Inner Rail Type Power Sliding Door

Development of Inner Rail Type Power Sliding Door Masahiro KYOTO* Toshiya SHIMPO** Takehiro IWAMI* ** Fumihiko KOBAYASHI* ** * Fumitoshi TAKENAKA* ** * Kouji KAMIO* ** *

Abstract This paper outlines the development of a power sliding rear door for the new eK WAGON. The door is the first of its kind applied to bonnet type minicars. With bonnet type minicars, the distance between the rear door and the rear end of the vehicle is short and thus, if the rear door is of a sliding type, the distance available for the sliding door center rail is too short to provide the necessary longitudinal length of the door opening. The method adopted to resolve this problem is the Mitsubishi Motors Corporation (MMC) original inner-rail-type sliding door mechanism with the center rail on the door. Employed along with this mechanism is a module design applied to the numerous functional components of the power sliding system, in which these components are subassembled on a module panel for their collective quality control during production. Key words: Door, Desigh, Modularize

1. Introduction Power sliding doors are commonly found on minivans whose popularity is now soaring in Japan. However, such doors are not common in the minicar segment; they are offered on only a limited number of one-box type models and on none of the bonnet type minicars. Nevertheless, there is a potential demand for power sliding doors among users of bonnet type minicars who typically own them as second family cars. They want power sliding doors for such reasons as preventing their children from bumping the door against a car parked nearby when opening/closing the door and the convenience of door opening/closing when carrying shopping bags. In response to such desires of customers, MMC has developed a power sliding rear door applying the company’s original inner door rail mechanism for the new eK WAGON; this is the first of its kind for bonnet type minicars.

2. Packaging strategies 2.1 Inner rail mechanism With bonnet type minicars, there is only a short distance available between the rear end of the rear door and the rear edge of the car body. This is the main reason why the conventional outer rail type sliding door system has not been used for bonnet type minicars to date; more particularly, it is impossible to install a sufficient length of center rail on the quarter panel. The MMC original inner-rail-type sliding door system with the center rail built into the door overcomes the problem. Fig. 1 shows the difference between the outer-railtype and inner-rail-type sliding door systems. Sliding doors generally use three rails, i.e. the upper, center and lower rails. With the inner-rail-type system, the center *

Body Design Dept., Development Engineering Office

** * Function Testing Dept., Development Engineering Office

rail is located inside the rear door, and this enables the car to have a larger door opening. In the system used on the new eK WAGON, the door opening is as wide as 530 mm when fully opened without the door protruding beyond the rear edge of the body. This width is sufficient for passengers to get in and out of the car easily. The inner-rail-type design also eliminates the need for installing a garnish, which is necessary for aesthetically covering the center rail that is installed on the outer surface of the car body with an outer-rail-type system. The result is a clean and neat body appearance. 2.2 Head clearance The new eK WAGON inherits an overall height of 1,550 mm from the previous versions to fit in multistory car parks. This height is rather too low for cars with a sliding door, making it difficult to secure sufficient head clearance for the front passenger and easy entry/exit. The measures employed to solve the problem are the following: a cover that is located below the upper rail to help reduce the height of the rail, and the upper rail layout was optimized to minimize the protrusion of the head lining into the cabin. These methods have successfully provided an adequate head space and ease of entry/exit (Fig. 2). While developing the sliding door system for the new eK WAGON, the quality in terms of ease of entrance/exit and cabin comfort was evaluated and verified repeatedly using a dedicated mock-up, which was modified every time the design was changed in any detail.

** Electronics Engineering Dept., Development Engineering Office ** Mitsubishi Automotive Engineering Co., Ltd. **

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Development of Inner Rail Type Power Sliding Door

3. Structure of the inner-rail-type power sliding door 3.1 Components Fig. 3 shows the components of the inner-railtype power sliding door system. The system includes the following basic components: the upper, center and lower rails; the upper, center and lower roller arms; and the rollers which roll inside the rails. It also includes the latching/locking components, most of which are arranged in the area above the center rail. These include the front and rear latches that retain the door in the fully closed position, and the locking mechanism that holds the door in the fully open position, which is subassembled on the upper roller arm and the lower guide. The system also has a release actuator that unlatches the door during power sliding operation of the door and a lock actuator that locks/unlocks the door. The inside and outside handles of the door are of a lever type for reduced effort and enhanced ease of operation by the following. The lever type handles allow the latching/locking device to be released to be selected by changing the turning direction, which enables the user to release the front and rear latches when opening the door and the upper and lower open locks when closing the door without difficulty. These locking mechanism operations are coordinately controlled via a link assembly. Located in the lower portion of the door are the power sliding door unit, the control unit, and the power feeder unit that relays both battery power and signals. For added safety, a touch sensor is provided on the front edge of the door to prevent an obstacle or passenger from being trapped as the door closes.

Fig. 1

Inner-rail-type design vs. outer-rail-type design

Fig. 2

Upper rail layout

3.2 Power sliding door unit Fig. 4 is a schematic drawing showing the principle of operation of the power sliding door. The open and close cables, the ends of which are attached to the center arm, are routed via the front and rear pulleys respectively, and wound round the cable drum that is located at the center of the door and forms an integral part of the power sliding motor unit. The door is opened and closed as the drum takes up a cable and pays out the other cable. As shown in Fig. 5, the door drive cables are linearly arranged between the center arm and front pulley and between the center arm and rear pulley. This eliminates the need to use cable outer casing and thus reduces frictional resistance and ensures smooth and stable movement of the door. Fig. 3 Components arrangement

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Development of Inner Rail Type Power Sliding Door

Fig. 4

Schematic of power sliding door operation

Fig. 6 shows the external appearance of the power sliding door module. The locking/latching mechanism parts and harnesses are subassembled on the upper portion of the module panel while the power sliding door unit parts are grouped on the lower portion of the panel.

4. Control of power sliding door

Fig. 5

Power sliding door cable layout

Fig. 6

Power sliding door module

3.3 Module design The locking/latching components, power sliding door unit components and electric harness parts are modularized to integrate the complicated locking/latching mechanism and power sliding related components into a single module for collective quality control and improved assembling efficiency during production.

4.1 System configuration Fig. 7 shows the configuration of the control system for the power sliding door. The control unit, which governs opening and closing of the power sliding door, is installed inside the door. The unit receives power from the vehicle’s power supply circuit via the power feeder unit, and also receives control switch inputs and vehicle status data via the power feeder unit. The control unit issues commands to the sliding door motor and rear latch motors based on these signals in addition to the signals from the locking/latching switches and the sensors within the door. 4.2 Control of door operation The power sliding door is controllable using any of the driver’s switch, rear switch, door handles, and key switch for remote control. The driver’s power switch is used to switchover between power sliding and manual sliding of the door. Also, the control system has a function for prohibiting power sliding of the door during fuel refilling and driving. Speed control of the sliding door motor at the stages just before fully closing and fully opening motions of the door is programmed so as to reduce the risk of injury and increase the impression of quality. The speed-change sensing system, which consists of the pulse sensor in the sliding door motor and the touch sensor at the front end of the door, is designed to prevent becoming trapped by the closing door.

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Development of Inner Rail Type Power Sliding Door

Fig. 7

System diagram

5. Summary The power sliding door system that features MMC’s original inner-rail-type sliding door technology has been successfully tailored for installation on the new eK WAGON. The system is the first of its kind not only in MMC but also in the entire bonnet-type minicar segment. The power sliding door system will be developed by refining its components for even greater user comfort.

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Masahiro KYOTO

Toshiya SHIMPO

Takehiro IWAMI

Fumihiko KOBAYASHI

Fumitoshi TAKENAKA

Kouji KAMIO