JPH11321259A - Suspension arm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure rigidity required during normal travel of a vehicle and maintain a travelable state even under the action of high load. SOLUTION: A stress concentration part 18 is provided at a C-line view part in a second arm part 10C extended along a line segment A connecting a point P and a vehicle body side restriction point R of an upper arm 10 made of cast iron. The second arm 10C can therefore apply support force to input load F to its maximum, while a travelable state can be maintained since the second arm is not deformed into a vehicle body front part from the stress concentration part 18. Compared to a high rigidity cast iron upper arm, design reference load with deformability can be lowered so as to reduce weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension arm having a restraining point on a vehicle body, which is a mounting portion to a vehicle body, and a wheel-side restraining point, a mounting portion on a wheel support for rotatably supporting a wheel.

[0002]

2. Description of the Related Art There are various types of suspension types and suspension arms. In this case, the conventional technology is exemplified by a cast iron upper arm used for a double wishbone type suspension. I will explain.

[0003] Since this type of upper arm is an important security part, not only good suspension performance is required, but also a running function is ensured even when a predetermined high load (high load) is applied to the vehicle body. Such performance is required.
For this reason, conventionally, the design reference load of the upper arm is set high, and very high rigidity is secured. Therefore, the weight of the upper arm was inevitably increased.

[0004] In consideration of the above fact, the present invention secures the rigidity required during normal running of a vehicle and can maintain a running state even when a predetermined high load is applied to the vehicle body. Another object of the present invention is to provide a suspension arm that can be reduced in weight.

[0005]

According to the first aspect of the present invention, there is provided a vehicle-side restraining point serving as a mounting portion to a vehicle body and a wheel-side restraining point serving as a mounting portion to a wheel support rotatably supporting a wheel. A suspension arm having an arm portion extending along a line connecting the vehicle-side restraint point and the wheel-side restraint point, and having a predetermined high load acting on a predetermined position in the arm portion. It is characterized in that a stress concentration portion for sometimes deforming the arm portion is provided.

According to a second aspect of the present invention, in the suspension arm according to the first aspect, the stress concentration portion is a center line of an arm portion with respect to a line connecting the vehicle-side constraint point and the wheel-side constraint point. The offset is set based on the offset amount up to and the cross-sectional shape of the arm portion.

According to a third aspect of the present invention, there is provided a suspension arm according to the first or second aspect, wherein the suspension arm is made of cast iron.

According to the first aspect of the present invention, a line connecting the vehicle body side restraining point serving as a mounting portion to the vehicle body and the wheel side restraining point serving as a mounting portion to a wheel support for rotatably supporting the wheel. Since the arm portion of the suspension arm extends along the line, higher rigidity (particularly, rigidity against a compressive load) is secured as compared with a suspension arm whose arm portion does not extend along the line segment. can do.
For this reason, sufficient rigidity is secured against a load input during normal vehicle running.

On the other hand, since a stress concentration portion is provided at a predetermined position in the arm portion of the suspension arm, when a predetermined high load acts on the vehicle body, the arm portion is deformed starting from the stress concentration portion. Since the arm is not broken even if it is deformed, the vehicle is in a runnable state. Therefore, the occupant can make the vehicle travel to the nearest place in an emergency evacuation.

This will be described in comparison with the conventional suspension arm. In order to prevent the arm portion from being broken in the conventional suspension arm having no deformability (that is, to prevent the arm from falling into a state where the vehicle cannot travel). Therefore, it was necessary to set the design reference load very high. However, in the present invention, the arm portion is deformed at the stress concentration portion when a predetermined high load is applied to the vehicle body (that is, as described above, the deformation occurs). Even if the traveling state is maintained), the design reference load of the arm portion can be reduced. For this reason,
The weight of the suspension arm can be reduced.

According to the second aspect of the present invention, the above-mentioned stress concentration portion is offset from the line connecting the vehicle-side restraint point and the wheel-side restraint point to the center line of the arm portion and the cross-sectional shape of the arm portion. Because we decided to set based on
The following effects are obtained.

First, when the maximum offset amount is determined, the setting range of the stress concentration portion can be optimized based on the determined maximum offset amount. That is, it is possible to specify an optimal range as the setting range of the stress concentration portion based on the maximum offset amount. Next, by changing the cross-sectional shape of the arm portion within the set optimum range of the stress concentration portion specified in this way, it is possible to surely concentrate the stress on the portion where the cross-section is changed. That is, the portion whose cross section has been changed reliably serves as the deformation starting point of the arm portion.

According to the third aspect of the present invention, since the above-mentioned suspension arm is made of cast iron, it is possible to effectively utilize the inherent characteristics of cast iron, which has significantly higher compressive strength than tensile strength. Can be.

In the case of a suspension arm made of cast iron, a stress concentration portion can be formed as it is during the casting process.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An upper arm 10 according to an embodiment of the present invention will be described below with reference to FIGS. The upper arm 10 according to the present embodiment is an upper arm applied to a double wishbone type front suspension.

FIG. 1 shows an upper arm 1 according to this embodiment.
0 is shown, FIG. 2 is a left side view of the upper arm 10, and FIG. 3 is a right side view of the upper arm 10. As shown in FIG. In these drawings, the arrow FR appropriately shown indicates the front side of the vehicle, and the arrow IN indicates the inside in the vehicle width direction.
Further, the arrow UP indicates the upper side of the vehicle.

As shown in these figures (particularly FIG. 1), the upper arm 1 as a "suspension arm"
0 is configured as a so-called A-shaped arm. Further, the upper arm 10 according to the present embodiment is made of cast iron. In general, this type of upper arm 1 made of cast iron is used.
0 is often adopted when there are restrictions on the suspension layout (that is, restrictions on the installation space).

The upper arm 10 includes a base 10A located outside the vehicle width direction, a first arm 10B extending substantially inward in the vehicle width direction from the base 10A, and a vehicle front inside from the base 10A. And a second arm portion 10C extending obliquely toward the second arm portion. In addition,
Of these, the second arm 10C corresponds to the “arm” in the present invention.

At the outer end of the base 10A, a substantially hemispherical receiving portion 12 which is opened downward is integrally formed. The receiving portion 12 and an upper end of a wheel support (steering knuckle) (not shown) for rotatably supporting the wheel (front wheel) are connected to each other via an upper ball bush (not shown) so as to be relatively rotatable. Therefore, the point P shown in FIG. 1 is a wheel-side constraint point of the upper arm 10.

A receiving portion 14 which is formed in a ring shape in a side view is integrally formed at the tip of the first arm portion 10B. Similarly, an annular receiving portion 16 is integrally formed at the tip of the second arm portion 10C. These receiving parts 1
An outer cylinder of a body-side bush (not shown) is press-fitted into 4, 4. The body-side bush is constituted by an outer cylinder and an inner cylinder arranged concentrically and an elastic body (rubber) interposed between these inner and outer cylinders and vulcanized and bonded to both. By being attached, the first arm portion 10B and the second arm portion 10C are connected to the body side so as to be relatively rotatable. Therefore,
The point Q shown in FIG. 1 is a vehicle-side restraint point of the first arm portion 10B, and the point R is a vehicle-side restraint point of the second arm portion 10C.

Here, in the present embodiment, the second line A along the line segment A connecting the wheel side constraint point P and the vehicle body side constraint point R described above.
The arm portion 10C is extended, and the second arm portion 1
Predetermined position at 0C (in the present embodiment, the section viewed from the arrow C line)
The feature is that the stress concentration portion 18 is formed in the second embodiment.

More specifically, when the vehicle is running, a load F substantially on the front side of the vehicle is applied to the wheel-side constraint point P of the upper arm 10.
Is input, but the second arm 10
By extending C so as to be stretched, it is intended to make full use of a characteristic (a characteristic that compressive strength is significantly higher than tensile strength) of cast iron described later.
In other words, this means "extended along a line segment A connecting the wheel side constraint point P and the vehicle body side constraint point R" in the present invention. In other words, the second arm portion 10 with respect to the line segment A
This means that the offset amount B to the center line D of C is within a predetermined range.

That is, assuming that the second arm portion is considerably curved than the second arm portion 10C in the present embodiment, the offset amount B of the second arm portion is naturally larger than that in the present embodiment. It becomes considerably large, and in that case, it cannot be stretched against the load F, and is expected to be deformed by a load lower than a predetermined design reference load, so that characteristics unique to cast iron cannot be utilized. In order to avoid this, in the present embodiment, the second arm portion 10C extends along the line segment A.

Next, the details of the stress concentration portion 18 (why the stress concentration portion 18 is provided and how to set the stress concentration portion 18)
To mention.

First, the reason why the stress concentration portion 18 is provided is to specify a deformation (buckling) site or a deformation (buckling) starting point of the second arm portion 10C (obtain a fuse effect). And to specify the deformation (buckling) direction.

Next, a method of setting the stress concentrating portion 18 will be described. The stress concentrating portion 18 corresponds to the second arm portion 10C with respect to a line segment A connecting the wheel side constraint point P and the vehicle body side constraint point R.
Offset amount B to the center line D and the second arm 1
It is set based on the cross-sectional shape of 0C.

That is, the maximum value of the offset amount B is represented by B
_MAX , the stress concentration portion 18 is located at the position corresponding to the B _MAX.
Is ideal, but considering the suspension layout depending on the type of vehicle, etc., the setting requirements are generally “B ≧ B _MAX for setting the stress concentration portion 18.
× 0.3 ”may be satisfied. A position indicated by an arbitrary B value within a range satisfying this expression is a meaning of “a predetermined position in the (second) arm portion (10C)” in the present invention. Note that the coefficient of 0.3 in the above equation is experimentally obtained, and in the present embodiment, a more preferable range is “B ≧ B _MAX for setting the stress concentration portion 18”.
The stress concentration portion 18 is set with “× 0.8” as a setting requirement.

Further, in this embodiment, the "stress concentration portion 1"
At the position of B satisfying “B ≧ _BMAX × 0.8 which sets 8” (the portion viewed from the arrow C line), the cross-sectional shape of the second arm portion 10C is changed. That is, a configuration is adopted in which the dimension E in the width direction of the second arm portion 10C is increased from the stress concentration portion 18.

In the present embodiment, the second arm 10
The present invention is applied only to C, and the present invention is not applied to the first arm portion 10B. This is because other components such as a torque arm (not shown) are arranged on the first arm portion 10B side. This is because it is not suitable for providing a stress concentration portion and deforming.

Next, the operation and effect of this embodiment will be described.

FIG. 4 shows typical characteristics of cast iron. As shown in this figure, when a tensile load (vertical axis + side) was applied to the cast iron test piece, fracture occurred at a relatively early stage, but a compressive load (vertical axis-side) was applied. In some cases they show very high strength. As described above, cast iron inherently has a material property that the compressive strength is much higher than the tensile strength.

In order to make the most of such material properties of the cast iron, in the present embodiment, the second arm portion 10C of the upper arm 10 is connected to a line segment A connecting the wheel-side restraint point P and the vehicle-body restraint point Q. , Higher rigidity (particularly, rigidity against a compressive load) can be secured as compared with the upper arm in which the arm portion does not extend along the line segment A. For this reason, sufficient rigidity can be ensured with respect to a load input during normal vehicle traveling (a load input in a load area (ie, a normal load area) equal to or less than a design reference load Y in FIG. 5 described later). it can.

On the other hand, when a predetermined high load is applied to the front portion of the vehicle body (when a load is input in a high load region equal to or more than a load S (> Y) in FIG. Since the stress concentration portion 18 is provided at the portion of the second arm portion 10C viewed from the arrow C, the second arm portion 10C is deformed with the stress concentration portion 18 as a starting point. Since the second arm portion 10C is not broken even if deformed, the vehicle is in a runnable state. Therefore, the occupant can make the vehicle travel to the nearest place in an emergency evacuation.

This will be described in comparison with a conventional high-rigidity cast iron upper arm. In order to prevent the second arm portion from being broken in the conventional upper arm having no deformability (that is, the upper arm cannot be moved). 5), it was necessary to set the design reference load Y ′ very high as shown in FIG. 5. However, in the upper arm 10 according to the present embodiment, a predetermined height Since the second arm portion 10C is deformed by the stress concentration portion 18 when a load is applied (that is, the traveling state is maintained even if the second arm portion 10C is deformed as described above), the design reference load of the second arm portion 10C is set to Y. '
It is possible to set Y to be lower than ΔY by ΔY. Therefore, the weight of the upper arm 10 can be reduced.

Summarizing the above, according to the upper arm 10 of the present embodiment, the rigidity required for normal vehicle running is ensured, and when the predetermined high load is applied to the front part of the vehicle body, Can maintain a state in which the vehicle can run, and furthermore, the weight can be reduced.

Further, according to this embodiment, the above-mentioned stress concentration portion 18 is offset from the line A connecting the wheel side constraint point P and the vehicle body side constraint point Q to the center line D of the second arm portion 10C. Since the setting is made based on the amount B and the cross-sectional shape of the second arm portion 10C, the following operation is obtained.

First, once the maximum offset amount _BMAX is determined, the setting range of the stress concentration portion 18 can be optimized based on this. That is, as described above, the optimum range as the setting range of the stress concentration portion 18 can be specified based on the maximum offset amount B _MAX . Next, by changing the cross-sectional shape of the second arm portion 10C within the set optimum range of the stress concentration portion 18 specified in this way, it is possible to surely concentrate the stress on the portion where the cross-section is changed. Can be. That is, the portion whose cross section has been changed reliably serves as the starting point of the deformation of the second arm portion 10C.

As a result, according to this embodiment, the optimum setting range of the stress concentration portion 18 is clarified and the second arm portion 10C
Can be clarified.

Further, according to this embodiment, since the upper arm 10 is made of cast iron, the stress concentration portion 18 can be formed as it is during the casting process. In other words, by manufacturing a mold such that the width dimension E of the second arm portion 10C changes (increases) at the portion indicated by the arrow C in FIG. The stress concentration portion 18 can be obtained as a product shape. Therefore, the formation of the stress concentration portion 18 can be facilitated.

In this embodiment, the upper arm 1 of the double wishbone type front suspension is used.
However, the present invention is not limited to this, but can be applied to various types of suspension arms.

In the present embodiment, the present invention is applied only to the second arm portion 10C of the A-shaped upper arm 10. However, the present invention is not limited to this, and the present invention is applied only to the first arm portion depending on the shape of the arm. Alternatively, the present invention may be applied to both the first arm portion and the second arm portion.

Further, in the present embodiment, the present invention is applied to the upper arm 10 made of cast iron. However, the present invention is not limited to this, and the present invention is applied to a suspension arm made of a pressed steel plate or a forged suspension arm. You may.

Further, in the present embodiment, the second arm 10 is connected to a line segment connecting the wheel-side restraint point P and the vehicle-side restraint point R.
Although the stress concentration portion 18 is set based on the offset amount B to the center line D of C and the cross-sectional shape of the second arm portion 10C, the offset amount B is larger as the weight (degree of dependence). The present invention according to claim 1 includes a configuration in which the stress concentration portion 18 is set based only on B, that is, a configuration in which the stress concentration portion 18 is set without considering a change in the cross-sectional shape.

On the other hand, according to the present invention, it is necessary to set the stress concentration portion 18 based on the offset amount B and the sectional shape of the second arm portion 10C. The present invention is not limited to the configuration in which the cross-sectional shape is changed by using the method of changing the width direction dimension E as in the present embodiment, but various configurations can be adopted. For example,
A configuration in which a concave portion is provided at a portion where stress concentration is desired may be adopted.

Further, in the above description, when a predetermined high load acts on the front part of the vehicle body, the second arm 10
Although C has been described as being deformed starting from the stress concentration portion 18, this means a state at the time of finally being deformed.
That is, even if the C-line section provided with the stress concentrating portion 18 is not the maximum stress generating portion at the initial stage (that is, it is not the initial deformation portion), the stress concentration of the C-line arrow portion finally ends. Part 1
That's all you need to do if you deform at 8. For example, even in the initial stage, even if the vicinity of the vehicle body-side constraint points Q and R of the upper arm 10 is slightly deformed, the deformation starting point in the final state may be the stress concentration portion 18 as viewed from the arrow C line. This is upper arm 1
This is because, in an actual product of 0, the stress distribution may change due to the deformation in the initial stage.

[0046]

As described above, the suspension arm according to the first aspect of the present invention has a vehicle body side restraining point which is a mounting portion to the vehicle body and a mounting portion to the wheel support which rotatably supports the wheel. The arm portion is extended along a line connecting the wheel-side restraint point, and a stress concentration portion for deforming the arm portion at a predetermined high load action is provided at a predetermined position in the arm portion. In addition, the rigidity required during normal vehicle running is ensured, and even when a predetermined high load is applied to the vehicle body, it is possible to maintain a running state, and furthermore, it is possible to reduce the weight. Has the effect.

According to a second aspect of the present invention, in the suspension arm according to the first aspect of the present invention, the stress concentration portion extends to a center line of the arm portion with respect to a line connecting the vehicle body side restraining point and the wheel side restraining point. Since it is set based on the offset amount and the cross-sectional shape of the arm portion, there is an excellent effect that the optimum setting range of the stress concentration portion can be clarified and the deformation starting point of the arm portion can be clarified.

In the suspension arm according to the third aspect of the present invention, since the suspension arm is made of cast iron in the first or second aspect of the invention, the rigidity of the arm portion is ensured by the manufacturing method (casting) as it is. In addition to this, there is an excellent effect that the stress concentration portion can be easily formed.

[Brief description of the drawings]

FIG. 1 is a plan view of an upper arm according to the present embodiment.

FIG. 2 is a left side view of the upper arm shown in FIG. 1;

FIG. 3 is a right side view of the upper arm shown in FIG. 1;

FIG. 4 is a graph showing representative characteristics of cast iron.

FIG. 5 is a graph for explaining the effect of using the cast iron upper arm according to the present embodiment in comparison with a conventional high-rigidity cast iron upper arm.

[Explanation of symbols]

 10 upper arm (suspension arm) 10C second arm part (arm part) 18 stress concentration part

Claims (3)

[Claims] 1. A suspension arm having a vehicle body side restraining point serving as a mounting portion to a vehicle body and a wheel side restraining point serving as a mounting portion to a wheel support for rotatably supporting a wheel, wherein the vehicle body side restraining point is provided. And an arm portion extending along a line connecting the wheel-side restraint point and a stress concentration portion that deforms the arm portion at a predetermined high load acting at a predetermined position on the arm portion. A suspension arm, characterized in that: 2. The stress concentration section is set based on an offset amount to a center line of the arm section with respect to a line connecting the vehicle body side constraint point and the wheel side constraint point, and a sectional shape of the arm section. The suspension arm according to claim 1, wherein: 3. The suspension arm according to claim 1, wherein the suspension arm is made of cast iron.