Method of designing torsion bars used for trunk lid

Patent metadata

Field	Value
Publication number	US-10229242-B2
Application number	US-201615086009-A
Country	US
Kind code	B2
Filing date	Mar 30, 2016
Priority date	Mar 30, 2016
Publication date	Mar 12, 2019
Grant date	Mar 12, 2019

Abstract

In a design method of torsion bars used for a trunk lid, free shapes of the torsion bars unhitched from the trunk lid are designed. A center line model of the initial free shape is geometrically and statically created on the basis of a design specification. The center line model of an open shape is created from the free shape model and is deformed into a center line model of a closed modified shape. The center line models of the analyzed closed shape and the target closed shape is compared with each other to obtain a difference torque and a difference vector occurring between corresponding nodes on the center lines. The center line model is so changed as to decrease the difference torque and the difference vector.

First claim

What is claimed is:

1. A method of designing a torsion bar used for a trunk lid, the torsion bar being given a target closed shape in a state in which the trunk lid is closed and an open state in which the trunk lid is open, and being given a free shape in a free state in which the torsion bar is unhitched from the trunk lid, the method comprising:
(a) a step of inputting design specifications including target torque occurring in the torsion bar in the target closed shape, a rotational angle by which a movable end of the torsion bar is rotated from the target closed shape to the open shape, the target closed shape to be specified by coordinates of nodes, and a wire diameter of the torsion bar;
(b) a step of creating a center line model of the target closed shape based on the coordinates of the nodes of the target closed shape;
(c) a step of geometrically and statically creating the free shape corresponding to the target closed shape, and creating a center line model of the free shape based on coordinates of nodes of the free shape;
(d) a step of creating a center line model of the open shape based on the center line model of the free shape, and rotating the center line model of the open shape by the rotational angle to thereby create a center line model of an analyzed closed shape;
(e) a step of obtaining difference torque between the target torque and an analyzed torque of the analyzed closed shape;
(f) a step of comparing the center line models of the analyzed closed shape and the target closed shape with each other to thereby obtain a difference vector occurring between corresponding nodes on center lines of the center line models of the analyzed closed shape and the target closed shape;
(g) a step of changing the center line model of the free shape so as to decrease amplitudes of the difference torque and the difference vector, thereby obtaining a modified center line model of a modified free shape, when the amplitudes of the difference torque and the difference vector are not both within predetermined tolerances, respectively, and returning to the step (d) so as to repeat the steps (d) through (g) based on the modified center line model of the modified free shape; and
(h) a step of finishing a design of the torsion bar, when the amplitudes of the difference torque and the difference vector are both within the predetermined tolerances, respectively.

2. The method of claim 1 , wherein the step (d) comprises:
a step of rotating a movable end of the center line model of the free shape by an angle Δθ, which is set based on the target torque, thereby creating the center line model of the open shape; and
a step of rotating the center line model of the open shape by the rotational angle to thereby create the center line model of the analyzed closed shape.

3. The method of claim 1 , wherein the center line model of the target closed shape is created based on a calculation of bending points for the torsion bar and has curved and linear portions on which the nodes are set.

4. The method of claim 1 , wherein the step (h) comprises, when the amplitudes of the difference torque and the difference vector are both within the predetermined tolerances, respectively:
determining the center line model of the analyzed closed shape as a final model; and
determining the center line model of the free shape corresponding to the final model as the design of the torsion bar.

5. The method of claim 4 , further comprising:
(i) a step of simulating a locus of a full stroke of the final model concomitant with opening and closing of the trunk lid to check for interference with other vehicle parts.

6. The method of claim 5 , further comprising changing the target closed shape in response to the step (i) indicating that the final model interferes with the other vehicle parts, and performing steps (b) through (i) based on the changed target closed shape.

7. The method of claim 6 , wherein the changing the target closed shape includes adding or removing a bend point for the torsion bar in the target closed shape.

8. The method of claim 4 , wherein steps (a) through (h) are performed for a pair of torsion bars, to obtain final models and designs for the pair of torsion bars; and
wherein the method further comprises:
(i) a step of simulating loci of full strokes of the final models for the pair of torsion bars concomitant with opening and closing of the trunk lid to check for interference with other vehicle parts.

9. The method of claim 8 , wherein the step (i) is carried out on the premise that the torsion bars are fixed to each other.

10. A design device comprising a processor and a memory storing a program executable by the processor to perform the method of claim 1 .

11. A method of designing a torsion bar used for a trunk lid, the torsion bar being given a target closed shape in a state in which the trunk lid is closed and an open state in which the trunk lid is open, and being given a free shape in a free state in which the torsion bar is unhitched from the trunk lid, the method comprising:
(a) a step of inputting design specifications including target torque occurring in the torsion bar in the target closed shape, a rotational angle by which a movable end of the torsion bar is rotated from the target closed shape to the open shape, the target closed shape specified by coordinates of bending points of the torsion bar, and a wire diameter of the torsion bar;
(b) a step of creating a center line model of the target closed shape based on the coordinates of the bending points of the target closed shape;
(c) a step of geometrically and statically creating the free shape corresponding to the target closed shape, and creating a center line model of the free shape based on coordinates of bending points of the free shape;
(d) a step of creating a center line model of the open shape based on the center line model of the free shape, and rotating the center line model of the open shape by the rotational angle to thereby create a center line model of an analyzed closed shape;
(e) a step of obtaining difference torque between the target torque and analyzed torque of the analyzed closed shape;
(f) a step of comparing the center line models of the analyzed closed shape and the target closed shape with each other to thereby obtain a difference vector occurring between corresponding bending points for the analyzed closed shape and the target closed shape;
(g) a step of changing the center line model of the free shape so as to decrease amplitudes of the difference torque and the difference vector, thereby obtaining a modified center line model of a modified free shape, when the amplitudes of the difference torque and the difference vector are not both within predetermined tolerances, respectively, and returning to the step (d) so as to repeat the steps (d) through (q) based on the modified center line model of the modified free shape; and
(h) a step of finishing a design of the torsion bar, when the amplitudes of the difference torque and the difference vector are both within the predetermined tolerances, respectively.

12. A design device comprising a processor and a memory storing a program executable by the processor to perform the method of claim 11 .

Assignees

• Nhk Spring Co Ltd

Inventors

• Kobayashi Yoshio
• Nishizawa Shinichi
• YASUDA Nobuhisa

Classifications

• E05F1/1238 Primary

  specially adapted for vehicles · CPC title

• E05Y2201/624

  Arms · CPC title

• G06F30/17 Primary

  Mechanical parametric or variational design · CPC title

• E05Y2900/548

  Trunk lids · CPC title

• G06F30/23

  using finite element methods [FEM] or finite difference methods [FDM] · CPC title