MOVEMENT

9R

Spring Drive

Spring Drive is a unique watch technology. It generates energy like every other luxury mechanical watch but combines this with an electronic regulator to deliver a level of precision that no mechanical watch can match.
The development of Spring Drive was possible because Grand Seiko is one of the very few manufacturers with mastery of both electronic and mechanical watchmaking.

MECHANISM

Bringing together mechanical
and electronic watchmaking for the best of both worlds.

The two key elements behind the function of any watch are its power source and its time control system.

Spring Drive is a unique movement that combines the high torque of a mechanical watch with the high precision integrated circuit (IC) control system of an electronic watch.

Power source

Control system

Mechanical watch

Mainspring
High torque 

(motive force driving the watch)

The wound-up mainspring exerts force to turn gears at a set speed as it unwinds, while the speed control and escapement mechanism consisting of the balance, pallet, and escape wheel govern overall precision. While precise. even the most accurate Grand Seiko models cannot compete with the accuracy of a quartz watch, with a daily rate of +8/-1 seconds.

Quartz watch

Battery

Lower torque compared toh
a mechanical watch

The battery sends electricity to a quartz oscillator, whose precise vibrations are detected by an integrated circuit (IC). The IC then moves the gears forward by exactly one second. The precision control of the IC allows for a high standard of accuracy, with Grand Seiko quartz models achieving a yearly rate of ±10 seconds.

MECHANISM

Powered by the mainspring

Spring Drive is powered by a mainspring, just like all other mechanical watches. This traditional way of generating power allows the watch to be entirely autonomous, with no need for a battery or other power source.

Winding the mainspring by turning the crown or by moving the wrist stores energy which is then transferred to gears and used to move the watch hands as the spring unwinds over time.

By taking advantage of the high level of torque afforded by the mainspring, the caliber needs no other power to move the long, wide hands in the smooth glide motion that is Spring Drive’s signature.

MECHANISM

The Tri-synchro regulator

Spring Drive utilizes an exclusive speed control mechanism, incorporating an IC, an electronic brake and a quartz crystal.

Without a mechanism to adjust the speed at which the mainspring returns to its unwound state, it would unwind rapidly and the watch would come to an abrupt stop. To realize the goal of precise timekeeping, a mechanism to control the speed at which the spring unwinds is needed.

The Tri-synchro regulator developed for Spring Drive fulfills this role.

As its name suggests, the Tri-synchro regulator uses three types of energy to regulate the moving parts and establish synchronicity:

  • 1. Mechanical power, from the mainspring
  • 2. Electrical power, creating a reference signaling via an IC/quartz oscillator
  • 3. Electromagnetic power, to apply a brake via a rotor/stator.

These three forces work in harmony to regulate the way the spring unwinds and to make possible the precise movement of the second hand.

TRI-SYNCHRO REGULATOR
1. MECHANICAL POWER

Generating electrical power from the unwinding mainspring

Spring Drive uses a system identical to that of a pedal-powered bicycle light to generate electrical power. A rotor connected to the end of the gear train acts together with a stator wound by wire to generate power. In a Spring Drive watch, the rotor, or glide wheel, makes eight full revolutions every second, generating a slight electric current.

TRI-SYNCHRO REGULATOR
2. ELECTRICAL POWER

Transmitting a precise signal through a quartz crystal oscillator

The electrical power generated by the glide wheel is used to activate a quartz oscillator and IC.
The quartz oscillator vibrates at exactly 32,786 Hz, transmitting a precise reference signal to the IC.

TRI-SYNCHRO REGULATOR
3. ELECTROMAGNETIC POWER

Applying the brake to control speed

The IC compares the reference signal from the quartz oscillator with the revolution speed of the glide wheel, and intermittently applies a magnetic brake when it detects that the glide wheel is operating too fast. This regulation of the glide wheel is transmitted to the gear train, ensuring that the watch hands move with precision.

CRAFTSMANSHIP

Master craftsmanship in assembly and adjustment

Spring Drive combines the best elements of both mechanical and electronic watches. While three-hand versions have over 200 components, versions with more functions, such as the Spring Drive chronograph have well over 300, all of which are assembled by hand.

The application of lubricating oils ensures the smooth interaction of all the components and there are no fewer than 80 lubrication points in the three hand caliber and 140 in the chronograph. The oils are applied by hand and both time and great skill are required to ensure that that the oils are applied with precision.

Design plans are based on tolerances down to the one hundred of a millimeter. The final adjustments and refinement of the components are completed by hand, because no machine can match the skills of our craftsmen and women – watchmakers whose superior craft gives rise to the extreme precision of Spring Drive.

History

In 1977, Yoshukazu Akahane, a young watch engineer, decided to attempt the seemingly impossible, the creation of an ‘everlasting’ watch. His aim was a traditional watch, powered by a mainspring, that would deliver the one-second-a-day precision of which the company’s electronic watches were already capable. 28 years and 600 prototypes later, he realised his dream and Spring Drive was presented to the world. In 2007, and in the spirit of Akahane’s relentless pursuit of perfection, the Grand Seiko Spring Drive chronograph was born.

9R SPRING DRIVE MOVEMENT

9R SPRING DRIVE MODEL