Koyo delivers 7,7m diameter slewing bearing for one of Japan’s largest tunnel excavation shield machines

Keeping rotational run-out to 0.1 mm with a diameter of 7.7 m

JTEKT’s large slewing rim bearing is sold under the Koyo brand, which goes by the motto “Key of your operation”, and was adopted in the shield machine used in tunnel excavation for the portion of the Tokyo Outer Ring Road which runs for a length of 16.2 km to join the Kan-Etsu Expressway and Tomei Expressway. The 16.1-meter diameter cutter shield used in this shield machine is the largest in Japan; even bigger than the one approximately 14 meters in diameter used when constructing the Tokyo Bay AquaLine opened in 1997.

JTEKT developed Japan’s largest slewing rim bearing with a 7.7 m diameter, in order to support the rotation of this large cutter shield. The cutter shield is used to dig up soil and cut through hard rock, therefore its performance greatly affects the efficiency of tunnel excavation work. The newly developed slewing rim bearing has a diameter of 7.7 meters, but at the same time is able to keep rotational run-out down to around a mere 0.1 mm due to using special polishing technology, thus improving the cutter shield’s rotational accuracy. The new bearing is highly regarded by users due to adopting optimal materials and heat treatment technology so as to offer sufficient durability and reliability to accomplish long-term construction work during which part replacement is difficult.

Realizing high rotational accuracy even if transported in installments and assembled on-site

Due to Japan’s narrow roads, generally large shield machines are transported to excavation sites in a number of separate segments. For the Tokyo Outer Ring Road tunnel excavation also, the slewing rim bearing was sent in four segments and assembled on-site. Compared to integrated-type shield machines, machining of shield machines with a split design is much more difficult, including aspects such as distortion control during heat treatment.

“JTEKT was selected to participate in this project due to being recognized as the only Japanese manufacturer capable of manufacturing large slewing rim bearings requiring split design, and for the high technological capabilities.”

“The newly developed slewing rim bearing has a diameter of 7.7 meters, but at the same time is able to keep rotational run-out down to around a mere 0.1 mm due to using special polishing technology, thus improving the cutter shield’s rotational accuracy.”

JTEKT was selected to participate in this project due to being recognized for its track record of supplying bearings to a high number of shield machines, both small and large, as the only Japanese manufacturer capable of manufacturing large slewing rim bearings requiring split design, and for the high technological capability accumulated through such experience. The demand for tunnel excavation work in Japan is set to grow further in the future in areas such as railway and road infrastructure.

As an “Only One” manufacturer of large slewing rim bearings, JTEKT will continue to promote further product development and contribute to the advancement of infrastructure both in Japan and abroad.