Bring the Key System of the Next Generation Bring the Key System of the Next Generation

The Spirit of Monozukuri—6 The Spirit of Monozukuri—6
The Story Behind the Development of the Smart Key System The Story Behind the Development of the Smart Key System
Smart Key System

Pocketed Smart Key Locks and Unlocks the Door Technology of the Future Pocketed Smart Key Locks and Unlocks the Door Technology of the Future

In the very near future, no longer will you need a key to drive a car...

Released in 2000 summer, the third-generation Toyota’s Celsior, serving as the flagship model, came with an epoch-making technology that made every automotive enthusiast picture a future where drivers no longer need car keys.

Dubbed the Smart Key System, the new mechanism allows the driver to keep the key fob pocketed and unlock the door by gripping the handle.

The key is identified via one of several antennas in the car's bodywork and a radio pulse generator in the key housing. The system verifies the information on the key, which is linked to the car owner’s identification, to unlock the door. In addition, drivers can also lock, start the vehicle, and even open the luggage compartment door without physically inserting a key.
At the time, smart keys were already available from Daimler-Benz and other European auto manufacturers that had launched some models featuring keyless entry. Domestic players in the industry, including Toyota Motor, and suppliers to them could not allow themselves to lag behind.

Smart Key System

When the key comes within 1.0 m of the driver’s car, the smart key identifies the car owner identification and the door automatically unlocks with a touch of the door handle.

  • The antennas identify and confirm the presence of the key in the vehicle detection range. The antennas identify and confirm the presence of the key in the vehicle detection range.
  • The door automatically unlocks with a touch of the door handle. The door automatically unlocks with a touch of the door handle.

Needs Nothing More Than a Touch of the Door Handle Evolution from the PES Needs Nothing More Than a Touch of the Door Handle Evolution from the PES

In the fall of 1997, Toyota Motor, Denso, Tokai Rika, and Aisin, formed a quartet to develop a next-generation keyless entry system.
Aisin was responsible for the door transmitter, door handle antenna, and trunk external transmitter and its antenna, each unto itself a core technology in keyless access.
The locking/unlocking in a smart key system prevents car theft, hence is required to be reliable, secure, and free from failure or malfunction.

Aisin had prototyped a system called Passive Entry System (PES), which was proposed to automobile manufacturers in 1996.
PES was a system capable of identifying the presence of the key to unlock the door with a touch of the door handle.
Keyless entry systems before that required the button on the key be pressed to unlock the door. The technology in the PES system, in that aspect, was a step ahead of the others.

Incorporating the PES technology into the new smart key system was the plan.
More specifically, the idea was to have an antenna in the door handle recognize the presence of the key and verify the information linked to it when the driver comes to the car before the driver touches the door handle.

Aisin-designed Components of Smart Key System

  • Car Car
  • Trunk external transmitter Trunk external transmitter
  • Locking switch/Input sensor electrode/Antenna/Door handle Locking switch/Input sensor electrode/Antenna/Door handle
  • Door transmitting antenna Door transmitting antenna

“That Unused Technique May Work.” Dig Up the Method Left Neglected for 15 Years to Create a Human Sensor for Vehicles “That Unused Technique May Work.” Dig Up the Method Left Neglected for 15 Years to Create a Human Sensor for Vehicles

How can sensors know the driver is going to open the door?—It was a question at the very core of the project. Another element critical to the success was to develop an antenna reliable enough to transmit radio waves within the design coverage range.

The electronic engineering task force responsible for the development of the sensor came to a dead end. Then, one day, a manager who headed the team recalled something and said,

“You remember you came up with the idea that used the capacitance theory? That may work in what you are doing right now.”

To illustrate the point, assume you are listening to a radio station. It is often the case that touching the radio receiver or approaching it changes the sensitivity of the radio receiver. The change in the capacitance of the antenna of the receiver is what causes that.
What he suggested was that phenomenon familiar to everyone might work in the sensor under development.

Almost a decade and a half before that, the mechanism had once been applied to prototyping an anti-pinching sensor for power windows.
“You are right. That may work.”

A sensor that detects the change in an electric charge when a person touches an object was named “human sensor.”
No one can get in a car without touching the door handle before driving the car.
The idea was to leverage the capacitance, the degree of change in the electrical charge of the sensor system.

“If this works, the technique that ended up in the prototype may come in a practical product...,” they thought.

Capacitance

The ability to collect and store energy in the form of an electrical charge. Also referred to as “electrostatic capacity” or “static capacitance”. A human body can act as a capacitor.

Weather, Body Fat Percentage, and More—Everything Has to Be Factored in for a Sensor Capable of Handling Anything Conceivable. Weather, Body Fat Percentage, and More—Everything Has to Be Factored in for a Sensor Capable of Handling Anything Conceivable.

It was, however, not an easy task to turn the idea into a product.
There were so many things that had to be factored in. Capacitance on a door handle can vary depending on conditions, e.g., when it is wet, the body capacitance of the driver, the force applied when it is held, whether the driver is wearing gloves, the weather, etc.
To determine the best-suited parameters, they needed to monitor capacitance and identify how changes trended.

The project team planned a body capacitance monitor program.
Factors affecting body capacitance include the physique and constitution of persons.
Nearly 30 individuals took part. The variations in body capacitance of each were monitored.

They reproduced conditions as similar to everyday behaviors as possible.
When it started raining, they rushed outside with a door handle-attached test panel in their hand to collect data in rainy conditions. Slowly, but steadily, data was collected until everything needed was in their hands.