member geometry of the cross member provides its inertial torsional moment and bending.
During the last few years, non-rigid axle technology has made significant progress in the lower and middle sectors of the automotive manufacturing market due to the numerous benefits offered. These advantages include a good balance between operation and design, and the fact that manufacturing costs are low, mainly due to the use of an all-welded construction assembly.

These advantages lead the ground system designer to consistently push the technology to absolute limits. In fact, non-rigid axles face a certain number of limits, including the lifespan that depends on the durability of each component that undergoes large elastic deformations, and a delicate balance of longitudinal and lateral stiffness. Yes.
The desire for ever-increasing comfort and operability is particularly addressed in the design of non-rigid axles for solutions that introduce torsional stiffness between two trailing arms. This axle, widely known as “anti-roll bar” or “ARB”, is a superior axle assembly that limits rolling of the vehicle body during cornering and at the same time reliably eliminates transmission of road surface unevenness to the body. The purpose is to maintain vertical flexibility.

However, extending non-rigid axle technology to large vehicles (large sedan passenger cars, minivans or even commercial vehicles) without any trade-off with operational quality is a static resistance to accidental forces or axles Regardless of the fatigue strength for a load cycle that represents the life of the assembly, the component that receives the most stress will lead to its absolute operating limit.
Thus, the connecting element or cross member forms one of the difficult-to-develop components, especially in terms of durability and operation.

Currently, cross members connecting longitudinal arms of non-rigid axles are manufactured using two different technologies.
In the first technique, the cross member is manufactured from a sheet-like metal element that is bent (or pressed) to create a U-shaped, V-shaped or L-shaped cross section. These cross members typically must be combined with an anti-roll bar that provides torsional rigidity to the axle.

The second technique incorporates an anti-roll stiffness function in the cross member.
In this case, the cross member is manufactured from a tube having a substantially circular cross section, and a deformation step is performed at least in the center of the tube (so that part of the wall is crushed against another part of the wall), The desired torsional and bending stiffness can be obtained (eg Peugeot 806® or Opel Zafira®)

The wide variety of anti-roll stiffness necessary to meet the requirements is provided by changing the cross-sectional shape of the cross member and / or by changing the tube thickness.
The present invention applies to cross members manufactured using this second technique. These cross members are known under the names “closed cross member” or “closed cross member”.

In general, all non-rigid axles that use a tube cross member have a recess with a U-shaped or V-shaped cross section in the central region.
The tube of the cross member is deformed only in the lateral direction to reduce its torsional rigidity, and a cross-section having a large torsional inertia (for example, a circular cross-section) is maintained at the end, so that the welding to the suspension arm Is easy.

On the other hand, the non-rigid axle cross member is characterized by a large bending stiffness and a small torsional stiffness, and it is necessary to accurately measure the torsional stiffness (relative to the anti-roll stiffness of the axle). .
As far as closed cross-section crossmembers are concerned, total stiffness is provided by the crossmember, and its torsional inertia is carefully selected to match the anti-roll stiffness required for technical specifications. As a result, the axle anti-roll stiffness tolerance is entirely dependent on the same crossing of the cross member itself.

During the manufacture of a closed cross-section axle cross member (due to tube deformation), the manufacturer typically faces difficulty in meeting the anti-roll stiffness tolerances specified by the car manufacturer according to technical specifications.
One factor affecting anti-roll stiffness is tube thickness variation.

The problem is to reduce the sensitivity of the axle anti-roll stiffness to tube thickness variations.
The degree of size is such that a variation of ± 0.1 mm in tube thickness results in an axle anti-roll stiffness tolerance range of about three times in technical specifications.

Several solutions have been applied to this problem of maintaining control over the anti-roll stiffness of a closed section torsion beam axle.
The first solution is to use a classification method to work with the tube supplier to control tube thickness variations (due to rolling and welding processes).
In reality, however, the possibilities for such solutions are relatively limited.

The second solution is to use the same processing again on the tube obtained by rolling and welding processes in order to improve the thickness tolerance.
While this solution has proven effective, the associated costs are high. Thus, the overall cost of the axle is increased, which usually does not meet the demands of automobile manufacturers.

According to another solution, a hot pressing process is performed which improves the control of the geometric shape of the cross section formed.
In reality, however, it has been found that this technique cannot reduce sensitivity to thickness variations.

According to yet another solution, the sheet metal of the tube at both ends of the cross member is connected using a “clinch” method (punching one metal sheet into the other).
This solution can better control the actual length variation of the operating area (the area with the minimum torsional inertia) but does not compensate for tube thickness variations.

The present invention is particularly aimed at reducing the disadvantages of the prior art.
Specifically, the object of the present invention is to propose a technique for producing a cross member having a closed cross section of a non-rigid axle, which can better control the variation in torsional rigidity of the cross member as compared with the prior art solution. It is.

Another object of the present invention is to provide such a technique that is simple in design and easy to implement.
Another object of the present invention is to propose a manufacturing method corresponding to such a technique.

These objectives, together with other objectives that will become apparent later, are intended to be machine tool equipment for producing a cross-section of a closed cross section connecting two longitudinal arms of a non-rigid axle of an automobile. Realized. The machine tool equipment equipment holds the cross member in a predetermined position and at least one mold that cooperates with a punch to form a twisted zone of a certain length on the closed cross section of the cross member. And the length of the twist zone can be changed by adjusting the length of the mold and / or the punch.
This therefore provides an adaptive system that allows adjustment of the length of the torsional zone of the cross member (also known as the “actuation zone”) and thus its torsional stiffness.

Such changes in the length of the torsional zone should be made simply by adjusting the punch and mold dimensions of the forming machine tool equipment and in a manner integrated with the machine tool equipment. Can be achieved. This will be described in more detail later.
According to a preferred solution, each of the mold and the punch comprises at least two parts that can be moved away from each other.

This in turn provides a particularly simple and effective way to adjust the machine tool equipment to match the desired torsional stiffness of the cross member.
According to a first embodiment, the two parts of the mold and / or the punch can be actuated by at least one actuating cylinder.

According to a second embodiment, the two parts of the mold and / or the punch are held by screw means and are continuous with each other.
In this case, the machine tool equipment preferably comprises a set of shims that can be arranged between the two parts of the mold and / or the punch.

In this case, the set of shims can include a variety of shims of different thicknesses that can cover a certain range with the desired accuracy.
According to an advantageous solution, the holding means comprise at least one variable displacement clamp.
Such a clamp contributes to the module characteristics of the machine tool equipment and can adapt the machine tool equipment to both the thickness and length of the cross member.

The present invention also relates to a method of manufacturing a cross-section of a closed cross-section for connecting two longitudinal arms of a non-rigid axle of an automobile, wherein the method works on the closed cross-section of the cross member in cooperation with a punch. Using machine tool equipment comprising at least one mold forming a torsion zone of a certain length and means for holding the cross member in a defined position, the length of the mold and / or the punch Adjusting the length of the torsional zone by adjusting the height.
Preferably, the method includes a preliminary step of calculating the length of the torsion zone according to the desired torsional stiffness of the cross member and the wall thickness of the cross section.
According to an advantageous solution, the method comprises the step of adjusting the movement of the two clamps forming the holding means.

  Other features and advantages of the present invention will be more fully apparent from the following description of preferred embodiments of the invention, presented as a completely non-limiting exemplary embodiment and shown in the accompanying drawings.

1-3, a closed cross-section cross member is manufactured from the tube 1 according to the prior art, and the cross-section of this tube is deformed using a press to produce a twisted zone.
A conventional machine tool equipment includes a punch 2 and a die 3 which are operated by a press machine to form a twist zone in cooperation with each other, and clamps 4 pressed against both ends of the tube 1.

In the first stage, the tube is placed on the press, a clamp is placed near the tube to secure the tube, and then the press is closed.
FIG. 2 shows a step of forming a twisted zone having a predetermined fixed length, in which the tube is crushed between the mold 3 and the punch 2.
At the end of the forming step, the press is opened (thus the mold 3 and the punch 2 are separated from each other) and the clamp is removed from the tube (FIG. 3).

As shown in FIGS. 4a and 4b, the twisted zone of the cross member having the closed cross section is a name given to the zone L corresponding to the center of the cross member.
In such a cross member, the cross-sectional geometry of the tube, the tube thickness, and the length of the torsion zone are important factors in obtaining the torsional rigidity of the cross member.

In addition, for any cross-sectional shape and tube thickness, when the twist zone length ΔL varies, the twist stiffness R of the cross member varies as follows. That is, when L increases, R decreases, and conversely, when L decreases, R increases.
Therefore, when the length of the torsion zone L is minimum, the torsional rigidity of the cross member is maximum (FIG. 5). Conversely, when the length of the torsion zone L is maximum, the torsional rigidity of the cross member is minimum (FIG. 6).

As described above, the principle of the present invention shown in FIG. 7 makes it possible to change the length ΔL according to the length of the required twist zone by making the lengths of the punch 2 and the mold 3 adjustable. There is.
For this purpose, according to the embodiment shown in FIG. 8, each of the punch 2 and the mold 3 has two parts 2a and 2b, and 3a and 3b, respectively, which can be moved toward and away from each other. It is possible to vary ΔL.

The separation between the components 2a and 2b and the separation between the components 3a and 3b are performed by placing one or more shims 6 between them.
Of course, the number and thickness of shims are selected to match the desired ΔL.

The punch parts 2a, 2b are held together with the shim 6 by means of a threaded rod 5. The same applies to the mold parts 3a and 3b and the shim 6.
Furthermore, the movement of the clamp 4 is controlled by a hydraulic cylinder actuator (not shown) that translates the clamp.

The length of the punch and mold can be changed by hydraulic control, for example using an on-board cylinder according to another possible embodiment.
Such adaptive adjustment of machine tool equipment is performed on the press machine during each manufacturing process, with or without partial disassembly of the machine tool equipment (one process is a specific average Defined by a batch of tubes characterized by tube thickness).

Before assembling machine tool equipment, calculate the length of the torsion zone according to the tube thickness. This is done according to the stiffness defined in the technical specifications.
Therefore, with such machine tool equipment, it is possible to form components in a plurality of steps during the manufacturing period.

FIGS. 9-11 are graphs illustrating one example of a torsional stiffness tolerance band obtained by the present invention as a function of a given variation in thickness and a given amount of change in operating length.
The graph of FIG. 9 shows the tube thickness variation (3.35 mm to 3.55 mm) of one batch of tubes.

The graph of FIG. 10 shows the variation in working length (corresponding to the length of the torsion zone).
The graph of FIG. 11 shows output data regarding torsional rigidity.

In the above embodiment, the tube length tolerance of ± 0.1 mm is ± 2 m.m. by varying the operating length (labeled L in FIG. 4 a) from 618 to 700 mm. It becomes possible to adapt to a tolerance band of rigidity of daN / °.
Without changing the length of the working zone (i.e., using prior art techniques), the tube thickness variation would be ± 7.25 m. It causes a variation of daN / ° (± 8%).

1 shows a step in the production of a closed cross-section member according to the prior art. 1 illustrates the next step in the production of a closed cross-section member according to the prior art. 1 illustrates the next step in the production of a closed cross-section member according to the prior art. a and b show the influence of the twisting zone of the cross member on the twisting rigidity of the crossing zone. The influence which the twist zone of a cross member has on the twist rigidity of the said cross zone is shown. The influence which the twist zone of a cross member has on the twist rigidity of the said cross zone is shown. 1 is a schematic diagram illustrating the overall principle of the present invention. 1 is a schematic diagram of a preferred embodiment of the present invention. FIG. 6 is a graph illustrating one example of a torsional stiffness tolerance band obtained by the present invention as a function of a given variation in thickness and a given variation in operating length. FIG. 6 is a graph illustrating one example of a torsional stiffness tolerance band obtained by the present invention as a function of a given variation in thickness and a given variation in operating length. FIG. 6 is a graph illustrating one example of a torsional stiffness tolerance band obtained by the present invention as a function of a given variation in thickness and a given variation in operating length.

Claims (9)

  Machine tool equipment for manufacturing a cross-section of a closed section connecting two longitudinal arms of a non-rigid axle of a motor vehicle, in cooperation with a punch (2) on the closed section of the cross-member The mold (3) and / or the punch comprising at least one mold (3) forming a twist zone of a certain length (L) and means for holding the cross member in a defined position Machine tool equipment, wherein the length (L) of the torsion zone is adjustable by adjusting the length of (2).   Each of the mold (3) and the punch (2) includes at least two parts (3a), (3b), (2a), (2b) that can move away from and approach each other. A machine tool equipment facility for manufacturing a cross member having a closed cross section according to claim 1.   The two parts (3a), (3b), (2a), (2b) of the mold (3) and / or the punch (2) are actuated by at least one actuating cylinder, Machine tool equipment for manufacturing a cross member having a closed cross section according to claim 2.   The two parts (3a), (3b), (2a), (2b) of the mold (3) and / or the punch (2) are held together using screwing means (5) and are continuous with each other. The machine tool equipment for manufacturing a cross member having a closed cross section according to claim 2, wherein   A set of shims (6) that can be arranged between the two parts (3a), (3b), (2a), (2b) of the mold (3) and / or the punch (2); A machine tool equipment facility for manufacturing a cross member having a closed cross-section according to claim 4.   Machine tool equipment for producing a cross member with a closed cross-section according to any one of the preceding claims, characterized in that the holding means comprise at least one variable movement clamp (4).   A method of manufacturing a closed cross-section cross member connecting two longitudinal arms of a non-rigid axle of a motor vehicle, in cooperation with a punch (2), having a constant length on the closed cross-section of the cross member ( L) using machine tool equipment comprising at least one mold (3) forming a twisted zone of L) and means for holding the cross member in a defined position, the mold (3) and / or Or adjusting the length (L) of the torsion zone by adjusting the length of the punch (2).   8. A cross member with a closed cross section according to claim 7, comprising the preliminary step of calculating the length (L) of the torsion zone according to the desired torsional stiffness of the cross member and the wall thickness of the cross section. Manufacturing method.   9. A method of manufacturing a cross member with a closed cross section according to claim 7 or 8, characterized in that it comprises the step of adjusting the movement of the two clamps (4) forming the holding means.

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