KR100958981B1 - Tube type torsion beam for rear wheel suspension of automobile using double pipe - Google Patents

Abstract

The tubular main steel 10 is press-formed through a hydroforming method, whereby a center portion C forming an open cross section with both ends A and a transition portion B connecting both ends A and the central portion C are formed. As a torsion beam consisting of a), the reinforcing steel 30 is fitted on both sides of the main steel (10) to surround both ends (A) and the transition portion (B), by pressing the reinforcement steel in the state where the reinforcing steel 30 is fitted A tubular torsion beam for a rear wheel suspension of a vehicle using a double pipe is introduced, characterized in that the thickness of both ends A and the transition part B becomes thicker than the center part C. According to the tubular torsion beam for the rear suspension of the vehicle using the double tube, it is possible to obtain a torsion beam of improved performance by improving the strength of the transition portion and extinguishing the torsion in the center portion.

Torsion Beam Strength, Suspension

Description

Tubular torsion beam for rear suspension of vehicle using double pipe {TUBE TYPE TORSION BEAM FOR REAR WHEEL SUSPENSION OF AUTOMOBILE USING DOUBLE PIPE}

The present invention

A tubular torsion beam for a rear suspension of a vehicle using a double pipe.

Suspension of the vehicle is a structural device that prevents the impact of the road surface generated during driving from being transmitted to the vehicle body or the occupant, and improves ride comfort by relieving the impact of the road surface while adjusting the stability of the road's traction while driving. It should be designed to increase the In addition, it must be designed to maintain a constant stiffness and endurance performance in the event of continuous road impact. Suspension deformation or cracking has a fatal adverse effect on the running stability of the vehicle, so durability design plays an important part in the functional design of the suspension system.

In particular, the torsion beam suspension system, which is mainly used as the rear wheel suspension system of a small vehicle, requires a stable durability design of the torsion beam because a continuous torsional load acts on the torsion beam. In such a torsion beam suspension device, the cross-sectional shape of the torsion beam plays an important role in the durability performance. The cross-sectional shape of the torsion beam can be variously designed according to the characteristics of the vehicle. However, the cross-sectional shape must be closely determined in relation to the roll stiffness and the roll strength of the vehicle at the beginning of the design.

In other words, since the torsion beam connects the left wheel and the right wheel, it is an important component for maintaining the overall rigidity of the rear suspension and determining the dynamic characteristics when driving the vehicle. Therefore, the torsion beam must be designed to have appropriate roll stiffness according to the weight of the vehicle against torsional deformation or bending deformation generated when the left wheel and the right wheel are reversed. It must be designed to have roll strength and to maintain the fatigue life from running.

Torsion beams are classified into three types according to their position on the trailing arm. The first is the coupling of the torsion beam to the mounting bush. In this case, since the torsion beam transmits only the torsion load purely, when the horizontal load is applied to both side ends, the moment is largely acted on the mounting site, and thus the mounting length is adjusted. The second is the case where the torsion beam is coupled in the middle of the trail arm, and the torsion beam receives a large bending load. Since the torsion beam has to have a large cross-sectional area in order to withstand such a load, there is a case where the required rigidity is not satisfied. Therefore, it is necessary to reduce the load on the torsion beam. The method of reducing the load is to adjust the cross-sectional shape of the trailing arm and to use the bushing instead of the welding portion. In general, the method of changing the cross-sectional shape of the trailing arm is widely used. Finally, a combination of the two is the case where the torsion beam is combined between the trailing arm's center and the mounting bush for simultaneous torsion and bending.

That is, it is possible to design such that the torsion mainly acts on the beam by minimizing the bending according to the position of the coupling portion. Therefore, the torsion beam can be designed in an open cross section, and the length from the point of action of the force to the mounting bush is not too long, and thus can bear the horizontal load sufficiently. Such torsion beams are commonly called CTBA (Coupled Tortion Beam Axle). However, such a torsion beam having an open cross section has a problem in that it is difficult to obtain a shape satisfying both strength and rigidity at the same time.

The present invention has been proposed to solve this problem, and an object thereof is to provide a tubular torsion beam for a rear suspension of a vehicle using a double pipe having an open cross section and at the same time having the strength and rigidity required for the torsion beam.

To achieve the above object, a tubular torsion beam for a rear suspension of a vehicle using a double pipe according to the present invention is formed by a tubular main steel being press-molded in different shapes over the entire length through a hydroforming method. A torsion beam comprising a central portion forming both ends and a "V" shaped open cross section coupled to a ring arm and a transition portion connecting the both ends and the center while the cross section is changed, both ends of the main steel. And a tubular reinforcing steel formed to enclose the transition portion, and the main steel is press-molded in the state where the reinforcing steel is inserted, so that the thicknesses of both ends and the transition portion are thicker than the center portion.

In addition, the reinforcing steel may be formed so that its thickness is within 3 mm and is in close contact with the outer circumferential surface of the main steel.

On the other hand, the main steel may be press-molded after the reinforcing steel is fitted and coupled through welding.

In addition, the main steel may be press-molded to form beads together with the reinforcing steel after the reinforcing steel is fitted.

According to the tubular torsion beam for a rear wheel suspension of a vehicle using a double tube having the structure as described above, by forming the tubular steel in a hydroforming manner, the torsion beam can have an open cross section while securing strength and rigidity.

In addition, by combining the reinforcing steel to the outside of both ends of the tubular steel after molding to improve the strength of the transition portion and to be able to digest the torsion in the center portion can be obtained a torsion beam of more improved performance.

Hereinafter, with reference to the accompanying drawings looks at the tubular torsion beam for the rear wheel suspension of the vehicle using a double pipe according to an embodiment of the present invention.

1 is a perspective view showing a tubular torsion beam for a rear wheel suspension of a vehicle using a double pipe according to an embodiment of the present invention. The torsion beam is formed by pressing the tubular main steel 10 into a different shape over the entire length through a hydroforming method, thereby forming both end portions A and "V" coupled to the trailing arm in a closed cross section. "A torsion beam consisting of a central portion (C) forming an open cross section of the shape and the transition portion (B) connecting the both ends (A) and the central portion (C) while the cross section is changed, both sides of the main steel (10) A tubular reinforcing steel 30 formed to enclose both ends A and the transition part B is fitted, and the main steel 10 is press-molded in the state where the reinforcing steel 30 is fitted to both ends A and the transition. It is characterized in that the thickness of the portion (B) becomes thicker than the central portion (C).

The torsion beam is fitted by fitting the reinforcing steel 30 of a predetermined length to both ends of the tubular rod-shaped main steel 10, and integrally formed by the hydroforming method. The hydroforming method includes a preforming step of preforming a tubular steel having a circular cross section to be seated in a mold of hydroforming; A hydroforming preparation step of seating the preformed tubular steel on the lower mold and lowering the upper mold; And sealing through the axial punches installed on both sides of the mold, supplying and pressurizing hydraulic oil to finally form the torsion beam, and simultaneously feeding the both ends of the steel using the axial punch to increase the thickness of both ends compared to the center portion. It is composed.

2 is a perspective view of a suspension device provided with a torsion beam. The torsion beam suspension system includes a pair of left and right trailing arms 2 interconnected by the torsion beam 10, and a bushing sleeve 1 having a rubber bush mounted on the front end of the trailing arm 2 includes a vehicle body. Pivotally coupled to In addition, the rear end of the trailing arm 2 is provided with a spring seat 3 on which the suspension spring is mounted and a damper bracket 4 on which the shock absorber is mounted, and outside the rear end of the trailing arm 2. The wheel carrier 5 and the spindle plate 6 is installed to engage the rear wheel of the vehicle. The bush sleeve 1, the trailing arm 2, the spring seat 3, the damper bracket 4, the wheel carrier 5 and the spindle plate 6 are the basic components constituting the torsion beam suspension. Such a torsion beam is composed of the main steel 10 and the reinforcing steel 30, and is formed so that its cross-sectional area is gradually narrowed from both ends A so as to finally remain constant at the center C. In addition, the reinforcing steel 30 is a tubular steel whose thickness is within 3 mm, is formed to be in close contact with the outer peripheral surface of the main steel (10). This is because, when the thickness exceeds 3 mm, the formability of the hydroforming is deteriorated. In addition, the length is formed to include the transition portion (B) starting from both ends (A). The reason will be described later.

3 is a stress distribution diagram when the reinforcing steel is not coupled to the torsion beam, and FIG. 4 is a stress distribution diagram when the reinforcing steel is coupled. With reference to this it looks at the reason why the reinforcing steel is coupled and the length is formed to include the transition portion.

Although torsion beams are classified as axle suspensions, they have to be designed with relatively low demand stiffness to play a part as independent suspensions because they require ride comfort and adjustment stability in recent years. In particular, in the case of the torsion beam of the present invention having a closed cross section, there is a transition part and a maximum stress value is obtained at this part. In order to lower the maximum stress value, when the stress is lowered through increase in thickness, increase in overall volume, and increase in cross section, roll stiffness is increased relatively, and thus the role of the independent suspension device cannot be expected. Therefore, reinforcing steel is used to maintain the required rigidity at a certain level without changing the overall thickness, cross-sectional area, or shape. Using the reinforcing steel, the thickness of the transition part where the maximum stress occurs is increased, and the finite element method is used to design it.

In order to obtain the stresses in the continuum by finite element modeling, it is very important how closely the model is modeled. In general, the finite element modeling method for examining the performance of a chronograph is modeled with a beam element and a spring element for a part that must exhibit rigidity. In particular, when the structural analysis of such a model is actually performed, there are many differences between the previous analysis results and the experimental results of the actual parts. In this case, the final model is completed by modifying the used model by adjusting the stiffness values of the members. Finite element modeling of torsion beam components requires a lot of time to model as closely as possible due to the complex geometry and structure. For this reason, the overall modeling uses 4 node shells a lot, but in the case of thick members, the general shell theory does not provide accurate solutions. When modeling as a solid, it is possible to increase the accuracy of the thick bracket and welded model, but in the case of the calculation time and very thin members, there is a disadvantage that the solution does not converge due to shell locking phenomenon. To solve this problem, mesh modeling was performed to maintain structural performance by appropriately adjusting solids and shells (Quad4 and Tria3), and bushes and joints were modeled using rigid elements (RBE2 and RBE3). do.

As the actual vehicle travels, the suspension is in rolling motion, which results in repeated torsion and bending loads. Roll stiffness is calculated with the reaction force obtained at the nodal point by imposing a displacement condition for the behavior perpendicular to the tread between the spindle centers of the wheel mountings. Stress information can be obtained by applying structural and structural conditions after imparting boundary and load conditions to the fastening part of the suspension system. At this time, the load imposes a torsional jounce and a rebound load. Inertia relief virtual boundary conditions were used to model the boundary conditions most closely to the actual suspension.

In the case of tubular beams, the stability is evaluated based on the stress of the combination of the normal and shear stresses. These stresses usually occur at transitions. Especially in the case of asymmetric torsion beams, the displacement of stress rarely occurs. This is because the externally attenuated resistance due to an external load is primarily applied at the transition part. When evaluating roll stiffness, reaction force is the most influential factor.Reaction force is a result of external displacement load, and when the torsion beam is easily twisted, the reaction force is low and relatively high when it is not twisted well. Will have As a result, the center portion or the transition portion of the torsion beam becomes the portion having the greatest influence. However, since the stress concentration in the transition part is directly connected to the breakage of the part, the method of making the center portion of the torsion beam well twisted is most effective. One of the methods for satisfying the strength and rigidity characteristics is a method using a reinforcing steel. This is because the reinforcing steel can be used to thicken the dislocation portion where the maximum stress portion exists, and the center portion of the beam that influences the rigidity can be designed relatively thin.

Table 1 shows the data comparing strength and stiffness with and without reinforced steel. Points a and b of FIG. 3 mean nodes of maximum stress and minimum stress, respectively, and nodes c and d of FIG. 4 also mean nodes of maximum stress and minimum stress. The point a of FIG. 3, which is the case without reinforcing steel, is applied with a stress of 704 MPa, and the point c with the reinforcing steel is applied with a stress of 665 MPa. This indicates that the maximum stress acts on the same transition part and the value decreases by 5.5%, which means that the strength of the transition part is improved. In addition, although the strength of the transition part is improved, the overall rigidity is almost unchanged, and thus the amount of torsion absorbed in the center part is almost the same. In other words, while securing strength superior to that of the prior art, rigidity comparable to the conventional one is also secured.

The joining method of such reinforcing steel can be largely two. One of them is welding, and the reinforcing steel 30 is fitted to the main steel 10 so that the main steel and the reinforcing steel are joined by welding. After coupling, the torsion beam is press-molded by using hydroforming.

The other is to press-molded such that the bead 32 is formed together with the reinforcing steel 30 after the reinforcing steel 30 is fitted into the main steel 10. The main steel 10 and the reinforcing steel 30 are molded together in the same shape, and at the same time, the bead 32 is added to the mold to bond the main steel 10 and the reinforcing steel 30 to each other through the beads 32. It does not flow after. This bead shape is well illustrated in FIG. 1. The addition of the bead 32 shape affects not only the bonding force of the main steel and the reinforcing steel but also the increase in strength of the transition portion of the torsion beam.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims It will be apparent to those of ordinary skill in the art.

1 is a perspective view showing a tubular torsion beam for the rear wheel suspension of a vehicle using a double pipe according to an embodiment of the present invention.

Figure 2 is a perspective view of the suspension device is installed in the torsion beam shown in FIG.

3 is a stress distribution diagram when the reinforcing steel is not installed in the torsion beam shown in FIG. 1.

4 is a stress distribution diagram when the reinforcing steel is installed in the torsion beam shown in FIG.

<Description of the symbols for the main parts of the drawings>

A: Both ends B: Transition part

C: Central part 10: Main steel

30: reinforcing steel 32: bead

Claims (4)

The tubular main steel 10 is press-molded into a different shape over the entire length through a hydroforming method, whereby both ends A and "V" coupled to the trailing arm 2 in a closed section. In the torsion beam consisting of a central portion (C) constituting an open cross section of the shape and the transition portion (B) connecting the both ends (A) and the central portion (C) while the cross section is changed, Both sides of the main steel 10 is fitted with a tubular reinforcing steel 30 formed to surround both ends (A) and the transition portion (B), the main steel 10 in the state where the reinforcing steel 30 is fitted When the pressure molding is performed, the thicknesses of the both ends A and the transition part B become thicker than the center part C, and the bead 32 having a double structure formed by binding the main steel 10 and the reinforcing steel 30 is formed. Tubular torsion beam for the rear wheel suspension of the vehicle using a double pipe. The method according to claim 1, The reinforcing steel 30 is a tubular torsion beam for a rear wheel suspension of a vehicle using a double pipe, characterized in that the thickness is within 3 mm and is in close contact with the outer peripheral surface of the main steel (10). delete delete

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