Overview of the Toei Mita Line New Rolling Stock (6500 Series)

The Toei Mita Line opened in 1968 (Showa 43), and the entire line was completed with the opening of the section between Meguro and Mita in 2000 (Heisei 12). In 2018 (Heisei 30), it celebrated its 50th anniversary.
At the time of opening, the line was operated with 6000 series semi-stainless steel cars, but between 1993 (Heisei 5) and 2000 (Heisei 12), the 6300 series all-stainless steel cars were introduced, and 22 years have passed since then.
The current Mita Line connects with the Tokyo Metro Namboku Line and operates through-service with the Tokyu Meguro Line.
As development along the line, including the Tokyu Meguro Line, has progressed and a further increase in the number of passengers using the Mita Line is expected, it was decided to proceed with an 8-car train configuration to alleviate congestion. To achieve a drastic increase in transport capacity and further service improvements, it was decided to introduce the 6500 series, a new 8-car train model, with a total of 13 sets (104 cars) for the first batch.

Design Concept

(1) Design Review by the Design Review Team

Regarding the major interior and exterior designs, which were items for consideration at the beginning of the design phase, a design review team composed of members from departments other than the rolling stock department was formed to aim for improved recognition and appeal of the Mita Line. The basic concept was "Smart + Comfort," and it was finished with a functional beauty that is free of waste so that it will be loved as a commuter train for many years.
The exterior design expresses a sense of presence as part of the city that carries transportation, with a smart form. By making it a simple box shape, including the front section, elements that would become visual noise for the destination display and headlights were kept to a minimum.
The interior design uses the line's color, blue, while utilizing glass materials extensively to create a sense of transparency and cleanliness. The seats at the ends of the cars are designated as priority seats, and free spaces have been provided in every car. The hand straps have a new shape that is easy to grip, and by placing some at a lower position, combined with the vertical grab poles, it is now possible to provide more passengers with the opportunity to hold on. The height of the luggage racks has also been lowered to make them easier to use. In this way, aiming for a "people-friendly train," universal design concepts were incorporated throughout. Furthermore, a 3-screen LCD display was introduced above all doors as an in-car information display, enabling the provision of multilingual and highly visible information, making it possible to provide sufficient guidance to visitors to Japan.

Main Specifications and Train Configuration

The train configuration consists of 8 cars, with Car 1 on the Nishi-Takashimadaira side and Car 8 on the Meguro side, arranged as Tc1 + M2 + M3 + T4 + T5 + M6 + M7 + Tc8 from the Nishi-Takashimadaira side.
The car body cross-section has a flat configuration where the sides rise vertically, achieved through ingenuity such as using the eaves shape as a rain gutter. The floor height is set at 1130mm, taking into account the prevention of reverse steps at the platform, and the gap between the car and the platform is minimized as much as possible by keeping the entrance threshold within 3mm of the vehicle gauge.
The M cars are configured in 2-car units, with two pantographs placed on each M2 and M6 car, and DC 1500V is supplied from the M2 car to the M3 car, and from the M6 car to the M7 car. The low-voltage power supply device is a static inverter using IGBT elements, with an output of three-phase 440V, 260kVA.

Rolling Stock Overview

(1) Car Body Structure

The car body structure is an aluminum alloy double-skin structure, and high structural strength is ensured by assembling large extruded shapes using laser-MIG hybrid welding, which provides deep penetration while reducing heat input and distortion. The front structure also uses an aluminum alloy frame-skin structure, ensuring the necessary strength and rigidity where needed.

(2) Passenger Cabin Equipment

Passenger cabin equipment incorporates many universal design concepts. In addition to clarifying the area near the doors by distinguishing the floor color, yellow tape-like markings are placed on the side sliding door lining plates to improve the visibility of the door edges.
The window glass uses IR-cut green glass to reduce the feeling of heat. Double-pane glass is used for the side sliding door windows to suppress condensation on the glass surface during winter.
The seats are cantilevered long seats, and by making them 6-person seats between doors, the space near the doors is expanded, improving fluidity during boarding and alighting. The seat width per person is also more spacious than in conventional cars. The seat surface has a bucket shape that distinguishes each seat, and together with the protective bars provided in the middle, the seating position for one person is clarified, allowing more passengers to use the seats. The upholstery for general seats is a dark blue moquette with a fine pattern arranged with a herringbone design so that dirt is not easily noticeable. Priority seats use a green color that is compatible with the blue series, providing identification from general seats while maintaining a sense of unity. In addition, the partition next to the seats has been enlarged, taking into account safety such as preventing contact between passengers.
The door operating device is an electric door operating device of the rack-and-pinion type using a brushless motor. Door opening and closing control is performed by a microcomputer-based control device, making it possible to perform various controls such as opening/closing speed, cushion control, and door obstruction prevention control.

(3) Train Control and Management System (TCMS)

A Train Control and Management System (TCMS) with further expanded functions from the Train Information System (TIS) installed in the 6300 series has been adopted.
While the conventional TIS was a distributed control system where each central device and unit station performed calculations/control, the TCMS adopts a centralized system where various calculation functions are consolidated in a central unit. For this reason, the unit stations that were placed in each car in the TIS have become transmission units specialized in data transmission functions in the TCMS.
The inter-car transmission speed has been significantly improved from 9600bps of the TIS to 100Mbps, and the control system, which is important for train operation safety, is a dual-line system.

(4) Control Method

The main circuit is a system that controls a totally enclosed three-phase induction motor with a 2-level VVVF inverter. A 1C4M system is adopted, in which one inverter controls four main motors, and each inverter box is configured with two groups of inverters. A Hybrid-SiC control device using SiC (silicon carbide), which has low loss and can operate at high temperatures, is used for the main circuit elements. Compared to conventional products, the regenerative braking characteristics can be improved, so energy-saving effects such as reduced energy consumption can also be expected.
Commands such as power running and braking from the driver's cab are transmitted by the TCMS, which calculates torque by taking into account notch conditions and vehicle load conditions, and then allocates tractive force and braking force to each VVVF inverter device and brake control device.

(5) Bogie

The bogies are coil spring axle-beam type bolsterless air-spring bogies. For the air springs, we have adopted a design with a lower overall height to accommodate a lower floor, and lower horizontal stiffness to allow for smooth passage through sharp curves.
The tread brakes utilize unit brakes that do not require brake stroke adjustment and one-touch shoe cotters to improve maintainability.

For the rail lubrication system, we have adopted a gyro-type curve detector, which is more precise than the conventional mechanical detection method, to achieve efficient lubrication.

(6) Brakes

The braking system is an electric command air brake with regenerative braking. There are five types of brakes: service brakes, emergency brakes, security brakes, snow-resistant brakes, and parking brakes.
The service brake performs load-responsive control and electro-pneumatic coordinated control via TCMS train brake force control. By prioritizing the regenerative brakes of the motor cars, energy-efficient operation and reduced brake shoe wear are achieved.
The parking brake is the first of its kind to be installed on Mita Line rolling stock, allowing for the prevention of vehicle rolling by applying braking force via spring force while the train is stabled.
To prevent wheel flats and extended braking distances due to sliding during braking, a slide-re-adhesion control function is provided to temporarily reduce the braking force of the sliding bogie and promote re-adhesion.

(7) Crew Cab Equipment Layout

Two TCMS screens are installed in the driver's cab. This allows for the display of driving information and fault information for equipment within the train, as well as various indicator lights and gauges. If one screen fails, the remaining healthy screen can display the information for both screens. In addition, a video display is installed separately from the TCMS screen; when an emergency alarm is activated, the security camera footage from the relevant car is displayed on the video monitor, which is expected to facilitate rapid situation confirmation on one-man operated trains.
As for the master controller, the number of notches is the same as the 6300 series, with 4 power notches and 7 service brake notches. Furthermore, the main switches for handling door opening/closing and departure are arranged on the table surface in colors and layouts compliant with through-service vehicle standards.

(8) Vehicle Information Collection System

To realize better transportation services, we have introduced a vehicle information collection system that can automatically collect data such as vehicle status, fault conditions, and driving information.
This system transmits information collected by the TCMS to a cloud service using high-speed wireless communication equipment installed on the train, allowing various vehicle data to be checked on ground-based PCs. By introducing this system, we achieve 'real-time visualization of vehicle status' and 'automatic accumulation of vehicle data'.
'Real-time visualization of vehicle status' allows not only the driver but also dispatchers and maintenance personnel to share detailed, real-time information on the vehicle's status while running (brakes, speed, congestion, etc.) and its condition during abnormalities, enabling vehicle operation based on status and faster fault response.
Furthermore, 'automatic accumulation of vehicle data' allows for detailed trend analysis for each piece of equipment by automatically accumulating data collected by the TCMS. By utilizing these results, we aim for more effective preventive maintenance, such as grasping degradation trends and optimizing parts replacement cycles.

Conclusion

The 6501 set, the first of the 6500 series, was manufactured by Kinki Sharyo Co., Ltd., which has a factory in Higashiosaka City, Osaka Prefecture. After Class A transport to the Koshigaya Freight Terminal, it was transported by road to the Shimura Rolling Stock Maintenance Depot between November 3 and November 6, 2020 (Reiwa 2). Subsequently, in parallel with various test adjustments and confirmation of running safety, the second and subsequent 6500 series sets were manufactured and delivered, and the ground facility upgrades for 8-car trains were completed. Commercial operation of 8-car trains began in stages from May 2022 (Reiwa 4), and the introduction of all 13 sets was completed on October 1, 2022.
In addition, on the Mita Line, besides the 8-car train upgrades, we also implemented support for through-service from Hiyoshi Station to Shin-Yokohama Station in conjunction with the opening of the Tokyu Shin-Yokohama Line.
In closing, I would like to add that the introduction of the Mita Line 6500 series was realized through the cooperation of many involved parties, including the rolling stock manufacturer.

Reference: Kinki Sharyo Co., Ltd. 'Mita Line 6500 Series Rolling Stock Overview (1st Batch)'