JP2011088461A - Suspension structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suspension structure having sufficient connection strength between a trailing arm and a torsion beam and easily ensuring productivity, cost reduction, and a reduction in the number of parts. <P>SOLUTION: The suspension structure includes a pair of right and left trailing arms 2 and a torsion beam 7 connected between the pair of the trailing arms 2. The torsion beam 7 includes: a central portion 7M including a pair of leg parts extending downward and a circular connecting part for connecting the leg parts and having a first cross-sectional shape S1 opened downward; a connecting portion 7C including an end part connected to the trailing arm 2 and having a triangular second cross-sectional shape S2 opened downward; and a gradually changing portion 7G having a gradually changing cross-sectional shape Sg gradually changing from the first cross-sectional shape to the second cross-sectional shape from the central portion to the connecting portion. The gradually changing portion 7G is disposed near the trailing arm 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vehicle suspension structure including a pair of left and right trailing arms and a torsion beam coupled across the pair of trailing arms.

  As prior art document information related to this type of suspension structure, there is Patent Document 1 shown below. In the suspension structure described in Patent Document 1, a gusset straddling between a trailing arm and a torsion beam is disposed and welded to both the trailing arm and the torsion beam. Therefore, it is possible to give sufficient strength to the connecting part between the trailing arm and the torsion beam. It is said that it can be close to the value.

Japanese Patent Laying-Open No. 2005-8123 (paragraph 0017, FIG. 1)

  However, in the suspension structure described in Patent Document 1, since a reinforcing gazette is provided in addition to the trailing arm and the torsion beam, productivity, cost, reduction of the number of parts, weight reduction of the vehicle weight, etc. It was disadvantageous in terms.

  Therefore, in view of the problems given by the suspension structure according to the prior art exemplified above, the object of the present invention is to provide sufficient strength to the connecting portion of the trailing arm and the torsion beam, and to improve productivity, cost, and parts. An object of the present invention is to provide a suspension structure that can easily secure a reduction in the number of points and a reduction in vehicle weight.

The first characteristic configuration of the suspension structure according to the present invention is:
A suspension structure comprising a pair of left and right trailing arms and a torsion beam connected across the pair of trailing arms,
The torsion beam has a central portion having a downwardly opened arch-like first cross-sectional shape including a pair of legs extending downward and an arc-shaped connecting part connecting the pair of legs, and the tray A connecting portion having a triangular second cross-sectional shape including an end portion connected to the ring arm and opened downward, and the second cross-sectional shape from the first cross-sectional shape toward the connecting portion from the central portion. Having a gradually changing portion with a cross-sectional shape gradually changing to
The gradual change site is located near the trailing arm.

Torsional stress is applied to the torsion beam when the vehicle travels on a corner of a road or a sharp curve. Generally, when the cross-sectional shape is constant in the longitudinal direction, the inflection point that is the weakest against torsion is the torsion beam. It appears at the opening side end of the cross section.
However, in the suspension structure according to the first characteristic configuration, the cross-sectional shape of the torsion beam is not constant in the longitudinal direction, and the arch has high torsional rigidity because the central portion has legs extending parallel to each other and is close to a pipe shape. On the other hand, a triangular second cross-sectional shape having a sufficient bending rigidity in the vertical direction is employed for the connecting portion with the trailing arm, but the twisting rigidity is inferior, Between the connecting portions, a gradually changing portion whose sectional shape gradually changes from the first sectional shape to the second sectional shape is disposed. As a result, the inflection point that is the weakest against twisting is moved from the opening side end to the top side of the torsion beam, so that cracking due to twisting is hardly generated at the opening side end of the torsion beam cross section. Become. For the same reason, when the cross-section of the torsion beam has an inverted U-shape (∩-shape) or an inverted V-shape (∧-shape) that opens downward, a stone or the like that is flipped up by a wheel during traveling Since the lower end portion of the cross section of the torsion beam with which the foreign object collides does not coincide with the inflection point, the durability of the torsion beam is improved.

  The second characteristic configuration of the present invention is that the circumference of the torsion beam in the cross section is constant in each cross section in the longitudinal direction of the torsion beam.

  In such a configuration, the second cross-sectional shape inevitably has a larger vertical dimension than the first cross-sectional shape, so a cutout for welding with the trailing arm is provided at the connection portion. Is obtained with a margin, and a strong connection structure is secured between the two members without using an auxiliary member such as a gusset. As a result, it is easy to improve productivity at the time of assembling the vehicle, cost, reduction of the number of parts, weight reduction of the vehicle weight, and the like.

  In addition, in such a configuration, in the press work for obtaining the above-described cross-sectional shape from a flat steel plate, a simple shape rectangular steel plate having a constant width along the longitudinal direction may be used as a starting material. The productivity is high and the yield is good when processing.

It is a side view which shows the rear part of the vehicle provided with the suspension structure by this invention. It is a side view which shows the suspension structure by this invention. It is a top view which shows the suspension structure by this invention. FIG. 4 is a perspective view showing a main part of the suspension structure of FIG. 3. It is sectional drawing of the center site | part of a torsion beam, and a connection site | part. It is a schematic diagram explaining the operation of a torsion beam. It is sectional drawing which shows the connection part by another embodiment.

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated, referring drawings.
FIG. 1 schematically shows a rear portion of a vehicle to which a suspension structure according to the present invention is applied.
This suspension structure includes a pair of left and right trailing arms 2 and a torsion beam 7 connected across the pair of trailing arms 2.

  As shown in FIG. 2, each trailing arm 2 generally has a pipe shape with a round cross section, and extends in the front-rear direction of the vehicle body. An annular bush 3 is provided at the front of each trailing arm 2 so as to be swingable around the axis X of the vehicle body frame. On the other hand, an end plate 4 for connecting the spindle 4 a of the wheel 20, a spring receiving member 5 for attaching the spring 21, and a support bracket 6 connected to the shock absorber 22 are provided at the rear part of the trailing arm 2. ing.

The torsion beam 7 is given a sectional shape opened downward by bending a substantially rectangular steel plate along the longitudinal direction with a press to obtain bending rigidity and torsional rigidity.
As illustrated in FIG. 3 and FIG. 4, arc-shaped notches 7R are formed at both ends of the torsion beam 7, and both ends of the trailing arm 2 are engaged with the notches 7R. The members 7 and 2 are welded.

The cross-sectional shape of the torsion beam 7 is not constant along the longitudinal direction of the torsion beam 7, and includes a portion where the cross-sectional shape changes in a part of the longitudinal direction.
More specifically, the torsion beam 7 includes a central part 7M located at the center of the left and right sides of the vehicle body, a connecting part 7C connected to the trailing arm, a central part 7M, and a connecting part 7C. It is divided into a gradual change site 7G located between the two.

  As shown in FIGS. 4 and 5, the central portion 7 </ b> M has a generally scissors-like shape that is open downward and includes a pair of legs that extend downward and an arc-shaped connection that connects the pair of legs. A first cross-sectional shape S1 having an arch shape is provided. More precisely, as shown in FIG. 5 (a), the first cross-sectional shape S1 of the central portion 7M has a relatively large-diameter arc-shaped connection portion d1 and a linear shape diagonally downward from both ends of the connection portion d1. A pair of intermediate portions d2 and a pair of leg portions d3 extending in parallel directly below each end of the intermediate portion d2.

  7C of connection parts are provided with 2nd cross-sectional shape S2 of the generally scissors shape (an example of a triangular shape) open | released below. More precisely, as shown in FIG. 5B, the second cross-sectional shape S2 of the connecting portion 7C also has a relatively small-diameter arc-shaped connection part f1 and extends from both ends of the connection part f1 in a C shape. And a pair of legs f2. Note that the radius R1 of the arc that forms the connection portion d1 of the first cross-sectional shape S1 is about 2 to 3 times the radius R2 of the arc that forms the connection portion f1 of the second cross-sectional shape S2.

The gradually changing portion 7G has a gradually changing cross-sectional shape Sg that changes generally continuously from the first cross-sectional shape S1 to the second cross-sectional shape S2.
As shown in FIG. 4, the gradually changing cross-sectional shape Sg includes an arc-shaped connection part e1, a pair of intermediate parts e2 extending linearly diagonally downward from both ends of the connection part e1, and downward from both ends of the intermediate part e2. It is comprised with a pair of leg part e3 extended. From the boundary with the central portion 7M toward the boundary with the connecting portion 7C, the arc-shaped connecting portion e1 is gradually reduced in diameter, the intermediate portion e2 is gradually shortened, and the leg portion e3 is gradually lengthened. . Further, the extension angle of the leg e3 gradually decreases from the downward direction at the boundary with the central portion 7M toward the open leg angle (a predetermined angle within a range of 40 ° to 45 °) at the boundary with the connecting portion 7C. It has changed.

  The gradually changing portion 7G is disposed in the vicinity of the trailing arm 2, and a central portion 7M, a gradually changing portion 7G, and a connecting portion 7C are provided for portions extending from the midpoint CP in the longitudinal direction of the torsion beam 7 to the left or right. (7M: 7G: 7C = 50 to 70:15 to 25:15 to 25), and a particularly preferable ratio is (7M: 7G: 7C = 60: 20:20).

  However, the length of the connecting portion 7C is made as close to zero as possible, and the torsion beam 7 is substantially composed of only the central portion 7M and the gradually changing portion 7G in length (7M: 7G = 70 to 80: : 20-30) or (7M: 7G = 75: 25).

  The first cross-sectional shape S1 assigned to the central portion 7M has a square shape (arch shape), which is sufficient in the vertical and horizontal directions among the simple cross-sectional shapes obtained by bending the steel plate into a shape opened downward. Not only has bending rigidity, but also has a high torsional rigidity. This is to fulfill the original purpose of the torsion beam, which is to suppress the twisting between the left and right trailing arms 2. The central portion 7M not only has a constant cross-sectional shape along the longitudinal direction, but also has vertical and longitudinal dimensions that are substantially constant along the longitudinal direction.

  Next, the second cross-sectional shape S2 that is assigned to the connecting portion 7C and that is opened downward is inferior in torsional rigidity to the first cross-sectional shape, but is sufficient in the vertical direction. It is employed as a shape that has bending rigidity and that can easily ensure a larger vertical dimension than the first cross-sectional shape S1. The larger size in the vertical direction is that the notch 7R for welding with the trailing arm 2 is formed with a margin so that a sufficiently strong connection structure between the two members without using an auxiliary member such as a gusset. Fulfills the role of ensuring

The gradually changing cross-sectional shape Sg, which is assigned to the gradually changing site 7G and gradually changes from the first cross-sectional shape S1 to the second cross-sectional shape S2, is a site where the cross-sectional shape changes abruptly between the central site 7M and the connecting site 7C. This is a configuration that is intended not to be formed.
Another intention of providing the gradual change portion 7G between the central portion 7M and the connecting portion 7C is to improve the durability of the torsion beam 7.

  That is, torsional stress is applied from the trailing arm 2 to the torsion beam 7 when the vehicle travels on a corner of a road or a sharp curve. When the cross-sectional shape opened to one side of the torsion beam 7 is constant along the longitudinal direction, the inflection point (maximum stress location) due to the torsional stress is generally the opening side end of the cross-section of the torsion beam 7 (the cross-section is It is thought that it appears in the lower end portion if it is in the shape of a letter or a bowl.

  Therefore, as in this embodiment, when the cross-sectional shape of the torsion beam 7 is a square shape or a square shape that opens downward, the lower end portion of the cross-sectional shape is made of pebbles or rubble that is spun up by wheels during traveling. Since a foreign object collides, it is disadvantageous from the viewpoint of the durability of the torsion beam 7 that an inflection point due to torsional stress appears at the lower end.

  However, when the applicant processes the steel plate for torsion beam into a cross-sectional shape opened to one side by pressing, if the processing is performed so that the above-described gradual change portion 7G is generated near both ends in the longitudinal direction, FIG. 3 and FIG. As shown in FIG. 5, there is an interesting phenomenon that the inflection point T moves inwardly from the end of the cross section of the torsion beam in the gradual change site 7G (upward from the lower end in the cross section shown in FIG. 5). It was confirmed by estimating the stress distribution by structural analysis.

  That is, in the suspension device according to the present invention, the newly obtained knowledge is applied, and the gradually changing portion 7G is provided between the central portion 7M and the connecting portion 7C of the torsion beam 7, as illustrated in FIG. The inflection point T due to torsional stress moves inward from the end of the beam-shaped cross section (moves upward if the cross section is in the shape of a letter or letter), so that pebbles, rubble, etc. The location where the foreign object collides does not coincide with the inflection point, and as a result, the durability of the torsion beam 7 is improved.

  Furthermore, although the shear center of the torsion beam 7 having a cross-sectional shape opened downward exists at a position somewhat spaced upward from the upper end of the cross section, according to the present invention, the inflection point T is the end of the cross section of the torsion beam 7. Since it moves inward from the part (lower end) and approaches the center of shear, cracks due to torsion hardly occur at the lower end of the torsion beam 7 for that reason.

  Note that the cross section of the torsion beam 7 or the line length of the cross section, in other words, the circumferential length of the cross section is constant in each cross section in the longitudinal direction. Therefore, in press working, it is only necessary to use a rectangular steel plate having a constant width along the longitudinal direction as a starting material, so it is only necessary to use a rectangular steel plate having a simple shape as a starting material. Yield during processing is also improved.

  Further, when the vehicle travels on a corner of a road or a sharp curve, bending stress in a direction parallel to the road surface is also applied to the torsion beam 7, but this configuration shows an exaggerated example in FIG. Thus, since the knowledge that the bending of the torsion beam 7 occurs with the left and right inflection points T located outside the gradual change site 7G close to the trailing arm 2 as a fixed point has been obtained by structural analysis, The swing width can be secured as large as possible, and a large load is hardly transmitted to the joint between the torsion beam 7 and the trailing arm 2, so that the ride comfort of the vehicle is greatly improved.

  A pair of press reference holes PH is provided at the upper end in the vicinity of the left and right end portions of the gradually changing portion 7G. This press reference hole PH is engaged with two pins (not shown) protruding from a part of a mold (not shown), so that the rectangular steel plate of the material is made from the initial stage to the final stage of press working. Plays a role in preventing movement relative to the mold.

[Another embodiment]
<1> As illustrated in FIG. 7, the cross-sectional shape of the connecting portion 7 </ b> C includes a small arc-shaped connection part f <b> 1, a pair of first leg parts f <b> 2 extending obliquely downward from both ends of the connection part f <b> 1, It is good also as a form comprised with a pair of 2nd leg part f3 extended in parallel directly under each edge part of the leg part f2. However, in this case, it is preferable that the length of the second leg portion f3 gradually decreases along the longitudinal direction of the torsion beam 7. In this case, with respect to the cross section of the gradually changing portion 7G, the length of the leg e3 gradually decreases from the boundary with the central portion 7M toward the boundary with the connecting portion 7C, but the angle remains constant and remains constant. The part e2 may have a configuration in which the length is gradually increased and the inclination angle is gradually increased at the same time.

<2> The top of the torsion beam 7 shown in FIG. 4, that is, the whole or part of the connection part d1, the connection part e1, and the connection part f1 may be configured as a horizontal plane instead of a curved surface.

  As suspension structures for vehicles that have sufficient connection strength between a pair of left and right trailing arms and a torsion beam, and that are easy to ensure productivity, cost, reduction in the number of parts, etc., passenger cars and commercial vehicles, trucks, and Available for buses.

2 Trailing arm 7 Torsion beam 7C Connection part 7G Gradual change part 7M Central part 7R Notch S1 1st cross-sectional shape S2 2nd cross-sectional shape Sg Gradual change cross-sectional shape T Inflection point (maximum stress location)

Claims (2)

A suspension structure comprising a pair of left and right trailing arms and a torsion beam connected across the pair of trailing arms,
The torsion beam has a central portion having a downwardly opened arch-like first cross-sectional shape including a pair of legs extending downward and an arc-shaped connecting part connecting the pair of legs, and the tray A connecting portion having a triangular second cross-sectional shape including an end portion connected to the ring arm and opened downward, and the second cross-sectional shape from the first cross-sectional shape toward the connecting portion from the central portion. Having a gradually changing portion with a cross-sectional shape gradually changing to
A suspension structure in which the gradually changing portion is disposed in the vicinity of the trailing arm. The suspension structure according to claim 1, wherein a circumferential length of the torsion beam in a cross section is constant in each cross section in a longitudinal direction of the torsion beam.

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