JP5053874B2 - Vehicle suspension arm and manufacturing method thereof - Google Patents

Description

  The present invention relates to a vehicle suspension arm and a method for manufacturing the same, and more particularly to a technique for forming a suspension arm by secondary processing of an extruded shape made of aluminum alloy.

Conventionally, a suspension arm of a vehicle such as an automobile is generally formed by using a relatively inexpensive steel material in combination with press molding and welding (for example, see Patent Document 1). However, in recent years, further weight reduction is required with increasing C0 ₂ reduction request, aluminized of the suspension arm is in progress. As a method for forming the suspension arm into an aluminum alloy, a casting method (for example, see Patent Document 2) and a method for secondary forming a hollow extruded shape (for example, see Patent Documents 3 and 4) are known.

  When trying to make an aluminum alloy of parts, it is necessary to suppress as much as possible the increase in the unit price of the parts due to the increase in material costs and costs in the manufacturing process due to market demands. In order to alloy the suspension arm with an aluminum alloy at a low cost, the method of secondary forming a hollow extruded profile without a welding process is most advantageous.

  By the way, the suspension arm of the automobile is pivotally supported by the vehicle body structure at the base end portion so as to be swingable, and a knuckle for supporting the wheel is connected to the tip end portion narrower than the base end portion. In a lower arm in a multi-link type or double wishbone type rear suspension, a receiving surface of a coil spring is provided at an intermediate portion in the arm longitudinal direction.

  Since this receiving surface needs to be larger than the diameter of the coil spring, the intermediate portion of the lower arm is generally configured wider than the distal end portion and the proximal end portion. Therefore, the cross-sectional shape of the lower arm is greatly changed along the longitudinal direction thereof, and when such a lower arm is formed from an extruded profile having a uniform cross-sectional shape in the longitudinal direction, the lower arm has a coil spring receiving portion. There is a method of using an extruded profile having a corresponding width and compressing its end in the width direction, or conversely, a method of forming the receiving portion of the coil spring by expanding the intermediate portion of the extruded profile in the width direction. is assumed.

  Among these methods, the method of expanding the intermediate portion of the extruded profile is accompanied by thinning, and it is difficult to ensure the strength of the coil spring receiving portion that requires high strength. Therefore, the method of compressing the end of the extruded profile in the width direction is advantageous, but when the end of the extruded profile is crushed as it is from both sides with a press, the deformation position is not stable and it is difficult to ensure accuracy. It is. High dimensional accuracy is required for the attachment portions at both ends of the lower arm, but this accuracy requirement cannot be met.

  Therefore, in Patent Document 3, plastic deformation is induced in the central portion of the upper surface and the lower surface by making the plate thickness of the upper surface and the lower surface of the extruded profile smaller than the plate thickness of both sides. However, if the upper and lower surfaces of the extruded profile are made thinner, the overall strength is insufficient, and it is not possible to withstand vertical bending input and downward input from a coil spring.

JP 2002-316228 A Japanese Patent No. 38733641 International Patent Publication No. 01/32979 International Patent Publication No. 2005/002890

  In contrast to the method of crushing the edge of the extruded profile from the both sides with a press, the center of the extruded profile is cut into a slit in the longitudinal direction, and this cut is used as a compression allowance from both sides with a press. If the compression is performed, the deformation position is stabilized and the dimensional accuracy can be secured. However, this method divides both side surfaces of the arm end portion, making it difficult to ensure the torsional rigidity necessary for the suspension arm.

  Another problem when the suspension arm is formed of an aluminum alloy extruded profile is securing the holding force of the bush. Generally, the base end of the suspension arm is pivotally supported by the vehicle body structure via a bush for the purpose of absorbing vibration and three-dimensional displacement input from the axle side. When the suspension arm is composed of a profile, the bush that is press-fitted into the punched hole of the extruded profile will be held only by the thickness of the side of the extruded profile, ensuring the holding force of the bush after press-fitting. It is difficult.

  In particular, when a bush having an aluminum alloy outer cylinder is press-fitted into an aluminum alloy suspension arm, the press-fitting allowance cannot be increased due to galling problems, and it is more difficult to secure a holding force. is there. In addition, when the outer cylinder of the bush is made of iron, there is a problem that electric corrosion occurs between the suspension arm made of aluminum alloy.

  The present invention has been made in view of such a situation, and an object of the present invention is to form a suspension arm from an extruded shape made of an aluminum alloy at a low cost and to be rotatable to the vehicle body structure side or the axle side. A suspension arm for a vehicle that provides the required dimensional accuracy and torsional rigidity for the connecting portion to be connected, particularly the arm base end portion pivotally supported on the vehicle body structure side, and also has excellent holding force for the bushing outer cylinder, and It is to provide a manufacturing method.

In order to solve the above problems, the present invention provides:
A suspension arm for a vehicle formed by secondary processing from a hollow aluminum alloy extruded shape having an upper surface portion and a lower surface portion connected by at least two side wall portions and having a substantially rectangular cross section in the longitudinal direction. And
One end portion of the extruded shape member is divided by a slit-shaped notch portion having an upper and lower shape that extends in the longitudinal direction from the edge to the center portion in the width direction of the upper surface portion and the lower surface portion, and both side portions thereof are the notch portions. Is formed with a narrow width by being abutted by bending from both sides with a deformation margin, and a cylindrical connecting member is inserted into a through-hole penetrating each side wall portion at both narrow side portions, And the both ends which protruded from the said through-hole of the said connection member to the side are expanded, the said both side parts are integrally connected by the crimping of this said expansion end part, and the said one end part connects the said connection member. The vehicle suspension arm is rotatably connected to the vehicle body structure side or the axle side.

Moreover, it is preferable that the both end portions of the connecting member are expanded at a plurality of locations at a predetermined pitch in the circumferential direction. Further, the connecting member is a bush composed of an inner cylinder, an outer cylinder, and a rubber portion interposed therebetween, and the outer cylinder of the bush is fitted into the through hole, and the outer cylinder It is preferable that both end portions of the extruded shape member are widened, and one end portion of the extruded shape member is pivotally supported on the vehicle body structure side via the bush. Further, the upper surface portion of the extruded shape member extends in the width direction beyond the connection portion with each of the side wall portions, and a coil spring is disposed at a longitudinal intermediate portion of the extruded shape member not including the both side portions. It is preferable that a receiving portion is provided.

Further, the present invention provides a method for manufacturing the above vehicle suspension arm,
From the one end portion of the extruded profile, a step of cutting the upper surface portion and the width direction center portion of the lower surface portion into a slit shape having an upper and lower shape in the longitudinal direction;
Bending both sides of the one end portion of the extruded profile divided by the slit-shaped notch, and abutting them from both sides; and
Drilling a through-hole penetrating each side wall at one end of the extruded profile;
Inserting a cylindrical connecting member into the through hole of each side wall; and
The manufacturing method includes a step of expanding and caulking both end portions protruding laterally from the respective through holes of the connecting member, and connecting the both side portions integrally.

Furthermore, it is preferable that the step of integrally connecting the both side portions includes expanding and caulking the both end portions of the connecting member at a predetermined pitch in the circumferential direction.

Since the suspension arm for a vehicle according to the present invention is configured as described above, it is the minimum necessary by a simple processing with a small number of man-hours such as cutting and bending from a hollow aluminum alloy extruded shape having a uniform square cross section. With the limited plastic deformation, the narrow end can be accurately formed, and both sides of the arm divided by the slit-shaped notch are firmly connected by caulking of the expanding end of the connecting member, so that the suspension The torsional rigidity and strength necessary for the arm are ensured, which is advantageous in reducing the weight while reducing the manufacturing cost of the suspension arm.

Moreover, in the aspect in which the both end portions of the connecting member are expanded at a plurality of locations at a predetermined pitch in the circumferential direction, the expanding end portion of the connecting member has a petal shape or a polygonal shape instead of a simple circular shape. By doing so, the rigidity of the expanded end portion itself is increased, and the torsional rigidity of the entire suspension arm is greatly improved as well as the removal load of the connecting member is improved.

  Further, the connecting member is a bush composed of an inner cylinder, an outer cylinder, and a rubber portion interposed therebetween, and the outer cylinder of the bush is fitted into the through hole, and the outer cylinder In the embodiment in which both ends of the arm are widened, both the caulking of the suspension arm and the caulking of the bush are formed, a special connecting member can be omitted, and the suspension arm can be manufactured with less man-hours. The bush can be firmly connected to the suspension arm, and the holding force to the bushing outer cylinder is excellent. In addition, since it is not necessary to press fit the bushing outer cylinder, there is no galling problem even if the bushing outer cylinder is made of an aluminum alloy, and the bushing outer cylinder is made of an aluminum alloy. Can be prevented.

  Further, the upper surface portion of the extruded shape member extends in the width direction beyond the connection portion with each of the side wall portions, and a receiving portion of a coil spring is provided in the longitudinal intermediate portion of the extruded shape member. In the aspect, the projecting portion secures a necessary width in the receiving portion, and the suspension arm itself can be reinforced, and the coil spring receiving portion requiring a large cross section and the vehicle body structure side or the axle side requiring a small cross section are provided. This is advantageous when the connecting end portion is formed into a hollow aluminum alloy extruded shape having a substantially square cross section.

The present invention, since the adopted method for manufacturing a suspension arm as described above, can be plastically deformed without difficulty in bending by a press of the both side portions of the extruded shape member end from both sides, excellent dimensional accuracy The connecting end can be formed, and both divided parts are firmly integrated by fitting the connecting member and expanding and caulking the end to secure the torsional rigidity required for the suspension arm. This is advantageous in reducing the weight while reducing the manufacturing cost of the arm. Moreover, since each said process can be performed only by cold processing, the temperature adjustment between processes is unnecessary and it is the best for continuous processing and automation of a process.

  Further, the step of integrally connecting the both side portions includes expanding and caulking the both end portions of the connecting member at a plurality of locations intermittently at a predetermined pitch in the circumferential direction. At least at the initial stage of expansion and caulking deformation of both ends, compressive stress is concentrated in several places in the circumferential direction, so that it is possible to reduce the compressive load required for expansion deformation of both ends of the connecting member, The stress applied to the deformed portion can be reduced, and unnecessary deformation can be prevented.

  That is, if both ends of the connecting member are expanded over the entire circumferential direction by means of a disc-shaped or conical presser, the peripheral length change of both ends of the connecting member is obtained to obtain an equivalent expansion amount. The outer peripheral portion is likely to crack, but the both ends of the connecting member are intermittently expanded in the circumferential direction by the method of the present invention while minimizing the change in the peripheral length at the expanded end portion. A large amount of expansion of the portion can be ensured, which is advantageous in improving the connection strength.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an embodiment in which a vehicle suspension arm according to the present invention is implemented as a lower arm 1 in a rear suspension of an automobile. In the figure, the rear suspension is a multi-link suspension in which a knuckle 4 that rotatably supports a wheel 3 is swingably connected to a vehicle body structure 5 via a plurality of links including a lower arm 1 and an upper arm 2. The coil spring 6 is interposed between the intermediate portion 13 of the lower arm 1 and the vehicle body structure 5. A base end portion 11 of the lower arm 1 is pivotally supported by the vehicle body structure 5 via a bush 7, while a distal end portion 12 of the lower arm 1 is rotatably connected to a lower portion of the knuckle 4.

  FIG. 2 is a perspective view showing the lower arm 1. In the base end portion 11 which is narrower than the distal end portion 12 and the intermediate portion 13, as shown in FIG. It is fixed and constitutes a rotation connecting part with the vehicle body structure 5. The front end portion 12 is formed in a fork shape bifurcated by a U-shaped cutout portion 120, and through holes 20 penetrating the both side portions 121, 122 laterally are respectively drilled. It constitutes a rotating connecting part. The intermediate portion 13 is provided with a receiving member (13) for the coil spring 6.

  As shown in FIGS. 4 to 7, the lower arm 1 is formed by secondary processing a hollow aluminum alloy extruded profile 1 </ b> A having a substantially rectangular cross section in the longitudinal direction. As shown in FIG. 6, the extruded profile 1A as a raw material has a substantially square cylindrical shape in which a flat upper surface portion 14 and a lower surface portion 15 are connected by two side wall portions 16 and 17 on both sides thereof. However, both sides 14 a, 14 a of the upper surface portion 14 extend in the width direction beyond the connection portions with the side wall portions 16, 17, and the width of the upper surface portion 14 is wider than the lower surface portion 15. Yes.

  When forming the lower arm 1 from such an extruded profile 1A, first, as shown in FIG. 4, from the edge of the base end 11 and the distal end 12 of the extruded profile 1A, the upper surface portion 14 and the lower surface portion. 15 center portions in the width direction are cut out in a slit shape along the longitudinal direction to form U-shaped cutout portions 110 and 120. FIG. 7A shows a cross section of the base end portion 11 in which the notch portion 110 is formed.

  Next, as shown by arrows in FIG. 5, both side portions 111, 112 of the base end portion 11 divided by the notch portion 110 are compressed by pressing from both sides with a press, and the opposite edge portions of the notch portion 110 are bent. Match. At this time, the side portions 111 and 112 are only subjected to gentle bending stress and shear stress within a limited range centered on their base portions, and are formed with a minimum plastic deformation. There is no reduction in accuracy or strength. FIG. 7A shows a cross section of the base end portion 11 which is compressed from both sides and becomes narrower. In addition, as shown in FIG. 1, you may perform the bending process which curves the extrusion-shaped material 1B in the thickness direction as needed.

  Further, the through holes 10 and 10 are formed through the side wall portions 16 and 17 of the both side portions 111 and 112 that are abutted, and the side wall portions 16 and 17 of the both side portions 121 and 122 are also penetrated at the distal end portion 12. Then, the through holes 20 are formed. Note that the through holes 20 and 20 of the distal end portion 12 may be drilled before the cutout portion 120 is formed.

  Next, the bush 7 is fitted into the through holes 10 and 10 of the base end portion 11. As shown in FIG. 7 (c), the bush 7 is composed of an outer cylinder 71, an inner cylinder 72 disposed coaxially with the outer cylinder 71, and a rubber portion 73 filled between the inner cylinder 72 and the inner cylinder 72. It is longer than the outer cylinder 71 and protrudes from the end of the outer cylinder 71 to both sides. The outer cylinder 71 of the bush 7 is made of an aluminum alloy like the extruded shape member 1A. As shown in FIG. 8A, the bush 7 is inserted into the through holes 10 and 10, and both end portions of the outer cylinder 71 and the inner cylinder 72 of the bush 7 are side wall portions of both side portions 111 and 112. 16 and 17 project sideways.

  Next, as shown in FIG. 8 (a), the projecting end portions 71a of the outer cylinder 71 of the bush 7 are pressed between the pair of pressing elements 8, 8 from both sides, and as shown in FIG. 8 (b). In addition, by expanding and crimping both end portions 71a (71c), both side portions 111 and 112 of the abutted base end portion 11 are connected by the outer cylinder 71 of the bush 7 and the bush 7 is connected to the base end portion 11 The through holes 10 and 10 are fixed.

  The pusher 8 used for expanding the bushing outer cylinder 71 is a hollow cylinder having at least a tip having a cavity 80 at the center so that the bushing outer cylinder 71 can be pressurized without interfering with the bushing inner cylinder 72. Is formed. The pressing surface of the pressing element 8 can be a simple flat surface or a conical surface, but as shown in FIGS. 9A and 9B, it is intermittently projected at a predetermined pitch in the circumferential direction of the end surface 82. It is preferable to provide a plurality of (four in the illustrated example) convex portions 81.

By pressurizing the bush outer cylinder 71 using such a presser 8, the expanded portions 71c of the outer cylinder both ends 71a are intermittently provided at a predetermined pitch in the circumferential direction (four locations in the illustrated example). Thus, as shown in FIG. 11, the expanded portion 71c has a petal shape or a polygonal shape. Thus, as compared with the case of uniformly expanding the entire periphery, to minimize changes in the peripheral length of the expanding portion 71c, it is possible to ensure a large amount of expansion indicated by d _C -d _B in FIG. 11 It is possible to improve the connection strength due to the expansion.

  Further, at least in the initial stage of the expansion and caulking deformation of both ends 71a of the outer cylinder, the compressive stress concentrates at several places in the circumferential direction (four places in the illustrated example), so plastic deformation starts at a relatively low load in this part. In addition, the compressive load required for the expansion deformation can be reduced, the stress applied to the non-deformed portion such as the central portion of the bush outer cylinder 71 can be reduced, and unnecessary deformation of the bush 7 can be prevented.

  Further, as shown in FIGS. 10 (a) and 10 (b), the inclination angles at which the respective convex portions 81 ′ projecting intermittently at a predetermined pitch in the circumferential direction of the end surface 82 ′ project toward the central axis. If the pressing element 8 'having θ is used, the expansion deformation of the outer cylinder both ends 71a is induced by the inclined surface, and the compressive load required for the expansion deformation can be further reduced, and the center shift during the expansion deformation is corrected. There are also benefits.

  In addition, in the bush outer cylinder 71 of the said embodiment, although the case where the four expansion parts 71c were arrange | positioned by the 90 degree space | interval in the circumferential direction was shown, the installation number and arrangement | positioning of the expansion parts 71c are other than this. It can also be. As described above, the expanded portions 71c are intermittently arranged at a predetermined pitch in the circumferential direction. That is, as a basic type having symmetry in the circumferential direction, (1) the expanded portion 71c is circumferentially or the like. There are a mode of being arranged at intervals and a mode of (2) the expanding portions 71c being arranged symmetrically with respect to each of a plurality of symmetry axes set at equal intervals in the circumferential direction through the center of the bushing outer cylinder 71. For example, this is an arrangement that is shifted by ± 10 degrees so as to be symmetric with respect to three symmetry axes set at intervals of 120 degrees in the circumferential direction, and of course, the convex portions of the pressers 8 and 8 'used for processing. 81 and 81 'are also arranged corresponding to this.

  Next, in order to verify the fixing strength of the bush 7 and the connection strength of both side portions 111 and 112 of the arm base end portion 11 in the suspension arm (1) of the present invention, the fitting tolerance between the bush outer cylinder 71 and the through hole 10 is confirmed. And an experiment for examining the relationship between the load and removal load of the bushing outer cylinder 71 were performed as follows.

In the experiment, a bush outer cylinder made of an aluminum alloy having a thickness of 2 mm was used. The amount of protrusion a = 6.0 mm from the arm side wall of the bush outer cylinder, and the amount of expansion of the bush outer cylinder (d _C −d _B ) In the case of 0.8 to 1.4 mm, when the spreader is opened using the presser 8 (inclination angle θ = 0 °) shown in FIG. 9, and the presser 8 ′ (inclination angle θ shown in FIG. 10). = 10 °), the fitting tolerance (d _B −d _H ) between the outer diameter (d _B ) of the bushing outer cylinder and the inner diameter (d _H ) of the through hole is −0. The bushing outer cylinder was pulled out by varying 0.1 mm between 3 mm (loose fitting) and +0.3 mm (tightening), and the removal load (kN) was measured. For comparison, the same measurement was performed when the bushing outer cylinder was simply inserted (press-fitted) without being expanded.

  FIG. 12 is a graph showing experimental results. From this result, when the spread is performed based on the method of the present invention, sufficient fixing strength is obtained even when the fitting tolerance is negative, that is, loose fitting, the tolerance range of the fitting tolerance is wide and stable. This suggests that quality can be obtained. There is a tendency for the fixed strength to peak within the range of the interference fit. When only press-fitting is performed, sufficient fixing strength cannot be obtained. On the contrary, when the fitting tolerance is 0.2 mm or more, the fixing strength decreases.

  In addition, in the pressing element 8 ′ having a slope in the convex portion, the measured value of the removal load is stable, whereas in the pressing element 8 without the inclination, the measured value of the removal load is somewhat varied, The effects of minute eccentricity and rapid deformation at the time of expansion deformation can be considered. From this result, in order to maintain stable quality, it can be said that it is advantageous to use a pressing element 8 ′ having an inclined protrusion.

  Furthermore, as shown in FIG. 13, it is preferable to minimize the influence on the rubber characteristics of the bush 7 by arranging the expanding portion 71c so as to avoid the vertical direction Z and the horizontal direction W of the vehicle. In the illustrated example, the four expanded portions 71c are arranged at 90 ° intervals with a shift of about 45 ° with respect to the vertical direction Z and the horizontal direction W.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention.

  For example, in the above-described embodiment, the case where the suspension arm of the present invention is implemented in the lower arm of a multi-link suspension is shown, but it is also implemented in other types of suspension arms such as a double wishbone type and a trailing arm type. Is possible.

1 is a side view showing an embodiment in which the present invention is implemented in a lower arm in a rear suspension of an automobile. It is a perspective view which shows the lower arm of this invention embodiment. It is AA sectional drawing of FIG. It is a perspective view which shows the manufacturing process of the lower arm of this invention embodiment. It is a perspective view which shows the manufacturing process of the lower arm of this invention embodiment. It is BB sectional drawing of FIG. (A) is CC sectional drawing of FIG. 4, (b) is DD sectional drawing of FIG. 5, (c) is sectional drawing of a bush. It is sectional drawing which shows the expansion process of a bush outer cylinder. (A) is a front view which shows the example of the presser which performs the expansion | swelling process of a bush outer cylinder, (b) is the side view. (A) is a front view which shows the other example of the presser which performs the expansion process of a bush outer cylinder, (b) is the side view. It is an end view which shows the bush which performed the opening and closing process. It is a graph which shows the relationship between the fitting tolerance of a bush outer cylinder, and a removal load. It is a side view which shows the attachment condition of the lower arm base end part concerning this invention embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lower arm 1A, 1B Extrusion member 2 Upper arm 3 Wheel 4 Knuckle 5 Car body structure 6 Coil spring 7 Bush 8, 8 'Presser 10, 20 Through-hole 11 Base end part 12 Tip part 13 Middle part (coil spring receiving part)
14 Upper surface portion 15 Lower surface portion 16, 17 Side wall portion 71 Outer tube 71c Expanded portion 72 Inner tube 73 Rubber portion 81, 81 ′ Convex portion 110, 120 Notch portion 111, 112, 121, 122 Both side portions

Claims (6)

A suspension arm for a vehicle formed by secondary processing from a hollow aluminum alloy extruded shape having an upper surface portion and a lower surface portion connected by at least two side wall portions and having a substantially rectangular cross section in the longitudinal direction. And
One end portion of the extruded shape member is divided by a slit-shaped notch portion having an upper and lower shape that extends in the longitudinal direction from the edge to the center portion in the width direction of the upper surface portion and the lower surface portion, and both side portions thereof are the notch portions. Is formed with a narrow width by being abutted by bending from both sides with a deformation margin, and a cylindrical connecting member is inserted into a through-hole penetrating each side wall portion at both narrow side portions, And the both ends which protruded from the said through-hole of the said connection member to the side are expanded, the said both side parts are integrally connected by the crimping of this said expansion end part, and the said one end part connects the said connection member. A suspension arm for a vehicle, wherein the suspension arm is pivotally connected to a vehicle body structure side or an axle side through a suspension. 2. The vehicle suspension arm according to claim 1, wherein the both end portions of the connecting member are expanded at a plurality of locations at a predetermined pitch in the circumferential direction.   The connecting member is a bush composed of an inner cylinder, an outer cylinder, and a rubber portion interposed therebetween, and the outer cylinder of the bush is fitted into the through hole, and both ends of the outer cylinder 3. The vehicle according to claim 1, wherein a portion is expanded, and one end of the extruded shape member is pivotally supported on the vehicle body structure side via the bush. Suspension arm.   The upper surface portion of the extruded shape member extends in the width direction beyond the connection portion with each side wall portion, and a receiving portion of a coil spring is provided at a middle portion in the longitudinal direction of the extruded shape member. The vehicle suspension arm according to claim 3. A method for manufacturing a suspension arm for a vehicle using a hollow aluminum alloy extruded profile in which an upper surface portion and a lower surface portion are connected by at least two side wall portions and have a substantially rectangular cross section in the longitudinal direction,
From the one end portion of the extruded profile, a step of cutting the upper surface portion and the width direction center portion of the lower surface portion into a slit shape having an upper and lower shape in the longitudinal direction;
Bending both sides of the one end portion of the extruded profile divided by the slit-shaped notch, and abutting them from both sides; and
Drilling a through-hole penetrating each side wall at one end of the extruded profile;
Inserting a cylindrical connecting member into the through hole of each side wall; and
A method for manufacturing a suspension arm for a vehicle, comprising: expanding and caulking both end portions of the connecting member protruding from the respective through-holes and connecting the both side portions together. The vehicle suspension according to claim 5, wherein the step of integrally connecting the both side portions includes expanding and crimping the both end portions of the connecting member at a predetermined pitch in the circumferential direction at a predetermined pitch. The manufacturing method of an arm.

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