KR101304752B1 - Torsion Beam Producing Method - Google Patents

Abstract

The present invention provides a torsion beam manufacturing method and a torsion beam which can increase the heat input of welding and increase the durability of the welded part, the preparation process of preparing to form a tube; An expansion process performed by a hydroforming method to expand the thickness of the end of the tube while increasing the thickness; And a finishing step of cutting the end after the pressurized feeding to form a welded part, wherein the expanding process is performed by mounting the tube in a mold to uniformly increase the thickness distribution of the end of the tube with respect to the extending direction of the tube. A torsion beam shaping method for pressure feeding an end of a tube with an axial punch comprising an inclined pressing surface and a torsion beam produced thereby.

Description

Torsion Beam Producing Method

The present invention relates to a method of shaping a torsion beam for use in a suspension of a vehicle.

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 Among them, the CTBA (Coupled Torsion Beam Axle) acts to increase the ride comfort because it keeps the body shaking when the vehicle is turning and maintains the balance of the vehicle.

When analyzing the load applied to the torsion beam in the CTBA module, it is divided into torsional load applied from the ground when the vehicle is traveling on the road, and the front / rear and left / right loads applied when the vehicle is turning, driving and stopping. Therefore, rigidity and durability for each load are required.

As disclosed in Korean Patent Laid-Open Publication No. 2006-0067546, a CTBA for a rear wheel suspension of a conventional vehicle is connected to a torsion beam 1 and a trailing arm 2 and a trailing arm 2 connected thereto as shown in FIG. It is comprised including the spring seat 3.

As shown in FIG. 1, reinforcing materials 4 and 5 are added between the torsion beam 1 and the trailing arm 2 to distribute the load acting on the weld between the torsion beam and the trailing arm due to an external force while driving the vehicle. In order to prevent breakage of the weld. In addition, it is designed to improve durability by relieving residual stress through post-heat treatment between the torsion beam and the trailing arm to strengthen the welded part.

However, when the reinforcement is used like the conventional torsion beam, the weight of the CTBA is increased, thereby lowering the fuel efficiency of the vehicle and increasing the carbon dioxide emission. When the reinforcement is removed, the conventional torsion beam is designed by the stamping method, so that the weld between the torsion beam and the trailing arm is weak, which causes the durability to be inferior. It becomes a factor.

On the other hand, as a method of processing the material is registered in the Patent No. 1060865, a hydroforming method is introduced. As shown in FIGS. 2A and 2B, the hydroforming is loaded with a material, that is, a tube (or tube) 130 formed on the lower mold 110b of the hydroforming apparatus 100, and the upper mold 110a. In the state where the press is lowered, the axial punch 122 of the axial cylinder 120 disposed at both ends of the tube proceeds in the axial direction and is then sealed, and at the same time, axial compress is applied to mount the mold and the axial punch. Is completed.

At this time, the tube 130 is fixed in a sealed state by the lower mold, the upper mold, and both axial punches 122, along with the accumulator pressure of the axial punch, a hydraulic pressure (arrow) is applied to the inside of the tube, and the mold The tube in the product forming part (face) f of the tube is expanded.

The present invention is to solve the above conventional problems, and to provide a torsion beam and a method for manufacturing the same to increase the area of the weld to exclude the separate welding reinforcement in the connection of the torsion beam and the trailing arm. do.

Moreover, an object of this invention is to provide the torsion beam which enables weight reduction of a vehicle, eliminating the necessity of a welding reinforcement material.

Furthermore, an object of the present invention is to provide a torsion beam capable of increasing the durability of the welded portion and increasing the heat input of the weld.

The present invention provides a torsion beam shaping method, thereby forming a torsion beam, to achieve the above object.

The present invention provides a preparation process for preparing a tube; An expansion process performed by a hydroforming method to expand the thickness of the end of the tube while increasing the thickness; And a finishing step of cutting the end after the pressurized feeding to form a welded part, wherein the expanding process is performed by mounting the tube in a mold to uniformly increase the thickness distribution of the end of the tube with respect to the extending direction of the tube. Provided are a torsion beam forming method for pressurizing an end of a tube with an axial punch comprising an inclined pressing surface.

The present invention further includes a bending process of bending the end portion of the tube with respect to the center portion before the expansion process, wherein the finishing step includes a bent portion having an extended torsion beam end after the expansion process. It can be cut inclined with respect to the welding portion.

In addition, the present invention may further include a cutting process for cutting the end of the tube to have a feeding portion parallel to the welded portion of the finishing step and extending from the cutting surface, and performed between the bending process and the expanding process. .

At this time, the feeding portion has a length of 80mm or less, the bending process may be bent the end of the tube between 5 ~ 45 degrees.

Meanwhile, in the present invention, the pressing surface of the axial punch may be inclined at an angle between 27 and 62.5 with respect to the extending direction of the tube.

In addition, the angle formed by the pressing surface of the axial deviation with respect to the extension direction of the tube may satisfy the range of -3 ° to + 30 ° than the angle formed by the welding portion with respect to the extension direction of the tube.

In addition, in the present invention, the inclined pressing surface of the welding portion and the axial punch may be parallel.

Alternatively, the present invention includes a weld configured to be welded to the trailing arm at both ends in the longitudinal direction; And a central part connected to the welding part and having a cross section along a longitudinal direction formed in a closed curve, wherein the welding part is formed to be inclined with respect to the longitudinal direction to secure weldability with the trail rim arm, and has a thickness greater than the thickness of the central part. To provide a torsion beam having a uniform thickness throughout the weld.

The present invention can provide a torsion beam and a method of manufacturing the same to increase the area of the weld to exclude a separate welding reinforcement in the connection of the torsion beam and the trailing arm through the above configuration.

In addition, the present invention can provide a torsion beam that can reduce the weight of the vehicle by eliminating the need for welding reinforcement,

Furthermore, the present invention can provide a torsion beam which can increase the durability of the welded portion and can increase the heat input amount and the lifetime of the weld.

1 illustrates a conventional coupled torsion beam.
2A and 2B are schematic views of a conventional hydroforming method.
3 is a perspective view of a torsion beam module in which the torsion beam of the present invention is connected to a trailing arm.
4 is a schematic diagram of a process for fabricating a torsion beam of the present invention.
5 is a diagram of a torsion beam according to the torsion beam process of the present invention, (a) torsion beam after the bending process, (b) torsion beam after the preforming process, (c) torsion beam after the expansion process The completed torsion beam after this (d) finishing process is shown.
FIG. 6A is a view schematically showing the expansion process, and FIG. 6B is a view showing the portion of the torsion beam cut in the finishing process and the tube thickness of the torsion beam end after the expansion process.
7 is a schematic diagram of another process for fabricating the torsion beam of the present invention.
8 is a diagram of a torsion beam according to the torsion beam process of the present invention, (a) a torsion beam after the bending process, (b) a torsion beam after the preforming process, (c) a torsion beam after the cutting process This (d) shows the torsion beam after the expansion process, and (e) the torsion beam completed after the finishing process.
9 is a view schematically showing an expansion process of the present invention.
FIG. 10 is a graph showing an angle formed by an extension direction of a bending portion of a tube and a pressing surface of an axial punch, and a thickness change at A point in an expansion process of the present invention.
11 is a graph showing the S / N curve of the DP780 steel grade.
FIG. 12 is a graph showing the results of substituting the S / N curves of FIG. 11 into the stresses at point A of the present invention.
13 is a cross-sectional view of an axial punch for hydroforming used in torsion beam fabrication of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

3 is a perspective view of a torsion beam module in which a torsion beam of the present invention is connected to a trailing arm, FIG. 4 is a schematic diagram of a process of manufacturing the torsion beam of the present invention, and FIG. 5 (a) is a torsion beam after a bending process, FIG. 5 (b) shows the torsion beam after the preforming process, FIG. 5 (c) shows the torsion beam after the expansion process, and the completed torsion beam after the finishing process of FIG. 5 (d).

As shown in FIG. 3, the torsion beam module of the present invention comprises a torsion beam 10 and a trailing arm 30, the trailing arm 30 being welded to the torsion beam 10, and thus the trailing arm. 30 and the torsion beam 10 are connected to form a torsion beam module.

Although not shown in FIG. 3, the trailing arm 30 is connected to the wheels of the vehicle and the spring seat 3 (see FIG. 1) in the same manner as the conventional trailing arm 30. Since the trailing arm 30, the spring seat 3, and the like are the same as the conventional trailing arm and the spring seat, detailed description thereof will be omitted.

The shaping method of the torsion beam 10 of the present invention is shown in FIG. As shown in FIG. 4, the torsion beam 10 of the present invention has a preparatory process of preparing a tube (S10), a bending process (S20) of bending the end 13 of the prepared tube to a predetermined angle, and an end portion 13 After pre-forming the bent tube to be inserted into the mold of the hydroforming process (S40) (S30), after blocking both ends of the tube to be pre-formed and inserted into the mold, and then insert the axial bias into the tube end Expansion process (S40) for hydroforming the tube into a mold by applying hydraulic pressure to the inside of the tube, and finishing process (S50) for cutting the bent portion bent from the tube expanded by the hydroforming into a shape corresponding to the trailing arm (30). Finally through the torsion beam 10 of the present invention is completed.

Since the torsion beam 10 in the process step is shown in FIGS. 5 (a) to 5 (d), the process step of the present invention will be described with reference to this.

As shown in FIG. 5 (a), the end 13 is bent in a straight tube having a circular cross section in the preparation step S10. The bending process S20 may be performed through a bending machine known in the art such as a bending machine, and a cutting process S50 is performed around the bending portion 12 that is substantially bent.

In this way, the tube 13 having the end 13 bent through the bending step S20 is performed by the preforming process S30 so that the center portion 11 and the end 13 can be inserted into a mold used in the hydroforming process S40. do. Preforming process (S30) is limited to the deformation that can be performed in the hydroforming method performed by the expansion process (S40), so that the expansion process (S40) can be performed within this range, in the present invention Since it is also used in the general hydroforming method, not the hydroforming method used, a detailed description thereof will be omitted.

In the preforming process (S30), the tube is pressed as a whole, the central portion 11 is formed in a substantially 'U' shape, is formed to be inserted into the hydroforming mold used in the expansion process (S40).

Tubes completed up to the pre-forming process (S30) is subjected to expansion process (S40) by a hydroforming method. The hydroforming process (S40) inserts the tube into the mold in the same manner as the general hydroforming process, then blocks both ends 13 of the tube, and then axial punches into the blocked both ends 13 (Fig. 2A). (See numeral 122) is inserted.

The axial punch pressurizes the inside of the tube with a high pressure fluid, thereby forming the tube into the shape of a mold. At this time, the axial punch is fed to pressurize the tube for the sealing of the tube. At this time, by the pressure feeding effect, that is, the axial pressure of the axial punch, both ends 13 of the tube are pressed in the mold, and accordingly The end 130 of the tube is thickened.

In this regard, FIG. 6A shows pressure feeding of the hydroforming process of FIG. 5C. As shown in FIG. 6A, the axial punch 122 in hydroforming has a plane perpendicular to the end. That is, the pressing surface 122a of the axial punch 122 is perpendicular to the extension line of the bending part 12.

6B shows the result of analyzing the hydroforming molding for the DP780 steel grade, and it can be confirmed that the thickness at the end portion after the expansion step (S40) becomes thick. Specifically, in FIG. 6B, it can be seen that the thickness at the end 13 of the tube is increased by the feeding effect of the hydroforming, and in the cutting line 15 to be the end of the torsion beam 10, 3.4 mm before molding. It can be seen that the tube having a thickness of 3.8mm has a maximum thickness. This results in the end 13 having a thicker thickness than the central portion 11, resulting in a thickness of the weld 14 to be welded to the trailing arm later.

On the other hand, as shown in Figure 5 (d), the tube after the hydroforming process (S40) is cut to fit the shape of the trailing arm 30 to be welded around the bending portion 12. The cutting line 15 to be cut is shown in FIG. 6B.

In the present invention, the cutting is made to fit the shape of the trailing arm 30 around the bending portion 12, so that the area welded with the trailing arm 30 in proportion to the bent angle is increased. Can be. That is, when the trailing arms 30 are the same, the bending angle θ may increase, so that the area of the welded portion that abuts on the trailing arms 30 may increase in a relationship of approximately (1 / cosθ).

At this time, the bending angle θ is advantageously between 5 and 45 °, but less than 5 ° does not increase the weld area according to the bending, the effect is not expressed, if the angle exceeds 45 ° hydroforming is difficult to perform Because.

Since the torsion beam 10 of the present invention is shaped as a tube member, as shown in Fig. 5 (d), the cross section along the longitudinal direction at the central portion 11 forms a closed curve, and the welded portion to be welded with the trailing arm. Since the weld part 14 is formed centering on the bending part 12 for the increase of 14, the weld part 14 has a bent shape.

In addition, the welding part 14 may have a thickness larger than that of the central part 11, so that an area of the welding part welded to the trailing arm 30 may be increased.

In addition, the torsion beam 10 according to the present invention is the most equivalent of the torsion beam 10 while maintaining roll stiffness, roll durability, and deformation characteristics equivalent to those of the conventional torsion beam 1. Durability can be improved under high speed and high input load conditions. This is because the thickness of both ends of the torsion beam is increased by the feeding effect of the hydroforming, and the durability of the weld is improved by increasing the welding area of the torsion beam and the trailing arm by expansion.

6A and 6B, the cutting line 15 may be inclinedly cut at an angle equal to or different from an angle bent with respect to the extension line of the bending part 12 to expand the cross-sectional area. Accordingly, it is not parallel to the end face 16 of the tube, that is, the pressing surface 122a of the axial punch 122. Thus, the distance from the cutting line 15 to the end face 16 of the tube is not constant.

In this case, the effect of the thickness increase by the pressure feeding of the axial punch 122 increases as the axial punch 122 gets closer, but the cutting line 15 is not parallel to the pressing surface 122a, so that the axial punch 122 ), The distance from the cutting line 15 is different, and thus the thickness is increased. This can be confirmed by looking at the thickness of the point B where the distance from the axial punch 122 is closest to the dust point A in FIG. 6B.

In this way, the welded portion 14 along the cutting line 15 may not only have a nonuniform thickness distribution but also have a relatively low thickness at one point A, thereby making the durability weak.

7 to 12 show a method of manufacturing a hydroforming torsion beam to make the thickness uniform in such a weld 14 and a hydroforming torsion beam thereby.

Another shaping method of the torsion beam 10 of the present invention is shown in FIG. As shown in FIG. 7, the torsion beam 10 of the present invention has a preparatory process of preparing a tube (S10), a bending process (S20) of bending the end 13 of the prepared tube to a predetermined angle, and an end portion 13 A cutting step (S25) for cutting the bent tube to have a feeding part 17 parallel to the subsequent welding part 14, and a pre-forming that the tube is inserted into the mold of the hydroforming step (S40) after the cutting step. Forming process (S30), the expansion step (S40) of blocking the both ends of the tube formed in the pre-formed and inserted into the mold, and then inserting the axial shift into the tube end to apply a hydraulic pressure to the tube to hydro-form the tube into a mold shape, and The torsion beam 10 of the present invention is finally completed through the finishing process S50 of cutting the bending portion bent from the tube expanded by the hydroforming to a shape corresponding to the trailing arm 30.

At this time, the cutting process (S25) may be unnecessary when the initial tube shape is designed in consideration of bending. That is, if the cutting line 15 and the end 16 are substantially parallel in the shape after the bending process S20, the cutting process S25 may be omitted.

Since the torsion beam 10 in the process step is shown in FIGS. 8 (a) to 8 (e), the process step of the present invention will be described with reference to this.

As shown in FIGS. 8A to 8E, the end 13 is bent in a straight tube having a circular cross section in the preparation step S10. The bending process S20 may be performed through a bending machine known in the art such as a bending machine, and a cutting process S25 and a finishing process S50 are performed around the bending portion 12 that is substantially bent.

In this way, the tube 13 having the end 13 bent through the bending process S20 is cut at a predetermined distance l from the cutting line 15 so as to have the feeding part 17 parallel to the shape of the final welding part 14. (S25). That is, the remaining part is cut off at the end 13 leaving the feeding part 17 parallel to the welding part 14.

Thereafter, the preforming process S30 is performed so that the center portion 11 and the end portion 13 can be inserted into the mold used in the hydroforming process S40. Since the preforming process S30 is limited in the deformation that can be performed in the hydroforming method performed by the expanding process S40, the expanding process S40 is performed within this range.

In the preforming process (S30), the tube is pressed as a whole, the central portion 11 is formed in a substantially 'U' shape, is formed to be inserted into the hydroforming mold used in the expansion process (S40).

Tubes completed up to the pre-forming process (S30) is subjected to expansion process (S40) by a hydroforming method. The hydroforming process S40 inserts a tube into a mold in the same manner as a general hydroforming process, and then closes both ends 13 of the tube, and then an axial punch is inserted into the blocked both ends 13.

9 shows a hydroforming process for shaping with an axial punch 122 of the present invention. As shown in FIG. 9, the end 13 of the tube is cut leaving a feeding portion 17 parallel to the cutting line 15, the pressing surface 122a of the axial punch 122 being angled relative to the extension direction of the tube. It is configured to be inclined with φ, and the end face 16 is configured to be inclined with an angle α with respect to the extending direction of the tube approximately parallel to the cutting line 15.

Thus, the weld 14 is fed the same distance from the axial punch 122, and thus the thickness is equally thick, so that the weld 14 may have the same thickness after the hydroforming is finished.

At this time, the feeding unit 17 is preferably configured to have a distance l of 80 mm or less from the cutting line 15, that is, the welding unit 14 (see FIG. 8B). As mentioned above, since the effect of the pressure feeding by the axial punch 122 varies depending on the distance, when larger than 80 mm, the increase in thickness is insignificant, and the welding portion 14 reinforcement effect cannot be expressed.

FIG. 10 is a graph showing an angle φ formed between the extension direction of the bending portion 12 of the tube and the pressing surface 122a of the axial punch 122 in the expansion process of the present invention, and the thickness change at the A point. It is. Here point A is the innermost point and is the same as point A, the thinnest point in FIG. 6B.

As shown in FIG. 10, when the angle (phi) of the pressing surface 122a of the axial punch 122 and the bending part 12 of a tube exceeds 62.5 degrees, there is no change in the thickness of A point. However, the thickness began to increase, starting with 62.5 °. As the angle φ of the pressing surface 122a of the axial punch 122 and the bending portion 12 of the tube were less than 27 °, buckling occurred at the point A. Accordingly, the smaller angle φ was obtained from the experimental data. I didn't get it.

On the other hand, Table 1 below shows the stress at each thickness.

turn Punch Angle (°) Thickness (t) Stress (MPa) One 62.5 3.38 267.14 2 48.7 3.46 261.61 3 42 4.30 214.70 4 37 5.07 181.19 5 27 5.49 187.40

As can be seen in Table 1 above, as the punch angle, that is, the angle φ between the pressing surface 122a of the axial punch 122 and the extending direction of the tube, the thickness of the point A changes, and accordingly , It can be confirmed that the stress at the A point is converted.

At this time, the bending angle θ of the extending direction of the tube is approximately 27.5 °, and the angle φ between the pressing surface 122a of the action punch 122 and the extending direction of the tube is affected by the bending angle θ, It is preferable that the angle φ formed by the pressing surface 122a of the axial deviation 122 with respect to the extending direction of the tube satisfies the range of -0.5 ° to + 35 ° from the bending angle θ.

11 shows an S / N curve of the DP780 steel grade, and FIG. 12 shows a graph in which the stress values of Table 1 are substituted for the S / N graph of FIG. 11.

As shown in FIG. 12, it can be seen that the endurance life of the weld 14 increases exponentially with the thickness of the weld 14. This means that the stress changes as the angle φ between the pressing surface 122a of the axial punch 122 and the extension direction of the tube changes, and the endurance life of the weld 14 changes as the stress changes. The increase means exponential.

Therefore, as shown in the present invention, when the axial punch 122 having the pressing surface 122a inclined with respect to the extending direction of the tube can be used, the endurance life of the weld portion 14 can be significantly increased.

Figure 13 shows a cross-sectional view of an axial punch for hydroforming used in torsion beam fabrication of the present invention. The lower mold 110b (see FIG. 2A) of the hydroforming apparatus is loaded with a material, that is, a tube (or tube) 10 to be formed, and the upper mold 110a (see FIG. 2A) is lowered by a press, and both ends of the tube are pressed. The axial punch 122 of the axial cylinder 120 (refer to FIG. 2A) disposed in the axial direction is sealed and at the same time, axial compress is applied to complete the molding of the mold and the mounting of the axial punch.

As shown in FIG. 13, the axial punch 122 used in the present invention has a pressing surface 122a that is inclined at an inclination angle φ with respect to the extending direction of the torsion beam 10, which is a base material, and thus the pressing surface inclined ( The torsion beam 10 is pressure-feeded with 122a), and the welded portion 14 of the torsion beam formed by such a hydroforming apparatus may have a uniform thickness throughout.

10: torsion beam 11: center portion
12: bending part 13: end
14: welding part 15: cutting line
16: cross section 17: feeding part
30: trailing arm 122: axial punch
122a: pressing surface

Claims (10)

A preparatory process of preparing to form a tube; And
And an expansion process performed by a hydroforming method to expand the tube while increasing the thickness of the end portion thereof.
In the expanding process, the tube is seated in a mold so as to uniformly increase the thickness distribution of the end of the tube, and then pressure feeds the end of the tube with an axial punch having a pressing surface inclined with respect to the extending direction of the tube.
A bending process of bending the end of the tube with respect to a central portion before the expansion process; and
Further comprising a finishing step of cutting the end after the expansion process to form a welded portion,
The finishing step is a torsion beam forming method of cutting the bent portion to have an extended torsion beam end after the expansion process inclined with respect to the extension direction of the tube to form the weld. delete The method of claim 1,
A torsion beam forming method, which is performed between the bending process and the expansion process, and cuts an end portion of the tube so as to have a feeding part parallel to the welding part of the finishing step and extending from the welding part. . The method of claim 3, wherein
The feeding part has a length of 80 mm or less, and the bending process is to bend the end of the tube between 5 to 45 degrees. The method of claim 1,
And the pressing surface of the axial punch is inclined at an angle between 27 and 62.5 ° with respect to the extending direction of the tube. The method of claim 5, wherein
Torsion beam forming method characterized in that the angle (φ) formed by the pressing surface of the axial deviation with respect to the extending direction of the tube satisfies the range of -0.5 ° to + 35 ° than the bending angle (θ). The method of claim 5, wherein
And a pressing surface of the axial biasing is parallel to the welding portion. delete delete delete

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