JP3330432B2 - How to design vehicle suspension parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of designing underbody parts such as an upper arm and a lower arm of a vehicle.

[0002]

2. Description of the Related Art Conventionally, in the case where undercarriage parts such as an upper arm and a lower arm of a vehicle are manufactured from an aluminum alloy, they are excellent in forgeability and have required mechanical properties such as tensile strength, proof stress, elongation and hardness. A method of forming a round bar made of aluminum alloy by forging is known. By the way, the production of such undercarriage parts requires a lot of complicated processes when it is attempted to forge from a round bar, so if a casting process is adopted as a part of the process and casting and forging are combined, Although it is possible to shorten the time, in the production of such parts, after designing the alloy components, first design the production conditions such as casting conditions, and then design the production conditions such as heat treatment conditions, for each process. It works in a way that optimizes it.

[0003]

However, in the case of such a method in which optimization is performed for each process, conditions for clearing the target value with an average value are pursued. There is a problem that the product quality is often not reproduced in the field at the site, and the dispersion of the optimum conditions is large.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a vehicle which has a mechanical property required for a suspension component.
The process of setting the target value and the alloy composition related to this target value
Multiple factors, including at least minute, casting and heat treatment conditions
The process of selecting
The process of setting the levels of
The process of planning and performing experiments, and analyzing and
How to design vehicle suspension parts consisting of the process of determining appropriate values
The step of performing the experiment comprises:
Of a type determined based on a combination of factors and multiple levels
Manufacture of castings and test pieces obtained from these castings
Is subjected to an elongation test.
By selecting the optimal level for each of the above factors,
The optimal level for the cast material
Multiple types consisting of multiple factors and one level determined in
Newly manufactured multiple castings for multiple training ratios,
This was forged, and the test piece obtained from the forged product was obtained.
In the elongation test to determine the optimal value,
Optimal level for each of the above factors from the elongation obtained from the forged product
And determine this as the optimal level for casting-forging.
It is characterized by that.

[0005]

[Function] Combination of casting and forging of vehicle suspension parts
When manufacturing by the method, many factors related to casting and forging
Numerous factors related to fabrication make it easy to determine manufacturing conditions
Can not do it. Therefore, in claim 1, the casting test
Optimum level for each factor using growth as an index for pieces
Decide. Next, cast-forged manufactured based on this decision
Optimal for each factor using elongation as an index for test pieces
Determine the standard. That is, the determination of the optimal level is performed in the first stage
(Casting test piece) and the second stage (casting-forging test)
Topies). This results in a minimal experiment
The most suitable optimal value could be determined.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for designing a vehicle suspension part according to the present invention will be described.

Conventionally, suspension arms such as an upper arm and a lower arm, which are suspension parts of a vehicle, are formed by forging an extensible aluminum alloy such as JIS 6061 material for weight reduction.

That is, for example, a round bar manufactured by extrusion molding or the like is formed into a desired shape by hot forging in three steps of three heats and three blows, and is finally trimmed to obtain a product.

[0009] However, such a forging method, which satisfies the strength requirements of the product,
There were many processes and there were problems in productivity and cost.

[0010] On the other hand, for example, JIS standard AC4CH material is known as an aluminum alloy suitable for casting. However, such a casting aluminum alloy has poor mechanical properties when it is made into a product such as a suspension component. There is a problem in terms.

In order to shorten the process by adopting a casting process in the conventional manufacturing process of the vehicle suspension parts, the design of alloy components, the design of casting conditions, the design of heat treatment conditions, and the like are appropriately performed. It is necessary to manufacture parts having the required mechanical characteristics, but it is necessary to obtain design values with good reproducibility of the quality in the field by minimum experiments while taking such comprehensive conditions into consideration.

Accordingly, the present invention is designed to design the suspension parts of the vehicle by the method shown in FIG.

That is, first, as a target value of mechanical properties required for underbody parts, 606 of aluminum alloy of JIS standard is used.
The same properties as those of one material are set, and specifically, the tensile strength (σ
_B ) 31.5 kgf / mm ² , proof stress (σ _0.2 ) 28.0 kgf / mm ² ,
The target was an elongation of 12.0% and a hardness (HRF) of 90.9.

Factors related to satisfying the target values are molten metal treatment, Si content as an alloy component,
Eight factors of Mg amount, Cu amount, solution heat temperature, aging temperature, aging time, and natural aging were selected.

[0015] Incidentally, Al-Mg-Si alloys are known as aluminum alloys having corrosion resistance and moderate strength, and also excellent in castability, and the strength is increased by adding Mg and Cu. And casting defects can be prevented by adding Si.

Next, two to three levels are set within the allowable range by changing the conditions of such factors.

That is, as shown in FIG. 2, for example, there are two levels of the presence or absence of the molten metal treatment, three levels of the Si content of 2.5 wt%, 3.5 wt%, and 4.5 wt%, and the others. There are three levels as shown in the table.

Next, the combinations of these levels are assigned to 18 types of experiments using an orthogonal table as shown in FIG. That is,
For example, in the experiment of No. 1, the level of all the factors (rows) was set to 1, and in the experiment of No. 2, the factor 1 (the molten metal treatment) and the factor 2 (the amount of Si) were set to the level 1, and the levels of the other factors were set to 2. And so on. An experiment is performed based on the allocated experimental plan, and the tensile strength (σ _B ), proof stress (σ _0.2 ), elongation%, and hardness (H) of the test piece manufactured from the cast product are obtained.
RF) and, for example, as shown in FIG.
Combine N ratios. SN ratio is a quality engineering term indicating stability
Yes, and the formula will be described later. Here, FIG. 4 shows an average of the SN ratio of the tensile strength (σ _B ) as an example. The other proof stress (σ _0.2 ), elongation%, and hardness (HRF) are also not shown but similarly. Desired.

Here, SN ratio = 10 × log (m ² /
σ ² ) ( log is a logarithm , m is an average value, and σ is a standard deviation), and a condition with a high SN ratio indicates a condition with high stability.

The vertical direction in FIG. 4 corresponds to the order of the factors described above. One row indicates the molten metal treatment, the second row indicates the amount of Si, and the third row indicates the amount of Mg. In the horizontal direction, the levels correspond to each other. The left side of one row has the molten metal treatment at the level 1 and the right side has the molten metal treatment at the level 2 at the left side. Is 3.5% at level 2 and 4.5% at level 3 on the right side.
With factor No1, level 1 is higher than level 2 in tensile strength (σB)
Is large, so level 1 is selected. Level for factor No2
Since 2 has a higher tensile strength (σB) than levels 1 and 3,
Select level 2. Similarly, for factor No. 3, the level
1, Level 3 for Factor No. 4, Level 2 for Factor No. 5, Factor
Level 3 for factor No. 6, level 1 for factor No. 7, factor No.
At step 8, level 1 is selected.

The combination of the above factors and levels is shown in FIG.
Write in the table. That is, the characteristic value (σ
B), factor Nos. 1 to 8 are arranged on the horizontal axis, and these factors N
Under o1-8, 1, 2, 1, 3, 2, 3, 1, 1, etc.
In particular, levels 1 to 3 are described. In addition, it attached to level 1-3
(Parentheses) will be described later. Detailed description is omitted.
However, other characteristic values (σ _0.2 , elongation, hardness)
Create the same table as Fig. 4 for each, and from the average of the SN ratio,
When picking out large levels of most numerical each column ing and as FIG.

The parentheses and non-parentheses in the table indicate the lower and higher ranks of the weighting result. Those without parentheses are those with higher weighting, and those with parentheses are those with lower weighting. . Incidentally, the weighting is performed by each characteristic value (σ
_B , σ _0.2 , elongation, hardness), the total sum of squares (S) in the 1st to 8th columns of the orthogonal table L is obtained, and the total sum of squares (S) is divided by the degree of freedom (f) for dispersion. (V).

Then, the elongation (%) of the characteristic values shown in FIG.
Line in the lower column of the figure,
Level ”. Here, the reason why attention is paid to elongation among the characteristic values is that it is necessary to emphasize plastic workability in a forging process after casting.

Next, a new on the basis of the results of the above experiment
A cast product is manufactured, the cast product is actually forged at various forging ratios, a test piece is made from the obtained forged product, and the optimum conditions are confirmed.

FIG. 6 shows a table obtained by measuring various characteristic values (σ _B , σ _0.2 , elongation, hardness) by forging at various forging ratios, and obtaining the SN ratio. The vertical axis of the figure shows the characteristic value (increase
, Σ _B , σ _0.2 , hardness), factors 1, 2, 3, 5 at the bottom
And 6, the levels 1, 2, or 1-3 are shown at the top. Here, the forging ratio indicates the relationship between the thickness of the material before forging H and the thickness of the material after forging h, where the forging ratio 1 is 0% forging ratio, the forging ratio 2 is 50%, The training ratio 3 is 67%,
The training ratio 4 corresponds to 75%, and the training ratio 5 corresponds to 80%.

It should be noted that in the table, No. 1 is a factor particularly effective for elongation (%) . No. 1 ( melt treatment ), 2 ( Si content ), N
o. 3 ( Mg content ), No. 5 ( solution temperature ), 6
( Aging temperature ) , elongation (%)
Other factors that do not affect 4 ( Cu
No.), No. 7 ( aging time ), The three factors of 8 ( natural aging ) are not described, but have no particular meaning. Then, the optimum level is read from the figure by the following procedure. Left factor
Child No. In column 1, growth is level 1 (top
(See levels 1 and 2 in the column) is large and level 2 is small. There
Then, select level 1 for growth. In σ _B under the
Selects level 1, level 1 for σ _0.2 , level 1 for hardness
You. That is, the factor No. For 1, σ _B is the level
1, σ _0.2 is set to level 1, elongation is set to level 1, hardness is set to level 1.
And make a list in the following figure.

FIG . 7 shows characteristic values (σ _B , σ _0.2 , elongation,
Hardness), and the horizontal axis represents factor No. In the table listing 1-8
Yes, Factor No. In the row of 1, σ _B is 1, σ _0.2 is 1, elongation
Is 1 and hardness is 1. Similarly, the factor N in FIG.
o. The characteristic values (σ _B , σ _0.2 ,
And hardness) and transcribed to FIG. What
The factor No. Figures 4, 7, and 8 have the same contents as FIG.
From the table (not shown), the characteristic values (σ _B , σ _0.2 , elongation, hardness)
Each level was determined and transcribed in FIG.

Then, in the same manner as described above , the row of elongation (%)
At the bottom of the table, which is referred to as "Optimal water
“Associative”.

Therefore, from the lower part of FIG.
(Yes), Si content is level 2 (3.5%), Mg content is level 1 (0.5%), Cu content is level 3 (0.2%), solution temperature is level 1 (520 ° C) Aging temperature is level 1 (170
C), aging time is level 1 or 3 (6 hours or 10 hours), and aging temperature is level 1 (0 days).

The factor No. About the aging time of 7 ,
Although two types were found as the optimum conditions, they were not particularly effective factors for elongation, and there was no significant difference between Level 1 and Level 3.

The above-described method of the present invention is summarized as follows.
Can be The method of the present invention can be applied to underbody parts of vehicles.
The process of setting the desired mechanical properties and the target
Fewer alloy components, casting conditions and heat treatment conditions
For selecting a plurality of factors including the above with reference to FIG.
Figure 2 shows several levels within the allowable range of these factors.
A step of setting while referring to a set of levels as shown in FIG.
The process of planning and conducting experiments based on
Of the vehicle consisting of the process of analyzing the data and determining the optimum value
It is a method of designing parts. And in the process of conducting the experiment
Is determined based on a combination of multiple factors and multiple levels.
Of castings of the type
Perform the elongation test on the piece, and the larger the elongation, the better
The optimal level for each factor,
Is the optimum level in the cast material (see the bottom of FIG. 5).
You. Next, several factors determined at the optimum level
A plurality of types of castings consisting of a single
Newly manufactured multiple parts for the mixing ratio, forged,
A test piece obtained from the obtained forged product is subjected to an elongation test.
Thus, a test result as shown in FIG. 6 is obtained. Then, the optimum value is determined.
Determining the factor from the elongation obtained from the forged product.
Choose the optimal level for each case
Determine the optimal level (see the bottom of FIG. 7)
I do.

Combination of casting and forging of undercarriage parts of a vehicle
Many factors associated with casting
And many factors related to forging make manufacturing conditions easy
Cannot be determined. Therefore, in the present invention, the casting
Optimum water for each factor using growth as an index for the stoppiece
Determine the standard. Next, the casting manufactured based on this decision
Of each factor in the index growth forging test piece to the target
Determine the optimal level. That is, the determination of the optimal level is determined by the first
After the stage (casting test piece), the second stage (casting-forging)
Test piece). As a result, with minimal experimentation
The optimum value with high reproducibility could be determined.

[0033]

As described above, the method for designing underbody parts of a vehicle according to the present invention sets the mechanical characteristics necessary for underbody parts as target values and comprehensively selects factors related to the target values. Then, each level is rationally combined and comprehensively examined with a minimum number of experiments, so that conditions with good reproducibility in the field can be rationally and efficiently obtained.

[Brief description of the drawings]

FIG. 1 is a process diagram of a design method of the present invention.

FIG. 2 is a diagram showing an example of setting factors and levels.

FIG. 3 is an example of an orthogonal table.

FIG. 4 SN ratio of tensile strength

FIG. 5: Combination of factors affecting variation and optimal conditions

FIG. 6 shows the S of the factor (factor for elongation) at each training ratio.
N ratio

FIG. 7: Combination of factors affecting the average value of each training ratio and optimal conditions

────────────────────────────────────────────────── ⁷ Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI // C22F 1/00 630 C22F 1/00 630A 690 690 Examiner Nao Yamaguchi (56) References JP-A-62-166044 (JP, A) Japanese Utility Model Hei 2-25305 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60G 7/00 B22D 46/00

Claims (1)

(57) [Claims] 1. A step of setting a target value of mechanical properties required for a suspension component of a vehicle, and a step of selecting a plurality of factors including at least an alloy component, a casting condition, and a heat treatment condition related to the target value. The steps of setting a plurality of levels within the permissible range of these factors, planning and executing an experiment based on a combination of these levels, and analyzing the experimental data to determine an optimum value. a method of designing around part, in the step of performing said experiments, the plurality of factors and a plurality of
Manufactures castings of the type determined based on combinations with standards
Test pieces obtained from these castings for elongation tests.
The criterion that the larger the elongation is, the better the
Choose the optimal level for each factor and use this as the
And suitable levels, a plurality of factors determined by the optimal level of the cast material 1
Of multiple types of castings with different training ratios
Newly manufactured several pieces, forged them, and obtained
Subjecting the test piece obtained from the forged product to an elongation test to determine the optimum value,
The optimum level is selected for each of the above factors, and this is cast-
Vehicles characterized by determining the optimum level in forgings
How to design both suspension parts.