Design of backdoor

Car back door is the door at the rear end used to provide access to storage compartment of the car or also in few car cases to the rear seats of the car.

Car back door assembly consists of several main parts namely;

1. Inner panel

2. Outer panel upper

3. Outer panel lower

4. Hinge reinforcement

5. Gas stay reinforcement

6. Wiper motor reinforcement

7. Latch and striker reinforcement

Design considerations for the parts and the assembly :

i) Inner panel :

1. The inner panel of back door assembly is started with a sealing flange design, in order to prevent the entry of rain water.

2. Nextly the entire inner panel is designed with suitable draft angle and surface regions and provided with suitable embosses on it.

3. The embosses are provided on the upper portions, side portions, middle portion and end bottom portion to mount hinges, gas stay mounts, wiper mounting and latch mounting respectively.

4. The embosses are given below the windsheild area in order to provide the strength to the back door assembly thus providing protection to the passengers in case of a back hit on a car.

5. For the rear end visiblity criteria, a cut out region is given for the windshield glass on the inner panel.

6. Also a cut out portion is provided on the left bottom portion to accomodate latch and striker motor for door locking purpose, to balance the centre of gravity a similar cut out portion is created on the right.

7. A cutout flange is given on the inner panel with some gap of 5mm in between to join it with mastic sealant, which in turn improves the NVH and also the strength of the sheet metal in its vicinity.

8. The thickness of the inner panel is 0.75mm.

Image : Inner panel

Image : line depicts the tooling direction for manufacturing

ii) Outer panel upper and lower :

1. The outer panel upper and outer panel lower are assembled over the inner panel by hemming process.

2. Cutouts are provided on the outer panel to provide room to the head lights and also a cutout is given for placing a windshiled glass screen for the rear end visibility.

3. The thickness of these outer panels are 0.75mm.

Image : outer panel upper

Image : outer panel lower

Image : Hemming of the outer panels over the inner panel

iii) Reinforcements :

1. The reinforcements are provided with a thickness of 1.5mm and are designed for the purpose of strengthening component on the mounting regions of the inner panel given for hinge mountings, gas stay mountings, latch mountings which are subjected to frequent loads during the opening and closing action of the door and for wiper motor mountings which is also subjected to a certain amount of loads during its operation.

Image : Hinge reinforcement

Image : Latch reinforcement

Image : Gas stay reinforcement

Image : Wiper motor reinforcement

iv) Hinge and latch assembly :

1. The latch emboss on the inner panel of the back door is designed in such a way that when the latch is placed on the emboss of the inner panel, the trajectory of the latch along the hinge axis hits the stricker for locking the door.

Thus after fulfilling all the design requirements and considerations the final assembly for the back door is completed.

Image : Final assembly of the back door