Design of backdoor
TAILGATE
Trunk lid and Tailgates are widely used in vehicles that do not allow transportation of large goods.
Trunk lids, liftgates, and tailgates are usually stamped with steel deep drawing sheets, thickness between 0.6 and 0.8 mm, both for the outer and inner panel. The inner panels are often reinforced in the hinges and struts attachment zones. Usually, the two main panels feature a contour hemming. In some cases, liftgates with a welded back window frame have been manufactured. Liftgates, as well as trunk lids, have been made up of high yield rephosforized steel, sometimes of aluminum or with an outer plastic panel (thermoplastic as Noryl GTXR, polycarbonate or thermoset, as BMC, SMC, and ZMC).
HINGES USED IN TAILGATES.
The liftgate hinges are embedded in the rear roof cross member, closer to the side roof end than to the roof centerline. They can be single joint hinges with a fixed axis, each half hinge being fastened by one or two screws when the roof has a small curvature. If the liftgate to roof surface borderline has a relevant curvature, that kind of hinge cannot be used, because the liftgate rotation could cause interference with the roof. To avoid this inconvenience, an articulated quadrilateral can be used (also known as pantograph hinge), the rotation center of which moves during liftgate motion as shown. These hinges feature a higher obstruction than the simple hinges and therefore are usually located close to the side liftgate end.
A: SINGLE JOINT THREE SCREW HINGE
B: PANTOGRAPH HINGE
In the case of the trunk lid, where the border center below the back window is usually positioned behind the trunk lid side edges, single joint hinges would cause interference with quarter panels or with back windows. In this case, pantograph or gooseneck hinges can be used, of which the attachment to the body is hidden below the back window lower cross member.
It is important to position the liftgate gas springs rods below so that the oil in the cylinder can always keep the gaskets wet so as to maintain the internal pressure. Regarding the influence of thermal variations, the requested load at 20◦C must theoretically be increased by 14%, to compensate for the gas pressure reduction at–20◦C and take account of the possible snow load. This means that, at +40◦C external temperature, the gas springs shall provide a 22% higher load than requested.
In any case, to lock the trunk lid completely, some energy is needed at first latch contact and therefore some amount of overrun, usually stopped by rubber dampers, positioned at trunk lid side rear end.
TAILGATE INNER PANEL DESIGN.
DRAFT ANALYSIS
The following snip shows draft analysis performed over the inner panel.
REINFORCEMENTS
Reinforcements were provided at the following locations to improve the load-bearing capacity locally.
1. HINGE MOUNTING REGION
2. GAS STAY MOUNTING
3. WIPER MOTOR MOUNTING
4. LATCH AND STRIKER MOUNTING.
2mm thickness is maintained uniformly across all reinforcements.
The following snip shows a sectional view of the complete Tailgate assembly with the outer on.
This concludes the design of tailgate.