# US 2017/0286591 A1 · Method of designing torsion bars used for trunk lid

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- Number: US 2017/0286591 A1
- Document ID: US20170286591A1
- Status: Published application
- Kind: A1
- Application number: 15/086,009
- Filed: 2016-03-30
- Published: 2017-10-05
- Earliest claimed: 2016-03-30
- Assignees: NHK Spring Co., Ltd.
- Applicants: Nhk Spring Co., Ltd.
- Inventors: Yoshio KOBAYASHI; Shinichi NISHIZAWA; Nobuhisa YASUDA
- Web page: https://patentgrep.com/patent/US20170286591A1

## CPC

- E05F 1/1238: {specially adapted for vehicles}
- G06F 30/17: Mechanical parametric or variational design
- G06F 30/23: using finite element methods [FEM] or finite difference methods [FDM]
- E05Y 2201/624: Arms
- E05Y 2900/548: Trunk lids
- E05F: DEVICES FOR MOVING WINGS INTO OPEN OR CLOSED POSITION; CHECKS FOR WINGS; WING FITTINGS NOT OTHERWISE PROVIDED FOR, CONCERNED WITH THE FUNCTIONING OF THE WING
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- E05Y: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES E05D AND E05F, RELATING TO CONSTRUCTION ELEMENTS, ELECTRIC CONTROL, POWER SUPPLY, POWER SIGNAL OR TRANSMISSION, USER INTERFACES, MOUNTING OR COUPLING, DETAILS, ACCESSORIES, AUXILIARY OPERATIONS NOT OTHERWISE PROVIDED FOR, APPLICATION THEREOF

## 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.

## Claims

### Claim 1

A design method of torsion bars used for a trunk lid, each of the torsion bars being given a target shape in a state where the trunk lid is closed, and being given a free shape in a free state where the torsion bars are unhitched from the trunk lid, the design method of the torsion bar having the free shape comprising:
(a) a step of inputting design specifications including target torque occurring in each of the torsion bars in the target closed shape, a rotational angle by which a movable end of each of the torsion bars 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 each of the torsion bars;
(b) a step of creating a center line model having the target closed shape on the basis of the coordinates of the nodes;
(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 on the basis of coordinates of nodes of the free shape;
(d) a step of creating a center line model of the open shape on the basis of 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 nodes on the center lines of the center line models; and
(g) a step of changing the center line model so as to decrease the amplitudes of the difference torque and the difference vector, when the amplitudes of the difference torque and the difference vector are not both within predetermined tolerances, respectively, and returning to the step (d), or a step of finishing the design method of the torsion bar, when the amplitudes of the difference torque and the difference vector are both within predetermined tolerances, respectively.

### Claim 2 (depends on 1)

The design method of torsion bars of claim 1, further comprising
a step of rotating a movable end of the center line model having the free shape by an angle Δθ so as to set the analyzed torque of the closed shape to be close to a predetermined torque specified in the specification, thereby create the center line model of a open shape; and
a step of executing an analyzing of rotating the center line model of the open shape by the rotational angle to thereby create the center line model of an analyzed closed modified shape.

### Claim 3 (depends on 1)

The design method of torsion bars of claim 1, wherein
the center line model is created based on a calculation of bending points for the torsion bars and has curved and linear portions on which the nodes are set,
the step (f) of obtaining the difference vector includes a step of obtaining the difference vector occurring between the nodes corresponding to each other, and
the step (g) of creating the center line model of the analyzed closed shape includes a step of changing the shape of the center line model of the initial free shape in order to also reduce the difference vector occurring between the nodes on the center lines, and rotating the center line model again to thereby create a center line model of a modified analyzed closed shape.

### Claim 4 (depends on 1)

The design method of torsion bars of claim 1, wherein
the center line model or the closed shape which is determined after the step of finishing the design method is defined as the final model, and the center line model of the initial free shape corresponding to the final model is determined as the designed torsion bar.

### Claim 5 (depends on 4)

The design method of torsion bars of claim 4, further comprising a step of simulating a locus of a full stroke of the center line final model concomitant with opening and closing of the trunk lid with respect to the center line final model of the closed shape to thereby check interference with other vehicle parts.

### Claim 6 (depends on 5)

The design method of torsion bars of claim 5, further comprising a step of changing the target closed shape specified by coordinates of the bend point position on the basis of the fact that the center line final model of the closed shape interferes with the other vehicle parts, wherein
the processing from the step (b) of creating the center line model to the step (g) of repeating the processing is executed on the basis of the changed target closed shape.

### Claim 7 (depends on 6)

The design method of torsion bars of claim 6, wherein
the step of changing the target closed shape includes a change in which a bend point for the torsion bar is added to or is eliminated from the target closed shape.

### Claim 8 (depends on 1)

The design method of torsion bars of claim 1, further comprising a step of simulating locus of full strokes of a pair of the center line final models concomitant with opening and closing of the trunk lid with respect to the center line final model of the pair of torsion bars to thereby check interference with other vehicle parts.

### Claim 9 (depends on 8)

The design method of torsion bars of claim 8, wherein
in the center line final model of the pair of torsion bars, a locus of a full stroke of the center line final model concomitant with opening and closing of the trunk lid is simulated on the premise that the torsion bars are fixed.

### Claim 10

A design method of torsion bars used for a trunk lid, each of the torsion bars being given a target shape in a state where the trunk lid is closed, and being given a free shape in a free state where the torsion bars are unhitched from the trunk lid, the design method of the torsion bar having the free shape comprising:
(a) a step of inputting design specifications including target torque occurring in each of the torsion bars in the target closed shape, a rotational angle by which a movable end of each of the torsion bars is rotated from the target closed shape to the open shape, the target closed shape to be specified by coordinates of bending points of the torsion bars, and a wire diameter of each of the torsion bars;
(b) a step of creating a center line model having the target closed shape on the basis of the coordinates of the bending points;
(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 on the basis of coordinates of bending points of the free shape;
(d) a step of creating a center line model of the open shape on the basis of 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 modified shape and the target closed shape; and
(g) a step of changing the center line model so as to decrease the amplitudes of the difference torque and the difference vector, when the amplitudes of the difference torque and the difference vector are not both within predetermined tolerances, respectively, and returning to the step (d), or a step of finishing the design method of the torsion bar, when the amplitudes of the difference torque and the difference vector are both within predetermined tolerances, respectively.

### Claim 11 (depends on 1)

A design device configured to design the torsion bars which provided with a processor configured to execute a program which embodying the method defined in claim 1.

### Claim 12 (depends on 10)

A design device configured to design the torsion bars which provided with a processor configured to execute a program which embodying the method defined in claim 10.