What AIZEN does

株式会社アイゼン (AIZEN Co., Ltd.) is a privately held Japanese precision manufacturer founded in October 1919 in Hamamatsu, Shizuoka Prefecture, with 275 employees and ¥50 million in registered capital. The company's core business is the manufacture of engine and mission functional parts — primarily engine connecting rods (コネクティングロッド) and transmission fork gear shifts (フォークギヤシフト) — for two- and four-wheeled vehicles, outboard motors, agricultural machinery, construction equipment, and industrial machinery. AIZEN supplies 100% of Suzuki Motor Corporation's domestic connecting rod requirements and serves other major OEMs including Kubota, Yanmar, NTN, and Mitsubishi Heavy Industries Engine & Turbocharger.

AIZEN's underlying technology stack is organized around three reinforcing capabilities: (a) micron-level precision machining (tolerances of 0.001mm) executed in split-type and one-piece connecting rod configurations through dedicated equipment; (b) in-house heat treatment including full-automatic carburizing/carbonitriding furnaces, gas soft nitriding (gas and oil cool), NTC (acid nitriding) treatment to Hv600-900, and 2.9 bar multi-flow pressurized vacuum quench and temper; and (c) in-house production equipment design and build executed by wholly-owned subsidiary Co., MIC (株式会社エム・アイ・シー), which designs jigs, automation, and dedicated machines such as connecting rod bolt-tightening stations using 2D/3D CAD. The four Hamamatsu factories (HQ Takatsuka, Ozawatori West for heat treatment, Ozawatori East, Hama-kita) operate alongside AIZEN SB (Thailand) Co., Ltd., established in 2011 for overseas OEM supply, and increasingly embed IoT-based production and quality monitoring with image-based dimension measurement.

Revenue is generated through B2B direct supply contracts with OEM manufacturers for components (one-time/license-style contracted part shipments) and through toll-based contract heat treatment services for over 150 customers monthly. The company markets exclusively via direct OEM sales relationships and supports that pipeline through targeted recruitment (Mynavi), industry sponsorships (Shizuoka University SUM formula racing team), and CSR/community engagement rather than traditional advertising. Pricing is negotiated individually with OEM customers and is not publicly disclosed. AIZEN has received consistent supplier recognition from Suzuki (Best Partner 2021, 2024; VA-VE Proposal Awards 2021, 2022) and Kubota (Director's Award Bronze 2022, Green Procurement Commendation 2024, Best Supplier 2025), and is held within the Arai/Mizutani founding-family ownership structure with Arai Hideyuki as President (since 2020) and Mizutani Kōzō as Chairman.

Name

AIZEN

Legal name

株式会社アイゼン

Website

https://kk-aizen.co.jp

Company type

Private

Founded year

1919

Operating status

Operating

Headcount range

251–500 employees

Short description

AIZEN (株式会社アイゼン) is a 106-year-old privately held Hamamatsu-based Japanese precision manufacturer producing engine connecting rods and fork gear shifts for automotive, motorcycle, agricultural, and construction OEMs, supplying 100% of Suzuki's domestic connecting rod needs and offering toll heat treatment to 150+ monthly customers.

Ownership category

akta.pro rank

Product category

Engine Connecting Rods and Precision Engine Components Manufacturing

NAICS

Precision Turned Product Manufacturing (332721), Industrial Machinery Manufacturing (33324)

SIC

Special Industry Machinery (No Metalworking Machinery) (3550), Industrial Process Furnaces & Ovens (3567)

akta.pro primary industry

Passenger Vehicle Engine Systems Manufacturing (ICE) (IMACAAAF)

Keywords

• Engine connecting rods
• Precision machining services
• Metal heat treatment
• Transmission components
• Automotive OEM parts

Headquarters

HQ city

Hamamatsu

HQ country

Japan

HQ region

Asia

Offices6 records

Markets served

GTM type

B2B

Offering type

Hardware or Manufacturing

Cost components

Personnel, Supply Chain, Technology or R&D, Infrastructure, Operations, Marketing or Sales

Revenue model

1. Connecting Rod Manufacturing: Design and manufacture of precision connecting rods (コンロッド) for automotive, motorcycle, outboard motor, agricultural, construction, and industrial machinery engines. The company produces both split-type (割型) and one-piece (一体型) connecting rods in various configurations (bolt/nut, dowel pin, fracture, reamer bolt types). Revenue is generated through direct B2B supply contracts with OEM manufacturers.
2. Fork Gear Shift Manufacturing: Production of fork gear shift components for automotive and motorcycle transmissions, providing total manufacturing from forging material through machining, heat treatment, grinding, and surface finishing.
3. Heat Treatment Processing Services: Contract heat treatment processing services including carburizing, carbonitriding, gas soft nitriding, NTC treatment, vacuum quenching, solution heat treatment, precipitation hardening treatment, normalizing, and annealing. The company processes parts for over 150 customers monthly and handles both internal and external (toll processing) heat treatment work.
4. Equipment and Machine Manufacturing: In-house design and manufacturing of production equipment, jigs, automation devices, and dedicated machines through subsidiary Co., MIC. Includes special-purpose machines for connecting rod bolt tightening and fully automated inspection-to-assembly lines.

Pricing tiers

Go-to-market motion2 records

Distribution channels3 records

Marketing channels5 records

Core offering

AIZEN manufactures ultra-precision engine connecting rods (split-type and one-piece) and fork gear shift components for automotive, motorcycle, outboard motor, agricultural, construction, and industrial machinery applications, with tolerances of 1/1000mm. The company also provides in-house metal heat treatment contract processing services (carburizing, carbonitriding, gas soft nitriding, NTC, vacuum quenching) serving over 150 customers monthly, and operates a subsidiary (MIC) that designs and builds production equipment and automation for its own lines.

Product overview

AIZEN is a precision manufacturing company specializing in connecting rods (con-rods) and fork gear shifts for engines. The product portfolio centers on split-type and monolithic connecting rods manufactured with micron-level precision, complemented by fork gear shift components for transmissions. The company also offers comprehensive heat treatment contract processing services as a major secondary business, handling carburizing, carbonitriding, gas soft nitriding, NTC treatment, vacuum quenching, and various annealing processes. The connecting rod and fork gear shift products are manufactured through forging, machining, heat treatment, grinding, and surface processing.

Differentiator

Problem solved

Functional benefit

Products and services

• Connecting Rods (コンロッド / Con-Rod)

Quantifiable outcome

• Tolerances of 1/1000mm (0.001mm) for connecting rods, verified through image dimension measuring instruments and IOT-compatible inspection machines.
• +2 more outcomes

Named customers6 records

Segments4 records

Ideal customer profiles3 records

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature8 records

Partnerships

Six partnerships are on record, tiered core and minor.

• AIZEN SB (Thailand) Co., LTD.coreStrategic or Co-development Partner · 1 January 2011Overseas subsidiary established in Thailand in 2011 for automotive parts manufacturing and sales, located in Rojana Industrial Park, Ayutthaya, Thailand. Represents the company's first major step as a global enterprise.
• AMZEN TECHNOLOGIES PVT.LTD (India)minorStrategic or Co-development Partner · 1 January 2010Technical assistance agreement for mechanical design and manufacturing signed in 2010.
• AMTEK AUTO LIMITED (India)minorStrategic or Co-development Partner · 1 January 1996Technical assistance agreement for connecting rod manufacturing technology. Initial agreement signed in 1996, renewed in 1999, and new agreement signed in 2007 for new engine connecting rod manufacturing technology.
• 株式会社MIC (M.I.C. / エム・アイ・シー)coreTechnology or IntegrationRelated company (関連会社) that designs and manufactures production jigs, automation equipment, and dedicated machines for AIZEN's production lines. Uses 2D/3D CAD for design and handles full process from design through machining, assembly, and adjustment. Established in 1986 with capital of ¥30,000,000.
• 中部電力ミライズ (Chubu Electric Power Miraiz)minorStrategic or Co-development PartnerPartner in the Enshu Decarbonization Project (遠州脱炭素プロジェクト), contributing to regional carbon neutrality through solar power generation introduction and surplus power sharing among participating companies.
• Suzuki Motor Corporation (スズキ株式会社)coreChannel Partner/ Reseller/ DistributorLong-term major customer and strategic partner. AIZEN supplies 100% of Suzuki's domestic connecting rod requirements. Suzuki recognized AIZEN with a commemorative plaque for long-term business relationship during Suzuki's 100th anniversary in 2020.

Scale indicators5 records

Recent moves12 records

Expansion highlights6 records

Direct peers

• Musashi Seimitsu Industry: Japanese precision components manufacturer focused on motorcycle and automotive transmission/engine components for OEMs including Honda and other Japanese/global names. Highly comparable B2B precision parts supplier model serving overlapping customer profiles.
• Bharat Forge: Indian-headquartered global leader in forging and machined engine components including connecting rods. Directly competes in the connecting rod segment at much larger global scale.
• Maruyasu Industries: Japanese precision auto parts maker with connecting rod manufacturing for automotive OEMs as a core line, supplying similar Japanese Tier-1 customers. Closest direct domestic peer to AIZEN in product scope and customer base.
• Bodycote: World's largest commercial heat treatment services provider. Closest direct peer to AIZEN's contract heat treatment franchise, operating in the same metallurgical services category.
• Riken Corporation: Japanese manufacturer of piston rings, valve seats, and other internal combustion engine components. Operates in the same ICE powertrain components category and supplies the same Japanese OEM customer base.
• TPR Co., Ltd. Listed Japanese manufacturer of piston rings and automotive engine/functional components. Similar product portfolio overlap (precision ICE parts) and similar Tier-1 Japanese OEM customer base.
• F.C.C. Tsuchiya: Japanese clutch and powertrain component manufacturer with global operations supplying Japanese OEMs. Comparable mid-cap Japanese precision parts supplier with Tier-1 customer relationships.
• EXEDY Corporation: Japanese manufacturer of clutches and drivetrain components serving automotive OEMs including Japanese marques. Directly comparable as a Japanese Tier-1 precision powertrain components supplier.
• Nippon Piston Ring (NPR): Long-established Japanese piston ring and cylinder liner maker with global operations. Direct peer in precision engine functional components supplied into the same Japanese OEM ecosystem.

Broad incumbents

• Mahle GmbH: Global Tier-1 supplier of engine components including connecting rods, pistons, and bearings serving most major OEMs. Overlaps with AIZEN's product category at much broader scale.

Market position

Strengths4 records

Weaknesses4 records

Competitive moat5 records

Key risks6 records

Key highlights7 records

Customer concentration

Compliance2 records

Revenue estimate

Valuation estimate

Number of profiles

Profiles3 records

Subsidiaries2 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about AIZEN