Recently, minivans have become popular, accounting for one in every four passenger cars today.
Why so? Practicality. Even the smallest kids can climb into them with ease and a three-generation family does not feel cramped when the car is loaded up with everyone. You also do not have to worry about getting wet in rainy weather.
Minivans often come with a foldable or removable center seat that opens up a ton of flexibility.
Amongst the number of features that deliver driving comfort, power sliding door systems (PSDs) may top the list.
The comfort of automatically opening/closing power sliding doors from the driver’s seat or handle operation has been welcomed on the market.
The safety and practicality PSDs provide are adopted by a lot of auto manufacturers for their minivans.
It was early summer in 1998. At Aisin, sales, design, and other task forces were in the heat of discussions to come up with a new PSD model.
“I'd say the next model should incorporate a new sliding mechanism that represents our innovative spirit.
The current drive unit that opens and closes the door takes too much space, sacrificing the ease of getting in and out of the vehicle.
And, the noise it makes is a bit annoying. Due to the bulkiness, only a limited number of car models can have it.”
“The current mechanism works well enough. Regardless of what kind of system a PSD has, every one of them is equipped with locking and closing mechanism for the door.
Doors alone, even if not part of a system, are still sellable and will bring a number of purchase orders from customers.”
Develop a new system? Or, improve the current one? Ideas and thoughts were shared, and the discussion got heated.
Finally, inspiring words came from the project leader who had been working for a long time on power door parts development.
“All right, everyone. No doubt that our next PSD model is a promising business opportunity.
Why not leverage the opportunity to come up with a genuinely innovative product?
Why not take a leap to become a systems manufacturer from a parts manufacturer? May the new system we give birth to be a robust pillar our body business.”
Be proactive, not reactive. Without realizing it, everyone in the room nodded to his powerful words.
That moment, in a real sense, marked the beginning of the project for the world' first PSD with a built-in motor drive.
Some may wonder why a PSD with built-in doors became the focus.
Automotive sliding doors were relatively new in the product portfolio of Aisin, first commercialized as manually-operated doors for the Toyota Raum released in 1997.
Toyota's Townace and Liteace Noah used Aisin's first PSDs, but they came on models with minor changes and didn't allow full design changes to the doors. The only option for moving the door was push-pull cable control with motor drive and a power supply unit located on the car body.
That resulted in “reduced space inside for a car” and left a lot of challenges.
From this background, project members were determined to accommodate all components, including the motor drive, into the door housing—an idea no other manufacturers had ever tried.
Creating a PSD that would still be considered top notch in the global automotive market even ten years from then became the goal of the project.
Four target car models, including Toyota’s Noah and Voxy, scheduled to be released in the fall of 2001, were selected.
The clock was ticking.
Push-Pull Cable System
Winds up cables to open/close the door. The sliding door motor drive and power supply unit are located on the car body.
The motor drive unit takes up some of the rear space of the car.
“Could you explain why the PSD unit has to be built inside the door? I think you are talking about something impossible, I mean, a door that accommodates all system components.”
The project leader answered,
“A car with doors that internally contain the whole unit would give plenty of space. Doorsteps that do not have to house a motor drive would improve passenger comfort.
A compact profile will allow such doors to be equipped on typical passenger cars.
Just think of a car, say, that comes with power sliding doors on both sides.
It will be an industry standard if we make it.
That's why. That' why we need to make it happen.”
“I see, but how? We have to do something unprecedented with no design materials to give us a clue.”
There were no documented materials, drawings, or other reference that could be of help in developing a totally new mechanism that was nowhere to be found in the world.
List of Functional Requirements for Self-Contained PSD
- ● Driver's seat remote control that opens and closes the doors
- Main control that switches between auto and manual modes located in the driver's seat position. Doors that open and close automatically with the touch of a button on the main control panel in the driver's seat position and a wireless remote controller.
- ● Power assist
- Actuates the open/close movements of the sliding doors when manually operated from the handles.
- ● Pinch prevention
- Just before people or objects are pinched, the door automatically reverses to prevent pinching.
- ● Speed control
- Slows door movement at the start and end of the stroke for safety reasons, and increases the speed midway through the stroke.
- ● Additional function
- The power supply unit supplies power for operating the power windows even when the sliding door are open.
.....It was past 11 o'clock on a February night in 1999 when suddenly the idea came to mind.
Three engineers -- the project leader and two others from car body design engineering -- were racking their brains trying to figure out a way to slide the door with fixed cables.
Then, all of a sudden, the moment came.
“You know, a firefighter controls his ascent and descent in a slow and deliberate manner. Can we apply that movement?”
“You mean, a firefighter turns to let the rope wrap around his body?”
“That's what I'm thinking. Suppose that the firefighter was a door. A door reeling a fixed cable in and out as it slides sideways should work in the same way that a firefighter controls his ascent and descent.”
The same mechanism moves a small boat we sometimes see in a park pond or an obstacle course. A person on the boat moves it along a rope stretched across the water, by pulling the rope, to the other side.
Let the boat and person represent the door and motor, fix one end of the motor cable to the car body, and allow the motor to wind up the cable, then, the door slides just like the boat.
The mechanical concept for sliding the door was decided.
How a Self-Contained PSD Works
Motor and power supply units built inside the door wind up the cable to slide the door.
Enclosing the units in the door provides more space for the car interior.