JP3442122B2 - Press molding method - Google Patents

Description

BACKGROUND OF THE INVENTION [0001] Field of the Invention The present invention is related to <br/> Ru press forming method to be molded without causing springback. 2. Description of the Related Art Conventionally, there has been known a molding method for preventing springback caused by press molding during press molding. As an example of such a molding method,
For example, in the case of Japanese Patent Publication No. 4-4047, a method is used in which the bending shoulder is pressed to a slight forging pressure. [0003] However, in the case of the above-mentioned technology, the springback stress is reduced by pressing the bending shoulder portion to reduce the thickness of the bending shoulder portion. There is a problem that even if the effect is obtained, it is difficult to obtain a further effect. [0004] In order to solve the above-mentioned problems, the present invention relates to a press forming method for preventing a spring back occurring at a bent shoulder portion during press forming, wherein the bent shoulder portion is formed. At this time, a punch having a curvature convex portion is provided on the bending shoulder portion in parallel with the ridge line of the bending shoulder portion, with a concave stepped portion recessed in a direction opposite to the forming bending direction of the bending shoulder portion.
The die with convex portions on both sides of the corresponding concave
Te, that you simultaneously form the bending shoulder portion and the concave shape Laid
Sign. The bent shoulder is formed with a concave stepped portion that is recessed in the direction opposite to the bending direction of the bent shoulder in parallel with the ridgeline of the bent shoulder, so that the opposite direction is positively provided. A springback moment is generated to achieve balance. An embodiment of the press forming method according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a molded product in which a step-shaped concave step is formed, and FIG. 2 is an experimental data table showing improvement of springback when the step-shaped concave step is formed. [0007] Generally when a bend as shown in FIG. 5 formed by press working, angle bending to release from the mold acts springback moment M _R in a decreasing direction. The amount of springback Δθ _R is
Assuming that the material is a work hardened material in which the relation between plastic stress σ and strain ε is represented by σ = Fε ⁿ (F is work hardening coefficient) and is in a plane strain state (two-dimensional problem), for example, curvature when bent at a bending angle theta _R in radius R is represented by general formula as follows. [0009] Equation 1 [0010] Here, n represents work hardening coefficient (n value), F is the work hardening coefficient (F value), E is Young's modulus, _{t 0} is the thickness. In the present invention, FIG.
As shown in (a), a step-shaped concave step d is formed at the center of the bent shoulder t of the molded product W so as to be parallel to the ridgeline 1 of the bent shoulder t, and this concave step d is formed. As a result, a moment in the opposite direction to the springback moment MR is generated to balance. FIG. 1B is an enlarged longitudinal sectional view of the bent shoulder t and the concave step d. The valley 1 b of the concave step d extends in the front and back directions of the paper so that the valley 1 b is parallel to the ridge 1. The portion and the portion extending outward from the valley portion 1b become the peak portions 1a and 1c, and the two peak portions 1a and 1c.
Then, a concave step d is formed at the bending shoulder t at one valley 1b therebetween so as to be parallel to the ridgeline 1. The concave step d not only reduces the surface thickness by simply depressing the surface, but also, for example, as shown in FIG.
As shown in (1), the whole is concaved in the direction opposite to the forming and bending direction. In the case of forming such a cross section as shown in FIG. 1B, R3 (or R0)
And a die having a curvature convex portion of R5 on both sides of a concave portion (the above-mentioned peak portions 1a and 1c) corresponding to the punch having the curvature convex portion (the above-described valley portion 1b). I have to. [0014] The concave step d that is recessed in the direction opposite to the forming direction causes springback in the forming and bending direction and springback in the opposite direction, thereby balancing the two. FIG. 2 shows a comparison between the springback of a molded article formed by the above method and the springback of a molded article formed by a conventional method. FIG. 2 shows the amount of springback (゜) when a steel plate (SPC) and an aluminum plate are formed under the processing conditions of a drawing depth of 30 mm and a processing speed of 25 SPM. , A triangle mark is formed with a punch having a curvature of R3, and a square mark is formed with a punch having a curvature of R0. As a result, it has been found that both a steel plate (SPC) and an aluminum plate are very effective. [0018] Here, the As apparent from the equation for obtaining the spring back amount [Delta] [theta] _R, originally, since the person R punch is large reverse torque is increased, but the spring back should be less, the experiment In the case of, the opposite result is shown. This is considered to be due to deviation from the theoretical value because the die is correcting the R stop portion. Incidentally, as shown in FIG.
A total of three bending radius parts having a radius of curvature of ₁ , r ₂ , and r ₃ are provided, and the bending direction of the central bending radius part is adjusted to two on both sides.
When the bending direction of the two bending round portions is reversed, the theoretical value of the springback amount Δθ at the point B when the point A is constrained in the vertical direction is calculated by the following equation. Next, FIG. 3 shows an example in which an embossed concave step d is locally added to the bending shoulder t. In this forming, the forming of the bending shoulder t and the forming of the embossed concave step d are simultaneously performed. FIG. 4 shows a comparison between the springback of the molded article formed by using the φ5 punch and the φ3 punch and the springback of the molded article formed by the conventional method. In this case, the effect is also large. The fact that the springback is negative indicates that the reverse moment is larger. As described above, the press molding method of the present invention
When forming the bending shoulder , the bending shoulder has a concave step recessed in a direction opposite to the forming bending direction of the bending shoulder, in parallel with the ridge line of the bending shoulder , a curvature convex portion. Punch and this
By die with convexities on both sides of the corresponding curvature concave,
The bent shoulder and the concave shape are formed at the same time.
In to generate a reverse moment are balanced, effectively it is possible to prevent the spring-back Te Me verge. Therefore, the dimensional accuracy of the press-formed product can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a molded article in which a step-shaped concave step is formed. FIG. 2 is an experimental data table showing improvement of springback when a step-shaped concave step is formed. FIG. 3 is a perspective view of a molded article in which an embossed concave step is formed. FIG. 4 is an experimental data table showing improvement of springback when an embossed concave step is formed. FIG. 5 is a simple bent springback. FIG. 6 is an explanatory view for explaining a bead-shaped bending springback. [Description of References] W Molded product t Bending shoulder d concave step

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kei Kiyama 1-10-1 Shinsayama, Sayama-shi, Saitama Honda Engineering Co., Ltd. (72) Inventor Tetsuya Wakabayashi 1-10-1 Shin-Sayama, Sayama-shi, Saitama (56) References JP-A-63-84730 (JP, A) JP-A-52-133864 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21D 5 / 01

Claims (1)

(57) [Claim 1] In a press forming method for preventing a spring back from being generated in a bent shoulder portion during press forming, when forming the bent shoulder portion, A punch having a curvature convex portion, in parallel with the ridge line of the bending shoulder portion, a concave step portion recessed in a direction opposite to the forming bending direction of the bending shoulder portion;
By die with convexities on both sides of the corresponding curvature concave,
You form the bending shoulder portion and the concave shape at the same time, press molding wherein a call.