Background and overview
In 2008, JR West developed the class Kiha122 single-car suburban diesel hydraulic multiple unit for use on the Kishin Line, following infrastructure upgrades including track reinforcement. A total of seven vehicles were manufactured that year to meet regional service requirements.
Car body
The vehicles feature unpainted stainless-steel bodies measuring 2,950 mm in width, with a bead-less exterior finish. A tricolor waistline band in orange, yellow, and white runs the length of each car below the windows, complemented by brown accents applied around the door cases. The cab end is constructed from steel and incorporates wide, bisymmetrical curved windscreens designed to reduce manufacturing cost. A gangway door is positioned at the center of the cab end.
Lighting equipment includes two pairs of sealed-beam headlights and auxiliary lamps mounted horizontally on either side of the gangway, with horizontally elongated rectangular LED taillights positioned below. Each side of the vehicle is fitted with two 1,300 mm-wide double-leaf automatic sliding doors, operated by WTK112 door mechanisms located above the door headers. Manual operation is possible via push-button controls adjacent to each door.
Window arrangements include four 1,470 mm-wide hopper windows between the doors and one fixed window per side. All windows utilize heat-absorbing double-glazing to improve thermal and acoustic insulation and prevent condensation. An LED destination indicator is mounted on each side of the carbody. Two WAU707 roof-mounted air conditioning units using R407C refrigerant are installed per vehicle, each incorporating internal loudspeakers for platform guidance announcements. Close-contact couplers are employed.
Bogies
The powered bogies are designated WDT65 and incorporate a two-axle drive system. Trailer bogies are classified as WTR248 and feature bolster-less secondary air suspension, conical multilayer rubber spring journal supports, and a single-link draw gear. The powered bogies utilize single-tread brake rigging, while trailer bogies employ both single-tread and disc brake rigging.
Traction unit and ancillary equipments
Propulsion is provided by a four-cycle flat-six diesel engine (SA6D140HE-2)
rated at 450 PS. The engine is equipped with a turbocharger driven by exhaust
gas flow, an intercooler, and a common-rail direct injection system designed
to reduce emissions, particularly nitrogen oxides (NOx). Power is transmitted
via a DW21 hydraulic transmission featuring a three-member single-stage
torque converter, multi-plate wet clutch, and a four-stage direct-coupled
range.
To maximize interior space, the radiator and heat exhaust fan unit are
miniaturized and installed beneath the floor. Equipment standardization
with JR West's electric multiple units—particularly the 223 series—was
pursued to reduce manufacturing costs and simplify maintenance, including
the adoption of beltless electrified systems.
An engine-driven generator (WDM112), powered via a constant-speed unit, supplies three-phase 440 V AC to the air conditioning and electric heating systems. This voltage is stepped down to 100 V AC or rectified to 100 V DC for control circuits and auxiliary equipment. The vehicles are equipped with a belt-driven air compressor (C600), selected due to reliability concerns with gear-driven compressors previously used on the KiHa126 series.
Control systems include the Train Information Control System (TICS), which operates on a programmable logic controller (PLC) platform to reduce wiring and relay complexity. The braking system is an electric-command pneumatic type incorporating jake braking. If jake braking performance falls below the required threshold, pneumatic braking is automatically engaged to supplement braking force.
Accommodation
Interior seating consists of a combination of 2+1 flip-over transverse seats located centrally and longitudinal bench seating at both ends of the transverse bays. Each longitudinal seat provides 440 mm of width per passenger, enhancing standing capacity and facilitating efficient boarding and alighting during peak periods.
Air conditioning ducts are installed above the ceiling, with slit-shaped vents used to improve interior aesthetics. Hanging straps are provided throughout the passenger compartment. Ticket vending machines, which issue boarding station tickets, are located near the doorways at the vehicle ends. Fare chart displays using seven-segment LEDs and fare boxes are positioned behind the driver's cab.
All vehicles are equipped with a wheelchair-accessible space and a universal access toilet located toward the front of the passenger compartment. The toilet system employs vacuum flushing technology.
Operations
The class Kika12 entered revenue service on the Kishin Line in March 2009.
Following completion of track reinforcement works, 100 km/h operation commenced
in March 2010. As of the present, these vehicles are deployed on regional
services between Himeji and Kozuki. |
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